THE LIVING ATRIUM- Designguidelines for qualityatriums

by KennethGardestad

Arkitekturexamen The RoyalInstitute of Technology Stockholm,Sweden 1980

SUBMITTEDTO THE DEPARTMENTOF ARCHITECTURE IN PARTIALFULFILLMENT OF THE REQUIREMENTSOF THE DEGREE MASTEROF SCIENCEIN ARCHITECTURESTUDIES AT THE MASSACHUSETTSINSTITUTE OF TECHNOLOGY

JUNE,1986

@ KennethGardestad 1986

The author herebygrants to M.I.T. permissionto reproduceand to distributepublicly copies of thisthesis documentin wholeor in part

Signatureof theauthor - Kenneth Gardestad Departmentof Architecture May 15, 1986 Certified by TimothyJohnson PrincipalResearch Associate ^ Thesis Supervisor Acceptedby JulianBeinart Chairman DepartmentalCommittee for GraduateStudents

.0 A

THE LIVING ATRIUM-* Design guidelinesfor quality atriums

by KennethGardestad

Submittedto the Departmentof Architectureon May 15, 1986 in partial fulfillment of the requirementsfor the Degree of Masterof Sciencein ArchitectureStudies

ABSTRACT

Moderntechnology has made it ecomicallyfeasible to span large glass-enclosedstructures which are sociallysufficient and convenient for less mobilegroups of the society like handicapped,elders and children to virtually spend days, weeks or even monthsin a comfortableindoor climate. However,it is plausiblethat anypositive effects of a manipulatedenvironment can turn sour if the createdclimate is not closely simulating natural conditions. There is a danger of building in faulty and shortsighted presumptionsneglecting the close relationshipthat exist betweensocial, biological,medical, technical and aestheticalneeds.

This thesis, divided in two parts, has the broad aim to strengthen the architectural and technical foundationfor a good atrium design in order to provide a suitable environmentfor the coexistenceof people and plants in relation to comfort, health, climate, technique, aesthetics, and energy consumption.The scientificpurpose is to establishnew design criteriaand methodsin order to create a B

useful base for intelligent decisions in fulfilling the ultimate vision of a living atrium. The study will specificallyfocus on design guidelineswith respect to climatic conditions affecting plant growth and humanhealth and comfortwithin atriums.

Part one is a discussionregarding major variablesaffecting human health,comfort and plant growthin atriums.Also included is a detailedstudy, recentlyconducted by the author, investigatingthe impactof new glazing technologyon plant growth.

Part two presentsvarious useful design guidelineswhich can be used to moderateclimatic conditions and enhanceplant growth in atriums.A detailed lighting investigation,conducted by the author,is also presentedas a design tool for determingthe distributionof illuminationlevels in top-lit atriumsduring overcast conditions. The method can be used to rapidly identify plant growth zones in an arbitrarily porportionedand top-lit light-well.

Thesis Supervisor: Timothy Johnson Title: PrincipalResearch Associate C

TITLE PAGE p. 1. ABSTRACT A-B TABLE OF CONTENTS C-D PREFACE E ACKNOWLEDGEMENT F-H INTRODUCTION 2-8.

PAR'T 1: MAJOR VARIABLES AFFECTING PLANT GROWTH AND HUMAN HEALTH AND COMFORT- A CALENDER OF CURRENT KNOWLEDGE REGARDING INFLUENCING PROPERTIES AND THEIR RELATED RESPONSES CHAPTER 1: PROPERTIES p. 9 - 44. CHAPTER 2: RESPONSES p. 45-71. CHAPTER 3: IMPACT OF DIFFERENT GLASS TYPES ON PLANT GROWTH A STUDY ON PLANT GROWTHRESPONSE TO DAYLIGHTTRANSMITTED THROUGH GLASSWITH DIFFERENTSPECTRAL ABSORPTION - CONDUCTEDBY THE AUTHORAT MITTHE SPRINGOF 1986. p. 72 - 90.

PARf 2: DESIGN GUIDELINES FOR A HEALTHY PLANT GROWTH AND

HUMAN HEALTH AND COMFORT IN ATRIUMS. CHAPTER 4: MAJOR LIGHTING MEASURING METHODS p.91 -98 D

CHAPTER 5: DESIGN GUIDELINES FOR QUALITY ATRIUMS

p. 99 - 109 CHAPTER 6: GUIDELINES FOR SKY LIGHT ILLUMINATION IN ATRIUMS

A REPORTON A STUDYCONDUCTED BY THEAUTHOR AT MIT THE SPRINGOF 1986. p. 110 - 150

CONCLUSION p. 151 - 152

APPENDICES p. 153 - 161

REFERENCES p. 162 - 163 BIBLIOGRAHPY p. 164 - 166 E

PREFACE

Almost ten years ago, when I was working on a project for new university facilities in Port Harcourt,Nigeria, I first encounteredmany intriquatedesign problemswhich were intinitely linkedto climate.Paradoxally I foundthat differenteconomical and technicallimitations, such as a rathertight budgetas well as an unreliableand sparcesupply of electricityfor air-conditioning and lighting, seldom put any aesthetical constraintson the design. On the contrary, these restrictionsnecessitated a sensitive play with massing,forms and detailing, which utilized passive means for climate control, while giving the buildings character and high levels of comfortand convenience.

Today, I'm increasinglyconvinced that a sensibleunderstanding of naturalclimatic resources, like the sun and the wind, and a well founded consciousnessof the physical and biological environmentaround us is an asset in the designprocess, not only in developingcountries, but all aroundthe globe independentof technicaland economicalstandards. This knowledgewill supply the designer with a sharp chisel for expressing fascinating architectural forms indeginousto the specific site, while meetingall the technical, economical,and functional demands of a modern society. "The Living Atrium" is only one aspect of the designed environment, however, the expected extensive use of atriums in the future and the implicationsthis mightimpose on the society,makes it well worth an interrogativeexploration.

Note: Coincidentially,Richard Saxon has devoteda sectionin his book, "AtriumBuildings- Developmer* and Design", to "the living atrium". The author acknowledgesthis, but believes that the concept hasbeenbrought a step further in this thesisthan in his versionof the theme. F

ACKNOWLEDGEMENT

No knowledge is derived out of nothing and obviously I have many to thank for their contributionto this thesis.Some have been specificallyessential for my understandingof the varied and often extensive academic and technical material that forms the spine of my investigation.However, much -if not all- of my studies would have been severely hampered withoutan economicbase to start from.I'm deeplygrateful to DeanJohn de Monchaux,head of the School of Architectureand Planning at the MassashusettsInstitute of Technology,for granting me money from the Cabot Fund, which enabled me to carry on my quest for knowledge beyond the usual limits in exceedingly strainful economic conditions. Also, scholarshipsgranted by the Fulbright Commissionand the Swedish-AmericanFoundation, though not directly linkedto this thesis, have formeda substantialfinancial and emotionalcore of my studies at the MassashusettsInstitute of Technologyand I'm forever thankful for their support. The elaborate study of plant response to the impact of light transmitted through variousglass types would not have been possiblewithout all the glass sampleskindly offered by GuardianIndustries Corporation,and I especiallythank Product DevelopmentEngineer JasonTheios for turningthe administrativewheel and supplyingme with neededdata.

Among the different responsesto my interrogativequestions there are some that crystilized and stood out a little further, though I've highlyappreciated them all. However,comments and suggestions by PhotobiologistChristos Mpelkas, Manager-PhotobiologicalApplications at

GTE Products Corporation,.Sylvania, have been extremely valuable for a more thorough understandingof plant responsesto different environmentalconditions. Mr. George Clark, G

former Presidentof the IlluminatingEngineering Society, has helped me to set up contacts within his field. Associateprofessor Harvey Brianat the MassashusettsInstitute of Technology has given me significantacademic support as well as suggestionsregarding daylight research methods.Mr. CharlieTilfor at SouthwallTechnologies Inc. has suppliedme with new research resultson plant responseto heat absorbingglass. I dearly appreciatedthe time and effortspent by Dr. RichardWurtman and Dr. Harry Lynchat the MassashusettsInstitute of Technologyfor explainingthe intricate effects of light on the human body. There are also colleagues and friendsacross the Atlanticwho have offeredme useful commentson the contentof my thesis. ProfessorAnders Liljefors at the Royal Instituteof Technologyin Stockholm,Sweden, has supplied me with insights regarding the important influence of psychologicalfactors on the human interpretationof light quality. Landscapearchitect Jan Str6mdahl,gave me the first lessonsin plant responseto light andthe importanceof balancingall influencingclimatic factors for a healthy plant growth. I also want to extend my gratitude to my collegue and friend, Architect Hakan Bj6rk, for accompanying me on a sometimesstressful but tremendously interesting atriumtour thoughoutnorthern America during the summerof 1985.

Of course, my deepest appreciation is reserved for my advisor Timothy Johnson, Principal ResearchAssociate at the MassashusettsInstitute of Technology.His sturdy knowledgeof generalresearch methods and technicalissues has guidedme past many possiblepitfalls, but

I'm also gratefulfor his personalbelief in the importanceof the topic and his encouragementat criticalmoments.

It is common, and this thesis is certainly no exception,to designate the last part of the H

acknowledgement to your deerest. So, it is withdelightful joy I take this opportunity to express my sincere respect and love for my wife and thank her for supporting me whole-heartedly throughout this hectic period despite a sometimes neglected family life. 2

INTRODUCTION

Duringthe last halfdecade there has been a revival throughoutthe westernworld of large glazed enclosuresoften referredto as atriums.The traditionaluse ofcentral top-lit cores for bringingdaylight deep intothe stucturehas, in the wakeof newtechnology, been expanded to meet moderndemands for multifunctional open spaces serving technical and human needs.It couldbe arguedthat this concentration of amenitiesand circulation paths to a glazed courtis an architecturalwhim withmodern technology and trends trespassing hand in hand overadventurous land to meetbusiness demand for rentablecommercial spaces.Large office blockswith interconnecting glazedatriums have thus beenpopping up like mushroomsin, a flourishingbut economicallyhardening market. The growth has been fast, usuallycombined with eithera shrewdunwillingness or a lackof professionalknowledge to foreseeeventual drawbacksand interrelated problems. The use,or misuse,of theword "atrium" has kicked off expectationsof profitableand functional common spaces trigged by the extraamenity of a multifariouslarge room. The responseto the historicallyreborn interestin 6!azed roomshas beenimmediate and manytimes superficial, without the necessary understandingof the underlayingcomplexity of the matters,creating architectural spaceswith severeproblems not copingwith the intricatebalance between aesthetics, comfort and economy. Regardlessof technical flawsthere is strongsupport for the notionthat the conceptwill be in tune with commercialand public requirements for a functionalenvironment and presumably will survive in a competitivemarket. However, the continuingdemand for atriumsis largelydependant on successfuldesign solutions portraying high technical performance, relevantcosts, human comfort andconvenience-all integrated to createa positivetotal experience. Moderntechnology has madeit ecomicallyfeasible to spanlarge glass-enclosed structures which are sociallysufficient and convenientfor less mobilegroups of the societylike handicapped,elders and childrento virtuallyspend days, weeksor even monthsin a 3

comfortableindoor climate. However,it is plausiblethat any positiveeffects of a manipulated environmentcan turnsour if the created climate is not closelysimulating natural conditions. There is a danger of building in faulty and shortsightedpresumptions neglectingthe close relationshipthat existbetween social, biological,medical, technical and aestheticalneeds.

For instance theabundant architectural use of exterior tintedand reflectingglass for new and old constructiondoes not only have an obvious visual impacton the urbanenvironment but might also havesubtle psychological,medical and biological effects on man and plants as transmittedlight has varied spectral qualitiesdepending onglass type.

This raises concern as there are escalating indicationsthat human medical and biological responsesto solar radiation, including wavelengths withinthe visual spectrum,are more diversethan visioned onlya decade ago. Spectralquality and intensitymight be relatedto seasonal affective disorder, melatonin secretion affecting sexual growth, sleepiness,the biologicalclock, and possibly ovulation.Infantjaundice, psoriasis, calcium metabolism, muscle strength and evencancer are other biologicaleffects purportedlylinked to electromagnetic radiation.The science of photobiologyis still quite young and the gathereddata is not yet conclusive,but the indicationsare calling foraftention and are strong enoug.1to "supportthe view that thedesign of light environmentshould incorporateconsiderations of humanhealth as well as visualand aestheticconcerns" ( Dr Wurtman,The Effectsof Light on theHuman Body, p.77)

There is also reasonto believe that thespectral composition of transmittedlight is essentialfor a healthy plant growth.Even though thereis a massiveexperience regarding plant growth bothfrom researchand simple observations,there are still many phenomenanot completely explained.The use of modernglazing materialshas createdconditions which find no actual. 4

comparisonswith traditional techniques.Aesthetical and technical reasons have tempted designersto use tinted or reflective glassto minimize heatgain without investigatingeventual side effects on plants. Hypotheticallyit is logical to assume that the proportionsof active wavelengthspenetrating the transmittingmedia is affectingplant responsein a similar manner as direct radiation froma lightsource, but sofar thereis no compoundedresearch to proveit.

With theexpected increasingnumbers of atriums -bothfor publicand commercialuse- it seems necessaryto scrutinizepertinent architecturalissues relatedto atriumswhich have not been properly addressed in order to fully understandthe potential impact of possible design solutions.Recent projects show for the most part that the interestfor atriums is revolving aroundtheir spatial and sometimes majestic expressions,often neglectingsensual qualities and requirements supporting the important interrelation between people and plants. Specificallythere is a lackof awarenessof the climaticprerequisites thatexist for plantsto grow, and grow well, within a man-madeenvironment. Plants oftenserve as movableafterthoughts, placedin nonusablespaces withinadequate daylight. Architectural voids understaircases are used as flower pots, at best lit by restrained artificial light. Usually thereis no correlation betweenplant speciesand offered climaticareas. Structuresare unintentionallypolluted by late decisionsto increaseillumination levels withgrow-lamps instead beingof designedat an early stage for adequatenatural daylighting and if necessary supplementaryartificial lighting. The conditionsfor the cohabitationof plants and peopleare also insufficientlyaddressed and there is definitelya greatdanger that many atriums,with the intent tobe a fu,ictional transition zone between the inside and the outside, will not live up to envissaged long term expectations.There is a needfor a differentapproach, regarding climatical functional atriums, coupledwith new designtools and pioneering techniquesreadily accessible, understandable, and usablein order to pushfor a changetowards better solutions. 5

Within therealm of thesenotions thereare specific issues, hitherto insufficiently investigated, whichneed to befurther discussedin order to establish criteriaand design methods for a good atriumdesign.

Thisthesis, divided in twoparts, has the broad aim to strengthenthe architecturaland technical foundationfor a good atriumdesign in order to providea suitableenvironment for the coexistenceof peopleand plants in relationto comfort, health,climate, technique, aesthetics, and energyconsumption. The scientificpurpose is to establishnew designcriteria and methodsin orderto createa useful basefor intelligentdecisions in fulfilling theultimate vision of a livingatrium. The study will specificallyfocus on designguidelines with respect to climatic conditions affectingplant growthand human health andcomfort within atriums.

Partone is a discussionregarding major variables affecting human health, comfort and plant growthin atriums.Also includedis a detailed study,recently conducted by the author, investigatingthe impact ofnew glazing technologyonplant growth.

Parttwo presents varioususeful design guidelineswhich canbe used tomoderate climatic conditionsand enhance plant growthin atriums.A detailedlighting investigation, conducted by theauthor, is also presentedas a designtool for determing thedistribution of illuminationlevels in top-litatriums during overcastconditions. The methodcan be usedto rapidlyidentify plant growthzones in anarbitrarily porportioned and toplit light-wall.

It hasto be pointedout thatas well as it is necessaryto describe thegoal f thisthesis it is equallyimportant to set thelimits in orderto preventany misunderstandingof presented materialas there are an abundance of differentparameters affectinga successful atrium design. Manyof thesevariables are possible to trackand define and this thesis dealswith someof 6

them. Without anydoubt the scrutinizingand interpretationof "all" influencing factorslie in the handsof a responsibledesign team.The membersprofessional skill andartistic intuitionas well as their knowledgeof the individualcomponents will ultimatelyaffect the quality of the final designand possiblyshow theway to a livingatrium.

At last it should be mentionedthat it is notwithin the scopeof this thesis to list historically significantatriums as suchinformation easily canbe obtainedin the litterature. However, it is relevant for the understandingof this study to recognizethe differences betweenthe traditionalRoman atrium defined as an enclosedcourtyard open to the sky and compare it to the transformedmodern use of the concept where almost anyglass-covered structureis consideredan atrium. Twoimportant relatively recent atriums claimed to have been influencing later development can serveas examples for the twodirections. JohnPortman's Hyatt RegencyHotel in AtlantaGa, erectedin 1967,is an extensionof the originalconcept. It is a tall constructionwith top-lightingand an interior courtyard enclosedon all sideswith opaque walls.Roch'sand Dinkeloo'sFord FoundationHeadquarters in New York City,built in 1968, is close to a built in conservatoriumwhere the outsideand the insideonly are separatedwith a thin climatically shielding glass wall.This thesis will make no destinction between these definitions but adopt thebroader use of the word without disregardingthe philosophical, historicaland empericaldifferences between the concepts.

It is interestingto notethat researchis going on worldwide in order to find some answersto plant responsein atriumswith fluctuating temperatures.It is raising interestespecially in countrieswith temperate climatewhere it is beneficialto extendthe mildseason withouthigh costsfor climatecontrol. TheSwedish Institute for Building Researchwill delivera paperon the subjectin the fall of 1986. 7

To putthis thesisin perspectiveit is necessaryto mentiona few butcertainly important and for the contextpertinant steps in the history of mankind.The earth, as is generallyunderstood, has existedfor millionsof years.The evolutionfrom microorganism to plantsand animallife has

been a slow processleading to the adjustedmetabolism and adapted behaviorthat is seen today. The struggle for survival and enhanced living conditions has governed human exploration of the unknown. Technological border lines have limited the architectural expression.From livingin the opento cavesto contemporaryconstructions of modernlife. The smallopenings penetratingthe walls ofantique and medevialdwellings were just large enuogh to maintaina relatively decentenergy balance.Theinventors of the hanging gardensthe of Romanempire used vegetationand water to modifya harshclimate. New building techniques of the gothic and islamic cultures opened the wall and exposed the structure with the introduction ofglass as a buildingmaterial. Large glass windowsbrought mysteriousand life enhancing lightdeep into the buildings..Theindustrial revolutionmade it possible to mass

producecheap building materialaccomodating the labor force in poorly lit and hastily built stacked houses while kings and despots surrounded themselves with highlyarticulated gardensand manipulatedwild landscapes.The 19thcentury developmentof glassand iron manufacturingmade it possible to span transparent skins over vast greenhousesand exebition areas. In the wake of medicalinsights during this enlighted century was the introductionof beneficiallight in hospitals asa valuablecontrol-factor of diseas. Dense urban housingdevelopments in smog polluted cities were seriously questionedat the turn of last centuryas a humanenvironment and city blockswere torn down to give roomfor light and air. The garden city with smaller individual houses was presented as an alternative. The functionalisticera furtheredthe concept and placed large appartmentagglomerates in the landscape.Here in the presentwe haveatriums as a climaticbuffer creatingresemblances and indicationsof life outdoors. Futuredevelopment might lead tocities completelycovered with a transparent skinas visionedby the late BuckminsterFuller. The livingatrium is not only a glass 8 coveredenclosed privatecourtyard. It is alsothe evolutionof mankind's striving for a betterlife. However,without an understandingof the different environmentalfactors that are prerequisitesfor a comfortable and healthylife,it will notbe possibleto get there. 9

CHAPTER 1: PROPERTIES

DISCUSSION

Throughtime and evolutionman and plant have adjustedto the specific environment [FP 1: MAJORVARIABLES immediatelysurrounding them. Climatic conditions like temperature,relative humidity, solar AFFECTING PLANT GROWTH AND radiation,light, soil quality, access to water,and air to breathhave all hada profund impacton HUMANHEALTH AND COMFORT theirdevelopment. Time has made it possiblefor manto migrateto climaticallymore favourable

locationsattuned to hisneeds in orderto avoidexessive climatic stess and million yearsof - A CALENDER OF CURRENT evolutionhas changedthe humanphysiology to correspondto life-sustainingrequirements. KNOWLEDGE REGARDING Early plantsfound their appropriate environment by following a streamof wateror a whiskof the INFLUENCING PROPERTIES AND wind. Evolutionintroduced more intricatemeans of survival and reproduction.Animals THEIRRELATED RESPONSES inadvertillytransported seeds to newdomains with sometimes different prerequisites starting a new processof adjustment.Man and plantsstill continuethis questfor an environmentin equilibriumwith their requirements. It is not possiblein thisstudy to lingerover these thoughts except forshortly stating that man and plants today live undersimilar conditionsthat existed millionsof yearsago. The sky, the clouds,the sun,the soil, the oxygen,the carbondioxide, andthe waterare still prerequisitesfor life. This chapterwill touch on a range of major properties thataffect conditions in atriums.

A: ATMOSPHERICPROPERTIES

GASES

The earthis surroundedby an approximately20 miles thick layerof atmosphericgases. Permanentgases liko oxygen(20.95%) and nitrogen(78 08%)appear in ilmrn(t the same 10

proportionsanywhere around the world. The remainingshare is split betweenargon (0.9%), smallportions of krypton,neon andxenon and a fluctuatingamount of carbondioxide, which is

usuallyaround 0.03%. This small portionof CO2 is tremendouslyimportant for plant growth.

There are also traces of ozon and water vapor (0.4%) which affect life on earthindirectly throughtheir filteringand reflectingproperties.

The proportionsof oxygen and carbon dioxide in the air are decisivefactors influencing plant respons.Surprisingly,. it is evident thattoo much oxygen has negativeeffects and even the

normal21% is inhibitingphotosynthesis. On the other hand, low carbon dioxide contenthas limiting effects on the photosynthetical process, which actually would be speeded up proportionallyif the carbondioxide were higherthan the normal ambientconcentration. 4

SOLAR RADIATION

The sunis constantlyemitting energyin the form of electromagneticradiation usually measured in quantasor photons expressedas a factor of frequencytimes Planck's constant(h).The frequency(f)does not change when radiationis transmitted throughor in reflectedby a specific mediumit only decreasesor increaseswhen it is absorbed.Wavelengths(1) and velocity(c) changeproportionally as they are reciprocalsin a simple equationhf=c/1. Hence the energy contentin a photon increaseswith shorter wavelengthswhich meansthat ultravioletradiation containsmore energy than infraredradiation.

The electromagneticspectrum spans the rangebetween shortwave cosmic rays and longwave radio waves. The wavelengthspertinant for atrium design form narrowband ranging from ultravioletradiation(UV) over visible radiation(VR)to infrared radiation(IR).Their respective internalproportions being around7%, 52% and 41%.(See fig.) 11

There are several conventionalways of expressingthe unitfor wavelengths.For this study

namometers(1nm=10-9 meters) are choosen. SOLAR SPECTRUM OUTSIDE-ATMOSPHERE SOLAR SPECTRUM ATSEA LEVEL BLACKHODYCURVE 5900K or 1367 250 - The amountof solar radiationhitting the atmosphereeis approximately430BTU/ft2hr IRRADIANCE -r7 W/m2 -This figure,known as the solar constant, is decreasedto around 295 BTU/ft2hror 2 938W/m at sea level as the incomingradiation is attenuatedby the earth'satmosphere. It is 200 partly absorbedand scattereddepending on wavelengthby oxygen, carbon dioxide, water vaporand the thin layerof ozone,or reflectedback to outerspace by water liquidcontent in the cloudcover. (Seefig 2, The Medicaland BiologicalEffects of Light, L. Thorington,p.30) 100-

Thereis a controversyover the properway of expressingillumination levels pertinent for plant 50 growth and seeing. Commonly,footcandles or the SI equivalancelumens/m 2 =lux is used. (1fc=10.76lux.) However, some argue that irradianceexpressed as W/m2 is the correct ,3 2 O4 0.6 0.8 1.0 1.2 1A 1.6 11 2.0 2.2 2.4 radiometricterm for lightintensity. 5 Otherscontend that W/m2 / nm is the adequate approach 0 0. Wavelength(jim) for plants, as they do not respondto light quantityper se but to the energycontent in each bandof the spectrum.There is a convincingtone in the remarkthat "it is reasonableto expect equal numbers of absorbedphotons of different wavelengthsto be equally effective , not equal quantitiesof energy."(Physiolgical Plant Ecology 1, p.43) However,at this stage I am ready toquestion the moreelaborate definition, even though I am preparedto acceptits impact on photosynthesis.Thisis due tothe fact that plantsseem to be respondingto the proportions of activewavelengths, hence not the accumilatedeffect of energy,nor photons,but ratherto the interactingstimulation of different frequencies. The introductionof the unit "photon" portrayinga functionof frequencyand Planck'sconstant is maybeone way of closingin on a relevantexpression, but for nowfootcandles(fc) will be used accompanied witha descriptionof spectralquality. It is also possibleto describethe efficiencyof lightfor variouswavelengths by 12

an "action spectrum", where energy is expressed as an inversely propo tional function of quantasand wavelengths.

