Passive Solar Design Strategies: Guidelines for Horne Building
Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With SufrPort From: U.S. Department of Energy Passive Solar Design Strategies: Guidelines for BODle Builders
Birmingham, Alabam.a
Passive Solar Industries Council Solar Energy Research Institute Charles Eley Associates This document was prepared under the sponsorship of the Solar Energy Research Institute and produced with funds made available by the United States Department of Energy. Neither the United States Department of Energy. the Solar Energy Research Institute. the Passive Solar Industries Council nor any of its member organizations. nor any of their employees. nor any of their contractors. subcontractors. or their employees. makes any warranty. expressed or implied. or assumes any legal liability or responsibility for the accuracy. completeness or usefulness of any infonnatlon. apparatus. product or process disclosed. or represents that its use would not infringe privately owned rights. The views and opinions do not
necessarily state or reflect those of the United States ~(.. !ment. the Solar Energy Research Institute. or any agency thereof. This docur .vas prepared with the
assistance and participation ofrepresentatlves from nl"'J organizauuCls. but the views and opinions expressed represent general consensus and available information. Unanimous approval by all organizations is not implied. C;UN I eN I ::;
Guidelines
Part One. Introduction ...... 1 1. Introduction to the Passive Solar Design Strategies Package, , , , , , , , , , , , , . , ,2 2. Passive Solar Performance Potential. . . . , . , , . . . , . . , , . , . , , , , , . . . . , . 5
Part Two. Basics of Passive Solar, , , .. , , ... , , ... , , .... , ...... 7 1. Why Passive Solar? More than a Question of Energy...... 8 2. Key Concepts: Energy Conservation, Suntempering, Passive Solar...... 9 3. Improving Conservation Perfonnance, , , . , , , , , , , , , , , , , , , , , , , , , , , , ,10 4. Mechanical Systems...... 13 5. South-FaCing Glass ...... 14 6. Thennal Mass. , . . , . , , , ...... , ...... , , . . . . , , . . . . , , . . . . . ,15 7. Orientation...... 16 8. Site Planning for Solar Access...... ~ ...... 17 9. Interior Space Planning ...... , . , , . , ..... , ...... " ..... , . 18 10. Putting it Together: The House as a System ...... 18
Part Three. Strategfesfor Improving Energy Performance in Birmingham, Alabama ...... 21 1. The Example Tables...... 22 2. Suntemper1ng .. ,.,"""""""',.,""""""", .. ,' ,23 3. Direct Gain. . . . , ...... 24 4. Sunspaces...... 27 5. Thennal Storage Wall, , . . . . , . . . . , . . . . , . . , , , , . , . . , . . . . , . . . , . 30 6. Combined Systems ...... 32 7. Natural Cooling Guidelines ...... 32
Worksheets
Blank Worksheets, Data Tables, and Worksheet Instructions
WorkedE~ple
Description of the Example Building...... 40 Filled in Worksheets ...... , ...... , ...... 43 Annotated Worksheet Tables...... 48
Appendix
Glossary of Tenns...... 51 References...... , ...... 52 Summary Tables...... , ...... , . . , , . . . . . , . . . . . , . . . . . , . . . . . 54 Technical BaSis for the Builder Guidelines...... 56
Birmingham, Alabama , '11....,.....,.' .. _ ....,.....,_.--11., • ..,_..." ..... ,,. ..." •• " ...... ""
PSIC expresses particular financial and technical support gratitude to the following of the GUidelines, several individuals: J. Douglas contributed way beyond the call Balcomb, SERI and lANL , of duty. Stephen Szoke, whose work Is the basis of the National Concrete Masomy Acknowledgements Guidelines: Robert McFarland, AssOCiation, Chatnnan of PSIC's LANL, for developing and Board of Directors: James Tann. programming the calculation Brick Institute of America. Passive Solar Design Strategies: procedures: Alex Lekov, SERI, Region 4, Cha1nnan of PSIC's Guidelinesfor Home BuO.ders for assistance in the analysis; Technical Committee: and Blon represents over three years of Subrato Chandra and Philip W. Howard. NAHB National effort by a unique group of Fairey, FSEC, whose research Research Center. past Chatnnan organizations and individuals. has guided the natural cooling of the Technical Conunittee. all The challenge of creating an sections of the guidelines: the gave unstintingly of their time. effective design tool that could members of the NAHB Standing their expertise, and their be customized for the spec1ftc Committee on Energy. especially enthusiasm. needs of builders in cities and Barbara B. Harwood, Donald L. towns all over the U.S. called for Carr, James W. Leach and the talents and experience of Craig Eymann, for the benefit of specialists in many different their long experience in building areas of expertise. energy-efficient homes: at U.S. Passive Solar Design DOE, Frederick H. Morse, Strategies Is based on research Director of the Office of Solar sponsored by the United States Heat Technologies and Mary Department of Energy (DOE) Margaret Jenior, Program Solar Buildings Program, and Manager; Nancy CarHsle and carried out primarily by the Los Paul Notarl at SERI: Helen Alamos National Laboratory English, Executive Director of (lANL), the Solar Energy PSIC: Michael Bell, fonner Research Institute (SERI) and Chairman of PSIC, and Layne the Florida Solar Energy Center Ridley and Elena Marcheso (FSEC). Moreno, fonner Executive The National AsSOCiation of Directors of PSIC: Arthur W. Home Builders (NAHB) Standing Johnson, for technical COmmittee on Energy has assistance in the development of provided invaluable advice and the Guidelines and worksheets: assistance during the Michael Nicklas, who worked development of the Guidelines. on the Guidelines from their Valuable infonnation was early stages and was drawn from the 14-country instrumental in the success of International Energy Agency the first pilot workshop in North (lEA), Solar Heating and Cooling Carolina: Charles Eley, for his program, Task VIII on Passive help in every aspect of the and Hybrid Solar Low Energy production of the Guidelines Buildings (see next page for package. more about the international Although all the members of context of Passive Solar Design PSIC, especially the Technical Strategies) . COmmittee. contributed to the
Birmingham, Alabama PASSIVE SOLAR DESIGN STRA TEGIES
Solar Design guidelines for Cities and towns in Strategies and the the U.S. • Booklet 4: "Design Tool International Energy Selection and Use" provides Agency guidance in the selection of design tools appropriate for each Valuable information from the step of the design process. International Energy Agency's • Booklet 5: "Construction Solar Heating and Cooling Details" identifies solutions to research program has been construction problems unique to integrated into Solar Design passive solar buildings. Strategies. • Booklet 6: "Passive Solar Under the leadership of the Homes: Case Studies" highlights U.S. Department of Energy the performance of buildings (Michael J. Holtz, Operating constructed and monitored by Agent on behalf of DOE) the lEA Task VIII countries. Task VIII is producing a series of • Booklet 7: "Design Design Information Booklets on Language" written primarily for a number of issues related to the design professionals and design and construction of students, deSCribes an approach passive solar residential to generating whole building buildings. Among the booklets design solutions based on will be design guidelines for each climate analysis and design of the 14 naUons participating in centered analysis. Task VIII. Solar Design • Booklet 8: "Post Strategies is the U.S. Construction Activities" contribution to this part of the discusses aspects of passive Design Information Booklet homes that are unique and may series. require attention by the All the lEA Task VIII Design occupants and home builders. Information Booklets will be PSIC would like to express its available from PSIC. The thanks to the Task VIII member booklets include: nations for the wealth of • Booklet 1: "Energy Design information their long-term Principles in Buildings" explains commitment to international the heat transfer principles solar research has made critical to the thermal comfort of possible. passive solar buildings. • Booklet 2: "Design Context" presents a checklist of factors to be conSidered in the design process. • Booklet 3: "Design Guidelines" specifically developed for each nation. "Solar Design Strategies" will present site-specific deSign
BlrmlDgham, Alabama Passive Solar Design Strategies GUIDELINES
Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department of Energy PASSIVE SOLAR DESIGN STRATEGIES 1
Part One: Introduction
1. Introduction to the Passive Solar Design Strategies Package
2. Passive Solar Performance Potential
Birmingham. Alabama 2 GUIDEUNES PART ONE: INTRODUCTION
1. Introduction to the Passive Solar Design Strategies BuilderGuide Passive Solar Design is a package in three basic parts: A spec1al builder-friendly • The Guidelines contain computer program called Strategies Package information about passive solar BuUderGuide has been developed techniques and how they work, to automate the calculations The idea of passive solar is and provides specific examples involved. in ftlllng out the four simple, but applying It effectively of systems which will save worksheets. The program does require informaUon and various percentages of energy: operates Uke a spreadsheet: the attention to the details of design • The Worksheets offer a user t11ls in values for the and construction. Some passive simple, ftll-in-the-blank method building. and the computer solar techniques are modest and to pre-evaluate the performance completes the calculations. low-cost, and require only small of a specific design. including all table lookups. and changes in a bullder's standard • The Worked Example prints out the answers. The practice. At the other end of the demonstrates how to complete results are the same as if you spectrum, some .passive solar the worksheets for a typical completed the worksheets systems can almost eliminate a residence. manually but it is much faster. house's need for purchased more convieuient. and less prone energy - but probably at a to arit1unet1c error. Many design relatively high first cost. variations can be evaluated very In between are a broad range quickly. of energy-conserving passive solar techniques. Whether or BuUderGuide is available from not they are cost-effective, the Passive Solar Industries practical and attractive enough Council. See page 53 for the to offer a market advantage to address. Computer data files any individual builder depends containing the information on on very specific factors such as pages 48-49 are available for local costs, climate and market 205 locations within the United characteristics. States. The user can then adjust Passive Solar Design for local conditions so Strategies: GUideltnesJor Home performance can be evaluated BuUders is written to help give virtually anywhere. builders the information they need to make these decisions.
BirmlDgbam, Alabama PASSIVE SOLAR DESIGN STRATEGIES 3
The Guidelines Part Three gives more The Base Case House is a Some principles of passive solar specific advice about techniques reasonably energy-efficient des1gn remain the same in every for suntempering, direct gain house based on a 1987 National climate. But the important systems, thermal storage mass AssOCiation of Home Builders thing about passive solar is that walls and sunspaces, and for study of housing characteristics, it makes better use of the natural cooling strategies to help divided into seven cUfferent opportunities in a house's offset air-conditioning needs. regions. The Base Case used for surroundings. So, many The Example Tables in Part Birmingham, Alabama is from fundamental aspects of the Three are also related to the 2,500-3,500 heating degree passive solar house's design will Worksheet numbers, so that you days region. The floor depend on the conditions in a can compare them to the construction is assumed to be small local area, and even on the designs you are evaluating. For slab-on-grade, because this is features of the building Site example, the Passive Solar typical in Alabama. itself. Many of the suggestions Sunspace Example Case which The examples show how to in this section apply specifically uses 40% less energy than the achieve 20,40 and 600A> energy to Birmingham, Alabama, but Base Case House (page 29) has: use reduetlons using three basic there is also infonnation in each • a ConseIVation Penonnance strategies: seetlon of the booklet which will Level of approx1m~tely 22,847 • Added Insulation: be useful in any climate. Btu/yr-sf, increasing insulation levels Part One introduces Passive • an Auxiliary Heat without adding solar features. Solar Design Strategies, and Penonnance Level of • 8untemperlng: increasing presents the penormance approximately 15,006 Btu/yr-sf, south-facing glazing to a potential of several cUfferent and maximum of 7% of the house's passive solar systems in the • a Summer Cooling total floor area, but without Birmingham climate. Although Penormance Level of 10,703 adding thennal mass (energy in practice many factors will Btu/yr-sf. storage) beyond what is already affect actual energy (In this example, the energy in the framing, standard floor penonnance, this infonnation savings are achieved by no coverings and gypsum wall will give you a general idea of increase in insulation over the board and ceiling sunaces. how various systems will Base Case, adding a sunspace Insulation levels are also penonn in your area. with south glazing area equal to increased. Part Two discusses the baSic 11% of the house's floor area, concepts of passive solar design and using a ceiling fan to cut and construction: what the some of the air conditioning advantages of passive solar are, load.) how passive solar relates to A Base Case house is other kinds of energy compared with a series of conservation measures, how the Example cases to illustrate primary passive solar systems exactly how these increased work, and what the builder's levels of energy-efficiency might most important considerations be achieved. should be when evaluating and using different passive solar strategies.
Birmingham, Alabama 4 GUIDELINES PART ONE: INTRODUCTION
• Passive Solar: using three The Worksheets number from one of the tables - different design approaches: The Worksheets are specifically for example, from the Solar Direct Gain, Sunspace, and tailored for Binningham, System Savings Fraction table or Thennal Storage Wall, and Alabama, and are a very from the Heat Gain Factor table. increased levels of insulation. important part of this package The Worksheets allow For all strategies, the energy because they allow you to calculation of the following savings indicated are based on compare on paper different perfonnance indicators: the assumption that the energy passive solar strategies or • Worksheet I: Conservation efficient design and construction combinations of strategies, and Performance Level: detenn1nes guidelines have been followed, so the effect that changes will have how well the house's baSic the houses are properly sited on the overall peIfonnance of the energy conseIVation measures and tightly built with high house. (insulation, sealing, caulking, quality windows and doors. The most effective way to use etc.) are working to prevent The Guidelines section has the Worksheets is to make unwanted heat loss in the been kept as brief and multiple copies before you fill winter. The bottom line of this straightforward as possible, but them out the first time. You can Worksheet is a number more detailed information is then use the Worksheets to measuring heat loss in British available if needed. Some calculate several different thennal units per square foot references are indicated in the designs. For instance, you could per year (Btu/sf-yr) - the lower text, and a list of other first calculate the peIfonnance of the heat loss, the better. infonnation sources can be the basiC house you build now, • Worksheet n: AuxiUary found in the References. Also then fill out Worksheets for that Heat Performance Level: included at the end of this book house plus added insulation determines how much heat has are a brief Glossary, a summary plus a sunspace, and then for a to be supplied (that is, proVided of the Example Tables for third possibility such as a by the heating system) after Binningham, Alabama, and two Thennal Storage Wall. taking into account the heat pages explaining some of the The Worksheets proVide a contributed by passive solar. background and assumptions way to calculate quickly and This worksheet arrives at a behind the Guidelines and with reasonable accuracy how number estimating the amount Worksheets called Technical well a design is likely to peIfonn of heating energy the house's Basis for the Builder Guidelines. in four key ways: how well it will non-solar heating system has to conserve heat energy; how much proVide in Btu/yr-sf. Again, the the solar features will contribute lower, the better. to its total heating energy needs; • Worksheet m: Thermal how comfortable the house will Mass/Comfort: detennines be; and how much the house's whether the house has adequate annual cooling load (need for air thennal mass to assure comfort conditioning) will be. and good thennal perfonnance. The Worksheets are Worksheet III calculates the supported by "look-up" tables number of degrees the containing pre-calculated factors temperature inside the house is and numbers for the local area. likely to vary. or "swing". during Some of the blanks in the a sunny winter day without the Worksheets call for infonnation heating system operating. A about the house - for example, well-designed house should have floor area, prOjected area of a temperature swing of no more passive solar glazing, and so than 13 degrees. and the less forth. Other blanks require a the better.