Energy=Quanta/wavelength

This approachis said to be the most accurateas it describesthe potentialeffect of different wavelengthson photosynthesis.From the formula it can be extractedthat red wavelengths contain more quanta than blue wavelengthsfor a given amount of energy.10 1The same sourceadvises that for practicalpurposesit is adequateto convertquantas to joules,or use the old standardof lux or footcandles,as it is easierto interpretethe values.

ULTRAVIOLET RADIATION

Most ultravioletradiation is absorbed by the ozone in the atmosphere.Only wavelengths longer than approximately 290 nm strikes the earth. Garrison et al has measured wavelengths down to 289nm, but ultravioletradiation is usuallyeffectively absorbed below 295nm. 7,102 The intensityvaries dependingon theoblique angle at whichthe sun's rays have topenetrate the ozone layer and the layers thickness.This is most vividly encounteredwhen the sun's altitudeis low asin the winteror at dusk and dawn.There might be seasonal differencesof up to fifteen timesmore radiation in the summer thanin the winter.8 80thers claim thisdifference to be aboutsevenfold. 9 However,there seemto be only relatively smallspectral differencesin the distributionof global irradiancereaching theearth's surface independent of season,time of day, sun angle,cloud cover and turbidity.10 It is however importantto note that scattered sky radiationhas proportionallyhigher content ofUV-B than direct sunlight.Il and thatheavy cloud cover can produceas high UV-Bradiation as clear days. Accordingto newstudies it couldbe 13 expected that between 40 % to 75 % of the total ultraviolet radiation, especially UV-B, reaches the earththrough diffused skylight. 103

Thereare threedifferent UV-bands: UV-A315-400 nm UV-B280-315 nm UV-C 100-280nm

Forthis studymostly UV-A and UV-Bwill be consideredexcept for the remarkthat UV-C has a stronggermicidial effect and energy radiatedat 253.7nmis morethan 90% effective.It might also cause materials to spelling. High energy wavelengthsless than 200nm can change oxygenin the air to ozone. 1 UV radiationhas low tissuepenetrating properties and UV-Ais less effectivethan UV-B. 2,13

VISIBLE RADIATION

Visible radiationspans a rangebetween approximately380-780nm. It is possiblefor the human eye to perceiveradiated energy as lightand colorswithin thatwavelength range depending on intensity.

The visiblespectrum is madeup of narrow bandsof wavelengthsinterpreted as colorsby the human eye-

380-436nmviolet 436-495nmblue 495-566nmgreen 566-589nmyellow 14

589-627nmorange (A) Photosynthetic Response 627-780nmred

(B) Chlorophyll Synthesis Thoughnot the most evident propertyof visible radiationit has been shown that"visible light is 14 apparentlyable to penetratemammalian tissues to considerabledepth" andthat canlead to Eye Sensitivit . a wider interpretation of"visible radiation" in the future. kA B

It has been long knownthat wavelengthswithin the visiblespectrum is eminentlyimportant for Il \ plant survival.Both intensityand spectral qualityas well as durationof radiationhave profound impacton plant response.(See fig. demonstratingsensitivity of the eye contra photosynthesis and clorophyllsynthesis. Sylvania Bulletine 0-352, p.2)

For a more detailed discussionregarding biological phenomenasee subheadingB in this chapterand chapter2: BiologicalResponses. 400 500 600 700 WAVELENGTH IN NANOMETER S

INFRARED RADIATION

Longwave globalradiation with internally differentproperties usually referred toas nearand far infrared radiaton.

Near IR 780nmto 3200nm Far IR 3200nmto 106nm

Near Infrared radiation.

Nearinfrared radiation is energydirectly emitted by extremelyhot objectslike the sun or 15

reflectedby a radiatedsurface and has the strongestheating effect of all typesof radiation.It penetratestissues easily and raisesthe temperatureof absorbingtissues due to direct impact.

Oxygen,water vaporand carbondioxide in the atmospherestrongly absorb muchof the short wave infraredradiation emitted by the sun. The infraredradiation reaching the globe has a rangebetween approximately780-3200nm.

Far Infrared radiation

There is a significantdifference between near infraredradiation and far infrared radiation.Far infrared,sometimes referred to as thermalradiation, is energyradiating from all warm surfaces like furnaces,radiators, people,plants, animals,and artificiallight fixtures.Object which have absorbednear IR reradiatesthe energyas far IR. Far IR indirectlyraises the ambient air temperatureby heatingsurfaces which conduct and convectthe absorbedenergy tothe air. The wavelengthsvary between3200nm to10 6 nm.

Daylight

The psychologicalperception of intensitylevel and color temperatureof daylightis seemingly inert toquite big changes,unless thereis an abrupt braeak in the regularpattern, like the sun suddenlypeeking through a hole in the cloud cover or swiftly disappearingbehind a passing cloud. However,the intensityvaries constantly,but the eye is raesonablyable to adapt to oscillatinglevels and alleviatesome of the differences.It has beenclaimed that daylight,made up of direct sunlight and diffuse skylight, has a characteristicallyuniform spectrum.1 6 That seems to be only partiallytrue. The fact is that pure solar radiation, excluding the sky component,incident on a horizontalsurface above the atmospherefollows a smoothcurve, 16 but it is also evident that atmospheric conditionschange theintensity as well as the color temperatureof transmittedradiation quite dramaticallywithin only smalltime intervals.(See fig 200 11, 12, 13, The Medicaland BiologicalEffects of Light, L. Thorington, p.40-41) (Phillips, 160 180I1 LightingIn ArchitecturalDesign, p.71 and figs7.3and 7.4). The thicknessof the cloud cover, 20 t (a(a LP moisturein the air, and pollution have different impacton the spectral distribution.Cloudy days 140 show an increasedproportion of bluewavelengths withonly partial discrepanciesin the red spectrumcompared to daylightwith clear skies.Overcast conditions with haze anddust, on the 20d400 0 -0 0 a an in red other hand, result in proportionalreduction of blue wavelengthsand increase Woveengto!rdateeg n milmcro wavelengths.It is not surprisingthat the altitudeof the sun also affectsthe spectral distribution.

Actually, solar altitudes below 10' change thespectrum radically. Thismode of daylight, Exterior illumination levels taken in Great Britain on two days in the same month. (A) referredto as twilight, has a striking emphasis onblue wavelengths,due to scatteredskylight, Cloudless sky until 10 A.M., then solitary white clouds at about half-hour intervals. (From Parry and far red wavelengths,due to refractedsunlight. Moon, Lighting Design.) (B) Overcast day with squalls and showers: rapid fluctuations due to (PhysiologicalPlant Ecology 1, D.C.Morgan and H.Smith,p.111) (See fig 4.1 p.111) heavy rain clouds. (From W. H1.Stevens, Principles of Lighting.) (See fig 16, The Medicaland BiologicalEffects of Light, L. Thorington,p.-4) Other studies indicatevarying energylevels for blue and red wavelengthsat twilight witha shift towardsthe red spectrum.(Physiological Plant Ecology I, F.B.Salisbury,p.152) (See fig 5.3 p.152)

B:ENVIRONMENTAL PROPERTIES

4-0 6-0 8-0 10-0 Noon 2.0 4-0 6-0 AM PM Environmental discussion (A)

Manhas adjusted cultureand physiologydepending on climate.Differences in skin color, clothingand building technology have gradually progressed to givemaximum protection and benefitsfrom the impact ofclimatic forces. Religions and philosophies have been markedby thewonders of theworld and miracles ofthe sky. The sun has beenworshiped forits lifegiving 40 60 8 0-0 Noon 2-0 4-0 6-0 lightand heat, the moonfor its subtlelight, the stars for their guidence, the cloudsfor theirrain, AM PM (B) 17

the tree for its shade andthe earthfor its food. Cultural,social and individualneeds have risen out of these natural phenomenadepending on access.Cultures, with an abundance of solar radiation,havenaturally not been as prune to regarddirect sunshineas equally favorabeas those whichmore evidentlydepend on the sun for survival.That is to say that the present intensity,duration and qualityof light aswell as shade,temperature, and humidityis regarded differently dependingon cultural,social and geneticbackground.

Climatical properties

Sunlight impactdepends on the positionof the sun in the sky, (its seasonalaverage altitude abovethe horizonwhich affects the duration, intensityand spectral qualityof daylight.)Several other factors, suchas the thickness of the cloud cover, air pollution,and other atmospheric propertiesnot mentionedabove, have togetherwith the orientationof the radiatedobject as well as the quality and quantity of shading obstacles modifying effects on the climatic environment. Nocturnal radiation,elevation abovethe sea level, and distancefrom influencing sea currents also moderateor accentuatethe ambientair temperature.Wind direction and velocity,access to open water,andvegetation have impacton relativehumidity and ambient air temperature.Topography,soil quality heatstorage capacity in surroundingmaterial and masses whethersoil, rock or water are all basic ingredientsin a developmentof regionalclimatic zones. Innumerablevariations and proportionalchanges ofindividual componentshave created a range of different climatic conditionsfor plant growth, animal lifeand subsequentlyhuman settlement.The climaticzones, as they are evidenttoday, have not beenstable but partof a slow and oscillatingprocess creatingchanging but rather narrow prerequisitesfor life and survival. 18

Geographical zones.

There are several theories regarding the nomenclature and classification of various geographical zones.However, according to W. Koppenthere are five definedclimate zones ranging depending on vegetation, latitude and altitude from tropical-rainy, dry, warm-temperate, cool-snow-forest and polar.1 7 Others refer to tropical as hot-humid, sub-tropicalas hot-aridor warm-humid,temperate as moderate-cooland arcticas cold.18 The intent is notto ponderabout differentvegetational geographical areas but to pointto the fact that macro-climaticvariations have been the fundamental causefor the developmentof the faunaas it is seentoday.

Comfort zones

It is interestingto note howthe definitionof comfortzones changes around theworld. British Drs. H.M.Vernon and T. Bedfordstate the ideal temperaturein the summerto be 66.1'F but differ in their opinion on how high a pleasant indoortemperature should be in the winter. Bedfordsuggests 64.7'F while Vernon is content with 62.1'F. Other sources givedata for comfort zones in Britainto rangebetween 58-70'F while it increasesin the UnitedStates to 69-80'F and in the tropics to 74-85'F.19 It is clear from Victor Olgyay'sdata that prefered temperaturesand relative humidity is highlydependant on geographicallocation, sex, age, individual acceptance,type of activity and clothing. Researchconducted in Denmark by Fanger, adoptedby A.S.S.A.E., indicates a morefavorable reaction to fasterair movement,as a counteractingfactor to highrelative humidity, than whatis advisedin VictorOlgya's bioclimatic chart. Allthis goesto say that is is necessaryto lookat regionalpreferences in orderto assess any valueto givenclimatic zones. 19

Atrium design related to climatic properties

Thereare several climaticproperties which have to be consideredin atriumdesign, if the goal is to errecta buildingwhich is energyefficient, comfortable, economical, regional, and sensitive to humanneeds. Theunderstanding of these conditionswill create an architecturewhich is unifying technology, economy, ecology, biology, psychology, and even medical considerationsin an aesthetic experience. It is obvious that descibed macro-climatical conditions creates a first base fromwhere it is possibleto make judgementstowards an adapteddesign. At the localsite it is necessaryto knowthe detailedconditions.

Location

The possible impactand affectof solar radiationon any surfacedepends on the incident angle and the intensityof the radiatingrays as well as the insulating,absorbing, transmitting, and reflecting propertiesof the material. Anyshading external componentslike protruding constructions, vegetation,neighboring buildings and site topographyalso affect the outcome as well as reflectionsfrom surroundingsurfaces. In this chapter onlythe intensityof the sunat differentlocations willbe considered.10 5

Orientation

The orientation and tilt of radiated surfacesaffect the efficiency of the solar radiation penetratingthe atmosphere.Accordingly, the total amount of possibleradiation striking a surface is a compoundedfactor of atmosphericconditions, season, time of day, location, orientationand tilt of surface.Architectural features can only, but powerfu,'y,modify these 20

terrestial conditions.

Climatic data

The tablebelow does not pretendto giveany completeclimatic data but merelypoints at general differencesin our natural environment.

Origin Temperature Humidity Daylength

Tropics Steady High Even 75-95'F 80% 12-14 hoursyear

Mean81'F round Fluctuatingat higher altitudes

Subtropics Moderate Drysummers Moderate seasonal seasonal differences Wetwinters differences Desertarid areas havewide daily temperaturespans

Temperature Widefluctuations Moderate Widefluctuations Warmto mild 60-80% 16-20hours 21

summers Coldwinters 30-40% 6-10hours

Arctic Mildsummers Regular Widefluctuations Coldwinters precipitation Summer18-24 h Winter 6-0h

C:BIOLOGICALPROPERTIES

Biological properties related to man and his need for solar radiation.

Discussion

It is obvious thatour eyes are vitally important for our performance whether it is forexecuting a taskor viewingan object.However, along with the retinasrole as a photoreceptor,there are newdiscoveries indicating that our eyesnot only havethe capacityof transmitting visual information the to brainbut alsoact as intermediate linksto the pineal gland,the adrenal medulla andthe pituitarygland affectingthe productionof melatonin,adrenaline and tropic hormones.(R.Wurtman, The Pineal,p.9) As a curiosait is interestingto notethat even though thesefindings have surfaced during thelast yearsthere has been an ancientmystique surroundingtheir bodily functions.The pineal glandwas earlyconsidered by Descartes as the centerof thesoul. (Webster's Encyclopedia) Today these "neuroendocrine transducers" are, in the light of modernscience, claimed to be controlledby nervoussignals generated by environmentallighting. (R.Wurtman, The Pineal,p.9) Other biologicalfunctions mainly affected byultraviolet radiationaresynthesis of vitaminD 3, erythemaor reddeningof the skin,melanin synthesis or darkeningof the skin causedby pigmental changes,thickening of the epidermis 22 of skin exposedto sunlight, photosensitizationaffecting rashes on the skin, and control of psoriasisand herpes virus.Blood producing organs as well as the ovariesand theliver are also affected.(The Effectsof Light on the HumanBody, R.Wurtman,p.68) Jaundicein newborn infants has been succesfully proven to be affected by light until the liver is capable to metabolizebilirubin. What partof the spectrumthat is most efficientis under investigation.Blue light is most effective in decomposingbilirubin but full-spectrumwhite light is, regardlessof reasonablespectral distrubutionof blue wavelengths, capableof lowering plasma-bilirubin levels. (The Effectsof Lighton the Human Body, R.Wurtman,p.74) Recently it has been documentedthat naturalor artificialsunlight incuding, ultravioletradiation, has a positiveeffect on workingcapacity, physical fitnessand muscularstrength. ( An Examinationof the Beneficial Actionof NaturalLight on the PsychobiologicalSystem of Man, Ph.C.Hughes,p.D603/3).

The eye.

Structure

The structureof the eye is brieflymade up of the cornea,the iris,the lens,the ciliarybody, the vitreous humor,the retina, thefovea, the macula,and the optic nerveconnected to the eyeat the blind spot.

Optics

The lens and the iris are the the major optical componentsof the eye.Muscles in the ciliary bodycause the lensto accommodatein order to bringan objectinto focus. 23

Light-sensation

The retina is the receivinglight-sensitive component of the eye. It consists of two different kinds of light-sensitivenerv endings, conesand rods,which are activated dependingon the light intensity.

The cones are concentratedto the fovea and are efficient for daylight vision only.They are reactingto intensitiesabove a luminancelevel of 3cd/m2 (LightingManual, PHILIPS, p.19.2.1)

or O.O1fL(Illuminating Engineering for EnergyEfficient Environments p.7) The propertyof the 510 55S eye to respondto luminanceabove 1fL is called "photopic vision"and is most sensitive to wavelengthsaround 555nm andcapable of distinguishingcolors andproducing sharp images.

The rods are increasingin numbersfrom the fovea andare sensitiveto lowluminance levels Cone

roughlybetween 10-6fL to ~ 1fL.This propertyof the eyeto see in the dark, especiallywith increasedperipheral vision,is called "scotopicvision" and is dominantly reactingto movement 2 and flicker.It peaksat 51Onm with the eye adapted to0.05cd/m , which is aboutthe upper limit I T G~ 400 500 600 of moonlightillumination. (Lighting Manual, PHILIPS, p.19.2.1) ( See fig 1-10,J-11, Illuminating Wavelength Engineeringfor EnergyEfficient Environmentsp.12-14) (See fig 1.4 and The Ergonomicsof Lighting,R.G.Hopkinson, p.23.)

There is an intermediate luminancezone at twilightwhere neitherthe cones northe rods are fully efficient.This propertyis called "mesopicvision.

Adaptation

Adaptationto lightor darkconditions does not happeninstantaneously, but varies for different 24

light levels.Generally it takesonly seconds to adaptto brighterlight levelswhile it is a matterof minutesand maybeup to 1 hour to completelyadjust to low light levels. (The Ergonomicsof Lightingp.20+ fig1.3) (fig1.4 p.21 )

Interpretation

Interpretationsof thesevalues indicatethat the humaneye is shiftingits sensitivityfrom the green-yellowpart of thespectrum towards the blue-greenwith diminishing lightintensities and that the rods andcones are nearlyequally sensitive to red wavelengths.It can also be 0 questioned whetherother visualproperties than thoserelated tophotopic visionhave any impacton atriumdesign. to- 1o 1 0o 10 Aop.lo.,,,i.o.n (10Or-L P*1. 1.4 Schematicdiagram showig the range of diseriminable luminanceat an given IrV of adaptation 'he limit linesshown a*inno snse asarpbounderies-gflare and lossof hig lightdetail gradually Human visibility lassiseas lumoinance increases; loss or shadowdetail gradually merge it subjectiveblack as luminancedecrease

The possibilityfor the human eyeto detectinformation is affectedby visual acuity which is dependingon mainlyfour variables: Size, luminance, contrast and time. Somedata interesting for atrium designis that the maximumvisual efficiency occurs whenthe surrounding luminance

(increasing) is between1 to 0.1times the luminance of thedisplayed object and that an object brighter than Contrst Senasiiviyversus L. over NormalIndoor Ranges the backgroundpresents the highestvisibility. Thereis, however,a drop off in visualefficiency if the lightlevel increases above a certainlimit

Low sensitivityrequires as the eyeis not infinitlyand evenly sensitive to contrast differences."As the levelof contrast high contrast Ti Highsensitivity requires sensitivityincreases, the visualsystem needs less contrast for a certain level visibility." of ii low contrast (Illuminating Engineeringfor Energy Efficient Environments p.23) (See fig 1.19and 1.21) It is alsointeresting to notethat the timefactor affecting visibility evens out at a luminancelevels of t~t~ approximately12 fL. Somecaution regarding the interpretationof this infomationis needed as the data available doesnot indicatesize of the viewedobject, which most definitely has to Contrast Sens.itviy versus Contrast 25

affect the critical time required. (IlluminatingEngineering for Energy Efficient Environments p.25)(See fig 1.23)

81- - - -_

Constants Other Biological properties related to man 4. Cras 3.6

2

Biologicalproperties like sex, age, color of skin are generally known to profoundly affect 6 12 100 1ow L, (f individual needs at the same time as it might lead to faulty conclusions to generalize Timeversus Li differences.Each individualhas his or hers preferencesgenerated from cultural,social and geneticroots and it is complicatedto measurethese values.One rather easily obtainedsource

of information,not based onsubjective valuejudgement, is data describingthe impactof UV-B radiation onhuman skin. As might havebeenn expectedblack skinneeds a larger doseof

radiationto produce vitaminD3. Up to six timesas muchas caucasianskin accordingto a study relatedby MickaelF. Holick. (B.M.E.of Light, p.9). The samestudy states that wavelengths between295-300nm are most effective in convertingenergy to vitamin D3 and that natural selectionhad favored theevolution of black skinin peopleliving near theequator and lightskin in those livingin areasdistant therefrom. "(p.5).

Affects of aging on the eye

The eye'spossibility to act as photoreceptorsis affectedby aging. "The older one gets, the more light is requiredto perform the same task." (Derek Phillips, Lighting, p.29.) Young children have the best vision while acuity, rangeof adaptation,accomodat.3n and distance resolutionis diminishingwith growingage. Presbyopiaor the diminishingability to focus clearly on close objects, due to weakeninglens muscles,is the most evidentdifference. (Lighting, D.C.Pritchard,p.8) Othersclaim thatblurred near vision beginningat the age of about 40 is "due to a hardeningof the lens substance".(Illuminating Engineering for Energy Efficient 26

Environmentsp.5) Changes also take place in the retinarequiring more stimulating radiation to see well. Cataractis a serious problemfor elderly personsas the optic mediain the eye,due to clouding overof the lens, is scatteringmore light causing sensations ofglare and impaired vision.(Lighting, D.C.Pritchard,p.8) The yellowingof the lens andcentral portions of the retina is decreasing theold eye'ssensitivity to blue wavelengths.However, it is also argued that these old-agesyndroms are counteractedby an increased experienceof detailsand inteligent intepretationsof the surrounding environment.(The Ergonomicsof Lighting,R.G.Hopkinson, p.23.) These findings have governedregulations for illumination levels throughoutthe world andthe IES Lighting Handbookcorrelates for the agefactor. Still,other relativelyrecent studies disclose thatno significantdiscrepancies in performancedue to light levels,within a span ofIfc to 450fc, could be detectedfor different age groups. On the contraryit was concludedthat "morale or sense of well-being" will "have a greater effect on performance than simple illuminationlevels." (The Effectsof Light on Health, P.M. Coxe, P.B.Reiser,W.M.Lam, p.27) Reducedglare, increasedcontrast and better physicalorganization were also regardedas superior solutionsto safety problems.(TheEffects of Light on Health,P.M. Coxe, P.B.Reiser, W.M.Lam,p.22)

PROPERTIES RELATED TO PLANTS

Similartheories can be adoptedto plants.Adjustment to prevailingconditions by selectionhas probablycaused the developmentof different genera andspecies according to their varying needs of climatic stimuli. However,these needs might vary dependingon time of day and season. Most plants regularilyused indoors have originated from the tropics and the subtropics with relatively favorable stable climate. Tropicalplants accustomedto steady temperatue,humidity and similar light conditionsthroughout the year are more sensitiveto changesthan plantsused to seasonaland diurnal fluctuations.The latter adjustingmore easily 27

to the restrainedconditions inside. *(Exotic Plant Manual,p.6). It has to b' pointedout that most common indoor plants come from higher altitudes in the tropics where temperature fluctuationsare relativelywide and temperaturesgenerally droppingat night. *(EPM, p.27). Researchis going on right now in order to investigateplant responsto extremefluctuations. *(SBFRSweden)

Even though plants do best in their natural or similar environment,they can adjust their biologicalproperties to fit less favorableconditions by a gradualacclimatization process. The rangewithin whichthe plants canadjust is dependingon genotypesand individualspecies in accordancewith the discussionabove.

PLANT PHYSIOLOGY

Basicallya plant is madeup of four majorparts: The roots,the stem, the leavesand the flowers with growingpoints complementingroots and stems. They allfulfill importantphysiological functionsin the lifecycle of plants.

Aerial growing points

The mainarea ofcell divisionwhere youngtissues of leaves, stemsand flowers are developed is concentratedto the aerial growingpoints. Major growing pointsalso producehormones to control rate of growthand shape of the plant. Somezones of the growing tips,together with 28

young leaves, are active in detecting changes in day length thus controlling seasonal flowering.(S.Scrivens, Interior Planting in LargeBuildings, p.15)

The stem

The functionof the stemis notonly to supportthe plant but also to act as a transportingmedia for nutrients,carbohydrates, and water. It is also a storagearea for carbohydrates.Most stems are rigidand easilydamaged by bending.Especially grasses and palmtrees are sensitiveas their conductivetissue cannot be renewed.(S.Scrivens, Interior P15. See fig p.15.)Some photosynthetic reaction, thoughin lesser content thanin leaves,also take place in branchesand stems.(R.L.Gaines, Interior Plantscaping, p.14)

Leaf anatomy

Basic structure The basicunits ofthe leavesarranged from the uppersurface are: The upper cuticle, the upper epidermis,the palisade layers, spongy mesophyll,the lower epidermis,and thelower cuticle with stomatalapertures. (See fig p.14and 16 in 15 and 16) The physical appearance of participating components are varying dependingon climatic conditions.The leaves retainsome carbohydratesas a reservefor functions during darkness. For aneasy comparision it is logicalto lookat extremeleaf structureswhich according to their environmentcan be calledsun leaves and shadeleaves. Cuticle The uppercuticle is usually coveredwith a waxyfilm toprotect from excesive solar radiationand consequentlyloss ofwater. In dry climates cansystems of hairsand scalesreduce this lossby creatinga wind reducing layerof air as well as increasereflection. (!6 p.15) 29

Epidermis

The upper epidermiscan have upto threeprotective layersreducing the impactof intense GMLGHT LOW LIG14T solar radiation,while it in shadelaeves is reducedto one.(16,p.56) ,c c

bl Protective

(See R.L.Gaines,Interior Plantscaping,fig p.14 and S.Scrivens, Interior Planting in Large a a

Buildings,p.16, fig 3.2) P - layer Palisades The palisade layers are made up of chloroplasts with light sensitive grana containing a n a chlorophyll. The different components can position themselves and change form in accordancewith the imposedlight intensity. The chloroplasts can aligne themselves along the "tutle Stomaital aperture palisadecell, and the disks in a single granumcan stack themselveson top of each other to 3.2 Sectionsthrough leatveof Ficus benjaminagrown in high and lotilight conditions toindicate some of the variations in leaf morphol- minimize the exposed surface. Reversely, it is possible for the chloroplasts to squeeze "gy'''"''''u''' ''""'""o'lig''"""'s't together,and the granato spreadout likea toppledstack of coins, in order to gain maximum accessto theradiated energy.(1 6, fig,p.57,60) This process,however, is slow andusually takes up to four or five weeks. Mesophyll The spongymesophyll contains some chlorophyll,but is less importantthan the palisadelayer as a converterof lightenergy to chemicalenergy. Its relativelylarge structuralvolume can be explainedby the plant's need to expose a large surface forthe exchangeof gases and absorptionof light. (R.vander Veen, Light and Plant Growth,p13) Stomates

Stomatesare small poresin the leaf to enablethe plant toexchange gases -like oxygen,carbon dioxide,and watervapor- with the atmosphere. Theyare usuallyfound on the undersideof the leaf surroundedby two guard cells, whichcontain some chlorophyll.The aperturesof the stomatesare dependingon the climatic conditionsof the plantsimmediate environment. They 30

are usuallyopen duringlight hoursand partially closedat lowlight levels.The dependanceon balancedclimatic conditionsis strong and is affecting the rate of photosynthesiswithin the plant. Extremeconditions, like an inadeqatewater supply,can limit the guardcell turgidityand make the leavesclose the stomates completely. A collapsed aperture is reducing the necessaryflow of carbonoxide and thus limitingphotosynthesis and growth. Pigments Chlorophyllis a highlylight-sensitive green pigment and themajor stimulantiW photosynthesis.

Thereare severaltypes of chlorophyll,usually referred to as (a) and (b),which are found in a ratioof about3 to 1 in higherplants. Even(c) and (d)types are mentionedin the litterature,but the (a) type is the most prominentin the photosyntheticalprocess. (R.van der Veen, Lightand Plant Growth,p14.) The chemical structureof chlorophyll reveals that the nucleusis constitutedof mineralelements like magnesium(Mg) andnitrogen(N) surrouned by carbon(C), oxygen(O),andhydrogen(H). Protochlorophyll, a green pigmentsimilar to chlorophyll,is not photosyntheticallyactive, but animportant precursorfor chlorophyll(a).The nucleus of the chemical structureof protochlorophyllis replacedwith iron(Fe)instead of magnesiumfound in chlorophyll.

Chlorophyll formsonly when protochlorophyllhas been exposedto light.(Environment& Plant Response, M.Treshow, p.101) Other pigments such as phytochrome is essential for photoperiodism."All organisms which are photosyntheticallyactive containchlorophyll". There are , however,other pigmentsas well, whicheffectively can transfer absorbedenergy to the chlorophyllmolecules, even thoughthey do not directly participate in the photosynthetical process,(R.van der Veen, Light and Plant Growth,p21.) Plants thatare red,yellow, brown, blue, and purple contain pigments such as carotenes (orange), anthocyanin (red), phycoerythrin,fucoxanthin, and phycocanintogether with smaller amountsof chlorophyll.The action spectrumof these plantscan thus be widened,though it appearsthat chlorophyll(a)is 31

the only strictlyessential pigment in photosynthesis.(R.van der Veen, Light and Plant Growth, p21.)

Roots

There are severalcomponents of the rootsystem servingdifferent functions. The main roots are responsiblefor the anchorageof the plant,major water and nutrient uptake,as well as food storage. The size of the root system is dependent on its environmentand the activity of photosynthesis.A systemin balanceusually means thatthe top growthis approrimatelyequal in volume tothe subterranean growth.The relative proportionsare often referredto as the root/shootratio. Functionand efficiencyof the root systemis highlydependent on thequality andquantity ofsoil andwater, as well as the oxygencontent in the soil.

The growing points of the roots have the same rapid cell division capacitiesas their aerial counterparts.

The roothairs are spreadingout closeto the growingpoints. Theyonly live for a few days until they are replacedafter serving as collectors ofwater andmineral salts, absorbed from the soilby osmosisor diffusion.

Photosynthesis

Photosynthesisis directly and indirectly essential for the survival of any living organisms. Photosyntheticallyactive plants and algaesconvert radiant energy to chemicalenergy for their own growth making it possible for higher life forms to indirectly make use of produced 32

carbohydratesand oxygen.It should be notedthat the vast majorityof photosynthetic activity takes place in living organisms in the oceans. Wherever thereis chlorophyll there is a photosynthesisreaction to availablelight. This indicatesthat the most vital part of the plant for this processis a healthy leaf, butalso that greenstems are involvedto somedegree.

"The biochemistryof photosynthesiscan be dividedin two phases",as sometimesclassified in the literature as "the light cycle" and "the carbon dioxide cycle".These cycles can not be performedwithout the presence of light energy,favorable temperatures,water, carbon dioxide, nutrients,and necessaryenzymes. (R.van der Veen, Light and PlantGrowth, p15.) Other more recent sources prefer to divide the process in a light and a dark reaction. (M.Treshow,Plant Response,p.103.) (S.Scrivens,Interior Planting in LargeBuildings, p.17) The divisionsare primarily thesame, however, the following discussionwill adopt the first mentionedprinciple to distinguishthe photosyntheticreaction from photoperiodresponses to "light anddark cycles".

1. The light cycle is initiated by a photochemical reaction to light energy and responsiblefor the productionof phosphates.Only a small portion,maybe1% to 2%,of availableenergy is used in this process. (R.van der Veen, Light and Plant Growth, p11.) Most energy is reflectedor absorbed by the leaf as heat and lost to the surroundingenvironment. A fraction of this absorbed energy,less than 1%, is reradiated,as chloropfyllfluoresces wave lengthsin the red andfar red withinthe leaf. The chemicalconversion can brieflybe explainedas a reductionof H radicals and oxidizationof OH radicals to free oxygenand hydrogenfor the productionof vitaminK. 33

2. The carbon dioxidecycle is the second step of photosynthesisand the actualprocess where carbon dioxide is absorbedto form differenttypes of carbohydrateslike glucose, and eventuallycellulose, fats,and proteins.(R.van der Veen, Lightand Plant Growth,p1 7.)

Normallyabout 75% of the producedcarbohydrates are used for building up the plants cell

walls and 15%to 20% for respiratoryactivities. The remainingshare "servesas substratefor carbohydrate,fat andprotein metabolism." (M.Treshow, Plant Response,p.103.)

Chemical reaction The totalchemical reaction for photosynthesiscan be expressedin a simplified formula:

6CO2+ 6H20+ RADIANTENERGY = C6 H120 6 + 602

Photosynthetical activity 4 1400 It is obviousthat a limitedamount of water, carbon dioxide,or radiatedenergy will affect the photosyntheticalactivity. More over, theprevailing temperature is also relatedto the carbon dioxidecycle, which seems to be most effectivein a temperaturerange between 100C to 300C 1000 (50-85'F). (S.Scrivens, InteriorPlanting in Large Buildings,p.17) Other sourcesclaim the photosyntheticaltemperature range to be between 4'C to 300C. (Environment& Plant

Response,M.Treshow, p29). The concentrationof carbon dioxideis influencedby the access 2 600 of fresh air withina closed environment.The optimalconcentration of 1000ppm to 1500ppmis hardto maintainin the winterand can raise a problemespecially during light hourswhen the plants are requieringcarbon dioxide for photosynthesis.(Sylvania Bulletin 0-352, p.5, fig 5) A 300 lowerratio than the normal0.03% affects the photosyntheticalrate andwill probably slowdown crop growth. On the other hand, an increasedgrowth will presumablyoccur due to higher concentrations.(Sylvania Bulletin 0-352, p.4, fig 4) The intensityof radiated energymust, 0 however,be classifiedas the most importantfactor influencingphotosynthesis. It could be 0 2 4 6 Light Intensity convenientto exclaim thatthe more energythe better,and this is true within limits. But, too 34

muchlight is asharmful as too little. It all dependson individualfactors as well as their relative balance. Different kinds of data have to be investigated before it is possible to make a judgement. Influencingfactors such as; type of plant exposed, length and quality of acclimatisation,dominent typeof leaves-whether shade or a sun laeves, amount ofwater, amount ofcarbon dioxide, amount and type of nutrients,prevailing leaf temperature,soil temperature,air temperature as well as the generalplant postureand age, haveall a part in the photosyntheticalprocess. Defiencies Plentyof absorbed lightenergy caninitially promote increased photosynthesis.However, too much lightwill cause dehydrationif the followingtranspiration rate excedesthe plants abilityto restoredissipated water or carbondioxide and nutrients,and eventuallyimpair photosynthesis. Extravagantly high intensities might also break down thechlorophyll molecules in a photooxidationprocess. Chlorophyllmust be constantlysynthetisized if the plant is going to

stay green andaviod yellowing of the leaves.A defiencyusually referred to ac chlurosis.

Photosynthetically active radiation: PAR

Traditionally wavelengthsbetween 400nm to 700nm, usuallyreferred toas light, have been claimed to activate photosynthesis.It has also been stated that all wavelengthsare not promoting photosynthesiswith equalefficiency, but that the productionis peakingin the blue spectrumat 435nm and in the red spectrumat 677nm. Thetypical double peak of theHoover curve has since 1937 been the general conceptionof a photosynthesisaction spectrum. However,Hoover's findings were based on pale green wheat leaves, and more detailed studies have indicated differencesin the action spectrumdepending on type of plantsand possiblyleaf thickness and color.Tree leavesshow a moreeven photosyntheticalresponse to the full spectrumcompared to pale herbleaves like lettuce.(Physiological Plant Ecology I, K.J. 35

McCree,p.47 and fig 2.4 and2.5) This seemsto be confirmedby other reportsindicating that the action spectra for a plant canopy is nearly flat.(Plant Response to Light Quality and Quantity,~H.M.Catheyand L.E.Cambell,p. 229)

Chlorophyll synthesis

Photosynthesiscan not occur without the necessaryformation of chlorophyll.That phasein the photosyntheticalprocess is usually initiated by light impinging onprotochlorophyll, and completedafter its conversionto chlorophyll(a).The process seemsto be reversedin darkness withinabout an hour. Someconifers and lower plantscan manufacturechlorophyll in darkness. (R.vander Veen, Lightand PlantGrowth, p24) Action spectrum for protochlorophyll to chlorophyll The actionspectrum for the transformationof protochlorophyll tochlorophyll is different than the actionspectrum for photosynthesis.There are moredistinct action bands affectingthis so calledchlorophyll synthesis and the curveis sharplypeaking in the blue and red wavelengthsat 445nm and 650nm. (Sylvania Engineering Bulletin 0-352, p.2 fig.1) Blue light seemsto acceleratechlorophyll production in stronglight while red and far red wavelengthsare activein weak light. (R.vander Veen, Light andPlant Growth,p112) Some sourcescontend thatthe distinctdubbel peak for chlorophyllsynthesis is much less pronouncedfor completeplants, and arguethat the influenceof other pigmentsand the scatteringof the leaf cells causethe curve to even out. Correlating with earlier reports on the effect of leaf thickness on photosyntheticalrate these findings show a similar respons for chlorophyll synthesis. (S.Scrivens,Interior Plantingin LargeBuildings, p.23 fig. 4.4) 36

Respiration

RespirationIs veryclosely related to photosynthesis,but contraryto that process,it goes on all the time-day and night, with or without light. The carbohydrates manufactured in photosynthesis,and stored in the plantcells, are converted to energy and used for plant metabolism.The temperatureof the surronding environment affects directly the rate of respirationindependant of the plantsneed. Otherfactors such as water availability,nutrients, carbondioxide and oxygen contentalso affectthe activity.Oxygen is used for the processand carbondioxide is releasedin a reversedscenario to photosynthesis.

Light compensation point

Plantsneed energy to survive and grow. They get this energy from photosyntheticactivity, and they use energy for metabolismin the respirationprocess. These two processesare relatedas they can restrict eachothers activities but also independentas they can freelymove

within those limits depending on external conditions. The more carbon hydrates the plant is able to produce for metabolismand set aside for storage in its cell walls the better is its possibilityfor survival and growth. The optimumrate of photosynthesisand respirationis uniquefor every plant but generallydepending on a combinationof several factorssuch as environmentalconditions, the plants nativehabitat and genetic disposition,age, leaf androot efficiency,and stage of acclimatization.Environmental factors include "light intensity,light quality,temperature, and moisturerelationships". C.A.Conover and R.T.Poole,Acclimatization of Indoor Foliage Plants,p.128) At certain levelsthese factorscoincide and the plant's photosyntheticactivity producesas much energy as the plant requires for respirationand development of growth. 37

The light compensationpoint is the state, where the production levelof carbonhydrates is in balance with the minimumrequirements for maintaininglife but not enoughto support any growth.One way to describe thelight level necessaryto maintainthis balanceis measuringthe amountof carbon dioxideused for metabolism.It has been found thatthe lightsaturated level of carbondioxide uptakevaries quite dramticallyfor sun speciescompared to shade species. Differencesof up to ten times higher ratesfor sun specieshave been common. (C.A.Conover and R.T.Poole,Acclimatization of Indoor Foliage Plants,p.126 and seefig.4.3 p.128)

Transpiration

Plantsmainly absorbenergy fromdirect solar radiation orreradiated far infraredradiation. A minor amount of energy is absorbed by conductionand convection. Energy not used in photosynthesis,and needed for maintaining a sufficient tissuetemperature, has to be dissipatedto preventdamage to the plant structure. Regularilyup to 70%to 90% is reradiated backto the environment,whilesome heat is lost due to effectsof conductionand convection. (Environment & Plant Response, M.Treshow, p.52) The remaining share of surplus energy is used toconvert water to water vapor within the cell structure. Up to 65% of absorbedheat energy can be convertedto latent energy in the evaporationprocess. (R.L.Gainesinterior Plantscaping p.24)The water vapor is tranferredto the atmosphere, mainlyvia the stomates and minutelythrough thecuticle, in a transpirationprocess, thus contributingto the plant'sheat control.It has been shown thatthe transpirationrate isaffecting the leaf temperatureas much as up to 9' C (16'F). (Environment& Plant Response, M.Treshow,p.54, fig 51) The close relationship between thephysical phenomena of evaporationand the physiologicalfunction of respiration makes it sometimes convenient to refer to the combined effectas an evapo-transpirationprocess. Theremight be other functions, related to transpiration, seeminglynot conveyedin the literature. Waterin the leaf cells has to be replacedonce it is 38

evaporatedand dissipated.The accompaniedpressure difference in the leaf causewater to be drawn from the roots bringing necessary nutrients, and carbohydrates needed for the metabolisminto the cells, makingtranspiration an essentialpart of the growthcycle as well.

The effect of the environment on transpiration

There is a dual relationshipbetween transpirationand the environment.The amountof energy absorbed depends on "leaf pigmentation and color, morphologicalcharacteristics of the plant,theexposure and orientationof the leavesto the sun", whichaffects the leavescapacity to reflectand transmit,and consequentlyto absorb the emittedenergy.(Environment & Plant Response,M.Treshow, p.52)

The rate of transpirationIs also dependenton atmosphericconditions like the water vapor pressurein the air, intensityof radiation,air movement andtemperature differences between leaf tissue andthe surroundingair. The intensityof radiation is the main variable affecting transpiration, but it is the combined effect of all contributingfactors during extremeconditions, thatcan have severe effectson plants. Bright light,high temperature,low relative humidity,and fast air movement,can spike the transpirationrate beyondthe capacity ofthe rootsand stem tosupply the cells with newwater. (R.L.GainesInterior Plantscaping p.25)

Affects of high transpiration rate on plant growth

Too high transpirationrate can causethe plant to wilt and eventallydie, if the amount of replacedwater doesnot meetthe plant'sneed. Theimmediate effect of this water stress is a diminishingturgidity of the leaf cells.The plant is counteractingthe pressuredeficiency, due to 39

uncontroledwater loss, by closing the stomates, however,at the sametime shutting out carbon dioxide needed for the second phase of photosynthesis.Subsequently, retarded photosynthesisis slowing down growthand causing eventual decay. There is a natural screening of inefficient leaves and usually old leavesadjusted to previous conditions are affectedfirst, while survivinggreenery tend toobtain a darkershade due to a relativeincrease in chlorophylldensity. ( PartlyR.L.Gaines Interior Plantscaping p.25)

PHOTOMORPHOGENESIS

There is some discrepancyregarding theclassification of photomorphogenicalresponses. Any change in the shape of the plants due to light should logically be defined as a photomorphogenicalresponse. However,the literaturedoes not follow that defintionclosely, but tends to separate between phototropism, photomorphogenesis and photoperiodism.(PhysiologicalPlant Ecology1, D.C.Morganand H.Smith,p.128) (Sylvania Bulletin0-352, p.3.) (S.Scrivens,Interior Planting in LargeBuildings, p.22) OPhotomorphogenesis is referring to the plants reaction to the ratio of red to far red wavelengths. Some studies indicate that high energy blue light also effect photomorphogenesis.(Physiological Plant Ecology 1, D.C.Morganand H.Smith, p.127) (SylvaniaBulletin 0-352, p.3.) OPhotoperiodismis plant responseto seasonalchanges in light quality, probablydue to the same propertiesgoverning photomorphogenesis. ePhototropismis the plantsreorientation towards a lightsource. (S.Scrivens, Interior Planting in

LargeBuildings, p.29 see fig 5.1 and 5.2) (Sylvania Bulletin0-352, p.2, fig 2)

Photoreceptors Three different typesof photoreceptorsare regarded to influence photomorphogenesis: 40

Chlorophyll,Phytochrome and the bluelight receptor. Chlorophyllhas already been discussed. The effects of the blue light receptoris still quite unknown,but it has an action spectrumin the blue bandbetween 350nm and 500nm with a peak at about450nm.

Phytochrome Phytochrome,a blue pigmentedprotein in the leafcell, is an enzymeacting asa photoreceptor controllingphotomorphogenesis. It exists in two reversableforms sensibleto red (Pr)and far red (Pfr) wavelengths,peaking at 6600nmand 735nmrespectively. The (Pr) form transmutes to the (Pfr) formunder red light radiation,while the processis slowlyreversed in the darkness. This last reaction,however, can be acceleratedby far red light radiation,and is dependenton temperature. (R.L.GainesInterior Plantscaping, see fig p.25) (SylvaniaBulletin 0-352, p.3)

It has been shown that the last exposureof far red or red light on plants is governingthe response,and that far red is the active component.Plants radiated withfar red light for 5 minutes after an 8 hour period in white fluorescent light "increased Internode extension by up to 400%"Ifthe plants,immediately after the far red lightperiod, wereexposed to redlight for 5 minutes the effect was fully neutralized. (PhysiologicalPlant Ecology 1, D.C.Morganand H.Smith,p.120)

PHOTOPERIODISM

Attuned responses Plants are reacting to different ratios between light anddark hours, originally an attuned responseto their naturalhabitat, in order to enhancepropagation and chancesfor survival.The responseto a seasonallight anddark cycleis calledphotoperiodism and is usuallyclaimed to 41

affect flowering, but other effects on plant growth areslowly beeing recognizedas vastly significant.Recent studies (1981) point at a rangeof differentresponses other than flowering. They all are important toplant development,but it is interstingto note that "the vegetative gowthof a plant is extremelysensitive to photoperiod",especially stem elongation,leaf growth and shape. (PhysiologicalPlant EcologyI, F,B.Salisbury,p.138) (R.vander Veen, Light and Plant Growth,p78.)

Daylength and night length It has beenshown possibleto neutralizethe effect oflong nightsby exposing plantsfor a short time in the middleof the dark period. The sameeffect canbe obtainedby illuminatingplants with weak light aftera period ofstrong light. (R.vander Veen, Light and Plant Growth,p.53 fig 35) The resultscan also be interpretedas a confirmation that the actuallength of the dark period exerts the strongest influenceon plant responseto daylength. However, without discardingthe generalappropriateness in this notion,it has recently(1981) been concluded from work on thephotoperiodism clock, that combinationsof conditionsduring the day and night exert a combined effecton photoperiodism. (Physiological Plant Ecology I, F,B.Salisbury, p.161)The naturalspectral conditionsmost likelyto affect phytochromeoccur at twilight, but other conditions,such as a vegetativecanopy transmitting much inthe far red range,can also influencephotoperiodism. Photoperiodic response types

Plantsare regularilygrouped into three photoperiodictypes traditionallydetermined by their needfor a certain period of daylengthto flower. 1. day neutral, 2. short day, increasingnight length 3. long day, decreasingnight length. Sometimesa fourth group is added depicting; daylengthintermediate, day-night limitations. (Plant Response to Light Quality and Quantity,~H.M.Catheyand L.E.Cambell, p240)

(PhysiologicalPlant Ecology I, F,B.Salisbury, seefig 5.1 and 5.2 p.i37) 42

Adjustment to changes Time has alloweddifferent species toadjust to exactchanges of day length.Studies in Nigeria on tropicalplants have shownthat slight differencesof only 15 minutescan preventor induce flowering.(M.Hunter andE. Hunter,The IndoorGarden, p.64) Interestingis that plants of the samegenotype seemto be able to adjustto a wide rangeof variationsin daylength.A relatively recentstudy in Scandinavia(1978) showed that plantsat threedifferent locations had adjusted

their photoperiodicalresponse, in this case shoot elongation,to the prevailingoptimal light- dark ratio. The criticalday forshoot elongationshifted from 14-16hours at the most southern latitudeto 16-18hours at a mid rangelocation and ended up reactingto 20-24 hoursabove the arctic circle. (PhysiologicalPlant Ecology1, F.B. Salisbury,p.149) Althoughthere are some exceptions,it is noteworthythat "cultivars produced by controlled breeding exhibit a wide rangeof photoperiodictypes withina species."(Physiological Plant Ecology1, F.B. Salisbury, p.149) Implications The implicationof thesefindings are moreextravagant than looselyinterpreted at first sight. First of all, it can be concluded that plants can adapt, within reasons, to almost any day-night cycle. Secondly,it is possible tobreede andacclimatize more durable plant speciesless sensitiveto extendedlight periods,reaching even 24 hours.