Blnnlngham, Alabama PASSIVE SOLAR DESIGN STRATEGIES 5
• Worksheet IV: Summer 2. Passive Solar The energy savings Cooung Performance Level: Performance presented in this example indicates how much air assume that all the systems are conditioning the house will need Potential designed and built according to in the sunnner (it is not, the suggestions in these however, intended for use in The energy penormance of Guidelines. U's also important sizing equipment, but as an passive solar strategies varies to remember that the figures indication of the reductions in significantly, depending on below are for annual net heating annual cooling load made climate, the specific design of benefits. The natural cooling possible by the use of natural the system, and the way it is section in Part Three gives cooling). The natural cooling built and operated. Of course, advice about shading and other gUidelines should make the energy performance is not the techniques which would make house's total cooling load - the only consideration. A system sure the winter heating benefits bottom line of this Worksheet, in which will give excellent energy are not at the expense of higher Btu/yr-sf - smaller than in a penormance may not be as summer cooling loads. "conventional" house. marketable in your area or as Please note that throughout So, the Worksheets provide easily adaptable to your designs the GUidelines and Worksheets .you with four key numbers as a system which saves less the glazing areas given are for indicating the projected energy but fits your other needs. the actual net area of the glass penormanceofthevarious In the following table, several itself. A common rule of thumb designs you are evaluating. different passive solar systems is that the net glass area is 80 • The Worked EDmple: To are presented along with two percent of the rough frame assist in understanding how the numbers which indicate their opening. For example, if a south design strategies outlined in the penormance. The Percent Solar glass area of 100 sf is desired, Guidelines affect the overall Savings is a measure of how the required area of the rough penormance of a house, a much the passive solar system is frame opening would be about worked example is included. reducing the house's need for 125 sf. The example house, constructed purchased energy. For example, of materials and design elements the Percent Solar Savings for the typical of the area, is a one Base Case is 9.1%, because even story, single-family 1500 sf in a non-solar house, the south passive solar design. Various facing windows are contributing design features, such as direct some heat energy. gain spaces, sunspaces, The Yield is the annual net increased levels of inSulation heating energy benefit of adding and thermal mass, are included the passive solar system, to Ulustrate the effects combined measured in Btu saved per year systems have on the per square foot of additional penormance of a house. Also, south glazing. many features are covered to The figures given are for a demonstrate how various 1,500 sf, single-story house with conditions and situations are a slab floor. The Base Case has addressed in the worksheets. A 45 sf of south-facing glazing. description of the design For the purposes of this features, along with the house example, the Suntempered plans, elevations and sections, house has 100 sf of south-facing are included for additional glass, and each passive solar support information. system has 145 sf.
Birmingham, Alabama 6 GUIDELINES PART ONE: INTRODUCTION
Performance Potential of Passive Solar Strategies In Birmingham, Alabama 1,500 sf, Single Story House Yield Percent Btu Saved per Solar Square Foot of Case Savin,. South Glass
Base case 9.1 not applicable (45 sf of south-facing double glass) Suntempered 17.4 53,342 (100 sf of south-facing double glass)
Direct Gain (145 sf of south glass) Double Glass 23.0 49,389 Triple or low-e glass 24.4 57,527 Double glass with R-4 night insulation 1 26.9 68,200 Double glass with R-9 night insulation 1 27.7 71,809 Sunspace (145 sf of south glass) Attached with opaque end walls2 22.7 52,547 Attached with glazed end walls2 22.1 49,844 Semi-enclosed with vertical glazing3 23.5 53,021 Semi-enclosed with 50' sloped glazing3 28.8 75,807
Thermal Storage Wall - Masonry/Concrete (145 sf of south glass) Black surface, double glazing 21.6 47,083 Selective surface, single glazing 27.6 71,527 Selective surface, double glazing 26.8 68,663
Thermal Storage Wall - Water Wall (145 sf of south glass) Selective surface, single glazing 31.3 85,857
1. Night insulation is assumed to cover the south glass each night and removed when sun is available. Experience has shown that many homeowners find this inconvenient and so the potential energy savings are often not achieved. Using Iow-e or other energy-efficient glazing is more reliable.
2. The attached sunspace is assumed to have, in addition to glazed walls, roof glazing at a slope of 30 degrees from the horizontal, or a 7:12 pitch. (See diagram SSB1 in the Worksheets.)
3. The semi-enclosed sunspace has only the south wall exposed to the out-of-doors. The glazing has a slope of 50· from the horizontal, or a 14:12 pitch. The side walls are adjacent to conditioned space in the house. (See diagram SSD1 in the Worksheets.)
Birmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 7
Part Two: Basics of Passive Solar
1. Why Passive Solar? More than a QuestioD of Energy
2. Key Concepts: Energy ConservatioD, SuntemperiDg, Passive Solar
3. Improving Conservation Performance
4. Mechanical Systems
5. South-Facing Glass
6. Thermal Mass
7. Orientation
8. Site Planning for Solar Access
9. Interior Space planning
10. Putting it Together: The House as a System
Birmingham. Alabama 8 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
1. Why Passive Solar? energy-efficiency - but added They just present their houses More than a Question insulation is invisible to the as the state of the art in energy prospective home buyer. A effiCiency and style, and they of Energy sunny, open living area lit by use passive solar as a part of the south-facing windows, on the package Houses today are more energy other hand, may be a key selling The U. S. Department of efficient than ever before. point. Windows in general are Energy and the Solar Energy However, the vast majority of popular with homebuyers, and Research Institute (SERI) new houses still ignore a lot of passive solar can make windows conducted extensive national energy saving opportunities - energy prcxlucers instead of surveys of passive solar homes, opportunities available in the energy liabilities. home owners and potential sunlight falling on the house, in Another example: high buyers. Some key findings: the landscaping, breezes and efficiency heating eqUipment can • passive solar homes work other natural elements of the account for Significant energy - they generally require an site, and opportunities in the savings - but it won't be as average of about 300Al less structure and materials of the much fun on a winter mOrning energy-for heating than house itself, which, with as breakfast in a bright, "conventional" houses, with thoughtful design, could be used attractive sunspace. some houses saving much more. to collect and use free energy. The point is not that a • occupants of passive solar Passive solar (the name builder should choose passive homes are pleased with the distinguishes it from "active" or solar instead of other energy perfonnance of their homes (over mechanical solar technologies) is conserving measures. The 90% "very satisfied"), but they simply a way to take maximum important thing is that passive rank the comfort and pleasant advantage of these solar can add not only energy living environment as just as opportunities. effiCiency, but also very saleable important (in some regions, Home buyers are also amenities - style, comfort, more important) to their increasingly sophisticated about attractive interiors, curb appeal satisfaction, and in their energy issues, although the and resale value. decision to buy the house, as average home buyer is probably In fact, in some local energy considerations. much more familiar with markets, builders report that • passive solar home owners insulation than with passive they don't even make specific and lenders perceive the solar. The "energy crisis" may reference to "passive solar". resale value of passive solar be temporarily over, but very few houses as high. people perceive their own household energy bills as getting Advantages of Passive Solar smaller - quite the opposite. So • Energy performance: Lower energy bills all year-round a house with significantly lower • Attractive living environment: large windows and views, sunny monthly energy costs year-round interiors, open floor plans will have a strong market • Comfort: quiet (no operating noise), solid const~ction, warmer in advantage over a comparable winter, cooler in summer (even dUring a power failure) house down the street, no • Value: high owner satisfaction, high resale value matter what international oil Low Maintenance: durable, reduced operation and repairs prices may be. • But there are many different Investment: independence from future rises in fuel costs, will continue • to save money long after any initial costs have been recovered ways to reduce energy bills, and some are more marketable than Environmental Concerns: clean, renewable energy to combat • growing concerns over global warming, acid rain and others. For instance, adding ozone depletion insulation can markedly improve
Birmlngbam, Alabama PASSIVE SOLAR DESIGN STRATEGIES 9
2. Key Concepts: In the same way. many of Although the concept is the measures that are often simple, in practice the Energy Conservation, considered part of suntempering relationship between the amount Suntempering, or passive solar - such as of glazing and the amount of orienting to take advantage of mass is compUcated by many Passive Solar summer breezes, or landscaping factors. and has been a subject for- natural cooling. or faCing a of conSiderable study and The strategies for enhancing long wall of the house south - experiment. From a comfort and energy performance which are can help a house conseIVe energy standpOint. it would be presented here fall into three energy even if no "solar" features diftlcult to add too much mass. general categories: are planned. Thermal mass will hold wannth • Energy Conservation: The essential elements in a longer in winter and keep insulation levels, control of air passive solar house are south houses cooler in summer. But 1nfiltration, glazing type and facing glass and thermal mass. thennal mass has a cost. and so location and mechanical In the simplest terms. a adding too much mass for just eqUipment. passive solar system collects thermal storage purposes can be • 8untemperiDg: a limited use solar energy through south unnecessarily expensive. of passive solar techniques; facing glass and stores solar The following sections of the modestly increasing south-facing energy in thermal mass - Guidelines discuss the size and window area, usually by materials with a high capacity location of glass and mass, as relocating windows from other for storing heat (e.g .• brick, well as other considerations sides of the house, but without concrete masonry. concrete slab. which are basic to both adding thennal mass. tile. water). The more south suntempered and full passive • Passive Solar: going beyond facing glass is used in the solar houses: improving conservation and suntempering house. the more thermal mass conservation perfonnance; to a complete system of must be provided. or the house mechanical systems; orientation; collection. storage and use of will overheat and the solar site planning for solar access; solar energy: using more south system will not perfonn as interior space planning: and glass. adding significant thermal expected. taking an integrated approach to mass. and taking steps to With too much glass and/or the house as a total system. control and distribute heat insuffiCient mass. solar energy energy throughout the house. can work too well. and the house What is immediately clear is can be uncomfortably hot even that these categOries overlap. on a winter day. For instance. a good energy conservation package is the necessary starting point of all well-designed suntempered and passive solar houses. There's no use collecting solar- energy if it is immediately lost through leaky windows or poorly insulated walls.
Birmingham, Alabama 10 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
3. Improving The thermal resistance of Slab edge Insulation should ce~/roof ..seDibUes.~ be at least two feet deep, Conservation and Doon is affected not only by extending from the surface of the Performance the R-value of the insulation floor. Materials for slab edge itself, but also the resistance of insulation should be selected for The techniques described in this other elements in the underground durabUity. One section relate to Worksheet I: construction assembly - material with a proven track Conservation Performance framing effects, sheathing, record is extruded polystyrene. Level. which IIleasures the interior drywall. and so on. The Exposed insulation should be house's heat loss. The energy Worksheets include tables that protected from physical damage conservation measures that show Equivalent Construction by attaching a protection board. reduce heat loss also tend to R-Values which account for for instance. or by covering the reduce the house's need for air these and other effects. For insulation with a protective conditioning. instance, ventilated crawlspaces surface. The most important and unheated basements Heated basement walls measures for improving the provide a buffering effect which should be fully insulated to at house's basic ability to conserve is accounted for in the least four feet below grade. but the heat generated either by the Worksheet tables. the portion of the wall below that sun or by the house's With attics, framing effects depth only needs to be insulated conventional heating system are are minimized if the insulation to about half the R-value of the in the following areas: covers the ceiling trusses, either upper portion. Insulation can be • Insulation by using blown-in insulation or placed on the outside surface of • AIr inftltration by running an additional layer of the wall, or on the inside surface • Non-solar gIazlng batts in the opposite direction of of the wall, or in the cores of the the ceiling jOists. Ridge and/or masonry units. Insulation eave vents are needed for If the basement walls are Adding insulation to walls, ventilation. insulated on the outside. the floors, ceilings, roof and materials should be durable foundation improves their underground, and exposed thermal resistance (R-value) - insulation should be protected their resistance to heat flowing from damage. In the case of a out of the house. finished basement or walk-out A quality job of installing the basement, placing insulation on insulation can have almost as the interior may be less costly much effect on energy than insulating the exterior performance as the R-value, so foundation. careful construction supervision is important. An inspection just Insu/atlon In an Attic Insulation should extend over the top ceiling before the drywall is hung joists and ventilation should be provided at identifies improvements which the eaves. are easy at that time but will In framed ceiling/roof make a big difference in the assemblies. an insulating energy use of the home for years sheathing over the top decking to come. will1ncrease the R-value.
Birmingham, Alabama PASSIVE SOLAR DESIGN STRATEGIES 11
Air Ill/iltration Sealing the house carefully to Checklist for Minimizing Air Leakage reduce air infiltration - air " Tighten seals around windows and doors, and weatherstripping leakage - is as necessary to around all openings to the outside or to unconditioned rooms; energy conservation as adding " Caulk around all windows and doors before drywall is hung; seal all insulation. Air will flow rapidly penetrations (plumbing, electrical, etc.); through cracks and creviCes in the wall. in the same way water " Insulate behind wall outlets andlor plumbing lines in exterior walls; flows through the drain in a " Caulk under headers and sills; bathtub. so even a small opening can allow heat to " Chink spaces between rough openings and millwork with insulation, or bypaSs the insulation and lead for a better seal, fill with foam; to big energy losses. " Seal larger openings such as ducts into attics or crawlspaces with The tightness of houses is taped polyethylene covered with insulation; generally measured in the " Locate continuous vapor retardants located on the warm side of the number of air changes per hour insulation (building wrap, continuous interior polyethylene, etc.); (ACH). A good. comfortable. energy-efficient house. built " Install dampers and/or glass doors on fireplaces; combined with along the guidelines in the table outside combustion air intake; on this page. will have " Install backdraft dampers on all exhaust fan openings; approximately 0.35 to 0.50 air changes per hour under normal " Caulk and seal the joint between the basement slab (or the slab on winter conditions. grade) and the basement wall; Increasing the tightness of " Remove wood grade stakes from slabs and seal; the house beyond that may improve the energy perfonnance. " Cover and seal sump cracks; but it may also create problems " Close core voids in top of block foundation walls; with indoor air quality. moisture build-up. and inadequately " Control concrete and masonry cracking; vented fireplaces and furnaces. " Use of air tight drywall methods are also acceptable The use of house sealing (see Reference 11); subcontractors to do the tightening and check it with a " Employ approRriate radon mitigation techniques (see blower door can often save the References 111 builder time and problems. especially when tIying to achieve particularly high levels of infiltration control.
Birmingham. Alabama 12 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
Non-Bolar Glazing Double-glazing of all non views or other elements in the South-facing windows are solar glazing is advisable. Low-e house's design dictate east considered solar glazing. The glazing on all non-solar windows windows, shading should be south windows in any house are may be an especially useful done with particular care. contributing some solar heat solution because some low-e West windows may be the energy to the house's heating coatings can insulate in winter most problematic, and there are needs - whether it's a and shield against unwanted few shading systems that wUl be signiftcant, usable amount or heat gain in summer. effective enough to offset the hardly VlTOrth IIleasuring VITill Manufacturers will provide potential for overheating from a depend on design, location and actual R-values for their large west-facing window. Glass other factors which are dealt windows (the thennal with a low shading coefficient with later under the discussions perfonnance of glazing can be may be one effective approach - of suntempertng and passive expressed either as an R-value for example, tinted glass or some solar systems. or its reciprocal, U-value; here types oflow-e glass which North windows in almost all thennal perfonnance values provide some shading while every climate lose significant are given in tenns ofR-value). A alloWing almost clear views. The heat energy and gain very little chart is also provided with the cost of properly shading both useful sunlight in the winter. Worksheets to show east and west windows should East and west windows are likely approximate window R-values be balanced against the benefits. to increase air conditioning for various types. (the As many windows as needs unless heat gain is Equivalent Glazing R-Value possible should be kept operable minimized with careful attention pertains to the entire rough for easy natural ventilation in to shading. frame opening of the window.) summer. (See also Orientation, But most of the reasons North windows should be page 1'6. Recommended Non people want windows have very used with care. Sometimes South Glass Guidelines, page little to do with energy, so the views or the diffuse northern 3L1, and Shading. page 35) best design will probably be a light are desirable, but in good working compromise general north-facing windows between effiCiency and other should not be large. Very large benefits, such as bright living north-facing windows should spaces and views. have high insulation value, or R-value. Since north windows receive relatively little direct sun in summer, they do not present much of a shading problem. So if the chOice were between an average-sized north-facing window and an east or west facing window, north would actually be a better choice, considering both summer and VlTinter perfonnance. East windows catch the moming sun. Not enough to provide Significant energy, but. unfortunately. usually enough to cause potential overheating problems in summer. If the
Birmingham, Alabama PASSIVE SOLAR DESIGN STRATEGIES 13
4. Mechanical • Night Setback. Clock In the National AsSOCiation of Systems thermostats for automatic night Home Builders' Energy-EffiCient setback are usually very effective House Project, all the rooms The passive solar features in the - but in passive solar systems were fed with low, central air house and the mechanical with large amounts of thermal supplies, as opposed to the heating, ventilating and air mass (and thus a large capacity usual placement of registers conditioning systems (HVAC) will for storing energy and releasing under windows at the end of it interact all year round and so during the night), night long runs. This resulted in good the most effective approach will setback of the thennostat may comfort and energy perfonnance. be to design the system as an not save very much energy. The performance of even the integrated whole. HVAC design • Ducts. One area often most beautifully designed is, of course, a complex SUbject, neglected but of key importance passive solar house can easily be but the three areas below are to the house's energy undermined by details like particularly worth noting in performance is the design and uninsulated ducts, or by passive solar houses: location of the ducts. Both the overlooking other basic energy • System Slzlng. Mechanical supply and return ducts should conservation measures. systems are often oversized for be located within insulated the relatively low heating loads areas, or well insulated if they in well-insulated passive solar run in cold areas of the house, houses. Oversized systems will and well sealed at the JOints. cost more in the first place, and The joints where the ducts tum will cycle on and off more often, up into exterior walls or wasting energy. The back-up penetrate the ceiling should be systems in passive solar houses particularly tight and caulked. should be sized to provide 100% of the heating or cooling load on the design day, but no larger. Comparing estimates on system sizes from more than one contractor is probably a good idea.
Birmingham. Alabama 14 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
5. South-Facing Glass The third limit on south When the solar glazing is facing glass is the total of all tUted, its winter effectiveness as South-facing solar glass is a key passive solar systems combined. a solar collector usually component of any passive solar which should not exceed 200/0 of increases. However. tilted system. The system must total floor area. Using more glazing can cause serious include enough solar glazing for south glass than this limit could overheating in the summer if it good performance in winter. but lead to overheating even in is not shaded very carefully. not so much that cooling winter. Ordinary vertical glazing is perforxnance in sununer will be For example, a passive solar easier to shade, less likely to compromised. The amount of system for a 1,500 sf house overheat, less susceptible to solar glazing must also be might combine 150 sf of direct damage and leaking, and so is carefully related to the amount gam glazing with 120 sf of almost always a better year of thermal mass. Suntempered sunspace glazing for a total of round solution. houses require no additional 270 sf of solar glazing. or 18% of thermal mass beyond that the total floor area. well within already in the wallboard. the direct gain limit of 12% and framing and furnishings of a the overall limit of 200/0. For a typical house. Passive solar design like this. thennal mass houses must have additional would be required both in the thermal mass. house and within the sunspace. There are three types of The Natural Cooling limits on the amount of south gUidelines in Part Three include facing glass that can be used < recommendations on the window effectively in a house. The first area that should be operable to is a limit on the amount of allow for natural ventUation. glazing for suntempered houses. This limit (without adding thermal mass) is 7% of the house's total floor area. For direct gam systems in passive solar houses, the maximum amount of south facing glazing is 12% oftota! floor area. regardless of how much additional thennal mass is provided. Further details about the most effective sizing of south glass and thennal mass for direct gam systems are provided in Part Three.
Birmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 15
6. Thermal Mass The thermal storage The design issues related to capabilities of a given material thermal mass depend on the Some heat storage capacity, or depend on the material's passive system type. For thennal mass, is present in all conductivity, specific heat and sunspaces and thermal storage houses, in the framing, gypsum density. Most of the concrete wall systems, the required mass wall and ceiling board, typical and masonry materials typically of the system is included in the furnishings and floor coverings. used in passive solar have deSign itself. For direct gain, the In suntempered houses, this similar specific heats. added mass must be within the modest amount of mass is ConductMty tends to increase rooms receiving the sunlight. sufficient for the modest amount with increasing density. So the The sections on Direct Gain of south-facing glass. But more major factor affecting Systems, Sunspaces and thermal mass is required in perfonnance is density. Thermal Storage Walls contain passive solar houses, and the Generally, the higher the density more tnfonnation on techniques question is not only how much, the beUer. for sizing and locating thermal but what kind and where it mass in those systems. should be located. The thermal mass in a passive solar system is usually a conventional construction material such as brick, cast concrete, concrete masonry, Heat Storage Properties of Materials concrete slabs, or tile, and is Density Heat Capacity usually placed in the floor or Material (lb/ft3) (Btu/in-sf- OF) interior walls. Other materials can also be used for thennal Poured Concrete 120 - 150 2.0 - 2.5 mass, such as "phase change" Clay Masonry materials, which store and Molded Brick 120 - 130 2.0 - 2.2 release heat through a chemical Extruded Brick 125 - 135 2.1 - 2.3 Pavers reaction. Water actually has a 130 - 135 2.2 - 2.3 higher unit thermal storage Concrete Masonry capacity than concrete or Block 80 - 140 1.3 - 2.3 masonry. Water tubes and units Brick 115-140 1.9 - 2.3 Pavers called ''water walls" are 130 - 150 2.2 - 2.5 commercially available (general Gypsum Wallboard 50 0.83 recommendations for these systems are included in the Water 62.4 5.2 section on Thermal Storage Wall systems).
Birmingham, Alabama 16 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
7. Orientation When glazing is oriented In the ideal situation. the more than 15 degrees off true house should be oriented east The ideal orientation for solar south. not only is winter solar west and so have its longest wall glazing is within 5 degrees of performance reduced. but facing south. But as a practical true south. This orientation will summer air conditioning loads matter. if the house's short side provide maximum performance. also sign1ftcantly increase. has good southern exposure it Glazing oriented to within 15 especially as the orientation goes will usually accommodate degrees of true south will west. The wanner the climate. suffiCient glazing for an effective perfonn ahnost as well. and the more east- and west-facing passive solar system. provided orientations up to 30 degrees off glass will tend to cause the heat can be transferred to - although less effective - will overheating problems. In the northern zones of the house. still provide a substantial level of general. southeast orientations solar contribution. present less of a problem than In Birmingham. magnetic southwest. north as indicated on the compass is actually three degrees east of true north. and this should be corrected for when planning for orientation of south glazing.
Blrmlngbam. Alabama PASSIVE SOLAR DESIGN STRATEGIES 17
8. Site Planning for also the figure on page 35 Solar Access showing landscaping for summer shade. The basic obj ectlve of site planning for maximum energy perfonnance is to allow the south side as much unshaded exposure as possible during the winter months. r...... i: ...... ~. As discussed above. a good Sola, Subdivision Layouts solar orientation is possible Solar access may be provided to the rear within a relatively large southern yard, the side yard or the front yard of solar ~ 2 Story Buildings AlloYied homes. arc. so the flexibility exists to achieve a workable balance Ideal Sol., Accea between energy performance and Bui/dings, trees or other obstructions should not be located so as to shade the south wall other important factors such as of solar builcings. At this latitude, A = 9 ft., B the slope of the site. the = 16 ft., and C = 36 ft. individual house plan. the direction of prevailing breezes for Of course, not all lots are large summer cooling, the views, the enough to accommodate this street lay-out, and so on. kind of optimum solar access, so But planning for solar access it's important to carefully assess does place some restrictions shading patterns on smaller lots even on an individual site, and to make the best compromise. presents even more challenges Protecting solar access is when planning a complete easiest in subdivisions with subdivision. Over the years, streets that run within 25 developers and builders of many degrees of east-west. because all different kinds of projects all lots will either face or back up to over the country have come up south. Where the streets run Sol., Subdivision Layout. north- south, creation of east Short east-west cul-de-sacs tied into north with flexible ways to provide south collectors is a good street pattern for adequate solar access. west cul-de-sacs will help ensure solar access. Once again, there is an ideal solar access. situation and then some degree Two excellent references for of flexibility to address practical Ideas about subdivision lay-out concerns. Ideally, the glazing on to protect solar access are the house should be exposed to BuUder's Guide to PasSive Solar sunlight with no obstructions Home Design and Land within an arc of 60 degrees on Development and Site Planning either side of true south, but JOT Solar Access. (See References reasonably good solar access will 15" and I\) still be guaranteed if the glazing is unshaded within an arc of 45 degrees. The figure on this page shows the optimum situation for providing unshaded southern exposure during the winter. See
Birmingham, Alabama 18 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
9. Interior Space Another general pI1nciple is 10. Putting it Planning that an open floor plan will allow Together: The House the collected solar heat to as a System Planning room lay-out by circulate freely through natural convection. consideI1ng how the rooms will Other ideas from effective Many different factors will affect be used in different seasons, and a house's overall penormance, at different times of day, can passive solar houses: • Orienting internal mass and these factors all interact: save energy and increase the mechanical system, the COnllort. In houses with passive walls as north-south partitions insulation, the house's solar features, the lay-out of that can be "charged" on both tightness, the effects of the rooms - and interior zones sides thus making maximum passive solar features, the which may include more than use of the mass. appliances, and, vezy one room - is particularly • Using an east-west partition importantly, the actions of the important. wall for thennal mass, but make people who live in the house. In In general, lMng areas and sure the interior space isn't each of these areas, changes are other high-actMty rooms should divided into a south zone which possible which would improve be located on the south side to may get too warm and a north the house's energy penormance. benefit from the solar heat. The zone which may get too cold. Some energy savings are closets, storage areas, garage • Using thermal storage walls relatively easy to get. Others and other less-used rooms can (see page 30); the walls store can be more expensive and more act as buffers along the north energy all day and slowly release d1ff1cult to achieve, but may side, but entzy-ways should be it at night, and can be a good provide benefits over and above located away from the wind. alternative to ensure privacy and good energy penormance. ClusteI1ng baths, kitchens and to buffer nOise when the south A sensible energy-efficient laundzy-rooms near the water side faces the street; house uses a combination of heater will save the heat that • Collecting the solar energy in one zone of the house and techniques. would be lost from longer water In fact, probably the most lines. transporting it to another by fans or natural convection important thing to remember through an open floor plan. about designing for energy • Providing south-facing penormance in a way that will clerestOries to "charge" north also enhance the comfort and zones. value of the house is to take an integrated approach, keeping in mind the house as a total system. On the the following page is a basic checklist for energy-efficient design. These techniques are dealt with in more detail, including their impact in your location, in Part Interior Space Planning Three. Uving and high activity spaces should be located on the south.
Birmingham, Alabama PASSIVE SOLAR DESIGN STRATEGIES 19
Checklist for Good Design
./ 1. Building orientation: A number of innovative techniques can be used for obtaining good solar access on less-than-ideal sites (see References 15 and 16). No matter what the house's design, and no matter what the site, some options for orientation will be more energy-efficient than others, and even a very simple review of the site will probably help you choose the best option available .
./ 2. Upgraded levelS of Insulation: It is poSSible, of course, to achieve very high energy-efficiency with a "superinsulated" deSign. But in many cases, one advantage of passive solar design is that energy-efficiency can be achieved with more modest increases in insulation. On the other hand, if very high energy performance is a priority - for example, in areas where the cost of fuel is high - the most cost-effective way to achieve it is generally through a combination of high levels of insulation and passive solar features.
" 3. Reduced air Inflhratlon: Air tightness is not only critical to energy performance, but it also makes the house more comfortable. Indoor air quality is an important issue, and too complex for a complete discussion here, but in general, the suntempered and passive solar houses built according to the guidelines provide an alternative approach to achieving improved energy efficiency without requiring air quality controls such as air to air heat exchangers, which would be needed if the house were made extremely airtight.
" 4. Proper window sizing and location: Even if the total amount of glazing is not changed, rearranging the location alone can often lead to significant energy savings at little or no added cost. Some energy-conserving designs minimize window area on all sides of the house - but .it's a fact of human nature that people like windows, and windows can be energy producers if located correctly.