Other studies seem to support these indicationsclaiming that flowering is not responding solely to the day-night cycle, but that "24-hour radiant energy from artificial sources can override the classical photoperiod responses". (Plant Response to Light Quality and Quantity,~H.M.Catheyand L.E.Cambell, p240) Flowering can also be induced by "temperature,time,light or any combinationof these".(R.L.Gaines Interior Plantscaping, p.25) 43

Quantitative and qualitative responses Quantitativeresponses are "relatively independentof the spectral compositionof the light source", exceptfor certainplants -likea few speciesof lettuce- whichare developinga pale foliage when radiatedwith extremely narrow wavelengthbands. (Plant Responseto Light Qualityand Quantity,~H.M.Catheyand L.E.Cambell,p240) In this case low pressuresodium lampswere used. However,it was found possibleto restorethe color with supplementrywide spectrumincadescent lighting.(Plant Responseto Light Qualityand Quantity,~H.M.Cathey and L.E.Cambell,see fig(a)p. 218 andfig(k) p.223). The sameresult interestingly evolvedfrom increasing the ambienttemperature level to 28'C (82'F). Some improvement in foliar deficienciesalso occurred after spraying with minorelements, particularily iron ions(Fe+2). Observations One observation,from the recited investigation,is of particularinterest. It was found that no discolorationof foliage ocurred, if plants grown under low pressure sodiumlamps were "exposedto even the dimmestsun of winter months".This impliesthat plantsare responding favorably to a broad spectrum independent of proportionalIntensity levels.Another, more scrutinizing, interpretation could possibly indicate, that it is enough with only slight levels of photoperiodicallyactive wavelengths to inducephotoperiodism. In any case,the presenceof all wavelengthsin a spectrumradiating plantsis beneficialto a healthy plant growth. Reservations It has to be pointed out thatmost plants grown in green houses today can show signsof "overshoot",if too much light is impinged on the leaf surface for too many hours. Light intensities of 24W/m2 (.400Fc) for 24 hoursdaily usually "develop chlorotic foliage and surpressedleaf and shoot development".Decreasing the "daylength"to lessthan 20 hoursor diminishingthe light intensity restores the green color to the leaves and resumes stem elongation.(Plant Responseto Light Quality and Quantity,~H.M.Cathey and L.E.Cambell, p.241) 44

PHOTOTROPISM

Plantsare usuallyseen to grow towardsthe lightefficiently utilizing their leaf structureto absorb as much as possible of the available energy. It has beenshown that photosynthesiscould increasebetween 10% and 23%,due toefficient orientationof the leaves.(Physiological Plant EcologyI, D.C.Morganand H.Smith,p.128) If the positionof the lightsource changes the plant foliage respondswith a movementtowards the new direction.The stems getelongated and the leaves faceagain the brightestlight source."Thisproperty whereby the directionof growth

is determinednot only bythe lightbut alsoby the directionof the light"istermed phototropism. (R.van der Veen, Light and Plant Growth, p25.) This reorientationis governed by a plant growthsubstance called auxin, which seems to be sensibleto mainlyblue wavelengths around 450nm.It has been shownthat irradiationon one side of a coleoptiletip promotes retardationof growth onthat specificside, thuscausing a bendingtowards the light source.(R.van der Veen, Light and PlantGrowth, p.27 and see fig 16) . That particularresponse is termed positive phototropism. Conversely, the bending away from a light source is called negative phototropism, seen in roots of certain plants. Leaves are mostly exhibiting transverse phototropism,with the surfaceperpendicular to the light source, usually in a horizontal position.Some plants, like certaincacti in hot-aridclimates, orienttheir leavesvertically so only the low morningand evening sun canshine on theirsurfaces. (R.van der Veen,Light and Plant Growth,p.32) 45

CHAPTER 2

DISCUSSION

Peopleand plants are respondingto the impactof the environmentin a varietyof ways.It is ViT, F : RESPONSES oftendifficult and fruitless to tryto depicta singlefactor responsible for a certainresponse. The combinedeffect of twoor multipleparameters can offset the impactof a majorfactor. Different

genotypes,species and individual plants can portray diverse or similarresponses to the same impactdepending on age,season, and time of day.Human responses might seem easier to track down.Our conceptionof the environmentand our needs are knownfrom our own experienceof just living,from employingour sensesand fromour abilityto communicate. However,despite of allthe millionyears that man has existed there are still unexplored scientific knowledgebetween impact and response.Some links are just surfacingwhile others are on the brinkof beingmanifested. The reseach field is vastand thisthesis makes no illusionsabout coveringit all, but this chapterwill concentrateon basic importantresponses and some significantindications with strong connections to the builtenvironment and atrium design.

2A: RESPONSESTO SOLAR RADIATION

Withoutthe sun lifewould not existas we knowit. It is the corewhich life is revolvingaround. Naturally,living organismsasa generalrule have to respondfavorably to the emittedenergy, as it is a necessecityfor survival.However, there are responsesdeveloped for the protection againstharsh impact, and both peopleand plantshave adopted specific responses to the differentwavelengths of the solar spectrumreaching the earth.They have also aquired sensorsto tracechanaes in interqty,and adjusted their rythm to the phasesof the sun and settheir biologicalclock according to the time it takesfor the earthto 46

spinaround its own axis.

Thereare three basic factors, as well as anycombination of them,affecting the impactand the outcomeof a certainresponse. Ointensity eDuration OQuality Quality,in this concept,is usuallydefined as the ratiobetween certain wavelengths.

Human biological responses to solar radiation

UV- ultraviolet radiation - RELATIVE BLUE Negative effects 'LIGHT HAZARD Ultravioletradiation is oftenreported as havingadverse effects on man.Several studies have

10000 I-NW XENON beenconducted to scrutinizepossible damages, mostly concerning the effectsof radiationon HEI PRESSURE6 RELATIVE 0 00 theskin, but also affects onthe retinaand thelens. There are normally no injuriesto the retinas UV SAFETY ' - - KW OUARTZHALOGEN andcorneas while out the sun. However, has beenfound that maligna, form of skin in it a 350-W TUNGSIEN 100- L7AMP MERCUW, PROJECTORLAMP 400-W MERCURY E HALIOE cancer,can develop from exessive exposure to the sunand other radiating sources containing CLG JACKET 15-W SOOIUM HGM PRESSURE ultravioletradiation. Other damages reported besides sunburn are, mutations, and chemically FLUOREENT,

inducedphototoxic and photoallergic reactions, irregular thinning of the epidermis,wrinkling of -0 -10 10 10 1Q00 10000 RELATIVE the skin,and graying of hair.(The Medical and Biological Effects of Light,M.A.Pathakp.329) wRSUrUV HAZARD . FLRUORESCENT Somestudies have tried to classifythe effectof radiationfrom artificial light sources, and have pESSURESODIUM.100- INCLING BLAC-LIHT TU hJAXGUARTZ MERC: GERMICIOAL concludedthat the riskfor damage relatedto the 6O-W FROSTED is time theeye and skin areexposed to the LHNAEESCENT E luminare.The values given refers to relativehazards less than 1 meterfrom the sourceafter 8 RELATIVE BLUE LIGHT SAFETY hoursof exposure.(TheMedical and Biological Effects of Light,D.H. Slineyp.117 see fig. 1) 47

Positive effects There is newexitement regarding old knowledge.Solar radiationhas been knownto influence the productionof vitamin D, and calciummetabolism for manyyears. The causeand cure for rickets was linked to thebeneficial sunlight in the 1920's."Itis now establishedthat, during exposureto sunlight, ultravioletphotons with energiesbetween 290 and 315 nm" penetrate

into the skinwhere most of the previtaminD 3 formation occurs,culminating between 295nm

and 300nm. (The Medical and BiologicalEffects of Light,M.FHolick p.4, see fig 4 p.7) The

equilibrationto vitaminD 3 takesthree days and is independentof ambientair temperature.It is

interestingto notethat vitaminD has a relativelyshort actionperiod. It has been shownthat 140- concentrationsincreases to a maximum value 24 hours after exposureto radiation and 120- UVR (MFPI KX)- * 4 of o 3 gradually returns to baseline values after7 days. (The Medical and Biological Effects 80- 1.5 60- Light,M.FHolick p.10, see fig 6 p.10)Indicating the importanceof regularintake of vitaminD3, z 40- either ingested in the diet or through exposure to ultraviolet radiation. The melanin 20-

pigmentationin the skin is a decisivefactor forvitamin D 3 formation. Melaninis an effective -10 234 7 14 21 TIME (DAYS) neutralfilter absorbingand reactingto all wavelengthsbetween 290nm and 700nm.Black skin needs upto six timesmore ultraviolet radiation to producethe same amountof vitaminD. This is proposedto be one of the reasons whyrickets among black childrenis reemergingin cities in the northeasternUnited States. (The Medicaland BiologicalEffects of Light,M.FHolick p.12) Also certainclasses of Asian immigrantsto industrialnorthern climates showan increased incidenceof the disease.(The Effectsof Lighton Health, P.M. Coxe, P.B.Reiser,W.M.Lam, p.10) It has been shown that outdoor activities increase levels of vitamin D, presumably credited to utraviolet radiation in natural daylight. The generally higher concentrationof ultraviolet radiationin sky lightat locationscloser to the equatoror at higheraltitudes also seem 48

to be contributing factors.(The Medical and BiologicalEffects of Light,R. M Neerp.17 see fig.2 and fig.3p.17)

Io - Duringthe last fifteen yearsnew findings have recognizeda differencebetween endogenous PALMBEACH - skin productionof vitaminD 3 and exogenousdietary vitaminD 2. Some claim vitaminD 2 to be 0

less effective than vitamin D3 , while others contendthey are biologicallyequivivalent. (The DETROIT DENVER W 40- p.73) (The Effectsof Lighton Health,P.M. Effectsof Light on the HumanBody, R.Wurtman, BOSTON SEATTLE Coxe,P.B.Reiser, W.M.Lam, p.10) Indications in Europethat D2 is toxic in largedoses has also 2i0- r . 0.98 4 curtailedits use. Britishstudies confirm thatfood intakeof vitamin D2 is insignificantin Britain.

Sunlight-stimulated skin productionwas concludedto be much moreimportant asa vitamin D 2800 600 4400 200 DAILY UV COUNT sourcethan intestinalproduction. Thiscan be comparedwith for instancethe U.S, where ANNUALMEAN

heavy D2 fortificationof food is still prevailing.Yet, a study of white adults livingin St. Louis concludedthat sunlight,due to its capacityto producevitamin D3 , was vastly moreimportant ALL CITIES than fortified food, as 70%to 90%of vitamin D in the blood of the tested was linkedto the D3 form.

E Whatis interestingto knowis the implications ofthese differences. The consequencesof an air 0 I polluted environment,curtailing the solar radiation, was widely encounteredduring the CN 0i industrialrevolution. Todayrickets is uncommon,but still exists. More significant is data indicating thata relativelyhigh numbersof elderlyare vitamin D-deficientin the northernU.S. Approximately10% of the elderly in Boston havea vitamin D deficiency,and "amongelderly FIGURE 2. Averageblood levelsor 25-OH vitaminD middle-agedmales working in roston.Detroit, Seattle individualsadmitted to Massachusetts Generalhospital with fracture of the hip, 21% were city, half of the men worked indoorsand half outdoors. vitamin D-deficient."(The Medical and BiologicalEffects of Light,R. M Neer p.19)Many elderly womensuffer from osteoporosis,due to inefficientabsorption of calcium, directly linkedwith 49

vitamin D deficiency.These data are noteworthy,but moredata aroundthe world has to be gatherd, to gain a completepicture of the current state. What is known is that vitamin D3 deficiencystill exists, despite readily availableoutdoor sunlight and vitamin D fortifiedfood, especiallyin certainvulnarable groups of the populationand that the problemmight increase in the future.The implicationsof these findingsindicate that, in some cases, it mightbe desirable to increase controlled utraviolet radiation, either through artificial means or exposure to daylight. It could be possible to alleviate the symptoms encountered in an enclosed environment,by incorporatingcertain types of transparentmaterial transmitting UV- radiation.

Otherbiological affects of ultravioletradiation include help for curing rareforms of leukemiaand immunesystem disorders. (The StateJournal-Register Sunday, December 9, 1984,p.35) Coal minorsin U.S.S.R.are exposedto UV-radiationevery day to protectagainst the development of black-lungdisease. Patients with psoriasis can be successfullytreated with exosure to 365nmUV-radiation after intakeof an photosensitizingagent called psoralens,with the active ingredientcuriously found in an Egyptianplant "used in ancienttimes to treat skin ailments". Also carrots,parsley and limecontain small amountsof it. (The Effectsof Lighton the Human Body,R.Wurtman, p.72)

VR-Visible radiation Infant jaundice

Besidesseeing, the obvious effect of visual radiation,there are more subtle indirecteffects, whichthe humanbody is respondingto.

Someyears ago it was noticedby coincidence,that infant jaundice-the yellowingof the skin due to concentrationof bilirubin in the blood stream- could be sufficientlyremedied, if the newborninfants were placednear an openwindow. The beneficialeffect was originallytraced 50

to the impactof sunlightand possibly ultraviolet radiation. However,it has beenshown that St EP blue lightis the mosteffective radiation in decomposingbilirubin, although it hasbeen proven M N DN ATECHLAMN rC that full-spectrumwhite lighthave equal effects regardless of therelative intensity of blue wavelengths.(The Effects of Lighton the HumanBody, R.Wurtman, p.74) Light-dark cycles

Accordingto newdiscoveries, there are strongindications that evolutionhas equippedman with biologicalclocks in rythmwith differencesin day lightcycles. This indirecteffect of light dependson the time the bodyis exposedto daylight,which varies with seasonal changes of I I _ t I hMaDNpIGsTy 2 4 W het) day length as well as the day and nightratio. Severalresponses have been foundto be 74

P01ASSIMANU M TAA S PH'E SPit S associatedwith these lightcycles. "Physical activity, sleep, food consumption, water intake, f UtIttK W OS Dilhtm re cAractrisi of1 many body temperatureand the ratesat which manyglands secrete,and hormones all vary with

1300Y TDL.01IIA LItRE periodsthat approximate24 hours."(The Effectsof Lighton the HumanBody, R.Wurtman, p.75see fig p.74)The cortisollevel also seemto varywith the same24 hourrythm in healthy humanbeings, while it has beenfound that blindness upsets the synchronizationwith daylight. S0011 OkiLAND CATECOIALLNE

Thefactors governing the specificrythms are not completelyknown and psychosocial factors POA 501)AN MEtBLE could be more importantthan light cycles. (The Effectsof Light on the Human Body, vt t NEF

R.Wurtman,p.76) UNNNt' 4 6 6 Sexual maturity Dialyrhythms are characteristic of many Observationsof earliergonadal maturation among blind girls comparedto a normalscore of humanpsychological functions. Whether these24-hour rhythms are producedby the girls,also point towards a connectionbetween lightand sexual maturity. (The Effects of Light dailylight-dark cycle or are simplyentrained by on the Human Body,R.Wurtman, p.77) (R.KOller, Ljusets Biologi, paper presented at the solar that cycle remainsto be unequivocally established.Each curve representsthe typical conferenceheld in Trondheim,May 1984 see fig.3 p.3) dailypeak for a physiologicalstate or for the levelsof particularsubstances that circulatein Skin diseases the bloodor are excretedin the urine. Visual lighttogether with photosensitazationagents havebeen usedto traet several skin diseasesby causing damage to invading organisms,such as herpesvirus and malicnant cells. Productivity 51

Several studies have been conductedin order to investigatethe impactof ligot on worker productivity.Mostly they havetended to look at illuminationlevels. Dr.H.R.Blackwell'sstudies of productivity,performed in a laboratory setting,has renderedmuch interestbut alsociticism. His work forms the basisfor lighting codes in the U.S. and Canada.(The Effects of Lighton Health, P.M. Coxe, P.B.Reiser,W.M.Lam, p.26) In a later statementDr. Blackwell claimsthat light from full spectrum luminares could increaseworker productivity close to 12%. Unfortunatelythe study conveyinghis remarksneglect to give any informationregarding the comparable source. (The State Journal-RegisterSunday, December9, 1984, p.36) Other studies in Sweden regardingthe impactof artificial light with different spectrum, show that fluorescent luminareswith a daylightspectrum gave the workers lessvisual problems and eye fatigue than personelworking in traditionalcold white light. Thesame study shows that the cortisol levelwas linked tothe accessof daylight,with decreased levelsfor personel workingfar awayfrom the windows,especially during the summer. Effects of light on the melatonin level and depression. The most intriguingdiscovery, and what can proveto be a newunderstanding ofthe indirect effects of light, is the inhibitioneffect light has on the melatonin level. The exact role of melatoninis still to be established.Its effect on the brainhas so far been linked to sleepiness

and inhibition of ovulation. Other functions includeraising the levels of serotonin- a - neurotransmitter, and modifying the secretion of other hormones and the electroencephalogram.It has beenfound that the melatoninlevel in the urin is cyclicallymuch higherat night between11:00P.M. to 07:00A.M. than during therest of theday. (The Effects of Lighton the HumanBody, R.Wurtman, p.77 see and correct figp.77) The melatoninconcentration in humansis notonly respondingto diurnallight-dark cycles, but also show annual variations.The concentrationis lower in the spring and in the fall, and the 11PM- ?AM- 3PM- 11PM- 7AM- 7A.M. 3 P.M. 11P.M. 7AM 3 P.M. nocturnalpeak is about two hours broader in the winter than in the summer with a delay TIME INTERVAL RHYTHM IN MELATONINSECRETION In humanbeings hashe occurring in the morning concentrationonly, accordingto preliminarydata from Stockholm. 52

(The Medical and BiologicalEffects of Light, D.F.Kripke,p.277) The seasonalchanges in concentrationcan possibly be traced to affect human physiologicand behavioralactions in diverseand drasticways. The annualrythms seem to be stronglyrelated to the avilabilityof sunshine. Hospitalizationand suicide rates tend to peak in the spring and in the fall. Conception might be linked to a photoperiodiccontrol as studies in Europe indicate that patterns of births seem to correlatewith differencesin latitude. There are even claims that menstruationamong Eskimowomen maycease during the long arcticnight. (F.Birren,Color & HumanResponse, p.21) Dysfunctionof the circadianrythm can causesevere depressions due to seasonalchanges and it has beenshown that the melatoninlevel is abnormallylow among depressedpatients. "Patients with seasonalaffective disorder-SAD are especiallysensitive to the shortdays of winter,which induce them in a clusterof symptomsincluding fatigue,sadness, hypersomnia,overeating,carbohydratecraving , andweight gain." (The Medicaland Biological Effects of Light, N.E.Rosenthalet al, p.267) Researchalso shows that depressioncan be treatedwith light,if the intensityof the radiatedfull-spectum light is aboveat least 250Fc.The duration of the treatment has to be longer than 3 hours, preferably 5 to 6 hous, and adjusted to the time of the day. Somestudies state, that eveningtreatment is as effectiveas the combined effect of shorter morning and evening exposures, while others suggests that evening

exposureis not as effective.(The Medicaland BiologicalEffects of Light, N.E.Rosenthalet al, p.267)(The Medicaland BiologicalEffects of Light, D.F.Kripke,p.277) Fact remains,that the treatmenthas proven to be successful.However, it is interestingto note that, the melatonin levelin patientswith seasonalaffective disorder-SAD is lowerat nightthan normallyaccounted for. This indicatesthat light treatmentof depressionis not actuallysuppresing the melatonin secretionas would have been logicallyexpected, but "causesrebound increases in nocturnal melatonin".(The Medicaland BiologicalEffects of Light,D.F.Kripke, p.278) This could possibly be explainedby a form of supersensitivityto light in depressedpatients and suggeststhat their dysfunctionis a combinationof this hypersensitivityto light and inadequatexposure to light 53

during the day. Jet lag and shift work Ther are other more subtle effects of light exposure affecting healthypeople. The human circadianrythm tend to be longer than24 hours and can be utilized togetherwith bright light exposureto manipulatethe melatoninlevel for treatmentof jet lag and maybealso for adjusting shift workersto changing workinghours.

Physiological effects of color

The scienceof color is fascinatingand has manydifferent aspects. The psychologicalimpact of color might well be more importantthan the physiologicalaspect, but new findings regarding the impact of light on human well-being can prove to increase the understanding of physiologicalfactors and eventuallyfind the linksaffecting psychological perception.

Everysensation in the brain of a color is originatingwith a light sourceseldom directed straight on to the eye, butoften reflectedoff an illuminatedobject or transmittedthrough a moreor less transparentmaterial. The reflectedor transmittedlight is modifiedby the absorbingproperties of the object. The eye is thus receivingredirected light with color qualities dependingon the light source as well as the illuminatedobject, beforethe highenergy photons strikethe retina and is interpreted as colors. Many studies and philosophiesare suggestingcertain human behaviorstied to the perceptionof colors. However,this thesiswill not go intoany details, but just brieflycite one source.

"In human beingsred tends to raise blood pressure,pulse rate, respiration,and skin response 54

(perspiration)and to exitebrainwaves. There is noticeablemuscular reaction (tension) and greaterfrequency of eye blinks. Blue tends to have reverse effects,to lower blood pressure

and pulse rate. Skin responsesis less, and brain waves tendto decline. The green region of the spectrumis moreor less neutral."(F.Birren, Color & HumanResponse, p.24) However, the same source cautions"that color effectsare allwaystemporary" and bodily responses, aftera longer exposureto the same color, might decline below normal. (F.Birren, Color & Human Response,p.23)

It is also necessaryto point at culturaldifferences and other factorsdiscussed earlier, which all can affectthe perception.

Infrared radiation

Positive effects Infrared radiationcan be used therapeuticallyfor sore muscles and other muscleskeleton injuries. (The State Journal-Register Sunday, December9, 1984, p.3) It also has a tremendousimportance as a direct heat sourcenecessary for maintaningheat balancein the body, compensatingambient air temperatureand metabolism.