" 5. Selection of glazing: Low-emissivity (low-e) glazing types went from revolutionary to commonplace in a very short time, and they can be highly energy-efficient choices. But the range of glazing possibilities is broader than that, and the choice will have a significant impact on energy performance. Using different types of glazing for windows with different orientations is worth considering for maximum energy performance; for example, using heat-rejecting glazing on west windows, high R-value glazing for north and east windows, and clear double-glazing on solar glazing.
" 6. Proper shading of windows: If windows are not properly shaded in summer - either with shading devices, or by high-performance glazing with a low shading coefficient - the air conditioner will have to work overtime and the energy savings of the winter may be canceled out. Even more important, unwanted solar gain is uncomfortable.
" 7. Interior design for easy air distribution: If the rooms in the house are planned carefully, the flow of heat in the winter will make the passive solar features more effective, and the air movement will also enhance ventilation and comfort during the summer. Often this means the kind of open floor plan which is highly marketable in most areas. Planning the rooms with attention to use patterns and energy needs can save energy in other ways, too - for instance, using less-lived-in areas like storage rooms as buffers on the north side.
" 8. Addhlon of thennal mass: Adding effective thermal mass - for example, tiled or paved concrete slab, masonry walls, brick fireplaces, tile floors, etc. - can greatly improve the comfort in the house, holding heat better in winter and keeping rooms cooler in summer. In a passive solar system, of course, properly sized and located thermal mass is essential.
" 9. Selection and proper sizing of mechanical systems, and selection of energy-efficient appliances: High-performance heating, cooling and hot water systems are extremely energy-efficient, and almost always a good investment. Mechanical equipment should have at least a 0.80 Annual Fuel Utilization Efficiency (AFUE). Well-insulated passive solar homes will have much lower energy loads than conventional homes, and should be sized accordingly. Oversized systems will cost more and reduce the house's performance. For guides to the selection of energy-efficient appliances, see References 13 and 14.
BIrmiDgham, Alabama 20 GUIDELINES PART TWO: BASICS OF PASSIVE SOLAR
Blrmlngham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 21
Part Three: Strategies for Improving E~~~ Performance in Bi gham, Alabama
1. The Example Tables
2. Suntempering
s. Direct GaIn
4. Sunspaces
5. Thermal Storage Wall
6. Combined Systems
7. Natural Cooling Guidelines
Birmingham, Alabama 22 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
1. The Example • Three numbers The R-values indicated in the corresponding to those on the Example tables are. of course. Tables Worksheets: ConselVation. approximate and are intended to Auxillruy Heat. and Cooling show how incremental In the following sections of the Performance (see page 4) improvements can be achieved. Guidelines. the primary passive The Example tables then show All R-values in the Examples solar systems - Suntempertng. how the house design could be and Worksheets are equivalent Direct Gain. Thennal Storage changed to reduce winter R-values for the entire Walls and Sunspaces - are heating energy by 20. 40 and construction assembly. not just described in more detail. 600A>. compared to this Base for the cavity insulation itself. As part of the explanation of Case. and take into account framing each system. an Example table There are. of course. other and buffering effects. is provided. The Examples ways to achieve energy savings Other assumptions are noted present the following information than those shown in the for each Example. However. one about a Base Case house. based Examples. The Examples are more general assumption is on a National Association of designed to show an effective important to note here. When Home Builders study of a typical integration of strategies. and a the Examples were calculated. it construction: useful approach to the design of . was assumed that natural • Insulation levels (ceilings the house as a total system. cooling strategies such as those and walls); Using any of these combinations deSCribed in these Guidelines • Insulation added to the would result in excellent were used. particularly in the perimeter of slab-on-grade peIformance in your area. very high-performance systems. construction. ; However. they are general The greater the percentage • Tightness (measured in air indications only. and using the reduction in heating energy changes per hour. ACH); Worksheets will give you more needs using passive solar • The amount of glass area on information about your specific design. the more shading and each side (measured as a design. natural cooling were assumed. percentage of floor area; the The Example assumes a The Examples show passive actual square footage for a 1.500 1.500 sf house. but the solar strategies. but an sf house is also given as a percentages apply to a house of Insulation Only Example table reference point); any size or configuration. (achieving energy savings only • The "percent solar savings" by increasing insulation levels. (the part of a house's heating without solar features) is energy saved by the solar provided in the Sununruy features): and beginning on page 5J.f • for comparison.
BIrmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 23 2. Suntempering Examples of Heat Energy Savings Suntempered Suntempered and passive solar 1,500 sf Single Story House houses both: • begin with good basic Base energy-conservatlon, Case 20% 40% 60% R-Values • take maximum advantage of Ceiling/Roof 27 25 35 46 the building site through the Walls 15 12 19 26 right orientation for year-round Slab Edge 5 1 6 9 1.8 1.8 1.8 energy savings, and Glass .9 • have increased south-facing Air Changes/Hour 0.75 0.66 0.74 0.52 glass to collect solar energy. Suntempertng is the simplest Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% passive solar system, and refers North 3.0% 4.0% 4.0% 4.0% to modest increases in windows East 3.0% 4.0% 4.0% 4.0% on the south side. South 3.0% 6.7% 6.7% 6.7% No additional thermal mass Solar System Size (square feet) is necessary, only the "free South Glass 45 100 100 100 mass" in the house - the framing, gypsum waIl-board and Percent Solar Savings 28% furnishings. 9% 18% 22% In a "conventional" house, Performance (Btu/yr-sf) about 25% of the windows face Conservation 26,934 24,503 19,428 14,208 south. which amounts to about Auxiliary Heat 24,472 19,928 15,070 10,169 12,373 9,276 7,085 4,944 3% of the house's total floor Cooling area. In a suntempered house, Summary: Insulation values and tightness of the house (as measured in the percentage is increased to a ACH) have been increased. The window area has been slightly maximum of about 7%. decreased on the west, increased Slightly on the east and north, and increased significantly on the south. The energy savings are more modest with this system, but suntempertng is a very low-cost strategy. Of course, even though the necessity for precise sizing of glazing and thermal mass does not apply to suntempertng (as long as the total south-facing glass does not exceed 7% of the total house floor area), all other recommendations about energy efficient design such as the basic energy conservation measures, room lay-out, siting, glazing type and so on are still important for perfonnance and comfort in suntempered homes.
Birmingham, Alabama 24 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
3. Direct Gain Glazing incorporation of significant Double glazing is recommended amounts of heavy thennal mass The most common passive solar for direct gain glazing in is a little more difficult. Thennal system is called direct gain: Birmingham. The Perfonnance mass floor coverings over sunlight through south-facing Potential table on page 6 shows basements. crawlspaces and glazing falls directly into the the relative performance of lower stories would generally be space to be heated. and is stored different types of direct gain limited to thin set tile or other in thennal mass incorporated glazing. You will note from this thin mass floors. into the floor or interior walls. table that yield increases by 16% When more mass is required. between double and triple or the next best option is for low-e glazing. Night insulation interior walls or interior masonry also improves energy fireplaces. When evaluating performance dramatically. In costs. the dual function of mass fact. as the Perfonnance walls should be remembered. Potential table shows. covering They often seIVe as structural the windows at night or on elements or for fire protection as cloudy days with the equivalent well as for thennal storage. of R-4 shades or other material Another option is to switch to will save almost as much energy another passive solar system as with R-9 material. But type such as attached slab-on studies have shown that only grade sunspaces or thennal relatively few homeowners will storage walls built directly on be diligent enough about exterior foundation walls. DlrectGBln operating their night insulation Sunlit thennal mass floors Direct gain is the most common passive solar system in residential applications to achieve those savings. should be relatively dark in Energy-efficient glazing. on the color. to absorb and store energy Sizing Limit other hand. needs no operation. more effectively. However. mass Total direct gain glass area and therefore is a more walls and ceilings should be should not exceed about 12% of convenient and reliable option. light in color to help distribute the house's floor area. Beyond both heat and light more evenly. that. problems with glare or Thermal Mass fading of fabriCS are more likely Thermal mass can be to occur. and it becomes more incorporated easily into slab-on difllcult to provide enough grade type buildings as either thennal mass for year-round floor covering. walls or veneers comfort. over interior walls. If the mass So the total south-facing is placed in the floor. it will be glass area in a direct gain much more effective if sunlight system should be between 7% falls directly on it. (the maximum for suntempered Effective materials for floors houses) and 12%. depending on include painted. colored or vinyl how much thennal mass will be covered concrete. brick (face brick or pavers have even higher used in the design. as discussed below. density than ordinary building brick). quarry tile. and dark colored ceramic tile. For houses built with crawlspaces or basements. the
Birmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 25
Ratio of Glass to Mass. The More south-facing glazing Thickness. For most materials, following procedure can be used than the maximum as the effectiveness of the thermal to detennine the maximum detennined here would tend to mass in the floor or interior wall amount of direct-gain glazing for overheat the room. and to increases proportionally with a given amount of thermal mass. reduce energy performance as thickness up to about 4 inches. If the amount of direct-gain well. After that. the effectiveness glazing to be used is already doesn't increase as Significantly. mown, thenna! mass can be A two-inch mass floor will be added until this procedure about two-thirds as effective in a produces the desired direct gain system as a four-inch proportions: mass floor. But a six-inch mass • Start with a direct gain glass floor will only penorm about area equal to 7% of the house's eight percent better than a four total floor area. As noted above, inch floor. the "free mass" in the house will The following figure shows be able to accommodate this the effectiveness of thermal much solar energy. mass in relation to density and • An additional 1.0 sf of direct thickDess. The vertical axis 1:40 for Floor gain glazing may be added for notn&.1 shows how many square feet of every 5.5 sf of uncovered. sunlit mass area are needed for each M... LOClltion .nd Effect/v."... mass floor. Carpet or area rugs Additional mass must be provided for south added square foot of direct gain. will seriously reduce the facing glass over 7% of the floor area The As you can see, performance ratio ofmass area to additional glass area effectiveness of the mass. The depends on its location within the direct gain increases start leveling off after a space. maximum floor mass that can be few inches of thermal mass. conSidered as "sunlit" may be estimated as about 1.5 times the south window area. • An additional 1.0 square foot of direct gain glazing may be added for every 40 sf of thermal mass in the floor of the room. but not in the sun. • An additional 1.0 square foot of direct gain glazing may be added for each 8.3 sf of thermal mass placed in the wall or O~------T-----~~-----+ o 5 10 15 ceiling of the room. Mass in the Thickness (inches) wall or ceiling does not have to be located directly in the M... Thielen ••• The effectiveness of thermal mass depends sunlight, as long as it is in the on the density of the material and thickness. This graph is for wall or ceiling mass in the same room, with no other walls direct gain space. between the mass and the area where the sunlight is falling. Worksheet m: Thennal Mass/Comfort should be used to make sure the house has adequate thermal mass.
Birmingham, Alabama 26 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
Examples of Heat Energy Savings Passive Solar-Dlrect Gain 1 ,500 sf Single Story House
Base Case 20% 40% 60% R-values Ceiling/Roof 27 25 32 42 Walls 15 12 17 23 Slab Edge 5 1 4 8 Glass .9 1.8 1.8 1.8
Air Changes/Hour 0.75 0.70 0.71 0.60
Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% South 3.0% 7.4% 9.3% 12.0%
Added Thennal Mass Percent of Floor Area 0.0% 2.7% 14.0% 30.0%
Solar System Size (square feet) South Glass 45 111 140 180 Added Thermal Mass 0 40 210 450
Percent Solar Savings 9% 20% 27% 38%
Perfonnance (Btu/yr-sf) Conservation 26,934 25,044 20,689 16,401 Auxiliary Heat 24,472 20,007 15,055 10,137 Cooling 12,373 9,661 8,535 7,690
Summary: Insulation and tightness have been increased. South-facing glazing has been substantially increased. For these examples, added mass area is assumed to be six times the excess south glass area.
BlnDlngham.. Alabama PASSIVE SOLAR DESIGN STRATEGIES 27
4. SUDspaces The sunspace floor is a good location for thennal mass. The The sunspace is a very popular mass floors should be dark in passive solar feature. adding an color. No more than 15-25% of attractive living space as well as the floor slab should be covered energy perfonnance. There are with rugs or plants. The lower many variations on the basic edge of the south-facing theme of the sunspace. and the windows should be no more possibilities for sunspace design than six inches from the floor or are extraordinarily diverse the planter bed to make sure the (References 17 through 29- mass in the floor receives include spectllc design ideas). suffiCient direct sunlight. If the Sun_pace_ The sunspace concept used Sunspaces provide useful passive solar windows sills are higher than in these Guidelines can be used heating and also provide a valuable amenity that. additional mass will have to homes. year-round. will provide most or to be located in the wall. Another good location for all of its own energy needs. and Thermal Mass thermal mass is the common will contribute to the energy A sunspace has extensive south wall (the wall separating the needs of the rest of the house as facing glass. so suffiCient well. sunspace from the rest of the thermal mass is very important. house). Options for the common Sunspaces are referred to as Without it. the sunspace is liable wall are discussed in more detail "isolated gain" passive solar to be uncomfortably hot during is below. systems. because the sunlight the day. and too cold for plants Water in various types of collected in an area which can or people at night. containers is another fonn of be closed off from the rest of the However. the temperature in energy storage often used in house. During the day. the the sunspace can vruy more doors or windows between the sunspaces. than in the house itself. so sunspace and the house can be about three square feet of four opened to circulate collected inch thick thermal mass for each Glazing heat. and then closed at night. square foot of sunspace glazing Clear, double-glazing is and the temperature in the should be adequate. With this recommended for sunspaces. sunspace allowed to drop. Adding the second pane makes a glass-to-mass ratio. on a clear The sunspace should not be large improvement in energy winter day a temperature swing on the same heating system as savings. Triple-glazing or low-e of about 30"F should be the rest of the house. A well coatings. on the other hand. will expected. designed sunspace will probably further improve comfort. but will need no mechanical heating have little effect on energy system. but if necessruy. a small savings. fan or heater may be used to Windows on the east and protect plants on extremely cold west walls should be small (no winter nights. more than l00Al of the total The sunspace should be Just sunspace floor area) but they are as tightly constructed and useful for cross-ventilation. insulated as the rest of the Like tilted or sloped glazing. house. glazed roofs can increase solar gain. but they can also present big overheating problems and become counter-productive. If either glazed roofs or tilted
Birmingham. Alabama 28 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE glazing are used in the Common Wall Some solar energy may be sunspace. special care should be There are a number of options transferred from the sunspace to taken to make sure they can be for the sunspace common wall. the rest of the house by effectively shaded during the In mUd climates. and when the conduction through the common summer and. if necessary. on sunspace is vety tightly wall if it is made of thermal sunny days the rest of the year. constructed. an uninsulated mass. But energy is mainly too. The manufacturers of frame wallis probably adequate. transferred by natural sunspaces and glazing are However. insulating the common convection through openings in developing products with better wall to about R-10 is a good the common wall- doors. ability to control both heat loss idea. especially in cold climates. windows and/ or vents. and heat gain (for example. roof An insulated common wall will • Doors are the most common glazing with low shading help guard against heat loss opening in the common wall. If coeffiCients. shading treatments during prolonged cold. cloudy only doorways are used. the and devices. etc.). periods. or if the thermal storage open area should be at least You'll note that in the in the sunspace is insufficient. 15% of the sunspace south-glass Performance Potential chart on If the common wall is a area. page 6. sunspaces with glazed masonry wall. it can also be • Windows will also provide roofs or sloped glazing perform used for thermal mass. in which light and views. The window very well. This analysis case it should be solid masonry area in the common wall should assumes effective shading in the approximately 4 to 8 inches be no larger than about 40% of summer. If such shading is not thick. Another option is a frame the entire common wall area. If economical or marketable in wall with masonry veneer. only windows are used. the your area. you should conSider Probably the most important operable area should be about using only vertical glazing. and factor in controlling the 25% of the sunspace's total accepting somewhat less energy temperature in the sunspace. south glass area. performance in winter. and thus keeping it as comfortable and efficient as possible. is to make sure the exterior walls are tightly constructed and well-insulated.
BlrmiDgb.am. Alabama PASSIVE SOLAR DESIGN STRATEGIES 29
Summer ventilation The sunspace must be vented to Examples of Heat Energy Savings Passive Solar-Sunspace the outside to avoid overheating 1,500 sf Single Story House in the summer or on warm. days in spring and fall. A properly Base 20% 40% 60% vented and shaded sunspace Case R-Values can function much like a Ceiling/Roof 27 24 28 38 screened-in porch. Walls 15 11 14 21 Operable windows and/or Slab Edge 5 1 2 7 .9 1.8 1.8 1.8 vent openings should be located Glass for effective cross-ventilation. Air Changes/Hour 0.75 0.74 0.67 0.74 and to take advantage of the prevailing summer Wind. Low Glass Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% inlets and high outlets can be North 3.0% 4.0% 4.0% 4.0% used in a "stack effect". since East 3.0% 4.0% 4.0% 4.0% warm. air will rise. These South (windows) 3.0% 3.0% 3.0% 3.0% ventilation areas should be at Sunspace 0.0% 6.8% 10.9% 17.0% least 15% of the total sunspace Solar System Size (square feet) glass areas. South Glass 45 45 45 45 Where natural ventilation is Sunspace Glass 0 102 164 255 insuffiCient. or access to natural Sunspace Thermal Mass 0 306 492 765 breezes is blocked. a small. Percent Solar Savings thermostat-controlled fan set at 9% 24% 34% 47% about 76D F will probably be a Performance (Btu/yr-sf) useful addition. Conservation 26,934 26,402 22,847 19,268 Auxiliary Heat 24,472 19,962 15,006 10,097 Cooling 12,373 10,857 10,703 10,958
Summary: Insulation and tightness (for the 60% case) have been increased. North and east-facing glazing have been increased slightly. The sunspace assumed here is semi-enclosed (surrounded on three sides by conditioned rooms of the house, as in Figure SSC1 of the worksheets), with vertical south glazing. The common wall is a thermal mass wall made of masonry. Sunspace glazing is assumed to be double.
Birmingham. Alabama 30 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
5. Thermal Storage Selective Surfaces Wall A selective surface is a special adheSive foil applied to the The Thennal Storage Wall- exterior side of the mass of also sometimes referred to as a Thermal Storage Walls. Trombe wall or an indirect gain Selective surfaces absorb a large system - is a south-facing percentage of solar radiation but glazed wall. usually built of radiate very little heat back to heavy masonry. but somet1Ines the out-of-doors {low emittance}. using water containers or phase To be effective, selective change materials. The masonry Th"""al Slol'llge Wall . surfaces must be applied A thermal storage wall is an effective paSSIve is separated from the glazing solar system, especially to provide nighttime carefully for lOOOAl adhesion to heating. only by a small air space. the mass surface. Sunlight is absorbed directly In Binningham, Alabama, a A masonry Thennal Storage Wall into the wall instead of into the selective surface will improve should be solid, and there living space. The energy is then Thennal Storage Wall should be no openings or vents released into the living space perfonnance by about 52%. either to the outside or to the over a relatively long period. The living space. Although vents to time lag varies with different Mass Material and the living space were once materials. thiclmesses and other Thickness commonly built into Thennal factors. but typically. energy In general, the effectiveness of Storage Walls, experience has stored In a Thennal Storage Wall the Thermal Storage Wall will demonstrated that they are during the day is released increase as the density of the ineffective. Vents between the during the evening and material increases. Thermal Storage Wall and the nighttime hours. The optimum thickness of house tend to reduce the The outside surface of a the wall depends on the density system's nighttime heating thennal storage wall should be a of the material chosen. The capability, and to increase the very dark color - an following chart indicates the temperature fluctuation in the absorptance greater than 0.92 is recommended thickness of house. Vents to the outside are recommended. Thennal Storage Walls made of similarly ineffective, and do little various materials. The summer heat gain from to reduce summer heat gains. a Thennal Storage Wall is much less - roughly 77% less - than Glazing from a comparable area of direct Double glazing is recommended gain glazing. for Thermal Storage Walls unless a selective surface is used. In this case, single glazing perfonns about the same as double glazing. The space between the glazing and the thennal mass should be one to three inches.
Birmingham, Alabama PASSIVE SOLAR DESIGN STRATEGIES 31
Mass Wall Thickness Examples of Heat Energy Savings (inches) Passive Solar-Thermal Storage Wall 1,500 sf Single Story House Density Thickness Material (Iblcf) (inches) Base Case 20% 40% 60% Concrete 140 8-24 R-Values Concrete Block 130 7-18 Ceiling/Roof 27 22 25 29 Clay Brick 120 7-16 Walls 15 10 12 15 Ltwt. Concrete 110 6-12 Slab Edge 5 0 1 3 Block Glass .9 1.8 1.8 1.8 Adobe 100 6-12 Air Changes/Hour 0.75 0.65 0.66 0.68
Glass Area (percent of total floor area) Water Walls West 3.0% 2.0% 2.0% 2.0% Water provides about twice the North 3.0% 4.0% 4.0% 4.0% heat storage per unit volume as East 3.0% 4.0% 4.0% 4.0% South 3.0% 3.0% 3.0% 3.0% masonry. so a smaller volume of Thermal Storage Wall 0.0% 6.8% 11.1% 17.0% mass can be used. In ''water walls" the water is in light. rigid Solar System Size (square feet) containers. The containers are South Glass 45 45 45 45 Thermal Storage Wall 0 102 166 255 shipped empty and easily installed. Manufacturers can Percent Solar Savings provide information about 9% 27% 39% 54% durability. installation. Perfonnance (Btu/yr-sf) protection against leakage and Conservation 26,934 27,627 25,001 22,119 other characteristics. At least Auxiliary Heat 24,472 19,962 15,036 10,114 30 pounds (3.5 gallons) of water Cooling 12,373 8,867 7,419 6,004 should be provided for each Summary: In the case of a Thermal Storage Wall, south-facing glazing square foot of glazing. This is and thermal mass are incorporated together. The estimates here assume eqUivalent to a water container a 12-inch thick concrete Thermal Storage Wall with a selective surface about six inches thick. having and single glazing. the same area as the glazing.
Birmingham. Alabama 32 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
6. Combined Systems 7. Natural Cooling Fortunately, many of the GuideUnes features that help maintain Although the previous sections comfort and reduce energy needs in winter also work well in have presented separate The term "natural cooling" is discussions of four different used here to describe techniques summer. For instance, systems, it isn't necessary to which help a house stay cool in additional thermal mass choose one and only one system. summer but which require little performs well year-round. In fact, passive solar features Masonry materials are equally or no energy. Natural cooling work well in combination. techniques work to help reduce effective in staying cool and For example, direct gain air-conditioning. not replace it. storing heat. If mass surfaces works very well in conjunction These techniques are useful can be exposed to cool night with a sunspace or thermal not only in passive solar houses. time temperatures - a storage wall. Since thermal but in "conventional" houses as technique referred to as "night storage walls release energy well. The strategies outlined ventilation" - they will help the more slowly than direct gain below - attention to the house stay cooler the next day. systems, they are useful for location. size and shading of A California utility found during supplying heat in the evening glazing. using the opportunities studies of small test buildings and at night, whereas the direct on the site for shading and that on hot summer days the gain system works best during natural ventilation, and using workmen at the facility always the day. Although using a fans - can reduce air . ate lunch in the masonry test sunspace, thermal storage wall conditiOning needs and increase building because it stayed much and direct gain system in the comfort even if the house has no cooler than any of the others. same house may result in passive solar heating features. (See Reference 9) excellent performance, such But shading is particularly The additional insulation combinations do require a large important in passive solar that increases winter south-facing area, and careful houses. because the same performance will also work to design to make sure the systems features that collect sunlight so improve summer performance by are well-integrated with each effectively in winter will go right conserving the conditioned air other and with the house's on collecting it in summer - inside the house. And some mechanical system. resulting in uncomfortably hot low-e windows and other glazing rooms and big air conditioning with high R-value can help bills - unless they are shaded shield against unwanted heat and the house is designed to gain in summer. help cool itself.
Blrmlngbam. Alabama PASSIVE SOLAR DESIGN STRATEGIES 33
The potential of some natural and low-energy cooling Cooling Potential Basecase 12,373 Btu/yr-sf strategies is shown in the following table for Birmingham. Energy lVorksheetIV:CooUng Savings Percent Performance Leveltndicates Strategy (Btu/yr-sf) Savings the total annual cooling load, No Night Ventilation1 and so can give an idea of how without ceiling fans 0 0% the passive solar features with ceiling fans 3,710 30% increase the cooling load and Night Ventilation1 how much reduction is possible without ceiling fans 2,260 18% when natural cooling techniques with ceiling fans 5,460 44% are used. High Mass2 It should be noted that the without ceiling fans 380 3% Cooling Perfonnance numbers with ceiling fans 370 3% presented in the Examples for each passive solar strategy 1 With night ventilation, the house is ventilated at night when temperature and humidity conditions are favorable. assume that the design also includes the recommended 2 A "high mass" building is one with a thermal mass area at least equal natural cooling techniques. This to the house floor area. is especially true of the higher percentage reductions; these assume better heating performance, but also better shading and other natural cooling strategies.
- Birmingham, Alabama 34 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
Glazing and so they may interfere with As mentioned earlier. poorly Added Window Cooling Load deSirable views. It is important placed windows can increase air to note, however. that some Added Annual conditioning loads dramatically. Cooling Load types oflow-e windows block It is generally best in terms of Orientation (Btu/yr-sf) solar tranSmission but also energy performance to carefully allow clear views. These North 44,180 size non-solar glazing as East 82,510 treatments are not indicated in the following table. South 72,840 recommended for south West 90,660 windows. Skylights 169,000 As the table shows, skylights Recommended Non-south Glass Guidelines These values are based on present a high potential for double glass with a shading overheating, and are usually Percent coeffiCient of 0.88. When glazing difllcult to shade properly. But with a different shading of Total skylights are very popular Orientation Floor Area coefficient is used the values may be scaled proportionally. features, and they save East 4% electricity by providing good North 4% natural daylight to the house. West 2% These numbers can be reduced In some parts of the country by shading as deSCribed in the almost every new house has at next section. least one skylight. A good As mentioned earlier. west Using special glazing or working compromise can usually facing windows present window films that block solar be achieved if skylight area is particularly difllcult shading transmission now shading limited, and if careful attention problems. If glazing is added coeffiCient) is an option often is paid to shading, either by above the levels indicated. the used in particularly hot trees or by devices such as roller need for shading will become climates. but the more effective shades or blinds. The even more critical. they are at blocking sunlight. manufacturer can usually give Cooling loads increase as the less clear they are. as a rule. guidance on shading options for window area increases. This a particular skylight design. relationship for Birmingham is shown in the following table for each of the cardinal window orientations. For instance when a square foot of west area is added or subtracted. the annual cooling load increases or decreases by 90.660 Btu/yr-sf.
Birmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 35
Shading Roof Overhangs. Fixed Shading strategies generally fall overhangs are an inexpensive into three categories: feature, and require no landscaping. roof overhangs and operation by the home owner. exterior or Interior shading They must be carefully deSigned, devices. however. Otherwise, an overhang that blocks summer Landscaping. The ideal site for sun may also block sun in the summer shading has deciduous LandllCllping for Summer Shad. spring, when solar heating is Trees and other landscaping features may be desired, and, by the same token. trees to shade the east and west effectively used to shade east and west windows. Even small trees such windows from summer solar gains. an overhang sized for maximum as fruit trees can help block sun solar gain in winter will allow hitting the first story of a house. Other landscaping ideas for solar gain in the fall on hot days. Trees on the south side can summer shade: The following figure may be used present a difficult choice. Even • Trellises on east and west to detenntne the optimum deciduous trees will shadow the covered with vines. overhang Size. solar glazing during the winter • Shrubbery or other plantings In Bimlingham, an ideal and interfere with solar gain. In to shade paved areas. overhang projection for a four fact. trees on the south side can • Use of ground cover to foot high window would be 16 all but eUminate passive solar preVent glare and heat inches and the bottom .of the perfonnance. unless they are absorption. overhang would be 12 inches very close to the house and the • Trees, fences, shrubbery or above the top of the window. low branches can be removed, other plantings to "channel" allowing the winter sun to summer breezes into the house. penetrate under the tree canopy. • Deciduous trees on the east However, in many cases the and west sides of the house, as trees around the house are shown above, to balance solar bigger selling points than the gains in all seasons. energy effiCiency and the builder must make a chOice. If a careful study of the shading patterns is done before construction, it should be possible to accomodate the south-facing glazing while leaving in as many trees as possible (see page 17, Site Planning for Solar Access). South Overhang Sizing In Birmingham, an ideally sized south overhang should allow fUll exposure of the window when the sun has a noon altitude of 37 degrees (angle A) and fully shade the window when the sun has a noon altitude of 74 degrees (angle B).