Negative effects High intensity exposureby infrared radiation can cause overheating.The body reacts by perspiring,increasing blood circulationand enlargingskin area.Sunstroke, brain damageand possibly deathare ultimate reactions. PLANT RESPONSES TO SOLAR RADIATION

UV-Ultraviolet radiation 55

Positive effects There are signs indicating that particularily long wavelengthsof ultraviolet radiation can stimulatephotosynyhesis. However, the generalconclusion is that UV-radiationis detremental. Eventhough some sourcesmaintain that ultravioletradiation is a necessarypart of a natural

environmentand basicallypositive.( J.Ott) This notionmight be encouragedby a studyon cacti andsucculents, which claims that it is possibleto induceflowering with supplementalultraviolet radiation when cultivating these plants indoors. A response not previously known to be successfulin an indoor environment.(Duro-Test Corporation, Form 815-7106R,1971) Dr. John Ott has claimedthat ultravioletradiation caused apples he used for an experimentto turn

red. However,other sources state that red colorationof apples is caused by strongblue light. (R.vander Veen,Light andPlant Growth, p113.) (C.Mpelkas, conversation)

Negative effects Allultraviolet radiation, that is wavelengthsbelow 400nm, are claimed to be harmful,and the shorter the wavelengthsthe greater the risk for damage. (C.A.Conoverand R.T.Poole, Acclimatizationof IndoorFoliage Plants, p.114) Small doses of UV-C can be direct lethal and readily inhibit photosynthesis.Nonlethal, but damaging effects of UV-C radiation include genetic alterations, mutations and reduced growth. UV-B can cause a reduction in leaf enlargmentand diminishthe rate of photosynthesis.Chlorophyll reduction is apparentafter extremelylarge doses, or after exposureto UV-Bin an environmentwith relativelylow visible radiation.Damage on leaves and reductionof photosynyhesisis caused by the cumulative effect of ultravioletradiation, even if the doses are relativelysmall. One importantfeature, alreadytouched but need to be stressed,is that the influenceof UV-Bon photosynthesishas shownto be totally dependenton the ratioof visibleradiation to ultravioletradiation rather than 56

the actual intensity. (PhysiologicalPlant Response1, M.M.Caldwell,p.186) (see own figure p.186)

It has been shown that the effectsof exposureto UV-C can be somewhatalleniated if if the organisms are radiated with low intensity or visible radiation beforeh.nd. The plant is UJ'V respondingto the impactof ultravioletradiation either by avoidenceor adaption.There is some

evidencethat plants adjusttheir leaf inclinationto protect from direct UV impactby declining their leaves slightly. This responseis increasinglypronounced with lower latitudes.However, even totally vertical leaves receivearound 70% of the possibletotal irradiationas most UV-B (j( radiation,40% to 75%, is part of the scatteredsky component.Absorption of UV radiationand different types of synthesisreactions in the leaves may also participatein the acclimatization process. Changes in cuticular thickness and mesophyll structure also take place. Plants previously not subjected to ultraviolet radiation are very sensitive to the high energy wavelengths,which are rapidlydamaging the leaves and eventuallywill fall off. On the other hand, leavesgrown in an environmentwith ultravioletradiation are moreprone to withstandits impact. The leaves becomesmaller, hardy, sometimeshairy, and develop a thicker cuticle. (C.A.Conoverand R.T.Poole,Acclimatization of IndoorFoliage Plants, p.114)

VR-Visible radiation

The overwhelmingpart of the plants'active spectrumlies in the visible radiationrange. Both quantitativeand qualitatativeresponses are basicallydepending on light. Photosynthesisand chlorophyll synthesis are generally quantitativeresponses increasing with light intensity. Photosynthesisis active over the whole spectrumwith peaks in the red and blue. Chlorophyll synthesis is predominantelya two-peak-curvein the red and blue ends of the spectrum. Qualitatativeresponses react to slight changesin wavelength ratios often independentof intensitylevels. The phototropicresponse is activatedby blue wavelengths.Photoperiodism 57

and photomorphogenicresponses are reactingto red, and far red, and possiblyhigh energy j fqPh blue wavelengths.(S.Scrivens, Interior Planting in LargeBuildings, p.29 see fig.5.1and 5.2)

Energy Information En gantilst we (qualtative Plant response to light quality rePpo h mge) response) PhOtOS VfltheOS I PhoromrphogefOsts arld Germination

Light does not affect seed germinationfor most cultivated plants, except for small-seeded species which require wavelengthsin the red spectrum,between 560nm to 690nm,with a peak at 660nmto effectivelygerminate. Germination for a few speciesare inhibitedby light and some still inhibitedby long exposuresto far-red. Seedlings

All seedlingsmost effectivelydevelop a compactgrowth as a responseto red wavelengthsat 660nm.(Plant Responseto Light Qualityand Quantity,~H.M.Catheyand L.E.Cambell,p.238)

Plant response to Illumination levels

Too little as well as too much light can be harmfulto plants.The exact detramentallevels are influncedby a varietyof parameters,such as temperature,fertilization, and most importanttime and intensity. Most plants can sustain shorter periods of extreme light conditions. Longer periods of high or low light levels will drastically diminish and even inhibit efficient photosynthesis.The rate of photosynthesisis directly linked to the intensityand will cease, if the light intensity is not enoughto induce the convertionof protochlorophyllto chlorophyll, and eventually cause -chlorosis- yellowing of the leaves. Too much light will inhibit photosynthesisand induce photo-oxidation,or bleachingof the chlorophyll, reversingthe synthesis back to protochlorophyll.High light levels also increase transpiration, risking dehydration, scalding and scorching of the leaves and eventually necrosis, if the plant's 58

capacityto replacethe dissipatedwater is inadequate.

The following materialis developedfrom "Plant Responseto Light Quality and Quantity" by H.M.Catheyand L.E.Cambell,p.244 to 248. Also A.S.H.R.A.E,1981, chapter 9.12-13, contain

the same basic data. It shouldonly be interpretedas a generaldescription of plant responseto certain light levels.It is obviousthat different typesof plants have different preferences.See chapter1and chapter5.

Display 0.3W/m2 (5 Fc)

The plantscan be displayedfor a shortertime, but no growthexpected.

Photoperlod 0.9W/m2 (15 Fc)

This low light intensity, in combination with daylight, is adequate for activating the photoreversibleblue phytochrome,thus regulating photoperiodicresponses, such as growth and flowering. Plants will not survive for a longer period. Deciduous trees lighted with 2 incadescentlight at 0.9W/m maintainvegetative growth over many months,while HID lamps cause discolorationand dormancy.Photoperiodic responses are dependenton wavelengths around660nm and 730nm,making incadescentlight with the main bulk in the red spectruma suitable light source. Photomorphogenicresponses require blue wavelengths,indicating a combinationof lightsources, or the use of broadspectrum luminares, as the best alternative.

Survival 3W/m2 (50 Fc)

Plantscan surviveand the light intensityis enoughto maintainthe greencolor. However,stems get elongatedand leaves are reduced in size and thickness. Photoperiod responsesdo not functionwell and no newfoliage is developed.Eventually the plantshave to be replaced. 59

Maintenance 9W/m2 (150 Fc) Plantscan grow for manymonths making it a convenientillumination base to startout from. It is possibleto growa wide rangeof plantsin this lightlevel. Most plants develop deep green foliage,large leaves, and exchange old leaves with new ones. It is possibleto regulategrowth byintruducing a 12 hourlight-dark cycle, coupled with lessfrequent watering and fertilizing, slowingdown the productionof newleaves. Minimumrequired light intensityfor slow growthaccording to A.S.H.R.A.E.(A.S.H.R.A.E, 1981,chapter 9.12-13)

Propagation- slow growth 18W/m2 (300 Fc) Plantscan be propagatedrapidly in this lightlevel if the plantsare illuminatedfor at least6-8 hoursdaily. Most plants can be brought to maturity,but the growth rate is stillquite slow.

Greenhouse- growth 24W/m2 (400 Fc) Plants can be grown year round in a glazed environment,if the natural daylightis supplementedwith this light intensity for 8-16hours daily. By tradition this is the irradiancethat bestcouples ambient sunlight with supplemental lighting boosting growth rates and creating a growingenvironment for rapid developmentand early flowering.Plants grown without supplementallight will growmuch slower. Supplemental lighting for 8 hoursa dayis muchless effectivethan 4 hoursapplied at nightbetween 20.00 and 24.00.

Growth chamber 50W/m2 (830 Fc) This is the standardlight level in growthchambers and can be usedto .simulateoutdoor conditions.It is possibleto growmost kind of plantsin lightintensities between 50-80W/m2, providing10-20% is incadescentlight with red andfar red wavelengthsand other affecting factorsspan a range between8-24 hoursdaylength, 20-80% relative humidity, 9-35'C 60

temperature,freeair flow, and a carbondioxide content of 300-500PPM.

Adequate light levels

Other studies indicateadequate plant growth at light levels between13pEm- 2 s- 1(~90Fc)to 2 1 26pEm- s- (~180Fc)for 12 to 18 hoursdaily. The quality of plant growthincreased with light

intensitiesand was best at 26pEm-2s-1(-180Fc). (C.A.Conoverand R.T.Poole,Acclimatization of IndoorFoliage Plants, p.146)

Continous lighting Continouslighting of some plants induces paling of foliage and loss of of pigmentsof the top-mostleaves. The trees can survivefor severalweeks and eventuallyretreive their original postureby reducingthe light periodby at least4 hoursor by increasingthe temperature2-4'C. Mineralelements might also be used (Fe2 +). (Plant Responseto Light Qualityand Quantity, H.M.Catheyand L.E.Cambell,p.247). Other studies claim that constant light reduce plant quality.(C.A.Conover and R.T.Poole,Acclimatization of IndoorFoliage Plants, p.145)

The effect of spectral distribution on plant growth It has been observedthat plants grow best when the spectral distributionis wide. Studies reporting on plant growth in interior environmentsclaim that Cool White fluorescentplus incadescentluminares provide superior conditionsfor growthcompared to only Cool White fluorescent.(C.A.Conover and R.T.Poole,Acclimatization of Indoor Foliage Plants, p.145) Othersassert that wide spectrumfluorescent lamps because of their propertyto closelyimitate the spectraldistribution necessary for photosynthesisis an efficientchoice. (SylvaniaBulletin 0-285,p.3, fig.2) 61

and coversthe whole rangeof the visiblewavelengths.

IR-Infrared radiation

Positive effects

About50% of the solar radiationreaching the earthis near infraredradiation. The energyratio actually impingingon plants is modified by the environment,and is also dependenton the absorbingqualities of the transparentmaterial it is transmittedthrough. The ratio of IR emitted from artificiallight is dependenton the lightsource. Far infraredradiation- thermal radiation- from

the surroundis not part ofthe solarspectrum. Some of this energyis absorbedby the plantsas heat in orderto obtain adequatetempertures necessary for metabolismand survival.

Negative effects There are claims that exposureto near infraredradiation.cause elongation. But, again, other experiments indicate no actual effect. (R.van der Veen, Light and Plant Growth, p.97) High intensityinfrared radiation can causesevere damage to the leaf structure,but the magnitudeof the injuriesare coupledto otherenvironmental factors and the inducedtemperature within the leaves.

Psychological responses to solar radiation.

UV-radiation

The different expected and experienced physical responses to UV-radiationis probably affectingthe psychologicalresponse. For instance,suntan is creating a positive response, whilesunburn cause a negativeresponse. 62

VR-Visible radiation-light The psychologicalperception of direct and reflectedvisible radiation,in this case preferably called light, is a balancedinterpretation of the total environment.Human individualfactors , such as cultural and genetic backgrunds,sex,age, as well as adjustedbehavior, play all a significant role in this process,together with the functional appropriatenessof the created space. Differentshades of darknessand brightness,light and shadow,glareand contrast,as well as colors in all nuances,have all a profound,but value judged, effect on our immediate perceptionof the physicalenvironment. See alsochapter1.

IR-Infrared radiation

The benefitsfrom infraredradiation as a heatsource to balancecold ambient air temperaturesis appreciated. A negative psychological response can be expected if the ambient air temperatureand infraredradiation coincide to createan uncomfortablehot environment.

The effect of light Intensity on leaf shape

Leavesof plantsgrown underhigh light conditionsare usuallyless green,thicker, shorter and smaller,than those grown in a low lightenvironment. It has alsobeen noticed,that sun grown plants possestwice as many leavesas shadegrown plants.However, the largerarea of each individualshade grown leaf offsetsthe quantitativeadvantage, making the shadegrown plants total leaf areaequal in size. (C.A.Conoverand R.T.Poole,Acclimatization of IndoorFoliage Plants,p.145) For leaf structure,due to differentlight levels,see chapter1)

The effect of color on leaf shape The color of the radiatinglight appearsto havethe most striking effect on leaf development. 63

Leavesgrown in red lightseem to be larger,elongate and "aquirea knobblysurface in contrast to those grown in green or blue light", while blue, violet and near ultravioletseem to be responsiblefor the more sturdier growthseen in plants developedin high light conditions. (R.vander Veen, Light and Plant Growth,p108-109) It has to be pointedout that the growth responseto the differentcolors of the spectrummay vary for individualspecies. Green light seemto be neutral.However, there are two importantobservations. Plants can convertsome of the green light energy, by fluorescence, to more efficient wavelengths utilized in photosynthesis,and at the same time affect photomorphogenesis.

Acclimatization to changing light intensities

Sun grown plants have adjustedtheir leaf structureto suit highlight conditions.Position and orientationof the leaves, thickness of the cuticle, and dispositionof the energy absorbing grana,are all in a protectivemode. However, the abundanceof energyhas also developedan inefficientleaf, with a relativelysmall amount of chlorophylland low utilization of absorbed energy. Changed conditions with lower light intensities will drastically impair the necessary productionof carbohydrates,and the plant has to adjustin orderto survive.It can basicallyreact in two ways: 1. increasethe chlorophyllcontent and changethe dispositionof the palisade layers and the grana to a more exposedmode. 2. exchangethe old leavesfor new more efficient leaves. Usuallythe plant respond in accordancewith both propositions.The first processcan take between 4 to 8 weeks, while the second process can be extendedover monthsor years. The reversed acclimatizationprocess requires even more drastic plant reactions.The cuticleis too thin to protectthe leaf from high energyimpact, and the plantcan not reactby changingleaf anatomy.Only retractionof the palisadelayers and redispositionof the granaremain, often resulting in damageto the leaves.

Plantsoriginally grown under shadeconditions in greenhouseshave provento have a higher 64

qualitythan acclimatized sun grownplants. (G.H.Manaker, Interior Plantscapes, p.200)

2B: RESPONSES TO AIR AND SOIL TEMPERATURE

The most immediateconsequencies of solar radiation,light intensity and temperaturelevels, are probablythe most importantphysical factors affecting life. It has beenshown that the light intensity can vary quite drastically, without impairing necessary physiological functions. However,the marginsfor the impactof temperatureare relativelynarrow. It has to be pointed out, that the sensationof temperatureis related to other parameters,such as the relative humidity,air movementas well as physiologicaland physicalreactions aquired to protectfrom a harsh impact. It is also a physical and psychologicalexperience of the combined effect of ambientair temperatureand direct radiatedenergy. As explainedin chapter 1, radiatedheat energycan be dividedin nearinfrared radiation and far, or thermal,radiation. This sectiondeals with responsesto temperaturelevels related to thermalradiation, conduction and convection.

Human biological responses to temperature levels

Every sensationof a comfortabletemperature has to be explained in its relation to the surrounding environment, and individual physiological conditions and psychological preferences.However, there are general responsesrelated to the human body. The deep body temperatureis relatively constant between 36 to 38'C (97 to 1OOF'), while the skin temperaturecan changewith the impact of the environment.The skin indoor temperatureis usuallyaround 32'C (90'F). For the body to functionwell, it has to obtain enough energyto maintain a constant temperature. This is performed by metabolism,physical work, and absorptionof externalheat energy.In the caseof a heat intenseenvironment, the body has to react by dissipating superfluous energy to prevent overheating. "The fundamental 65

thermodynamicprocess in heat exchange with the environmentcan be described by the generalheat balanceequation." (A.S.H.R.A.E, 1981, chapter 8.1)

S = M - (+W)± E ± R ± C

S > 0 => rise in bodytemperature

S = 0 => thermalequilibrium S < 0 => decliningbody temperature

Where the capacity to store(S) energy in the bodyis dependent on the balance between metabolism(M),mechnical work(W), evaporative(E) heat loss, heat exchangeby radiation(R), convection(C)and conduction.When the body is not in thermalequilibrium it has to react to maintainbalance. The rate of metabolismis ratherconstant, whileradiation and convectionis drasticallyrelated to the operetivetemperature. The body almost always lose some energy through evaporative cooling, but the loss is sharply increasing at higher temperatures. (A.S.H.R.A.E, 1981, chapter 8.2, fig 1) The body responds to low temperatures by restricting the bloodflow to the skin, and increases internal heat production by muscular tension, shivering,and spontaniousactivity. At hightemperatures the blood flow to the skin increases, effectuatinga more efficient heat loss through convectionand conduction.The body also 60 starts tosweat to enhancethe effectof evaporativecooling (A.S.H.R.A.E,1981, chapter 8.2) (A.S.H.R.A.E,1981, chapter 8.12, fig.11) It is noteworthy,that the human body is reacting * more dramaticallyto small changes in temperature levelsabove normal skii and body * - temperatures,than whenexperiencing temperature drops. 20 -

10 -

There are many individualfactors affecting the responseto the impact of absorbed heat. 0 - 0 2 0.4 0.6 08 1.0 2.0 4.0 6.0 8.0 100 Clothing,skin color,sex, age andadjustment to theprevailing conditionsall havea moreor less WAVELENGTH, y AheraieValues of SpectralReflectance for strong influenceon the perceived comfortlevel. (A.S.H.R.A.E, 1981, chapter 8.9, fig.5) While and IDark-NegroSkin 66

(A.S.H.R.A.E,1981, chapter8.14, fig.12) Other climatic conditions,such a, relative humdity and air movementare also directly linked to this effect. Many studies have tried to tie these factorstogether, often potrayingthe relationshipsin a graphicalpresentation. The pioneering work of V. Olgyay,and P.O.Fangerpresents some of the basicbioclimatic charts. A.S.H.R.A.E. has developeda newcomfort chart basedon their principles,which can be complemented,for more detailed information, with diagrams depicting the combined influence of humidity, ambientair temperature,wind velocity,and meanradiant temperature. See apendixsection.

Mean radiant temperature

Meanradiant temperature can balancethe impactof the ambientair temperature,but thereare limitationsto its influenceas discomfortcan arise from extremeassymetric exposure. Under normal conditionswith regularclothing that is businessdress- ,thereis a tolerancespan of about±5C in relationto the ambientair temperature.(A.S.H.R.A.E, 1981, chapter 8.26)

Comfort and health

It has been shown that regulatedindoor climates enhance comfort and health.(A.S.H.R.A.E, 1981,chapter 8.29) The marginsfor comfort are, as descibed,depending on severalfactors, but can be set withincertain limits. - Ambientair temperature:20'C-28'C (68'F-82'F) - Relativehumdity: 20%-80%

- Air velocity:0.1 r/s-1.5m/s (0.3ft/s-5ft/s

(A.S.H.R.A.E,1981, chapter 8.28-8.29, fig.22 and fig.23)

Plant response to air and soil temperatures

Most plant activitiesgoverned by light are also influencedby the temperaturelevel,which 67

exerts a strong influenceover plant development,both restrictingand promotinggrowth. The magnitudeof the influenceand severity of the damagesare dependenton the temperature level, duration,and speed of temperaturechanges allowingtime for adjustment. The effect of heat on plants is dependenton the transferringmedia, as well as the absorbing tissue. The temperaturedifference between the plantsand the environment,and betweenthe soil and theair, also playa significantrole. Plantsare losingor gainingheat depending on theprevailing conditions. Heat is lost, eitheras transferred thermal radiationfrom theplant tothe environment, including the nocturnalsky, or stipped off by air movementbecause of convection,or absorbedby the cooler soil due to conduction.Any combinationis also possible. Heat is gained,either as transferred thermalradiation to the plant from the environment,or as latent andsensible heat fromthe surroundingair, or absorbedby the stemfrom the warmersoil due to conduction.Any combinationis also possible.

Effect of temperatures on photosynthesis It can be arguedthat the ambientair temperature, andleaf temperatures,possibly affect the photosyntheticalactivity, throughthe temperature dependentsecond step in photosynthesis. On the other hand, it is also difficult to separatethe temperature influence from other contributingfactors. There are, however,indications pointingat an indirectassociation. Studies measuringthe influenceof temperature levelson photosynthesis,have been able to plota saturation curve,showing thedirect relationshipbetween therate of photosynthesisand light intensity,at differenttemperature levels.(R.van der Veen, Light and PlantGrowth, p18, fig.9.) Other sources contend that the duration of high temperatures affects photosynthesis negatively. (R.L.GainesInterior Plantscaping p.168, fig. p168)Some studies indicatean upper limit for photosynthesisat 32'C to35'C (90'F to 95'F), above which the rate will decline.

(G.H.Manaker,Interior Plantscapes, p.75) 68

Effect of temperatures on respiration Respirationis closely related to the temperaturelevel. Duringnormal conditionsand within certainlimits, a risingambient air temperaturepromotes a fasterrespiration rate. The rate seem to doublewith every 10C' (18F'),or 10'F,temperature increase between 10'C to 30'C (50'F to 86'F), a phenomenonsometimes referred to as the0-10 of respiration.(Environment & Plant Response,M.Treshow, p.54) (R.L.GainesInterior Plantscaping p.168, fig. p169)However, the aftermathis also an increasingdepletion of carbohydrates.That is, high temperaturescan cause an unbalancedmetabolic activity, by excedingthe productionof new chemicalenergy, or food, and exhaustingstored energy, eventually wearing down theplant. Low temperatures will generally slow down respiration,and enable the plant to conserve energy and keep in balancewith low light intensities.Extreme temperatures at both ends will reducerespiration. Night temperatures can preferably be 3'C to 5'C (5'F to 10'F) cooler than day time temperatures. Effect of temperatures on transpiration Transpiration is directly tied to temperature levels and relative humidity. High water vapor pressurein the air restrictsthe transpirationflow, but with risingtemperatures the water vapor pressurewill decrease,enabling an increasedgas exchange.A combinationof low relative humidity and a hightemperature can be detramentalto the plant. (Environment& Plant Response,M.Treshow, p.54, fig.5.1) Effect of temperatures on photoperiodism It is commonfor the photoperiodismactivity to be linked with temperature,and responses change due to combinationsof dalengthand temperatures.Both flowering and dormancy

seemto be affectedaccording to some sources."Flowering of many speciesis promotedby a brief to prolongedexposure to temperaturesclose to the freezingpoint." (PhysiologicalPlant

Ecology1, F.B.Salisbury, p.147) "A dormant condition can be maintainedby keepingthe plant at a low temperature."(R.van der Veen,Light and PlantGrowth, p.67) 69

Plant response to soil temperatures "Temperaturesdirectly influencethe availabilityand absorptionof mineralelements from the soil", as "nutrientsare tightly bound to the soil at low temperatures".(Environment & Plant Response,M.Treshow, p.56.) The abilityof the rootsto absorbwater is also influencedby the temperature,as the viscosityof water increaseswith decreasingtemperature, makingit more requiring for the plant to obtain necessary fluids and nutrients. (Environment & Plant Response,M.Treshow, p.56.) Seed germination is highlymarked by the temperature.At 20'C (68'F) germinationbegin to declineand will eventuallycease at 45'C (113F). (Environment& PlantResponse, M.Treshow, p75.)

Optimal temperature ranges Foliage

Everyplant can havea certainpreferred tempereature level, but mostplants seem to do well at a temperaturerange between 18'C to 24'C (65'F to 75'F). However,some plants, such as Cactus and Yucca prefer 13'C to 18'C (55'F to 65'F). Night temperatures should in both cases be about5C' (10F) lower.(G.H.Manaker, Interior Plantscapes, p.75) Roots Rootsgrown in soil temperaturesof about 18'C (64'F) seem to do best. (Environment& Plant Response,M.Treshow, p58.)

2C: ATMOSPHERIC IMPACT

The qualityof the air is a vital factorthat has to be seriouslyconsidered. The amountof oxygen and nitrogenis relativelystable, and normallydoes not affect the climaticsituation. However, moresignificant are the fluctuatingproportions of carbondioxide and watervapor. The relative humidityaffects both peopleand plants,while carbon dioxide is mainlya concernfor a healthy 70

plant development.Ions and stale air can cause severe nuisance,and pollutantscan play a small, but sometimesdevastating role. Many types of pollution can cause toxic damage to sensitiveplants as well as create an unhealhtyenvironment for people.Carbon monoxide and hydrocarbons from neighboring carparkings and streets, cigarette smoke, chlorine from desinfectionof water, ammoniafrom cleaning fluids, etc. (R.L.GainesInterior Plantscaping p.172.)(S.Scrivens, Interior Planting in LargeBuildings, p.22.)

Relative humidity for plants There is naturallya wide discrepancybetween optimal levels of relative humidity(RH),due to the original habitatof the plants.Most plantsprefer high levels,maybe 70% to 90%, but it has also beenshown that plants are relativelyunaffected even at 20% relativehumidity. Generally, 7 plantsthrive well at normallevels around 30% to 50%. (R.L.GainesInterior Plantscaping p.1 2.)

Ventilation and carbon dioxide Natural, or mechanical, ventilation should provide fresh untainted air for control of temperature and, if necessary,humidity. However, for a healthyplant growth,it is even more essentialthat plants are abundantlysupplied with air containingcarbon dioxide for photosynthesis."The level of carbon dioxide should kept between 1000ppm to 1500ppm". (SylvaniaBulletin 0-351, p.4.)Because,stale air aroundplants is depletedof carbondioxide and will impairgrowth. Also, a high contentof water vapor dissipatedin the evapo-transpirationprocess will exert a strong pressureon the intercellularwalls reducingtranspiration and eventually photosynthesisif the stale air is lingeringclose to the leaves.Any air movementwill have beneficialimpact on plant development. 71

2D: SOIL QUALITY

Allthe mineralelements, maybe 16 altogether,which are necessaryfor a healthyplant growth, are absorbedby the root systemfrom the soil. The nutrientsare continouslydemanded by the plant and have to be replaced once thesupply around theplant gets depleted.It is especially essential to restore major elements such as nitrogen, phosphorus, potassium, sulphur, magnesiumand calcium. Minor trace elements, including iron, are only needed in minute quantities,but can have a detrementalimpact if not supplied.