Birmingham, Alabama 36 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
A combination of carefully sized Ceiling Fans overhangs on the south windows Ceiling fans will probably save Ceiling Fan Sizes and shading devices on the other more energy than any other Minimum Fan windows will probably be an single cooling strategy. Studies Largest Room Diameter effective solution. Adjustable show that air movement can Dimension (inches) overhangs that can be make people feel comfortable at 12 feet or less 36 As seasonally regulated are another higher temperatures. a 12 - 16 feet 48 option. general rule, the thennostat can 16 -17.5 feet 52 be set 4 degrees higher without 17.5 - 18.5 feet 56 Shadlng Devices. External affecting comfort if the air is 18.5 or more feet 2 fans shades are the most effective moving at 100-150 feet per because they stop solar gain minute. This is enough air before the sun hits the building. movement to greatly improve A ceiling fan should have a A wide range of products are comfort but not enough to minimum clearance of ten available. from canvas awnings disturb loose papers. inches between ceiling and fan to solar screens to roll-down to provide adequate ventilation blinds to shutters to vertical in a standard room with eight louvers. They are adjustable foot ceilings. In rooms with and perfonn very well. but their higher ceilings. fans should be limitation is that they require mounted 7.5 to 8.0 feet above the home owner's cooperation. the floor. Usually external screens that can be put up and taken down once a year like stonn windows are more acceptable to home owners than those requiring more frequent operation. Interior shades must be operated. too. and have the further disadvantage of pennitting the sun to enter the house and be trapped between the window and the shading device. But highly reflective interior blinds and curtains are relatively low-cost and easy to operate. Another shading "device" well worth considering is a porch. Especially on the east and west sides. porches add pleasant spaces to houses and are excellent for providing shade to windows. Carports located on the east or west are another option.
Birmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 37
Ventilation The best possible When possible, the house should perfonnance of a whole-house be positioned on the site to take fan results when a timer. a advantage of prevailing winds. thennostat and a "humidistat" During the cooling season, the are used. so that the fan would prevailing wind is from the only operate when there is less northeast. Windows, stairwells, than 600Al relative hUmidity and transoms and other elements a temperature of less than 76'F. should be located for maximum Natural ventilation and cross-ventilation in each room. whole-house fans are effective at The free vent area (unobstructed Ventilation for Summer Cooling removing heat. but not at Natural ventilation is often impaired by openings like open windows) vegetation and topography. Ventilation fans moving air. Ceiling fans. on the do not depend on surroundings to be should be between 6-7.5% of effective. other hand. can often create total floor area. half located on enough of a breeze to maintain the leeward and half on the In cooling climates. a whole comfort at higher temperatures. windward side of the building. house fan is a good idea for and still use less power than Insect screens can reduce the assisting ventilation. especially required by air conditioning. By effective free vent area by as in houses with sites or designs using natural cooling strategies much as 5()OAl. Casement or that make natural ventilation and low-energy fans. the days awning windows have a 90% diftlcult. On the other hand. when air-conditioning is needed open area; double hung windows when the temperature is higher can be reduced substantially. have only 50%. than about 76°F. a whole-house Natural ventilation can help fan will not be very effective. keep houses cool and Research indicates that a comfortable at the beginning and whole-house fan should pull end of the cooling season and approximately 10 ACH. A rule of thus shorten the time when air thumb: for rooms with eight foot conditioning is required. But ceilings. total floor area natural ventilation can seldom multiplied by 1.34 will equal the do the entire cooling job. necessary CFM of the fan. For especially for less than ideal 10 foot ceilings. multiply floor sites with little natural air area by 1.67. movement.
Birmingham. Alabama 38 GUIDELINES PART THREE: STRATEGIES FOR IMPROVING ENERGY PERFORMANCE
BirmlDgham. Alabama Passive Solar Design Strategies WORKSHEETS
Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: . U.S. Department of Energy NOI'E: Please make copies of the blank worksheets and tables before entering numbers so that the worksheets may be used to evaluate several design options.
BirDlingham. Worksheets Alabanta Worksheet Reference Tab_
Table .....ut .... Dt 11a....u Table D .... Cue CoDHrfttloD PeIfol'lDaDce of AaaembUee PerfOl'lD&Dce (Btu/)'l""" R-nl.... (br-r..r/Bta) Base Case 26,934 ~ _wood with 2.2 A1-Ce11ngtlRoof1 ....rstripping ------eTable B-ProJected Area .a.QUStmeDt Jl'acton Allie Insulation R-value • with rigid 5.9 QJnstrucIion R-30 R-38 ~ R-«l _core Dearees off Solar System Type 27.9 35.9 46.9 57.9 I rue 00, TW, SSA SSB, South WW, SSD SSE Framed lnsulationR-vaJue sse Construction R·19 R·22 R-3O R-38 .,.. B-Perlmeter Beat Lo.. 0 1.00 o.n 0.75 ~ for SIabs-OD..Qrade ad 5 1.00 0.76 0.75 2x6 at 16"oc 14.7 15.8 16.3 BuemeDb (Btuth-r-ft) 10 0.98 0.75 0.74 2x6 at24"oc 15.3 16.5 17.1 15 Heated tklheated Insulated 0.97 0.74 0.73 2x8 at 16"oc 17.0 18.9 20.6 21.1 20 0.94 0.72 0.70 2x8 at 24"oc 17.6 19.6 21.6 22.2 SIab&-on- Bas&- Bas&- Crawl- 25 0.91 spaces 0.69 0.68 2x1 0 at 16"oc 18.1 20.1 24.5 25.7 Grede ment& ment& 30 0.S7 0.66 0.65 2x10 at 24"oc 18.4 20.7 25.5 26.8 None 0.8 1.3 1.1 1.1 2x12 at 16"oc 18.8 21.0 25.5 30.1 0.4 0.8 0.7 0.6 2x12 at 24"oc 19.0 21.4 27.3 31.4 R·5 R·7 0.3 0.7 0.6 0.5 R·ll 0.3 0.6 0.5 0.4 R·19 0.2 0.4 0.5 0.3 Table F-SOIar System Saving A2-FI'II1Itd Walls R·30 0.1 0.3 0.4 0.2 FraCtloDl
~kI Insulation R-vaJue Framing R·ll R·13 R·19 R·25 F1-01rect Gain 2x4 at 16"oc 12.0 13.6 _ c-Bea~ Detree Day. Load DGC1 'i)Cc.'"L 00C3 2x4 at 24"oc 12.7 13.9 (I'-day) Collector Double Low-e R·9Ni9ht 2x6 at 16"oc 14.1 15.4 17.7 192 Ratio Glazing Glazing Insulation 2x6 at 24"00 14.3 15.6 18.2 19.8 400 0.07 0.07 0.09 Double .alutlng Degree Days (Base 65°F) 300 0.09 0.10 0.11 Wall Tolal Thickness Onches) 200 0.13 0.14 0.16 Framing 8 10 12 14 BirnW 2,863 150 0.16 0.17 0.20 100 0.22 0.24 0.28 25.0 31.3 37.5 43.8 SO 026 0.2S 0.33 The R·vaIue of insulating sheathing should be added to 60 0.31 0.35 0.41 !he values in this table...... ln9 Degree Day Muhlpller 50 0.36 0.40 0.47 45 0.38 0.43 Solar 0.51 Passive 40 0.41 0.47 0.55 HeaIIti Glazing Area per 35 0.45 per Square Foot 0.51 0.60 A3--k1aulated Floors per a.. 30 0.49 0.56 0.66 e .05 .10 .15 .20 Insulation R-value FClr.1Il 25 0.54 0.62 0.72 Framing R·11 R·19 R-30 R-38 12111.13 1.14 1.15 1.16 1.16 20 0.60 0.69 0.80 1.,.12 1.13 1.14 1.15 1.16 15 0.67 0.77 0.87 2x6s at 16"oc 18.2 23.8 29.9 1.15 1.15 2x6s at 24"oc 18.4 24.5 31.5 1... .12 1.13 1.14 2x8s at 16"oc 18.8 24.9 31.7 36.0 11:&1.11 1.12 1.13 1.14 1.15 1ca1.al 1.11 1.12 1.13 1.14 2x8s at 24"oc 18.9 25.4 33.1 37.9 1.12 1.13 F2-Trombe Walls 2x10at 16"oc 19.3 25.8 33.4 38.1 l1][t.IIB 1.10 1.11 9.1UII6 1.08 1.10 1.11 1.12 TWF3 TWA3 TWJ2 TWI4 2x10 at 24"oc 19.3 26.1 34.4 39.8 1.10 1.12 Load Unvented Vented Unvented Unvented 2x12at 16"oc 19.7 26.5 34.7 39.8 8'![1..04 1.07 1.08 SJE1..03 1.05 1.07 1.09 1.10 CoII~tor ~ Non: ~18C. Night 2x12 at 24"oc 19.6 26.7 35.5 41.2 7.![1.D1 1.03 1.05 1.07 1.09 RatIO selective selectIVe live Insulation These R·values include the buffering effect of a TIU9 1.02 1.04 1.05 1.07 400 0.05 0.08 0.07 0.03 ventilated crawlspace or unconditioned basement BUS 1.00 1.02 1.04 1.06 300 0.07 0.10 0.10 0.06 6.114 0.97 1.00 1.02 1.04 200 0.11 0.14 0.16 0.12 s.a8.89 0.94 0.98 1.00 1.03 0.98 1.01 150 0.14 0.17 0.22 0.17 A4-Wlndowl 5.1.85 0.90 0.95 100 0.20 0.23 0.31 0.25 4.... 80 0.86 0.91 0.95 0.99 80 0.23 0.27 0.37 0.31 Metal 4.8.74 0.81 0.87 0.92 0.96 60 0.29 0.33 0.46 0.39 Standanl Frame wI s.us 0.75 0.82 0.88 0.93 50 0.33 0.37 0.52 0.44 Wood Melal Thermal 3.K1.58 0.68 o.n 0.83 0.88 45 0.35 0.39 0.55 0.47 Frame Frame Break mt.47 0.60 0.69 0.78 0.84 40 0.38 0.42 0.69 0.51 Double SI.32 0.49 0.61 0.71 0.79 35 0.42 0.46 0.63 0.56 114" space 1:8 1.4 1.5 30 0.46 0.50 0.68 0.61 1/2" space 2.1 1.6 1.8 25 0.51 0.55 0.74 0.67 Low-e 3.1 2.2 3.0 20 0.58 0.61 0.80 0.74 Triple 15 0.66 0.70 0.88 0.82 114" space 2.7 1.8 2.1 112" space 3.3 2.2 2.7 These R·values are for !he entire rough frame window opening. When storm sash is added, an additional 1.1 may be added. One half the R·value of moveable insulation may also be added, when appropriate.
Blrmlngham, Alabama General Project Information
Project Name AoorArea Location Date Designer
Worksheet I: Conservation Performance Level
A. Envelope Beat Lou Construction R-value Heat Description Area [Table AJ Loss Ceilingsltoofs + = + = Walls + = + = Insulated Floors + = + = Non-solar Glazing + = + = Doors + = + ---- = Btu/"F-h Total
B. Foundation Perimeter Beat Loss Heat Loss Factor Heat Description Perimeter [Table BJ Loss Siabs-on-Grade X = Heated Basements X = Unheated Basements X = Perimeter Insulated CrawlsQ!ce5 X = Btu/"F-h Total
C. Inftltration Beat Lon X X .018 = Btu/"F-h Builcing Air Changes Volume per Hour
D. Total Beat Loss per Square Foot 24 X + = BtuIDD-sf Total Heat Loss Floor Area (A+B+C)
"i·~ :, E. Conservation Performance Level
X X = Btu/yr-sf Total Heat Heating Degree Heating Degree loss per Days [Table CJ Day Multiplier Square Foot [Table CJ
F. Comparison Conservation Performance (From Previous Calculation or from Table D) Btu/yr-sf - Compare Line E to Line F Passive Solar Design Strateaies Worksheet D: Auxiliary Heat Performance Level
CompueLmeDtoLmeE
PSIC'. Worksheets for Home Builders Worksheet m: Thermal Mass/Comfort
A. Beat capacity of Sheetrock and Interior Furnishings Unit Total Heat Heat Floor Area Capacity Capacity Rooms with Direct Gain X 4.7 = Spaces Connected to Direct Gain Spaces X 4.5 = Btu?F Total
B. Beat Capacity of Mus Surfaces Enclosln, Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area [TC~ci~ Ie I Capacity TrombeWalis X 8.8 = Wate(Walls X 10.4 = EXRQsed Slab in Sun X 13.4 = ~XRQsed Slab Not in Sun X 1.8 = X = X = X = Btu?F Total
C. Beat Capacity of Mus Surfaces Enclosln, Spaces Connected to Direct GaIn Spaces Unit Heat Mass Description Total Heat (include thickiless) Area [TC~ci~ Ie I Capacity e Trombe Walls X 3.8 = Water Walls X 4.2 = X = X = X = BturF Total
D. Total Beat Capacity Btu?F (A+B+C)
E. Total Beat Capacity per Square Foot + BturF-sf Total Heat Conditioned = Capacity Floor Area
F. Clear Winter Day Temperature SwIn, Total Comfort P!9ected Area Factor [worksheet II) [Table I) Direct Gain X = Sunspaces or X = Vented Trombe Walls + = Total Total Heat Capacity
G. Recommended Maximum Temperature SwIn, Compare Line F to Line G
Passive Solar Design Strategies Worksheet IV: Summer CooUng PerformaDce Level
A. Opaque Surfaces
Radiant Barrier Absor~ Heat Gain Heatless FaclDr lance Factor Desaiption (Worksheet I) [Table J] [Table I<] [Table L) Load Ceiliogslroofs X X X = X X X = X X X = Wans X na X = X na X = Doors X na X = kBtulyr Total
B. Non-solar Gluing Rout Frame Net Area Shade Factor Heat Gain Description ea Factor [Table M] Factor [Table L) Load North Glass X 0.80 X X = East Glass X 0.80 X X = West Glass X 0.80 X X = Skvllghts X 0.80 X X = kBtulyr Total
C. Solar Glazing Solar System Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table MJ Factor [Table L) Load Direct Gain X 0.80 X X = Stora~Walis X 0.80 X X = Suns~ce X 0.80 X X = X 0.80 X X = kBtulyr Total
D. Internal Gain +( X ) kBtulyr Constant Variable Number of = Component Component Bedrooms [Table N] [Table N]
E. Cooling Load per Square lI'oot 1,000 X + Btulyr-sf (A+B+C+D) Floor Area =
11'. A£Uustment for Thermal Mass and Ventilation Btulyr-sf [Table 0]
G. CooUng Performance Level Btulyr-sf (E -F)
H. Comparison CooUng Performance (From Previous CelaJlation or from Table P) Btulyr-sf
Compare Line G to Line H
PSIC'. Workabeet. for Home Builders Passive Solar Design Strategies
F3-WllerW.... Table B-VDlt Beat Capacities Table L-Beat GalD Factors (Btu/F-sf) Load WWKJ WWB4 WWC2 Ceilinglroofs 51.1 Collector No Night Niht SelediYe Walls Inc! Doors 32.6 Ratio NIMtion Ins tion Surface Not1l Glass 44.2 H1 ...... Surfeces EncIoIIng DI*t Gain East Glass 82.5 e 400 0.08 0.04 0.05 8pICH West Glass 90.7 ~ 0.10 0.08 0.09 Skylighls 169.0 200 0.14 0.15 0.15 Thickness Qnches) Direct Gain Glazing 72.8 150 0.18 0.21 0.21 Material 2 3 4 6 8 12 Trombe Walls and 16.9 100 0.25 0.31 0.31 03) 0.37 Poured Cone. 1.8 4.3 6.7 8.8 11.3 11.5 10.3 Water Walls 80 0.37 Conc.Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 Sunspaces 60 0.36 0.46 0.46 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 9.0 SSA1 44.5 50 0.41 0.52 0.51 2.1 4.8 7.1 8.5 8.6 8.0 7.6 SSB1 44.5 45 0.44 0.56 0.55 ~oneBui Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 SSC1 16.9 40 0.47 0.60 0.59 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 SSD1 44.5 35 0.50 0.65 0.63 SSE1 44.5 30 0.55 0.70 0.68 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 25 0.60 0.75 0.74 Water 5.2 10.4 15.6 20.8 31.2 41.6 62.4 20 0.67 0.82 0.81 15 0.75 0.89 0.88 H2~oorns with no Direct Solar Gain Table M-Sha~ Factors Thickness (inches) Projection F4-Sunspaces Material 2 3 4 6 8 12 Factor South East North West load Poured Conc. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 0.00 1.00 1.00 1.00 1.00 Collector Sunspace Type Conc. Masonry 1.6 2.9 3.5 3.6 3.6 3.4 3.2 0.20 0.87 0.94 0.91 0.94 Ratio SSA1 SSB1 SSC1 SSD1 SSE1 Face Brick 1.8 3.1 3.6 3.7 3.5 3.4 3.2 0.40 0.79 0.83 0.82 0.83 F~Stone 1.9 3.1 3.4 3.4 3.2 3.1 3.0 400 0.13 0.11 0.07 0.14 0.11 Bui dar Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 0.60 0.70 0.75 0.73 0.76 ~ 0.16 0.13 0.09 0.80 0.65 0.67 0.69 0.68 0.17 0.14 Adobe 1.2 2.4 2.8 2.8 2.6 2.4 2.4 200 0.20 0.16 0.13 0.22 0.18 1.1 1.00 0.60 0.59 0.62 0.60 150 0.23 0.20 0.16 0.26 0.22 Hardwood 0.5 1.1 1.3 1.2 1.1 1.0 1.20 0.56 0.51 0.55 0.52 100 0.29 0.25 0.22 0.34 0.29 80 0.33 0.29 0.26 0.39 0.34 60 0.39 0.34 0.32 0.46 0.40 50 0.43 0.38 0.36 0.50 0.45 45 0.46 0.40 0.39 0.53 0.47 Table I-Comfort Factors (Btu/dl Table N-Intemal Gain Factors 40 0.48 0.43 0.42 0.56 0.50 Direct Gain 870 Constant Component 2,510 kBtulyr 35 0.52 0.46 0.45 0.60 0.54 Sunspaces and 290 Variable Component 1,050 kBtulyr-BR 30 0.56 0.50 0.49 0.64 0.58 Vented Trombe Walls 25 0.60 0.54 0.55 0.69 0.63 20 0.66 0.60 0.61 0.75 0.69 15 0.74 0.68 0.69 0.82 o.n e Table O-Thermal Man and Table J-Radlant Barrier Factors Ventilation Adjustment (Btu/yr-dl Radiant Barrier 0.75 TOlal Heat Night Night No Night No Night No Radiant Barrier 1.00 Capacity Vent wI Vent wINo Vent wI Vent wINo per Sf' Ceil. Fan Ceil. Fan Ceil. Fan Ceil. Fan 0.0 5,670 2,060 3,920 -200 1.0 6,910 3,600 5,160 1,340 2.0 7,560 4,360 5,810 2,100 Table K-60lar Absorptances 3.0 7,900 4,740 6,150 2,490 Color Absorptance 4.0 8,080 4,940 6,330 2,680 5.0 8,170 5,030 6,420 2,770 Gloss White 0.25 6.0 8,220 5,080 6,470 2,820 Semi1lioss White 0.30 7.0 8,240 5,100 6,490 2,840 I.,ight Green 0.47 8.0 8,260 5,110 6,510 2,860 Ketly Green 0.51 9.0 8,260 5,120 6,510 2,860 Medium Blue 0.51 10.0 8,270 5,120 6,520 2,870 Medium Yellow 0.57 Medium Orange 0.58 Total heat ~ty per square foot is calculated on Medium Green 0.59 Worksheet II~ Step E. l.ight Bull Brick 0.60 Bare Concrete 0.65 Red Brick 0.70 Medium Red 0.80 Medium Brown 0.84 Table P-Baae Case CoollDg Dark Blue-Grey 0.88 Performance (Btu/af-yr) Dark Brown 0.88 Base Case 1~3n
Table G-Bue Cue Auxlliuy Beat Performance (Btu/yr-tdJ Base Case 24,472
Birmingham, Alabama Worksheet instructions GeDeraJ Should the eaUmated conservation reduced by about 60 percent to account The Worksheets provide a calculaUon performance level be greater than for throw rugs and furnishings. pt"OCedure to estimate the performance desired, the designer should consider All a rule-of-thumb. exposed slab area bel of passive solar building destgns. It additional building insulation or should be considered to be In the sun is recommended that the results be reductng non-south glass area. only when It is located directly behind • compared to Worksheet calculations for south glazing. The maximum slab area the builder's typical house. Performance Wwksheet D .:'mrfu • .,. Beat that is assumed to be In the sun should levels for the NAHB base case used In PerfOl"lDUlCe LeYei not exceed 1.5 times the adjacent south the guidelines are also provided for ThIs Is an estimate of the amount of heat glass area. comparison. that must be provided each year from In Step F. the projected area of solar A separate worksheet is provided for the auxiliary heating system. It glazfng calculated on Worksheet II is the four separate performance levels and accounts for savtngs due to solar energy. used to calculate the comfort assocfated base cases. In Step A .the user may enter the performance level. The projected area of The worksheets are supported by a rough frame area of solar glazing, since it water walls and unvented Trombe walls number of data tables. The tables are is generally easier to measure the rough is excluded In this step. given a letter designation and are frame area than it is the net g1az1ng area. A high temperature swing indicates referenced next to each worksheet entry, The worksheet includes a net area factor inadequate thermal mass or too much when applicable. of 0.80 to account for window frames direct gain solar glazing. If the comfort The floor area used In the and mullions. If the designer enters the performance level is greater than desired calculations should not Include net glass area, then the net area factor Is (l3"F ra:ommended), additional thermal sunspaces. garages or other 1.00. mass should be added to the building or unconditioned spaces. The projected area of the solar direct gain glazing should be reduced. systems may be calculated using the Worksheet I-CoDHrYatiOD adjustment factors in Table E or by Worksheet lV--8ummer CoollDg Performance !.eYe. making a scaled elevation drawing of the PeifGI'IIIIIDce LeYei This is an estimate of the amount of heat building fac1ng exactly south and ThIs ts an estimate of the annual cooling energy needed by the building each year measuring the gIaz1ng area from the load of the building-the heat that needs from both the solar system and the scaled drawing. to be removed from the building by an auxiliary heating system. The projected area per square foot is air conditioner In order to maintain For Step A. it is necessary to measure calculated as the last part of Step A. comfort during the summer. the net area of surfaces that enclose This is used to determine the heating In Step A. only the envelope surfaces conditioned space. For walls. the net degree days adjustment used on that are exposed to sunlight are to be surface area is the gross wall area less Worksheet I, Step E. included. For instance. floors over the window and door area. The load collector ratio is calculated crawlspaces and walls or doors adjacent Rough frame dimensions are in Step B. ThIs is used to determine the to garages are excluded. generally used to measure window area. solar savings fractions In Step C. Steps B and C of the worksheet The R-values in Table A4 are for the The solar systems used In Step C account for solar gains. They use the rough frame window area. should be Identical to those used In Step rough frame area since this is easier to Heat loss from passive solar systems A. The first and last columns of Step A measure. The worksheets Include a net • is excluded. The surface area of direct are simply carried down. area factor of 0.80 to account for window gain glazing. Trombe walls. water walls The solar savings fraction is frames and mullions. If the net window and the walls that separate sunspaces determined separately for each type of area ts used. the net area factor is 1.00. from the house are Ignored. passive solar system by looking up Table M gtves the shade factor for Step A Includes consideration of values in Tables FI through F4. The windows with overhangs based on a insulated floors over crawlspaces. sunspace system types are shown projection factor. The projection factor Is unheated basements or garages. beneath Table F4. the ratio between the horizontal R-values are provided In Table A3 that If the awdliaJy heat performance level projection of the overhang from the account for the buffering effect of these calculated in Step D is larger than surface of window and the distance from unconditioned spaces. When insulation desired, the designer should consider the bottom of the window to the bottom is not installed In the floor assembly. but increasing the size of the solar systems of the overhang. When windows have rather around the perimeter of a or adding additional solar systems. I.e. sunscreens, tints or films, the shade crawlspace or unheated basement. Step thermal storage walls. factors in Table M should not be used. B should be used. Instead, a shading coefficient should be The perimeter method of Step B is Wwksheet DI-ComfOl"t detennfned from manufacturers' used for slabs-on-grade. the below-grade Performance LeYel literature. portion of heated basements. unheated ThIs is the temperature swing expected basements (when the floor is not on a clear winter day with the awdliary insulated). and perimeter insulated heating system not operating. crawlspaces (when the floor is not ThIs worksheet requires that two sub insulated). Heated basement walls that areas be defined within the building: are above grade should be considered in those areas that receive direct solar Step A gains and those areas that are connected Slab edge perimeter. unheated to rooms that receive direct solar gains. basements or perimeter insulated Rooms that are separated from direct crawlspaces adjacent to sunspaces gain spaces by more than one door should not be Included. should not be included In either The conservation performance level is category. calculated as the product of the heat loss Thermal mass elements located In per degree day per square foot (Step DJ unconditioned spaces such as sunspaces and the heatfng degree days. adjusted for are not included. the heat loss and solar glazing per An exposed slab is one finished with square foot. The adjustment is taken vinyl tile. ceramic tile or other highly If the cooling performance level is from Table C. based on data calculated conductive materials. Carpeted slabs greater than desired, the designer should • on Worksheet I. Step D and Worksheet H, should not be considered exposed. The consider reducing non-south glass, Step A exposed slab area should be further providing additional shading or increasing thermal mass.
PSIC'. Worksheets for Home Builders Passive Solar Design Strategies EXAMPLE
Passive Solar Industries Council National Renewable Energy Laboratory Charles Eley Associates With Support From: U.S. Department ofEnerg,y ______39
BirDlingham The Worked Alab8.Dla ExaDlple 40 WORKED EXAMPLE
The Worked Example The house has a semt The house is equipped with a enclosed sunspace with vertical ceiling fan to help reduce the Description of glaztng. The sunspace floor has air-conditioning load. North Ezample BuUcllng a four-inch thick slab-on-grade windows have an overhang with A 1.504 square foot passive with quany tile set in a mortar a projection factor of 0.30. East solar. single-family home is used bed. The sunspace is separated and west windows are small and to illustrate how to fill in the from the conditioned portion of have no effective overhang worksheets. See sketches for the house by sliding glass doors because of the gable roof. South the bulldIng layout. A variety of and a masonry fireplace wall. windows. including the design features have been Sunspace ventilation is provided sunspacewindows.havean incorporated into the house to to the outside by awning overhang with a projection factor help illustrate how to handle windows located at the top and of 0.20. different situations in the bottom of the south wall. Take-offs from the house are worksheets. South facing windows given in the worksheets. Refer The building selected has provide direct gain solar heating to the circled values in the good insulation as described on to the dining area. kitchen and worksheet tables to locate where Worksheet I. master bedroom. The south the various values which show The east portion of the house glazing in the kitchen and dining up in the worksheets come from. is slab on grade. The great room area provides heat to an exposed Performance is found to be and master bedroom are slab-on-grade ftntshed with satisfactory on all four constructed over a crawlspace. ceramic tile to provide direct worksheets. gain heat storage. The house faces 10 degrees to the east of true south.
r
~l Garage
4040 '/.1l~'-;;;;,;;;;;;;;;:;;:::::;? .OJ ~ Bedroom
Great Room I~~,. ;,.. N' ~~ ..).:., Master Bedroom
8088 14'
o 2 4 8 12 Floor Plan ---- PASSIVE SOLAR DESIGN STRATEGIES 41
- South Elevation
I
North Elevation
Section
Blrmln&ham. Alabama 42 WORKED EXAMPLE
..:';.
Birmingham. Alabama 43
NOTE: These worksheets are completed for the example house described on the previous pages. Also the reference tables are marked up showing how the numbers are selected.