It is of vital importancethat the soil is aeratedand can supply the rootswith oxygenneeded in respiration.Too muchwater can drenchthe roots andkill the plant. 72

CHAPTER 3

IMPACT OF DIFFERENT GLASS TYPES ON PLANT GROWTH A STUDYON PLANTGROWTH RESPONSE TO DAYLIGHTTRANSMITTED THROUGH GLASSWITH DIFFERENT SPECTRAL ABSORPTION -CONDUCTED BY THEAUTHOR AT MIT THE SPRINGOF 1986.

Discussion With the adventof largeglazed buildings,energy consciousnessdesigners have resortedto technical and architectural solutionsdependednt on glass with reflective and absorbing

properties. Reflectingglass has popularized completelyglazed curtain walls. However,the low

daylight levels,as well as environmentalconflicts with reflectedglare have not always seemed

adequate. Other designsolutions have utilized tintedglass in order to cut downheat gain. New glass technologyhas enabledmore ingenious methods,such as applyingheat reflective coatings on the glass plate or suspendedbetween plates. Though it seems unquestionable that technical problemsincluding heat control and glare reductionhave been well addressed, no actual study has beenconducted exploringthe possible biological concequencesof the impactof thedaylight transmitted through these glass types.

Objective In the wake of these notionsthis studyis intendedto increase theknowledge of how plants respond tothe solar spectrumwhen transmitted through the glass types used in large glazed constructions.

Hypothesis There is strong and persistant evidencethat a healthyplant growth is not only dependent on 73

light for energy,but also dependson thecombined effect of lightintensity,duration, as well as the spectral composition,(sometimes referred to as light quality). Plant responses,such as photoperidism, phototropism,and photomorphogenesisare also tied to certainwavelengths.

It seemsplausible, from studies available,to formulatean assumptionthat plantsare extremely sensitiveto small changesin spectral distribution.These nuances,whichmaybe not noticable to the eye, can presumablyaffect plant development.

Most research,often conductedin laboratoryenvironment, has concentratedon exploringthe impact of specific wavelengthson plant response. Onlya few studieshave looked at the influence ofthe transmitting media, and even fewer have touchedthe eventualimpact of various glasstypes. In order to obtain more information,the author choose to conduct an experimenton site at The MassachusettsInstitute of Technology.

Materials and methods

Glass types Six specific glass typeswith different spectral properties, were obtained from Guardian Industries.All glass types, but one, were insulatingunits with Low-Ecoating. Two of thesix were alsolaminated, as it was expectedthat laminatedglass will be used in sky lightsfor safety reasons

Fourcommonly used tintswere chosenassuming that varyingspectral distributionwould have an impacton the result:Clear, green,bronze and gray.

The glass delivered from Guardian Industriesare grouped below in accordancewith the 74

numberof the test cell,which they were placedon. Outboardlite Inboardlite 1. Low E on 1/4"green + 1/4"clear float glass

2. 1/4"dear float + 9/16"clear laminated The laminatedglass is madeup of (1/4"clear, 0.060 vinyl, 1 /4"clear) 3. Low E on 1/4"clear + 1/4" bronze 4. Low E on 1/4"clear + 1/4"gray 5. LowE on 1/4"clear + 1/4"clear 6. LowE on 1/4"clear + 9/16"clear laminated

It was alsodecided to coverone of the test cells with just 4milpolyethylene (rather than a glass sample),in order to observeif longwaveultraviolet radiation might have a possible influenceon the result,and to enablea comparisonwith a previouslytested material. Testcell 5 was thus dividedinto two separateparts: (5a), polyethyleneand (5b),Low E on 1/4"clear + 1/4"clear as above.

The dataobtained from the manufacturershowed transmission differencesbetween glass types. Both transmitted ultravioletradiation and total visual radiation,as well as nearinfrared radiationdistinguished each glass type. Submittedspectrographs from Guardianalso gave a graphicvisualization of the inherentspectral properties.

Experimental method

The specific phenomenon,had to be separated from other influencingfactor-, in order to create a comparableenvironment. Thus, it was decided to neutralizethe average daylight transmissiondifferences in order to obtain a pure spectral comparisonbetween the different glass types.It was also essentialfor the experiment toequalize air, and soil qualitiesbetween 75

each test cells, as well as allow transmitted light and temperature levels to be evenly distributed. The plant choosen for the experiment should respond to the intended observations.

Site A site had tobe picked,which allowed unobstructed daylight to enterthe testcells.After a few alternativesit was decidedto place thetest site on top of the existingSolar House,at the west endof BriggsField.

Construction

Frame The weather was expectedto be cold during the the experimentalperiod, and a weathertight construction with good insulatingvalues was determinednecessary. The size of the enclosure was dependenton the size of the choosentest cells. Eachcell had to be 2ftx 2ft, in order to createenough spacefor an adequatenumbers of plantsto develop withineach cell. It was also necessary tokeep the size of the volume at a minimumfor economicalreasons. Thus, it was decidedto use 3/8"thick and 4ftx 8 ft largewaferboard as the basicconstruction material. It was utilized toits full extent as floor constructionor cut to size and assembledas floor and wall panelsfilled withRi 1, 31/2"thick insulation,fastened to a frameof 2" x 4" studs. Roof Clear ACRYLITEFF, 4ft x 8 ft sheets,from Cyro Industrieswas usedas a transparentroof skin and screwedtightly to studs at each end of the base. Polyethylene,NBS voluntary standard PSI 7-69,4 mil thick, was fastenedon the inside of the pitched roof and spaced 2" from the acrylic,in order to diffusethe sunlightand minimizeheat losses.The gables,made of acrylic sheet, were designedto be easilydemountable, in order to enableventilation and accessto 76 the testhouse. Walls The walls,2ft high,were claddedwith triple polyethyleneto half the hight,to createa water tight soil basinand protectthe plantsfrom solublesalts in the waferboard.The remaining partof the walls, 1ft,were painted whitewith a latex coatingto scatterthe light and protectthe plantsfrom contactwith the raw board.The test cellswere separatedwith white paintedwaferboard, which did not quite reachthe soil, but left some cracksfor free airmovement between the cells.The crackswere, however,covered with blackrubberstrips to protect thefrom seeping light. The glass plateswere placedon top of weatherstrips and helddown by theirown weight. Ventilation and drainage A horizontal2" openingfor drainage wasarranged along thebottom end ofthe soilbasin.Small 1" holes weredrilled outbetween each test cell to enablefree air movement.Six inch long pieces of a 1" rubber hosewere tightly stuck into the holes to protectthe plantsfrom seeping light.However, during the testperiod it was noticedthat theventilation needed to be improved and moreholes, with similardetails, were alsodrilled to the outside.Later improvementsof the enclosureincluded a horizontalventilation exhaust along the separatingmiddle wall. It was also PLAN -TESTHOUSE decided to cut out a 2ft x 3ft opening in the acrylicsheet to allow forlongwave ultraviolet Test cells radiationto reachthe test cells closestto the opening. Layout The size of the foorplanmade it possibleto placethe test cells sideto side in a 2 x 3 pattern Acrylic andstill allowfor some free spaceat the opening.The created voidwas equippedwith a 750W Poiyehtylene electricradiator anda gutterfor drainage.The six cells were laterexpanded to seven,or actually Glass five full testcells and two half test cells. The test house was oriented with the longer sides Lettuce Soil facing north andsouth respectively.Counting from west to east the test cells closestto the Insulation northside werenumber 2, 4, and 6. The south side test cells were numbers1, 3, 5a, and5b. SECTIONTEST HOUSE (Seefig of test houseplan and section.) 77

Spectral Intensity To neutralizethe impactof varying intensitytransmitted throughthe differentglass types, itwas necessaryto measurethe averagetransmitted light in eachtest cell. The manufacturers own data, indicatingthe magnitude of thetransmitted light, was used as a first base. Actual light measurementswere also conducted foreach cell to complementthese data. A Minoltalight meterwas usedfor these readings.The lightmeteris cosine andcolor corrected,but gradedto be sensitiveto the human eye'sphotopic spectrum. The data recordedwas usedto calculate necessary reduction of area for each glass type,in order to correlate and equalize the transmittedenergy to eachtest cell. Regularduct tape was tapedonto the glass in a symmetric patternto allowan even lightdistribution. Monitoring equipment The changing externalclimatic conditions,and the possibleimpact of temperaturedifferences on the plants, made it essential to install temperature recording equipment. 7 different thermistorswere connectedto 6 of the test cells and onewas utilized to record the soil temperature. The air temperature in the test cell(5b) without a thermistor was estimated to equal the data obtainedfrom its neighbors.Recordings of externalminimum and maximumambient temperatures,and percent of available sunshine,were also collectedfrom the daily local newspapers. Soil The whole basinwas filled with a 12" deep layer of sterile,weed free,fabricated Pro-mix soil, andcarefully saturatedwith water.Any exess waterwas drained out.

Crop It was decidedto use a common,realatively fast growinglettuce seed, whichcould be easily monitored,and comparable,to other test results.Grand Rapidsseeds, from Stokes Seeds 78

Ltd, which has a normal growth period of about 45 days and is well adapted to ultraviolet radiation, were sewnin small, 13/4"x 13/4"x 2", individualpeat-pots and coveredwith 5mm soil mix. Theywere centrally placed,in bunchesof ten, on top of the soil in eachtest cell, and the cells were coveredwith the tested glass types. The peat-pots, with an average of two seeds, evenly spacedin each test cell and transplantedafter two weeksinto thesoil with the seedlings.A procedurewas usedto avoidroot damage,and preventtransplant shock mortality, causedby mechanicaltransplanting.

Test period The first cropwas sewn Feruary10, 1986,and cultivatedApril 30, 1986.

A secondcrop was sewnApril 5, 1986and is not cultivatedat thistime.

Observations The seedswere plantedFebruary 10, andthe weatherwas rathertypical for the season,that is

cold,and an approximately500/o/50% mix of overcast withsnow, and blue skieswith sunshine. The averagesunshine for the germinationperiod between February 10 to March3 was actually calculatedto 48%of availablesunshine. This is also reflectedin the relativelywide temperature swingsof the peat potsoil, ranging betweena minimum of 37'F to a maximumof 89'F. The soil temperatureincreased when the sun was shining. This could be expected, becauseat this stage the peat pots were still placed on top of the major soil basin and could hold very little mass. Whenthe peat pots were submergedinto the soil on March 3 the temperaturespan decreaseddrastically, between a minimumof 52'F to a maximumof 67'F. There werealso signs of overheatingof the ambientair in the test cells.This was noticedfor the first time onMarch 15, whenthe maximumreading slightly crossed overthe 100'Fmark. It was decidedto alleviatethis phenomenonby flipping the glass platesto atriummode, that is with the Low-Ecoating on the inside of the outer glassplate, or number2 as seen fromthe outsideso solargainswould be 79

minimized. The first tiny signs of cuttlings were noticed on March 15. The medium hight seemedto be between2mm to 5mm,and test cell 6 was showingthe leastsigns of sprouting. The decissionto flip over the differrentglass plates did not seem to have any effect. The ambientair temperaturewas still high, and a secondstep to cut downthe tendancyto overheat was implemented.Every test cell was connectedwith an upperand a lower 1" hole for better convectionflows. The holeswere tightly fitted with a 6" long rubber hose. and eventualcracks were sealedwith caulking.The soil was still moistfrom the first watering.Recordings of the first existingcuttlings were madeon March16. First observation

Test cell No.of cuttlinas Hight(mm) Comments February16.1986

1. 9 5-8 Signsof grey mould 2. 15 ~5 Cuttlingslook healthy

3. 12 ~5 Cuttlingsare a littleyellow

4. 6 3-5 Onlya little mould 5. 5 5-8 Signsof grey mould 6. 7 3-5 Cuttlingsa little yellowish

On that same day, a UV-window,2ft x 3ft, was cut out of the acrylicroof facing south. Studs were mountedto supportthe edges and a polyethylenefilm was addedas a replacementfor the acrylicsheet, and fastaenedwith caulkingto the existingacrylic. On February17 and the 19, newscannings of the conditionsrevealed some very dramaticdevelopment. 80

Secondobservation Testcell No.of cuttlings Hight(mm) Comments February17, 1906

1. 14 Somecondensation on the glass 2. 17 A lot of condensationon the glass 3. 15 Somecondensation on the glass 4. 12 Some condensationon the glass

5. 10 Mostcondensation on the glass 6. 16 Some condensationon the glass

Thirdobservation Testcell No.of cuttlinas Hight(mm) Comments February19. 1986

1. 19 No condensationon theglass 2. 24 No condensationon the glass 3. 18 20 No condensationon the glass 4. 17 No condensationon theglass 5. 18 No condensationon the glass

6. 21 No condensationon the glass

February23. A thermistorwas presseddown about 20mminto one ofthe peat pots, to get betterreadings of the soil temperature. February25. It seemsto be warmerin test cells alongthe southside. February26. Testcells 1 and 2 showednight time temperaturesaround the freezingpoint. 81

February 27. The peat pots in test cell 5 were divided into two groups, with five pots in each, and placedin two separate testcells, 5(a) and 5(b).

Fourthobservation Testcell No.of cuttlinas Hight(mm) Comments February27, 1986

1. 23 Most developed cuttlingswere 2. 27 around30mm tall, withtwo 3. 23 30 caracteristicallyheart-like 4. 21 shapedleaves. See fig.

5(a) 14

5(b) 10 6. 22

March3, itwas time to transplantthe peatpots. Pictureswere taken of theplant development, but unfortunatelythey nevercame out right.However, some observations were interesting. Mostdeveloped cuttlingswere around 50mm tall, witha thirdcenter leaf. However,plants in testcell 3 wereclearly elongated and about75mm tall.

Fifth observation

Testcell No.of cuttlinas Hight(mm) CommentsMarch 3. 1986

1. 23 50 slowgrowth. 2. 27 50 3. 23 75 clearlyelongated 4. 21 50 82

5(a) 14 50 fine sturdy growth 5(b) 10 50 the slowestgrowth.

6. 22 50 fine sturdygrowth

Aftertwo weeks of fast developmentthe growthseemed to slowdown, but alsomaintained a steadypace.

There were,however still some problems with overheating, and new ventilation holes had to be drilledto theouitside. The technique was the sameas for interiorholes. A 6"long rubber hose wasfitted in a 01"drilled hole and covered on theoutside with a lighttrap to protectfrom direct lightinto the cells.

Documentationpictures were taken on threedifferent occasions during the experiment.April

2, 21, and30, 1986.(A setof picturesof thelast photo session is includedat the endof this chapter.)On alloccasions it waspossible to detecta fewdifferences in plantgrowth between thetest cells. A generalestimation of the plantgrowth was also conducted the first two times.

Sixth, and seventhobservation

Testcell CommentsApril 2.and 21, 1986 1. Ratherslow Pictureswere taken on all 2. Well developed occasions.Scale was indicated

3. Elongated with a ruler. 4. Medium 5(a) Good development

5(b) Uneven develo)ment 6. Ratherslow 83

It was time to harvest themature crop on April 30, 1986because of high outside temperatures. Pictures,and measurementswere taken and data was recordedas documentation.The fresh weightwas measuredwith a regularbalance scale. It is presumed adequateto measurefresh weightas livingplants will be used in atriums.(See pictures of the last photosession at theend of thischapter.)

Eighthobservation Test Number Fresh Length Thickn. weight CommentsApril 30

of weight avg. 0 per Color 1986 cell stems grams Mm Mn stem grwth

1. 21 355 450 2-6 16.9 Evenbushy growth Pale-green

2. 19 674 550 4-12 35.5 Rather even growth

Palegreen, whitish,at the bottom

3. 21 459 21.9 2-7 475 Bushy growth Whitishpale green Scorchingat the top 84

4. 16 400 550 2-9 550 Unevengrowth Palegreen Scorchingat the top

5(a) 13 445 34.2 7-10 575 Evenstrong growth Notso palegreen

5(b) 8 211 26.4 3-10 450 The plantsgrowing towardsthe light Palegreen

6. 21 306 14.6 2-7 375 Unevenbushy growth Palegreen

Discussion Thescale of thisexperiment is forseveral reasons necessarily small,andthe resources limited. It is plausiblethat all influencingfactors have not beendetected or satisfactorilyremedied. However,the ambitionto isolatethe investigatedvariable, that is the spectraldistribution, has been a primeconcern. Some problems encountered are, for instancethe relativelyhigh temperaturesin the test cellsduring sunny days, and lowtemperatures at somevery frosty nights.It wasnecessary to increasethe ventilation to modifythe high temperatures, but also to 85

increase th2 air movement in the test cells. Slow air movement could possibly affect the concentrationof carbon dioxide and condensationcould create conditionsfor fungi. Mould was actually observedat the beginningof the test period, but was seeminglysatisfactorily controlled by new arrangements and technical solutions. Probably the most severe unaviodablefactor, was the relativelylow light levels,depending on the seasonbut also the tested materials themselves. The experiment had to be executed during rather stable conditions,presumably inside, as it was essentialto enablesome control of the impactfrom foul climaticconditions,like rain, frost, etc. The shieldingtransparent test house had to be there, and the transmissionvalues of the different glass types were given. The plant used for the investigationis the only factorthat actuallycould have been changed.Lettuce often need light intensitiesup to 1500Fc, whilethe real levelsinside the test cellsat the worstoccasions during an overcast day couldreach approximately 200Fc. Considering all these hamperingvariables, there are still some major observationsduring the experimentthat can be explained. For instance,the prolongedgrowth period,the spindlinessamong plants in some test cells, the often found uneven growth,but maybe most importantthe significantdifference in growth betweenthe test cells.

The long growthperiod is probablydue to the relativelylow light intensities.The light intensity was probably not not been high enough for an efficient photosynthesis, affecting the production of carbohydrates and the plant growth. However, there should not be a considerabledifference between the test cells, as they had been calibratedto transmitequal amountof averagedaylightlight. A possibilityremains that the actualcalibration, due to the light meter measuring most efficiently in the green-yellowspectrum, did not consider actual differencesin energy.It has to be remindedthough, that the objectof this experimentis to test plantsin an environmentsimultaniously used by peopleas well as plants,why it is pertinentto use footcandlesas an intensityunit for easycomparisons in a glazedconstruction. 86

It is probablyrelevant to point at the relativelylow light intensity also, as the cause for the spindlyand unevengrowth. One other factor could be uneven distributionof light. Signs of phototropisticresponse could be traced in some plants searchfor light. The stems were pointingin the same direction towardsthe slightlybrighter southfacing internal walls. However, this responsewas not observedin all test cells at all possiblelocations for this reaction.

The differencesin plant growthbetween the test cellsis the most striking observation.It must be feasablethat differencesin spectraldistribution between the tested glasstypes causethis reaction.The early elongationof cuttlingstems in test cell(3, bronze),might be an effect of a relativelyhigh proportionof wavelengthsbetween 600nm to 800nm.A highproportion of red wavelegnthsis interestinglyalso found in light transmittedthrough, gray glass. There was some indicationof elongatedgrowth in the test cell(4)with thatglass, but not aspronounced as in test cell(3). It is also posibleto point at temperaturedifferences as an affectingparameter.

Test cells (3) and (4) seemed to run warmer than any other cells, mCvbe effectuating elongation.However, the temperaturedifferences between the test cells and growthdo not correspond.Growth in the warmertest cells (3) and (4) is intermediatebetween the poorand good growthof other test cells. What is even more remarkable,the average temperaturesin test cell(1) and (2) are quite similar, still the yield is drasticallydifferent. (See fig of average temperatures) 90 _2 88 2 77 Lookingat the differentfresh weight data it is evidentthat the resultscan be placed in three 80 81 8 70 groups: 600 A. Testcells (2, laminatedclear) and (5a, polyethylene)with a highyield. so B. Testcells (4, Low-E,gray) and (5b,Low-E, clear) with a mediumyield. 1 2 3 4 5a 6 SOIL C. Testcells (1, Low-E,green) and (6, Low-E,laminated green) with a lowyield. ANVEWKADN EE~ MFREACHTESTCELL hfASLFMFORCEESTPMMO Testcell (3, Low-E,bronze) is swirlingbetween the low and mediumyield. 87

It is interesting that the glass typesthat let the spectrally least affected daylight through promotea higheryield. One result mediatingthis observationis the relativelypoor plant growth in test cell (5b, Low-E,clear). Thisis possibledue to the fact thatvery few stems eventually grew up in that cell. However, thereis still a drastic differencebetween Low-E, clear andthose transmitting relativelymuch in the greenspectrum, which seem to performthe worst. This could

possibly be explainedby the specific propertiesof photosynthesis,regularily reactingmore actively to wavelengths in the red and the blue spectrums. That is the plants could not efficientlyutilize the energyin the green spectrum.There are indicationsthat thisis especially true for pale greenplants like lettuce. Anotherinteresting interpretation of the result isthe fact, that ultravioletradiation, insofar as it reachedthe plants, neitherwas beneficialnor damaging. The good yieldsof both test cell (2, laminatedclear) and (5a, polyethylene), thelatter exposed to longwaveultraviolet radiation, might support thisinterpretation.

Conclusions It is possible that all theinfluencing factors affectingplant growth responseto the spectral distributionof transmitteddaylight through differentglass types, have passedundetected in this experiment. One condition which could have affected theresult is the differences in temperatures, thoughthe testfindings do not give any indicationof correlationbetween yield and temperature.Other affecting factors might be differencesin transmittedenergy and the small scale of the project. However,the results indicate sufficientlya relation betweenthe spectralditribution and plant growth.It seemspossible to attach a strong linkbetween the full spectrumdistribution, and a good plant growth.That is, panes withclear glass, or another materialthat lets untainteddaylight through, willstand a better chanceto supporta strongand healhtyplant growth. 88

Ar-

The different glass plates on top of the test cells are shadedwith tape in symmetricalpattern to compensatefor varyingtransmission properties 89 r 90

I I

V ~ I'

k U

I I 91

PART 2 : DESIGN GUIDELINES FOR A HEALTHY PLANT GROWTH AND

HUMAN HEALTH AND COMFORT IN ATRIUMS

CHAPTER 4

MAJOR LIGHTING MEASURING METHODS [PI[Y 2: DESIGN GUIDELINES

FOR A HEALTHYPLANT GROWTH Discussion AND HUMAN HEALTH AND COMFORTIN ATRIUMS It is notwithin the scopeof this thesis to reprint different daylightingmethods, the original sources are extensive and readily available.However, some general remarks regardingthe usefulness and appropriatenessof different methods are beneficial to the knowledgeand experienceof howdaylight enters buildings.

First of all, it is essentialto understandthe physical,physiological, and psychologicalfactors that govern our perceptionof light. Psychologicalfactors in this case,is a broadgeneralization of several compoundingvariables, some of them mentionedin chapter 1. That is, illumination levels, may not have any influence at all over comfort, convenience, performance, or aestheticalpreferences. However, as some light is necessaryto even conceptualizeforms, there is a logical agreement,that architectureis created from light. Theintriguing questions

could possiblybe narroweddown to what quantityis sufficientto enablecertain performances, and how the least amountof light should be distributed to enhance the perception of the environment.

The second obstacle which has to be surmounted, once some creteria for a suitable illuminationlevel has been settlod, is how these lighting levelsand quality p-evone rhould 92

be predictedat the design stage.There are several methodsfor calculatingthe intensityof illumination, some whichare moredetailed than others.Traditional calculation methods, such

as the point by point method,and the lumen method, haveutilized formulas and tables. The point by point methodis tideous,but useful in determiningisolux contoursas it allowsfor more detailedcalculations. The size and the positionof the window, as well as the positionof the specific points, affect the calculatedvalues, and usuallymaximum, average, and minimum levels are determined.The morecrude lumen methodwill suffice if estimations ofaverage intensitiesare adequatefor the solution, but will not considerthe impactof different window positions.Other methodsinclude utilization of protractorsto predictthe sky component,and can be sufficientlyaccurate for measuringthe influenceof overhangsand verticalfins. Recently the usefulrange of the protractormethod has beenexpanded to considerthe impactof the sun and the orientationof the windows.

The introductionof low cost micro computershave spurredthe developmentof severalsoft ware programs for daylighting, besides the more elaborate and expensive main ship in computer programs,the DOE-2, developedby the Departmentof Energy in the U.S. The differentprograms utilize graphics tovisualize illumination contours, and can be monitoredfor quick alternatives.However, difficulties in supplyingthe computerwith relevantinformation can lead to deceptivelyaccurate measurements,maybe based on wrongassumptions.

The most accuratemethod today for daylightingcalculations, despite moderntechnology, is physical modelling.The model can be hastily manufactured,without hamperingthe overall accuracy,and alsosupplies the designerwith valuableinformation of subtlelight qualities, such as shades,colors,contrasts, and textures.It is generallybest totest the model underreal sky conditions,but an artificialenvironment simulating the outside world, is advantageousif the weatherdoes not permitregular testing. It is possibleto build affordableartificial light-boxes, 93

whichare simulatingovercast conditions satisfactorily. MIT, actually owns one and it was utilized for the experimentdiscussed in chapter 6. The idea behind the light-box is simply a bright artificiallylit horizontalceiling made of translucentsheeting with mirror-claddedwalls. The scale of the modeltested can vary dependingon desiredaccuracy, but generallyit is easierto get a reliableresult from a largescale modelof approximately1: 50 (SI standard)or 1/4"= 1'-0"(U.S. standard). Photographsof the lighting model will enable good evaluation, and an often strikinglytrue-life atmosphere.

However,there are circumstances,especially early in the designprocess, when some rough estimationsof conceivedsolutions would facilitate correctdecisions. These rule of thumbscan often be handy in evaluatingaverage illuminationlevels, and several methodshave been suggested.

The regular approach, regarding illumination levels, is to describe the efficiency of the suggesteddesign in daylightfactors. When the externalhorizontal illumination changes, the interiorlight level changessimultaniously and proportionallywith the combinedeffect of three different parameters. Namely, 1, direct sky component(SC) 2, external reflective

component(ERC)3, internal reflectivecomponent(IRC). (R.G.Hopkinson et al, Daylighting, p.69-fig3.3)The summationof these parameters,the daylight factor(DF)is oxpressed as the ratio betweenthe internaldaylight at a certain point to the availableexternal daylight, and is usually quoted in percents.All these factors imply several influencingvariables, which all should be known in order to get an exact result. It is obviousthat a simplifiedmethod has to excludemany variables at the costof less accuracy.

Sidelighting

Sidelighting is more affected than toplighting, as the external reflective component, is changingwith the location.Obstructing buildings, vegetation, and different reflectiveground 94

materialmight influencethe total daylight factor, beyond a rough estimate. However, one exampleof approximazationsuggests a simple rule-of-thumbfor single sided unobstructed rectangularrooms. The daylightfactor is expressedas directly relatedto the ratio betweenthe net glassarea(Ag) to the totalfloor area(Af)multiplied by a factorof 0.2, for averageillumination, and 0.1 for minimum illumination. (H.Bryan et al, Daylighting a Resourcebook,p.5-46, unpublished)

Sidelightingrule-of-thumb. Method 1.

D.F.avg= 0.2 Ag/Af

D.F.min= 0.1 Ag/Af

The methodseems to be relatedto Frling's formula,which expressesthe averagedaylight factoras a productof a windowfactor(F) and coefficient of utilization(U)times the ratio between the net glass area(Ag) and the total floor area(Af). F= 0.5 for an unobstructed room, and U can vary between 0.2 to 0.5, but it is suggestedto use 0.4. (R.G.Hopkinsonet al, Daylighting, p280.)

The size of the room is necessarilyan influencingfactor to be considered.It can conveniently

be calculatedthat any increasein roomsize, abovea normalroom ratio of 2:2:1 (length,depth, height),will effectuatea decreasein the daylightfactor at 20 ft from the window,which is equal to half the proportionalchange of the total surfacearea. (R.G.Hopkinsonet al, Daylighting, p277.)

AD.F.= AAtotsurfacex 0.5 95

The positionof the openingalso affects the illuminationlevel. Thehigher the windowhead, the betterthe lightpenetration deep into the room.That is, a verticalwindow with the same areaas a horisontal openingwill allow lesslight deep into the room.The effect of a clerestorywindow couldbe anincrease of about50%. However, the samehorizontal window placed as a low view windowwill causea reductionof 50%compared to a normallyplaced window.(R.G.Hopkinson et al, Daylighting,p277.)

Another interesting formulafor calculation of the average daylight factor is known as the Littlefair/Plymouth expression. It is expressedas dependenton the total surfacearea instead of the floorarea.

Method 2.

D.F.avg= t AglassB / 2 x Atotsurface x (1-R 2)

t= diffuse transmittanceof glazingmaterial.

B= the anglesubtended, in degrees,from the centerof thewindow to the freesky. The useof this angle enables calculationswhere considerationscan be taken regarding obstructing objects.(D.C.Pritchard, Lighting, p.108)

It is interestingto comparethe two methodsmentioned. Consider a room with all sides 1Oft long andone wall completetycovered with glass.

R= averagereflectance ofall roomsurfaces. Method1.

D.F.avg= 0.2 Ag/Afand Ag=100, Af=100gives D.F.avg= 0.2 or 20%

Method2.

D.F.avg= t AglassB / 2 x Atot surfacex (1-R 2)

Assumet=1, B=90(no obstruction),R=50%

D.F-avg= 1 x I'3 x 90 / 2 x 600(1-0.52)=9000/ 900 = 10% 96

Thereis a differenceof 100%between the methodsand that might be expected

Toplighting The Fruling method canalso be applied for estimationsof toplighting, exchanging the sidelighting factorsfor others,associated with skylightmonitors.

Toplightingrule-of-thumbs. 50% averageindoor reflectance.

Method 3.

D.F.avg= 0.20 Ag/Af -forvertical monitors

D.F.avg= 0.33Ag/Af -for north-facingsawtooth openings

D.F-avg= 0.50Ag/Af -for horizontalskylights

Othersources suggest a little different approach,involving a room ratio,or sometimescalled room index.

Room index = I x w/ (I + w) x h

Method 4.

D.F-avg= U x Ag/Af

U= coefficient of utilization dependent on room index, light-well efficiency, and other transmissionloss factors.

The methodcould be useful foratriums, if the coefficientof utilizationtables were expandedto includetaller structures.As it is now,the roomindex only coversratios up to 0.6, whichis a space with a room height less than its sides. However, it seems possible to use the table for well efficiencyto obtain a relativelyreliable result. Theresults havebeen tested against emperical studies discussed in chapter 6. (H.Bryan et al, DaylightingA Resourcebook,p.5-46 fig.15, 97 unpublished)

Method 5.

D.F-avg= Ew x Ag/Af

Ew = efficiencyof well

Wellindex = wellheight x (wellwidth + welllength) / 2 x wellwidth x welllength.

Table1. (H.Bryanet al, DaylightingA Resourcebook,p.5-46 fig.15, unpublished)>

Still anotherapproach is takinginto account the shapeof the skylightskirt alongwith the sizeof the openingand reflectanceconsiderations. Lynes is expressingthe daylightfactor as variable dependenton LOR,or the lightoutput ratio times the ratio ofthe glassarea to the floorarea dividedby the impactof floorand ceilingreflectances. (Lynes, Principals of NaturalLighting, p.103)

Method 6. 0

D.F-avg= LORx Aglass/ Afloorx [1-(Rfloorx Rceiling)J

LOR is calculatedfrom a table,and is dependenton the ratioof the verticalcurb areato the 1 2 3 4 5 6 openingarea, and the reflectancefactor of thecurb. (Lynes, Principals of NaturalLighting, p.102, AREA OF VERTICAL CURS PL AN AREA Of OPENING will increaseLOR to value equivilentto the output fig8.2)It is alsoclaimed that a splayedskirt a Light output ratio of rough-cast glass < ratioof an uprightcurb with the sameceiling opening as the horizontalinternal area covered by the splayedskylight. (Lynes, Principals of NaturalLighting, p.101, fig8.1) A simpleuse of the .. " m4wtsad Qcr tableindicates that 2ft deep,1Oft by 1Oftopening, is about13 % moreefficient than a vertical openingof the samesize. The improvedefficiency increase to appximately33% if the depthof dome with splayed corb. the openingis1 Oft. The averagereflectance was assumed to be 50%and the splay45. 98

Another methodto approximatedaylight factors generatedby toplightingin atriums has been investigatedby the authorand will be discussedin chapter6 of this thesis.

There are manyaspects of the distributed daylightthat affect our perception.An efficient illuminationis not necessarily bright.On the contrary,the problems relatedwith too bright light, might overshadowthe existingqualities of thespace. A good daylightingdesign is funtionally efficient and enhancesthe shapes,the color nuances,the desiredtextures and the envisioned mood,and add a touchof mystery.Still, adequtelight intensities for plantshas tobe maintainedif a healthygrowth is considereda part of a serious design. Thesesometimes diametrically opposite requirementsmight lead to conflictsthat createspoor conditions for both people andplants. 99

CHAPTER 5 DESIGN GUIDELINES FOR QUALITY ATRIUMS

DISCUSSION

Any design startswith an envisioned function,with limitationsset by the locationas well as the technical and economical possibilities. A good design has merged the restraints into a functionalliving spacewith aestheticalqualities. It is possibleto defy the impactof siterelated climatic conditions and pay the price of either high energy costs or hampered comfort. However,a conceptin tune withthe climatemediates and utilizesthe influenceof the sunand extremetemperatures, while respondingto the influenceof culture, traditionand the existing physicalbuilt environment.These notionsform a first basefor a good atriumdesign harvesting specific climatic conditionsto create an architectureindigenous to the site.

Technical parameters affecting a good atrium design.

In the previous chaptersit has been explainedwhat biolocical,physical, and to a certain extent, psycolologicalcultural and socialproperties thatset the limitsfor survival,health, andcomfort in a built envircnrment.But, how should theserequirements be met andwhat are the possible technicaland architecturalsolutions to balanceseveral contradicting conditions, while creating a comfortableand pleasingindoor environment?

Daylight Daylightaffects our perceptionof a spacein manyways. Efficient illumination is not necessarily bright. On the contrary, the problems related with too bright light might overshadowthe existing qualitiesof the space, "becausethe quantityof light is not nearly as importantas its quality". (Rasmussen,S.T, Experiencing Architecture,p.189) A good daylighting design is 100

funtionally efficientand enhancesthe shapes,the color nuances,the desired texturesand the envisionedmood, andadds a touch of mystery. Still, adequatelight intensities for plants have to be maintainedif a healthygrowth is a part of a seriousdesign. These sometimesdiametrically oppositerequirements might lead to conflictsthat createspoor conditionsfor both people and plants.

Modes of daylight Daylighthas differentmodes, which all can be positivelyutilized if applied properly.It can create a senseof time, movement,orientation, tranquilityor activity,and pronouncenuances of colors and shapes.The relativelyuniform daylight of overcastskies gives a mellow,inactive, even light with few contrasts and an apparentfeeling of spatiousness.Diffused sunlight is somewhat stronger in contrasts, more directionaland warmer in color. Redirectedsunlight creates a modifiedtransition zone between the bright outsideand the darkerinside. Direct sunlight is an asset for intentionalcontrasts and playful manipulationswith shadowsand strong relationship with theoutdoors. The rich range of shades enhances volumes,textures, directions,and promotes a strong sense of enclosure.Colors canalso appear more saturatedin sunlight, though reflectionsfrom sunlit surfaces can create a specular appearence, thusfading the sensationof color.

Location The site choicein a rurallandscape and sparcelyurbanised areas is especiallysensitive to the impact of microclimaticconditions. The topographyas well as existing vegetationand wind directionsaffect the climate and has to be considered.An urbansite is moreuniform and the 101

microclimateis dependent on existing buildings around the site. Access to fresh air and unobstructed viewsare limited. Surroundingtall buildingscan cast shadowsover the site diminishingthe intensityof the sunas well as curtailingadequate accessto daylight.Increased wind speedsand turbulence, due to escalated and fluctuating air pressure aroundtall buildings, can also affect the structureof the atrium, as well as the comfort and safety of entrancesand pedestrian walkways.

Orientation The massing and orientation of the volumes and glazing that embrace the atrium havea profoundeffect on the climatic performance.The balanceof heatingand cooling is mainly dependent on the existing climatic conditions, but proper massing and orientation can enhanceor reduce theimpact of the sun. Commercialstructures have high internal energy loads,and it i usuallyadvantageous in temperateclimates to minimizethe heatgain. Energy performanceis directIty affectedby the orientationand the tilt of glass surfaces.Seasonal changes and diurnal differencesin solar altitude favor a lo igitudinal east-westorientation. Northfacingglass is the most attractive solution forreducing heat gain, but the high and hot summersun shiningfrom thesouth is also relatively easyto control.However, the easternand westernsun still maintainsa high intensity,but at low elevationsto the facade,making shading morecomplicated and energysavings less.

Daylight control

Glare Many attempts to maximizethe transmitteddaylight is curtailedby glare problemsas well as temperaturerelated disorders.The solution in modernstructures has often beenthe useof reflectiveand tinted glass. However,the sensationof glareis the relative experienceof too 102

brightlight compared to darkersurrounds, and emminentlyaffected by the eyesability to adapt. That is, even quite low lightlevels can imposea glare problemif the eyes have adoptedto a lesser ambient light intensityin the occupiedspace. There are two ways to overcomethe problem.Either an increaseof the light levelin the room,to adaptthe eyesto a higherintensity, or a reducedbrightness of the glare source.The approachto reducethe glaresource, in this case daylight,has the effect that the lightlevel in the room also decreases,why theannoying glare problemstill might exist.The thresholdfor obtaininga perceivedglare reductionrequires

that the daylighttransmittance of the glass is less than 30%. (Hopkinson,R.G., Daylighting, p.325.) The possibly gloomy effect of low transmittanceglass combined with a distorted spectrumreaching the interiorcan hamperhuman health and negativelyaffect plantgowth. See chapter2.

There are other probably more rewardingsolutions to glare, which can contributeto the architecturalexpression as well as the qualityof light.The approachis dependenton the mood desired as well as heat gain considerations. Different methodscan also havedrastic implicationsfor the aestheticalappearance, affecting both massingas well as detalingsof the facade.Control devices can be integratedwith the structureand the facadeor be fixed to the exterioror the interior once the buildinghas beenerrected. Shadingcan be appliedto the exterioror the interioror within the transmittingmedia. They can be fixedor movable, automatic or manual,translucent oropaque, horizontal,vertical or eggcrateshaped. The shape of the building can be manipulatedto allow self-shadingand direct sunlight can be modified by bouncingit off externalor internalwalls. Someexamples are L. Kahn'sdouble wallsystems in

Bangladesh,I.M. Pei'sCity Hall in Dallasand an office buildingin London,1 Finsbury Avenue by Arup Associates,and of coursemany traditionalold buildingswith deepreveals. See figs. The atrium itself can also serve as an indirectdiffusing light source reflecting softlight to adjoiningoffices. 103

Interior daylight control

The interiorof the atriumcan be manipulatedto reducesensations of glare, and at the same time add richness to thearchitectural experience. Canopies of vegetationcan be used as a buffer zone for modifing and diffusingthe direct light. The more intense light close to glazed openings can be efficientlyutilized by sun addaptedplanting material, while transmittingsoft modified light to zones occupied by people and shade grown plants underneath. The translucentpale greenbamboo canopies within the atriumof the IBMbuilding in NewYork, N.Y. is a successfulapplication of this approach.It should also be possibleto create translucent "waterfalls"of vegetationclose to verticalglazing, if the plantingmaterial is carefullychoosen and the surfacetemperature of the glasscontrolled. Similar use of vegetationon the outsideof the glazed fasadecan allowfor changeswith the season,transmitting more direct light in the winterwhen the heat is needed.

Other daylight control methodsinvolve the use of sunscreensof different material. One interestingexamle is I.M.Pei'sextension of theMuseum of Fine Arts in Boston,U.S.A., where mattfinished aluminum rods are placedclose to the glassto reducethe direct impactof sunlight and articulatethe shape of the roof structure.See fig. More apetizingsolutions integrate the screening effect with other functions to create an even richer architecture. Some good examplesare GatewayTwo, at Basingstoke,and One FinsburyAvenue in London,both in Englandand designed by Arup Associates.See figs. New forms are developedout of the integrationof several functions,such as maintenanceand glare control to create aesthetic functionalpleasure.

Artistic collaboration and architectural integration There is also a world open to artisticcollaboration and architecturalintegration with other arts. 104

The redirectionof visual interestto specialfocal points,will enhancethe spatial quality while perceptionallyreducing glare. There are many different possibleartistic methodsto achieve this integration.For instance,textiles can be usedas interiorflags and bannersfor the purpose of diffusingas well as redirectinglight. Diaphanous sculptures can createinterest as well as be used for funtional reasons.Hanging glass prismsand mobilescan refractand redirect lightto form changing patterns on surroundingsurfaces. The glass surface can be treated with differentstained glass methodsto createthe effecta translucentpainting, as well as transmita secondaryimage to floors andwalls. The authorsuggests applied use of glass in architecture depending on its function. Transparentglass covering openings should transmit a natural spectrum,while treated glass could be used for special effects. Eggcratelouvres of stained glass can diffuse direct sunlight,while maintainingthe valuable vertical light from toplighting during overcastconditions.

LAVA

Energycosts

Atriumscan contributeto energysavings. The experiencefrom manybuilt atriumsis that costs for the total structure is not increased. (The American Institute of Architecture, General Procedings,Building Redesign and EnergyChallenges, Boston, November,1984.) However, a generalnotion is that savingsin the U.S.,or in locationswith similarclimates, depend on the air-conditioningload and the desired indoor climate. Lightly conditioned atriums promote savings, while fully conditionedatriums seldom save on -energycosts, unless the atrium is enclosedwith heat reflectiveLow-E green glass. ( Johnson, T., conversation,Thesis, MIT 1986.) 105

Fire

There are still many issuesregarding fire preventionand smokecontrol that are unsolved.The natural chimney effect in tall structuresmay not be enoughfor smoke evacuationand could causeproblems unless supportedby powerfulfans. Usuallythe regularreturn air systemat the peak of the atrium is complementedby extrafans in caseof a fire in order to evacuatesmoke.

Anotherapproach is to limitthe numberof openstories facing the atrium.Fire codesin the U.S. suggesta maximumhight of threeopen stories.( U.S. BOCOA)The most recentdevelopment in Europeseparates the functionof the atrium,in the caseof a fire. The atrium is exclusively utilizedas a smoke exhaustchannel, while the evacuationof peopleis concentratedtowards fire escapesat the exteriorfacades. (Butt, L., Arup Associates,conversation London, 1986.)

Ventilation The need for fresh air and temperaturecontrol, usually necessitates mechanical systems for ventilation.The cost for a totallyclimatized atrium, however, can be high,so naturalventilation should be utilized as much as possible. The authour has noticed that, the ambient air temperature in traditional naturallyventilated palm houses can be quite comfortableeven during warm sunnydays, if the convectiveair flow is adequate.For instance,the Temperate Houseat Kew Garden,London, is totallyconditioned with outsideair in the summer,and is only heated during the cold season.The CrystalCathedral by Philip Johnson, in Los Angeles,is relying on natural convectionand solar heat gain throughoutthe whole year. Outside air is allowedto enter through openingsat the gradientlevel, while utilizingnatural convectionto exaust hot air at the roof top. The effect is causedby air pressuredifferences between the cooler outside air vis a vis the hotterair at the roof top, so its usefulnessis limitedto those conditions.However, ingenioustechniques to passivelyincrease the temperaturedifference couldbe a cost effectivealternative to mechanicalsystems. For instance,solar radiationcan be utilizedto heat up effective heat absorbingexterior roof surfaces,causing pressuredecrease 106 at the roof top and subsequentlyincreased convection. One very interesting energyreducing solution has been designed for the Royal Garden Hotel at Trondheim, Norway. The stratificationof air is utilizedto minimizeairconditioning to the first coupleof floors, whilehot air is exhausted at the roof top. The conceptwas tested for an atrium in Dallas, Texas, in the

Energy Conscious Design cource at MIT, 1985, with good result. ( Gardestad,K., course notes, EnergyConscious Design, MIT 1985.)

Royal Garden Hotel, Trondheim Temperature control There are manyinterrelated factorslinking daylightcontrol and lightquality with temperature control. Any attempt to mediatethe influenceof solar radiationon a transparentmedia has a subsequent effect on light quality. Problems andpossibilities related to the use of different glass types has already been mentionedin the section discussingdaylight control,which is relevant, because most oftentreated glass is born out of the sole purpose of reducing heat-gainswithout consideringlight quality.However, there are new glass technologies which utilize the different absorbingand reflectingproperties of inorganicor organic coatingsto reduce heat-gain,while maintainingmost of the intensityof the transmitteddaylight. (Johnson T., Vol IV, BOOK 2, chapter2, U.S DOE DocumentationProject, MIT Press, 1986.)Some of the emerging methodshave not yet beencommercially utilized, while others have madea fast move into the market. Most successfulamong different new technologiesis Low-Eglass, or low emissitivityglass, with coatings applied directly to theglass surface orto mylar films.The thin metal films, usuallysilver(Ag), reflects much ofthe far infraredradiation, while reducing thermal heat. The most effective applicationof far infraredreflective glass is for residential purposes,but atriumserrected in climateswith energycosts tied to heat-lossesmight find the methodattractive. The combined propertiesof Low-E coatings and lightgreen, iron rich,glass has the economicallyviable effect of absorbingnear infrared radiation, while transmitting much of the visible radiation,thus reducingheat gain due to solar radiation.It is posssibleto obtain a 107

daylight transmission of 64% while keeping the shading coefficient at 47%. (Johnson T., Vol IV, BOOK 2, chapter 2, not yet published.)It is about to claim a substancialnische in the commercialmarket. However,the natural propertyof green glass to increase the ratio of transmittedgreen wavelengths,might have negative consequencesfor plant growth. The possibleeffects are discussedin chapter3. of this thesis,and indicatesthat especiallygreen light, due lessefficient photosynthesis,might impair plant development.It has to be pointed out thatthe smallscale investigationis not decisive.Yet, it hintsa possibleconnection.

Artificial lighting It is not the intensionof this thesis to advocatethe use ofartificial lighting in atriums.On the contrary,much emphasisis put on adequateutilization ofnatural light. However, in caseswhere artificial lightingis necessaryto maintaina functionallight levc' for photosynthesis,it is important to supplythe environmentwith a full spectrumactive light. This does not imply that onelight source with this range is the best solution. Combinationsof light sources withdifferent wavelengths,might be as effectiveand at the same time enableadequate lighting of disparate functions.There are two consequentialobservations regarding lighting for plants, which the author wantsto bring tolife. It is widely consideredto be of vitalimportance that plants are suppliedwith relevantlight levels for an extendedperiod in order to maintaina healthyplant growth.This ismany times the cause for introducingartificial light in the atrium as the daylit period duringthe winterseason is consideredto be too short.However, that approach canbe contested,for a simple but paradoxicalreason. The author noticedat a visit to the Botanical Gardenat Kew, London, thespring of 1986,that the TemperateHouse, built in 1862, had no supplementalartificial lighting, but totally relied on daylight. That wasdespite of abundant plantingmaterial from tropical latitudes expectedto be especially sensitiveto small changesin daylength.It has to be addedthat London,famous for its overcastconditions, is situatednorth of the 50'th latitude with more pronounced differences in daylength than experienced 108

anywhere in the U.S. except Alaska. The conclusion may be daring, but the observation has to be interpretedas a supportfor the notionthat plantsin daylit atriumsare not dependenton the daylength.Thus, artificial lighting seemto be redundant,as long asthe light intensityaquired from daylightingis adequate.The second observationis more a compounded knowledgeof phototropisticplant responsegathered from discussions with Sasaki Associatesin Cambridge, Massachusetts,U.S., and C.Mpelkasat GTE, Sylvania,Danvers, Massachusetts, U.S. Plant tendencyto grow towards thelight can be avoided,if artificiallighting is appliedin a criss- cross fashion,illuminating the plants from all sides. Reflectivematerial, such as whitish crossed marble,can be introducedunderneath plantcanopies to re1irect light to the undersideof the leaves, opening the stomates for more efficient photosynthesis,while avoiding plant elongation.

Passivetechniques can advantageouslybe utilized in atriums,by exploiting the naturalstorage capacityof surrouding surfaces, whichis dependent on the density,thermal conductivity, and specific heat propertiesof the used material.The more mass, the better heat capacityand subsequentlyless fluctuatingdiurnal temperatureswings, which generallyinfluence climatic comfort and energycosts in a positive direction.The most common andinexpensive wayof storing heatis utilizingthe dual functionsof heavy masonryand concreteconstructions as load bearingelements and finishing material. Theoptimal performanceof the mass thickness is influencedby ambientclimatic conditions as well as modeof radiation, butgenerally "the diurnal heatcapacity for cementiousmaterials peaks around 11 inches".(Johnson T., Vol IV, BOOK2, chapter2, not yetpublished.) The optimalthickness of materials radiatedwith diffusedlight is redusedto half.

The surfacecolor has little impacton the storagecapacity, as long as the light is diffusedand the massevenly spreadout. (Johnson,T., The DirectGain Approach,p.103.) Darkcolors can 109 be utilized to obtain the maximal effect of direct sunlight on a small area. However, an atrium with large exposed surfaces will store heat sufficiently, even if the materials are of light nuances. Besides,the experienced light quality in an airy light atriumwill create good conditionsfor plant growth. 110

CHAPTER 6 GUIDELINLZ FOR SKY LIGHT ILLUMINATION IN ATRIUMS - A REPORT ON A

STUDY CONDUCTEDAT MITTHE SPRING OF 198

An atriumis not a qualityspace unlessthere is an adequatelight level forvegetation. It is a personalremark, which might not passuncontested. However, theintent of thesisis to supply designmethods which can alleviate solutions aiming at a healthyplant growth. Recommendedlight Intensities It hasbeen shownin previouschapters that plantsare dependenton certainminimum light intensitiesin orderto survive.Any increase in lightlevels is generallyenhancing plantgrowth. Theoptimal light level is determinedby the origin of the plantspecies, but also by an individual acclimatizationto prevailing conditions.Available sources on plantscapinggive slightly varying information regardingoptimal hourly lightlevels for certain plants.This is partly due to discrepanciesin calculating duration of requiredlight intensities. However,it is it is customary to divide plantsinto differentgroups according to their light requirements.The following recomendationsare interpretations of datafrom InteriorPlantscaping by R.Gaines. Plants are dividedinto four differentgroups depending on an increasing scaleof recommendedlight intensitiesto growwell, minimum intensities to keepa healthy greencolor, and maintenance lightlevels to sustainover a limitedtime without growth.

LIGHTLEVELS(Fc) RECOMMENDED MINIMUM MAINTENANCE

(for12 hours) LOW 75-100 50 30-50

MEDIUM 200 75-100 75

HIGH 500 200 100-150

VERYHIGH 1000 500 500 111

There is a need for useful calculation methods early in the design process in order to determineaverage illumination levels and possiblegrowth zones for plantsin top-lit atriums. Various calculation methodsfor average illumination levelshave also been presented in chapter3.

Hopkinson suggests(H.p.202 ) that illuminationlevels for extendedroof lights roughly canbe calculatedas proportionalto rooflight area to totalfloor area andthat total illuminationsuitably can be obtained through the B.R.S protractor method or simplified calculation methods (H.p.102).However, no informationis given regarding thelimits of the methodindicating only that detailedillumination calculations for rooflightsis notnecessary beyonda certainheight of the investigatedspace, presuming thatonly even light levels are desired. Other methods considerthe impactof height,but in the form of a room index,and the prerequisiteof an even light distribution.The influenceof differentreflectances on light distributionis alsoneglected in many cases.These factorsare of significantimportance for a thoroughunderstanding of light distribution.

The purposeof this study is to increasethe knowledgeof the existingrelationship between hight andlight levels in top-litatriums andthe influence of differentskylight configurations, and reflectances on light distribution. The result could supply the designer with a tool for suggestingpertinent growth zonesfor plants.

Limitations It was decided to contain the study to toplightingunder overcastconditions, as lowlight intensitiesare of critical importancefor plant survivaland any additionallight will increasethe 112

possibilitiesfor a healthy plantgrowth anyway . This impliesthat the diagrams onlyportray distribution of light affected by horisontal openings during overcast conditions and/or situationswhere the distributionof blue sky radiationis approximateto the distributionof global sky radiationon cloudy days.However, low light conditionsdue toovercast skiesare bften prevailingmore than 50% of the time, and plantsneed approximatelytwo days of sunshineto makeup fora cloudyday. Thus, the requiredminimum lightintensities have to be correlated to overcastconditions, making the useof the diagramsrather extensive.It is obviousthat direct sunlightas well as combinedvertical and horisontalopenings increaseillumination levelsand changeisolux contours depending on orientationand designof openings.

1Experimentali method

The influenceof different configurationson light distribution in a top-lit atrium was to be investigated.The configurationsshould vary in shape,relative aperture, and reflectance,while the surrondingsurfaces shouldvary in reflectance.Existing software programsfor daylighting were scanned in the beginning of theinvestigation, in order to possible utilize fastmicro computersfor the investigation process.However, it was impossibleto find any suitable and reliable programs, soit was decidedto employ empericalmethods. MIT owns a "light-box", approximatelly3ft by 4ft in plan and 3ft high, whichcould be rebuilt to fit the specialpurpose.

The light-boxsimulates overcast conditions by utilizinga bright artificiallylit horizontal ceiling madeof translucentsheeting with mirror-cladded walls.A hatch covers a 19 inchessquare hole in the bottompart of box to enablean eye'sview ofthe daylighttested rooms. The hatchwas simplydemounted and replacedwith a threefeet deep lightwell stickingdown from the bellyof the light-box.The lightwell was equipped witha movablefloor, to enable readingsof light levelsat differentdistances from the light-boxhole, or in this casepreferably calledthe skylight 113

level. Nine evenly spaced photosensorswere fixed to the floor and connected to a data acquisitioncontrol unit, number3421A, from Hewlett Packard. (See fig. of light-box.) The differentconfigurations were cut out of opaque foamcore,and pastedwith paper of different colors; white, beige, and flat black. The light well was cladded with similar colored paper. However,the runsfor mediumreflectances were conductedwith naturallycolored wafer board. (Seepictures of configurationsat the end of this chapter.)

Co nfig cara@n@

Shape

The differentshapes were cut out symmetricallyto simplifythe interpretationof the findings. However,some configurationsallowed for assymmetricalspacing in order to determinethe impactof assymmetryon lightdistribution. Aperture size

It was decidedto test the influenceof the aperturesize on light distribution,in orderto verifyor reject proposedapproximazations for light levels,which generally assumethat illumination levelsproportionally follow the size of the opening.Four sizes were chosen expressedas a percentageof the maximumopening. 100=100% 75=75%, 50=50%, 25=25%

Ref lectances

Everyconfiguration was also tested with differentwall and ceiling reflectances.Four shades rangingfrom blackto whitewere introducedas the controllingparameters. Three of themwill be 114

presentedin this thesis:

Black(S)=15%reflectance, but also glass surfaces Medium(M)=40%reflectance, usually theaverage value for manysurfaces. White(H)=85%reflectance, possible onlyon surfaceswithout glass.

Codes The codingof the differentconfigurations is a combinationof all affectingvariables, for instance A50H, indicatingshape=A, aperture=50%,and high=Hreflectance.

Mght woli

Photosensors It was possibleto utilize eightphotosensors spaced in aneven symmerticalpattern on the light well floor. It should have been nine,but the equipmentdid not allowfor moreconnections. This had no actual impact as the symmetry of the square floor plan and the configurations, only Comparative data of average light level required three positions, center, edge, andcorner. (See fig. of photosensorpositions) The Note: at different heights, apertures, and extrapositions were merelya safetymarginal. reflectances indicated a direct proportional correlation between size of aperture and H/D : The proportional ratio of hight to depth illumination levels, as long as the light was The impact of various distances between increments was tested at the beginning of the evenly distributed and the reflectance experiment,and it was found necessaryto record light levelsonly at five different heights,or medium(M). Surfaceswith high reflectances illuminatior distancesto the top, in order to obtain a sufficientlyeven curve.The five different heights(H) showedproportionally increased than 30% at shallow hights, were chosen in accordancewith their proportionalratio to the width, or depth(D),of the light levels of more 25% (H'D = 0.25), and a total aperture of well. These ratios were subsequentlycalled H/D and indicatedthe proportionalrelationship (See graphs in the appendix section.) between height and depth. 115

H/D=0.25, Note:The largemajority of atriumshave an H/D ratiobetween H/D=0.5 1.0 and 2.0.This ratio is sometimes referredto as S.A.R. (Bednar,Michael J., The New Atrium,p.66.) H/D=1.0 OPAQI-, SURFACs S = 15% [REFLEc7ANCT. H/D=1.5 NI =5% rFLECTANCE H/D= 2.0.

I I =85%TRIEFLECAANCT

FOSITIONSOF PHOTUSENSORS Severalconfigurations of various shapesand mentionedapertures were testedduring the CENTER experiment,with the purposeto eventuallytrack the H/D,where light levels tend to evenout CQRNER independentof the differentshapes. The recordedlight intensitieswere transferredto a MacintoshMultiplan spread sheet with ability to graphicallypresent threedifferent curves. The

-CEDGE horizontalaxis representsH/D, while the verticalaxis depictsthe daylightfactor(DF). it is . g . -- CENT ERq possibleto determinelight levels,in footcandlesor lux,for anyhight by reading off the daylight factorfrom thediagram and multiplyby the ambientlight leveland divide the sum by 100. Usuallyit was decidedto plotthe recordeddata of the center,the edge, andthe corner,but alsoother interelated comparisons were plotted. This thesis will onlydescribe some data from a -CENTER few differentconfigurations. (See fig. for explonationof differentsurfaces)

20-

" co C16180 A503

as-CWE CWE1 It was soonrealized that the heightand H/D ratio hada strongimpact on the measuredlight 0 65 ~ ~ .51 ~ 1 ~ o. =001 intensity,which was to be expected.The influence of differentreflectances was alsodirectly relatedto lightlevels, as well as the aperture.(see fig A25M,A50M, and A50H) However, the configuraticosmodified the tendency,and could even reversethe general trl id -f increasing 116 light levels. (See fig B50M. center) However,more astonishingwas the general tendency of _-EDGE £ light levels to be independentof photosensorpositions once H/D was higher than 1 to 1.5. A.50ME

The levels were hardly influencedby configurations,size of the aperture,or reflectances, 46- though a slight shift could be recognizedat H/D greater than 1. High reflectancesand large 40 DU apertures tended to close the gap betweenthe different light levels a little sooner. (Compare 26- CoVr.Ra fig B25M with B50M. and A50Swith A50H.)

Other observationsindicated that the total illuminationlevel was not proportionalto the relative a0A 0. - 70 1 1.26 Is 17 1 aperture,until H/D was closeto 2.0. (Seefig A25M,A50M, and A75M.)However, this could be explained by the impact of the variousconfigurations on light distributionat shallow heights. . _ EDGE6 CEN0FR Comparative data of averagelight levels at different heights, apertures, and reflectances 'ED -A50HE indicateda direct proportionalcorrelation between size of apertureand illuminationlevels, as coR4 long as the light was evenly distributed. Other interesting observations indicated that 6. illuminationlevels for mediumreflectances (M) were not drasticallyhigher than the light level for flat black reflectances.(S= black,and glasssurfaces). It was also possibleto graphicallypresent the absolute maximumand minimumlight intensitiesthat can be possibleto obtain in a top-lit atrium, given a certainconfiguration. (See fig. A25S,M,H.) Seenote on p. 114for moredetails. EDGE6 CORNEFR - CENTER 0-40401 COFNER

Test of findings in outdoor conditions findings Light-box recordings were tested under natural conditions, to verify the different 0.36 S .6 1 15 I 3 observed during the investigation.The impact of natural conditions on illumination levels followed astonishinglywell the investigatedmethod. (See fig.A50M-Lightbox-Out)

Conclusions

It has been shown that different configurationshave a drastic effect on light distribution, at shallow heH'its. That is, whenthe height over depth ratio(H.D)is less than 1 n The influnceis 117

gradually decreasing and the lightdistribution has evened out at a ratio of approximately H/D=1.5.This seemsto holdtrue for any aperturesize and variousreflectances, though some

small shifts are observed.Configurations with openingsemphasized towards the center seem A25SMH

M4 to have a slightly higher illuminationlevel, probablydue to a wider view 0Athe brighter sky M zenith. However,the averageillumination levels for configurationswith the same aperturesize S seem to be directly proportionalto the relativeratio of the aperture to the floor area. This

L.I S 0A 725 1 1.21 is 1.75 correspondsto earlier mentionedapproximate design methodsfor determiningaverage light levels. -- "" The relation could be expressedas D.F.avg= U x Ag/Af,where U is a utilization factor dependent on reflectance and the H/D ratio. A future developmentof an existing table in A25,5,75AMATCENTER indicatingthe close relationshipbetween a well index and the efficiencyof the well=U,might _ A5M prove to be a good solutionto the problemof determiningaverage light levels. (See figure, developedfrom DalightingA Resourcebookby Bryan.H.,et al p.7-42,in the right columnof 0.5 B &.M I 1.5 IA 1.76 this page)=see 1a.1*1.

WellIndex= Well heightx (Wellwidth + well length)divided by 100 - -. $...MSBox (2 xWellwidth x welllength) ~loom~CUT A50M LIGHTBOX Differentreflectances can playa majorrole in affectingillumination levels. However, the practical AND OUTSIDECOMP So. use of high reflectancewalls have limitationsbecause bright surfaces require scrupulous maintenanceand they alsocreate glare problems and limitthe use of interiorglass walls which MOM wiT 5 act as lightsinks. 0.76 es 0.75 1.26 Is 1.75

Not surprisingly the test indicatesthat the deeper the atrium the greater the influenceof surface brightnesses as the internal reflective component IRC increases proportionally. However,interestingto note is that flat blacksurfaces still reflect reasonablyenough to enable illuminationlevels to closelyfollow those of mediumhigh reflectance. ~1.. 4 00 iii

d 119

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0.25 0.5 0.75 1 1.25 1.5 1.75 2 151

CONCLUSION

Thisis a thesisthat wished it werea book.

The specificfeatures that distinguisha qualityatrium are severaland not necessarilyto be foundin technicalsolutions. On the contrary,many outstanding charachteristics are related to the qualityof health,comfort and aesthetic pleasure, while serving functional needs.

All life is dependenton the energyradiating from the sun, and neitherman nor plantscan survivewithout sufficient amount of it. However,plants seem to standin a closerrelationship to lightand is directlyaffected by its energycontent. There are alsoother documentedplant responses whichare linkedto the qualityof lightas wellas the intensitylevel. For one thing, plants haveaquired seasonal adjustment in orderto survive whenthe climateis harsh,while man hasbuilt shelters to protecthimself from severeimpact. These fundamental differences betweenclimatic preferences necessarily create problems when the optimalenvironments of man and plantsare desiredto merge.There are also new indicationsthat man is more dependenton light, than previouslyenvisioned. Changes in daylengthcan affect man's biologicalclock just as plantsare known to respondto thediurnal circle. Differentwavelengths andintensities might also be provento influencethe perfomanceand health of plantsas well as people.Still, buildingsare errectedwhithout climatic considerations with consequencesfor bothpeople and plants. For instance, windows with reflective or tintedglass take an increasing shareof the market.However, this thesishas indicateda link betweentransmitted light and plantgrowth, showing that plantsrespond favorably to a spectrumclose to naturaldaylight. It 152

has also been shownthat architecture whichis sensitive to climaticconsiderations can develop a rich and aestheically pleasingexpression, which otherwise wouldhave been lost. It has also been the purpose of this thesis to alleviate achitectural decisions to enable a quality environment.Maybe an increasedunderstanding of light distributionsin atriumscan lead to better solutions, where both peopleand plants can coexist in a healthy and comfortable environment. 153

APENDICES

-SPECTROGRAPHS OF VARIOUSGLASS TYPES AND ACRYLIC SHEETS USED FOR RESEARCHON PLANTGROWTH RESPONSE TO LIGHT QUALITYAS DESCRIBEDIN CHAPTER3.

- GRAPHSFOR DETERMINING AVERAGE ILLUMINATION LEVELS IN TOP-LITATRIUMS AS DISCUSSEEDIN CHAPTER6. 77-

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Transmission 5. (%) 403Q- .0

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9 - 249 266 298 3M 329 34 360 386 499 429 44M 469 489 Wavelength (nm) The Libraries Massachusetts Institute of Technology Cambridge, Massachusetts 02139

Institute Archives and Special Collections Room 14N-118 (617) 253-5688

There is no text material missing here. Pages have been incorrectly numbered.

/56/ I 6 169/ 162

REFEb ENCES

REFERENCES REFERRED TO AS NUMBERS IN CHAPTER 1. (other referencesinserted in the text.)

4 Treshow,Michael, Environment & PlantResponse, p.104-105. 5 Lange,0. L., Nobel,P.S., Osmond,C.B., Ziegler, H., PhysiologicalPlant Ecology 1,p.42 6 Scrivens,S., InteriorPlanting in LargeBuildings, p.31. See fig 5.3, p.30. 7 Thorington,L., The Medicaland BiologicalEffects of Light, p.36. Fig p.37. 8 Wurtman,R., The Effectsof light on the HumanBody, p.69. 9 Neer, RobertM., The Medicaland BiologicalEffects of Light, p.15. 10 Thorington,L., The Medicaland BiologicalEffects of Light, p.34. 11 Thorington,L., The Medicaland BiologicalEffects of Light, p.36. 7 12 Wurtman,R., The Effectsof light on the HumanBody, p. 1. 13 Philips,Lighting Manual, p.16.1. 14 Wurtman,R., The Effectsof light on the HumanBody, p.71 16 Lange,0. L., Nobel,P.S., Osmond,C.B., Ziegler,H., PhysiologicalPlant Ecology 1,p.110. 17 Lange,0. L., Nobel,P.S., Osmond,C.B., Ziegler,H., PhysiologicalPlant Ecology 1,p.110. 18 Classificationat Kew Garden,London. 19 Olgyay,V., Designwith Climate,p.17, referring to C.E.P.Brooks. 102 Lange, 0. L., Nobel, P.S., Osmond, C.B., Ziegler, H.Physiological Plant Ecology I, ,fig 6.3 p.176 105 Evans,M., Housing,Climate and Comfort,p.40. Also Bryan,H., classnotes, MIT Energyin Buildings,1984. 163

REFERENCES REFERRING TO PHOTOGRAPHS

Testhouse and test cells, Page 88-90 photographstaken by the author.

GatewayTwo, Arup Associates, Page 102 TheArchitects Journal, 3 August,1983, p.33.

GatewayTwo, Arup Associates, Page 103 TheArchitects Journal,3 August, 1983, p.33.

OneFinsbury Avenue, Arup Associates, Page 104 ArupAssociates Booklet, 1985, p.17. above

Stainedglass, Working with Light, Page104 AndrewMoor Associates, Cambridge House, below 356Camden Road, London N7 OLG, England.

Museumof FineArts, I.M. Pei, Page 105 photographtaken by the author.

RoyalGarden Hotel, CFJK Arkitektgruppe, Page 106 (P.Knudsen), Trondheim, Norway, above and below ContractInternational 21, box 1083,S-26901, BAstad, Sweden, p.1-2.

Light box and lightwell, Page 118-119 photographstaken by the author. 164

BIBLIOGRAHPY

-Andersson, Bruce, The Solar HomeBook, Brick House PublishingCo., Inc., Andover,Mass., 1976. -ASHRAE Handbook1981 Fundamentals,Ammerican Society of Heating, Refrigeratingand -Air-ConditioningEngineers, Atlanta, GA, 1985. -Austin, RichardL., Designingthe InteriorLandscape, Van NostrandReinhold Company, New -York, 1985. -Bainbridge,David, VillageHomes' Solar House Designs, Rodale Press, Emmaus, Pennsylvania,1979. -Bednar, MichaelJ., The New Atrium,McGraw-Hill Book Company, New York, 1986. -Bryan, HarveyJ., Kroner,Walter M., Leslie,Russel P., Centerfor ArchitecturalResearch RensselaerPolytechnic Institute, New York, July1981. -BuildingRedesign and EnergyChallanges, Printed in WashingtonDC, Nov 1984. -Caldwell,M.M., Plant Responseto Solar UltravioletRadiation, 029642 - QK710-E5,Encycl. Plant PhysiolNew Ser.p 169-107,1981 v 12. -Cathey, HM, Cambell,LE, Plant Responseto Light Qualityand Quantity,139833, Breed Plant Less FavorEnviron. p 213-257ill 1982. -Conover, C.A./.Poole, R.T., Acclimatizationof IndoorFolliage Plants, Horticultural Review v. 6 1984. -Evans, Martin,Housing, Climate andComfort, The ArchitecturalPress Limited, London, 1980. -Final Reporton The Effectsof Wavelength SelectiveFilm on GreenhouseEnergy and Plant Growth,Environmental Research Laboraty,The Universityof Arizona,1985. -Gaines, Richard,L., InteriorPlantscaping, Building Design for InteriorFoliage Plants, ArchitecturalRecord, New York, 1977. -Helms, RonaldN., IlluminationEngineering for EnergyEfficient Luminous Environments, Prentice-Hall,Inc., EngelwoodCliffs, NJ, 1980. -Hopkinson, R.G., Collins,J. B., The Ergonomicsof Lighting,Mac Donald & Co. Ltd., London, 1970. -Hopkinson, R. G., Petersbridge,P., Longmore,J., Daylighting, WilliamHeinemann Ltd., London, Melbourne,Toronto, 1966. -IES LightingHandbook, Illuminating Engineering Society of NorthAmerica, New York, 1981. -Johnson, TimothyE., Solar Architecture,The DirectGain Approach, McGraw-HillBook Company,New York, 1981. 165

-Kreider,Jan F., Kreith,Frank, Solar Heating andCooling, McGraw-Hill Book Company, New York, HemispherePubliching Corp., Washington,1976. -Kuler, Richard,Ljusets Biologi (The Biologyof Light),Tekniska H6gskolan, Lund, Sweden, 1981. -Lange, 0. L., Nobel,P.S., Osmond, C.B., Ziegler, H., PhysiologicalPlant Ecology 1, Responsesto the PhysicalEnvironment, Springer-Verlag, Berlin, Heidelberg, New York, 1981. -Larson, Leslie,Hanson, Donald, Climate and Comfort,The ArchitecturalPress Limited, London, 1980. -Lee, Richard,Forest Microclimatology, Colombia University Press, New York, 1978. -Manaker, GeorgeH., INteriorPlantscapes, Prentice Hall Inc., EngelwoodCliffs, NJ, 1981. -Olgyay,Victor, Design with Climate,Bioclimatic Approach to ArchitecturalRegionalism, PrincetonUniversity Press, Princeton, JN, 1983. -Passive Solar, Proceedingsof the 2nd NationalPassive Conference, March 16-18 1978, Universityof Pennsylvania,Philadelphia, Pennsylvania ,1978. -Philips, LightingManual N.V. PhilipsGloeilampenfabriken, 1975. -Phillips,Derek, Lighting in ArchitecturalDesign, McGraw-Hill Book Company,New York, Toronto, London,1964. -Rassmusen, Steen, Eiler, ExperiencingArchitecture, The M.I.T. Press,Cambridge, Mass., 1959. -Saxon, Richard,Atrium Buildings- Developmentand Design,Van NostrandReinhold, New York, 1983. -Scrivens, Stephen,Interior Planting in LargeBuildings, The ArchitecturalPress, London, HalstedPress Division, John Wiley& Sons,New York. 1980. -Van der Veen, R., Light and PlantGrowth, The MacMillan Company,New York, 1959 -Wurtman, RichardJ., The Effectsof Lighton the HumanBody, in Hormonesand ReproductiveBehavior, W.H. Freeman & Co, 1979.