Worksheets
Blrmlngbam, A1aJ»ama 44 General Project Information
Project Name Floor Area Location Date Designer
Worksheet I: Conservation Performance Level
A. Envelope Heat Lou Construction R-value Heat Description Area [Table A) Loss Ceilings/roofs "2.-1' !!l A"f1~~ l~8~ + l~'t = 1# ~"'L1... \~ C~"\.4£O~"L CE.'\A""-S ~u + Z8.~ = Jl Walls "i.- \~ l' '2- 4) S IolU., ''''AI i g~ + ,:].:::1 = ~, 'l..l~ A:t ~"I!.!!UI':; l~ + !I:l.' = S Insulated Floors + = + = Non-solar Glazing :21f1"'-C. ~-4U~ \.naI~i·' I{,:!~ fMa. ~~ + ~·S = %.!i + = Doors 11"1£1~ ~I!:!" !oI~~ fMIh c..d. QD + ". If = -r + = lL.t::t Btu/oF-h Total
B. Foundation Perimeter Heat Loss Heat Loss Factor Heat Description Perimeter [Table B) Loss Slabs-on-Grade lli~ X ~.AoiG = ~6 Heated Basements X = Unheated Basements X = Perimeter Insulated CrawlsQgC9s X = --r~ Btu/oF-h Total
C. InfIltration Heat Loss \u-t092 X o.l/fJ X .018 = \ \ "L Btu/OF-h Building Air Changes Volume per Hour
D. Total Heat Lou per Square Foot 24 X "l'J, + \'504 = ~.>19 Btu/DO-sf Total Heat Loss Floor Area (A+B+C)
E. Conservation Performance Level
~.-S1& X U'"1 X l.O~ = \51 't-' Btu/yr-sf Total Heat Heating Degree Heating Degree Loss per Days [Table C) Day Multiplier Square Foot [Table C)
F. Comparison Conservation Performance (From Previous Calculation or from Table OJ z..' 41'1'-\ Btu/yr-sf
Compare Line E to Line 11'
BlrmiDgham. Alabama 45 Worksheet U: AuD1iary Heat Performance Level
A. Projected Area of Pa88lve Solar Glazing
Solar System Rout!.rame Net Area Adjustment P~ected Reference Code Factor Factor [Table E) rea "D'~\ 8.. X 0.80 X &.~B = ~ ~~G--~ :z..eS X 0.80 X ().~S = ~':1 X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = "%.$\': 'L:J"Z- sf Total Area Totel Projected Area ~J"'Z. + \S"~ IJ. l~ Total Floor = Total Projected Projected Area Area per Area Square Foot
B. Load Collector Ratio 24 X .,,, + t..",z.. "l~ Total Total = Heat Loss Projected [Worksheet I) Area
C. Solar SaviDgs Fraction System Solar Savings Solar System Projected Fraction Reference Code Area [Table F) "'0&,\ 6~ X 11.~ = "'J \. 05 ~S"=: \ t,:S X ~.~~ = ~:t·15 X = X = X = X = X = to£.t.~ + '2.-'1"2- = "."t~ Total Total Solar Projected Savings Area Fraction
D. Amdllary Heat Performance Level
[1 - 0·'-6 ] X '~14t' s.~,g Btu/yr-sf Solar Conservation = Savings Performance Fraction Level [Worksheet I, Step E)
'Z..'"i'i:J"Z- Btu/yr-sf
Compare Une D to Line E
BlrmiDgbam. Alabama 46 Worksheet m: Thermal Mass/Comfort
A. Heat Capacity of Sheetrock and Interior Furnishings Unit Total Heat Heat AoorArea Capacity Capacity Rooms with Direct Gain L4,fr'i X 4.7 = '2..\6 , Spaces Connected to Direct Gain Spaces \';,.'1. X 4.5 = LfLll 'Lt~ 2..... Btu/OF Total
B. Heat Capacity of IIau Surfaces Enclosing Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area ITC~ci~ Ie ) Capacity TrombeWalis X 8.8 = Water Walls X 10.4 = Exoosed Slab in Sun X 13.4 = \JSC Exposed Slab Not in Sun X 1.8 = 2~i X = X = X = 1.'!.1 Btu/OF Total
C. Heat Capacity of IIau Surfaces Enclosing Spaces Connected to Direct Gain Spaces Unit Heat Mass Description Total Heat (include thickness) Area ITC~ci~ Ie ) Capacity TrombeWalis X 3.8 = Water Walls X 4.2 = {A&.£ ~&1~ ~ .. HI X '1.1 = Li \ \ X = X = ~ll Btu/OF Total
D. Total Heat Capacity Btu/OF (A+B+C)B"'~"
E. Total Heat Capacity per Square Foot ~'ttto + \~O~ = ~." Btu/OF-sf Total Heat Conditioned Capacity Floor Area
F. Clear Winter Day Temperature SwiIlg Total Comfort p~ected Area Factor o!i(sheet II) [Table I) Direct Gain ~ X 8JO = ,"030 Suns paces or X L~D = '-\]1.."" Vented Trombe Walls '" ~O'"J Qd + 6'i54t = \'1..·6 OF Total Total Heat Capacity
G. Recommended Maximum Temperature Swing Compare Line F to Line G
Blrmlngbam, Alabama 47 Worksheet IV: Summer Cooling Performance Level
A. Opaque Surfaces Radiant Barrier Absorp- Heat Gain Heat Loss Factor tance Factor Description [Worksheet I) [TableJ) [Table K) [Table L) Load Ceilings/roofs -:]0 X \.00 X ~.~J X <1.1 = ::1 'l..~ ,-, \..00 X X It. .~:::t X ~ •. I = 40t X X X = Walls .::, X na o.JO X 32...~ = ,'%..'g X na X = Doors ~ X na D.~G> X :l%...' = :z..~ kBtu/yr 'L~'Total
B. Non-solar Glazing Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M) Factor [Table L] Load North Glass ,",0 X 0.80 X Q. SJ X ~!:I:z.. = \'2..7l East Glass ~ X 0.80 X t.OD X 8i.·~ = l~' West Glass , X 0.80 X t. DO X !D. i = '-4.'K' Sk~lights X 0.80 X X = 7.D''Z- kBtu/yr Total
C. Solar Glazing Solar System Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M) Factor [Table L) Load Direct Gain &B X 0.80 X I). 8.8. X ,"1.. fl = Lf.'" tD Storage Walls X 0.80 X X = Sunse!!C8 "LDS X 0.80 X 0·8B X lE-IS = 1.~~ X 0.80 X X = 6~a(; kBtu/yr Total
D. Internal Gain UtO +( t.,-S-o X :r ) ~~~o kBtutyr Constant Variable Number of = Component Component Bedrooms [Table N) [Table N)
E. Cooling Load per Square Foot 1.000 X ''''I~l + \1"0'-( = \ 1'1~S Btu/yr-sf (A+B+C+D) Floor Area
F. AdJustment for Thermal Mass and Ventilation ,~~~ Btu/yr-sf [Table 0) tJo ~ll"'T v£,.rr , ....'t •• '" ~/l.£l""'....,~ f4.J G. Cooling Performance Level L\~"'> Btulyr-sf (E -F)
H. Comparison Cooling Performance (From Previous Calculation or from Table P) 12.11:1 Btu/yr-sf
Compare Une G to Une H
Blnnlngham. Alabama 48
Table A-EqulYaieDt Tbermal Table ~oDtiDued •• Table D-Baae C ..e CODservatloD Perfol'llUlDce of AssembUe. Perf01'lD&Dce (Btu/yr-st) R-valUe8 (br-F1f/Btu) Base Case 26,934 AS-Doo/'l Solid wood with 2.2 A1-Ct11lngtlRoofs Weatherslripping Table E-ProJected Area Attic Insulalion R-value Metal with rigid @ AtijustmeDt Factors Conslruction R-30 R-38 R-49 R-60 foam core Degreasoff Solar Syslem Type 27.9 @ 46.9 57.9 True 00, TW, SSA SSB, WW, SSD SSE Framed In . R-value Soulh sse Construction R-19 R-30 R-38 Table B-Perimeter Beat Lo.. o 1.00 0.77 0.75 Facton for Slabs-oD-Grade aDd 5 0.76 0.75 2x6 all6"oc 14.7 BasemeDts (Bta/h-F-ft) 10 0.75 0.74 2x6aI24"oc 15.3 15 I> 0.74 0.73 2x8aI16"oc 17.0 21.1 Healed Unhealed Insulaled 20 0.94 0.72 0.70 2x8 al 24"oc 17.6 22.2 Perimeler SIabs-on- Base- Base- Crawl 25 0.91 0.69 0.68 2xl 0 all6"oc 18.1 25.7 Insulalion Grade ments ments spaces 30 0.87 0.66 0.65 2xl 0 al 24"oc 18.4 26.S None 1.3 1.1 1.1 2x12 at 16"oc 18.8 30.1 R-5 0.8 0.7 0.6 2x12 at 24"oc 19.0 31.4 R-7 t 0.7 0.6 0.5 R-ll 0.3 0.6 0.5 0.4 R-19 0.2 0.4 0.5 0.3 Table F-801ar S,..tem SaviDg A2-framed Walls R-30 0.1 0.3 0.4 0.2 FractlODB
~~Ie Insulation R-value Framing R-ll R-13 R-19 R-25 F1-Dlrect Gain 2x4 all6"oc 12.0 13.6 Table C-Bea~ Deane Da,.. Load DGCl lu.-z- 00C3 2x4 al 24"oc 12.7 13.9 ~ - (F-day) Collector Double ow-e R-9 Nighl 2x6a116"Oc 14.1 15.4 7. 19.2 Ratio Glazing Glazing Insulallon 2x6aI24"oc 14.3 15.6 . 19.8 400 0.07 0.07 0.09 Double Ct-Htallng Deg .... Days (~F) 300 0.09 0.10 0.11 Wall Total Thickness (inches) 200 0.13 0.14 0.16 Framing 8 10 12 14 Birmingham 2,863 150 0.16 0.17 0.20 100 0.22 0.24 0.28 25.0 31.3 37.5 43.8 80 0.26 0.28 0.33 The R-value of insulating sheathing should be added 10 60 0.31 0.35 0.41 the values in Ihis table. C2-Htallng Deg .... Day Multiplier 50 0.36 0.40 0.47 45 0.38 0.43 0.51 Passive Solar 40 0.47 0.55 Heal Loss Glazing Area per 35 0.51 0.60 A3-lnsullted Floo/'l perSquara per Square FOOl 0.66 .20 30 ~ 0.56 Insulalion R-value Fool .00 .05 .10 .15 25 0.54 0.62 0.72 Framing R-l1 R-19 R-30 R-38 12.00 1.13 1.14 1.15 1.16 1.16 20 0.60 0.69 0.80 11.50 1.12 1.13 1.14 1.15 1.16 15 0.67 0.77 0.87 2x6s all6"oc 18.2 23.8 29.9 11.00 1.12 1.13 1.14 1.15 1.15 2x6s a124"oc 18.4 24.5 31.5 10.50 1.11 1.12 1.13 1.14 1.15 2x8s all6"oc 18.8 24.9 31.7 36.0 10.00 1.09 1.11 1.12 1.13 1.14 F2-Trombe Walls 2x8s a124"oc 18.9 25.4 33.1 37.9 9.50 1.08 1.10 1.11 1.12 1.13 2xl0 all6"oc 19.3 25.8 33.4 38.1 9.00 1.06 1.08 1.10 1.11 1.12 TWF3 TWA3 TWJ2 TWI4 2xl0 a124"oc 19.3 26.1 34.4 39.8 8.50 1.04 1.07 1.08 1.10 1.12 Load Unvenled Venled Unvenled Unvented 2x12 a116"oc 19.7 26.5 34.7 39.S 8.00 1.03 1.05 1.07 1.09 1.10 Collector Non- Non- Selec- Night 2x12 a124"oc 19.6 26.7 35.5 41.2 7.50 1.01 1.03 1.05 1.07 1.09 Ralio selective selective tive Insulation These R-values include the buffering effect of a 7.00 0.99 1.02 1.04 1.05 1.07 400 0.05 0.08 0.07 0.03 ventilated crawlspace or unconditioned basement 6.50 0.96 1.00 1.02 1.04 1.06 300 0.07 0.10 0.10 0.06 6.00 0.94 0.97 1.00 1.04 200 0.11 0.14 0.16 0.12 ~'" 5.50 0.89 0.94 0.98 1.03 150 0.14 0.17 0.22 0.17 4. -5.00 0.85 0.90 0.95 1.01 A4-Wlndows ii 100 0.20 0.23 0.31 0.25 4.50 0.80 0.86 0.91 0.95 0.99 80 0.23 0.27 0.37 0.31 Metal 4.00 0.74 0.81 0.87 0.92 0.96 60 0.29 0.33 0.46 0.39 Standard Frame wi 3.50 0.66 0.75 0.82 0.88 0.93 50 0.33 0.37 0.52 0.44 Wood Metal Thermal 3.00 0.58 0.68 0.71 0.83 0.88 45 0.35 0.39 0.55 0.47 Frame Frame Break 2.50 0.47 0.60 0.69 0.78 0.84 40 0.38 0.42 0.59 0.51 2.00 0.32 0.49 0.61 0.71 0.79 Double 35 0.42 0.46 0.63 0.56 114" space 1.4 1.5 30 0.46 0.50 0.68 0.61 112" space Cfr 1.6 1.8 25 0.51 0.55 0.74 0.67 Low-e 3.1 2.2 3.0 20 0.58 0.61 0.80 0.74 Triple 15 0.66 0.70 0.88 0.82 114" space 2.7 1.8 2.1 112" space 3.3 2.2 2.7 These R-values are for the entire rough frame window opening. When storm sash is added, an addilionall.l may be added. One half the R-value of moveable insulation may also be added, when appropriale.
BlrmlDgham. Alabama 49
F3-Water Walle Table B-UDit Reat Capacities Table ~Heat Gain Facto.. (Btu/ll'-sf) Load WWA'3 WWB4 WWC2 Ceiling/roofs 51.1 Collector No Night Ni ht Selective Walls and Doors 32.6 Ratio InsulaUon Insufation Surface North Glass 44.2 H1-Maa Sulfaces Enclosing Direct Gain East Glass 82.5 400 0.08 0.04 0.05 Spacee West Glass 300 0.10 0.08 0.09 Skyligh1S 200 0.14 0.15 0.15 Thickness (inches) Direct Gain Glazing 150 0.18 0.21 0.21 Material 2 3 4 6 8 12 Trombe Walls and 100 0.25 0.31 0.31 Poured Cone. 1.8 4.3 6.7 8.8 11.3 11.5 10.3 Water Walls 80 0.30 0.37 0.37 Cone. Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 Sunspaces 60 0.36 0.46 0.46 Face Brick 2.0 4.7 7.1 9.0 10.4 9.9 9.0 SSA1 44.5 50 0.41 0.52 0.51 FI~Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 SSBI 45 0.44 0.56 0.55 Buider Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 sse1
Table G-Bue Cue AudUary Beat Performance (Btu/yr-sf) Base Case 24,472
BlrmlDgbam. Alabama 50 WORKED EXAMPLE
BlrmlDgbam, Alabama PASSIVE SOLAR DESIGN STRATEGIES 51
Paulve So.... : design and construction Suntemperinl: a modest form of a direct techniques which help a building make gain passive solar system; suntempered use of solar energy by non-mechanical houses Increase south-facing glass to means, as opposed to active solar about 7 percent of a total floor area, but techniques which use equipment such add no thermal mass beyond the "free" as roof-top collectors. mass already in a typical house - gypsum board, framing, conventional Glossary PbueoCballlfe Materials: materials furnishings and floor coverings. such as salts or waxes which store and release energy by changing "phase"; most T~puaaueSwUc: a measure of the A.wdIlary ReatiDg System: a term for store energy when they tum liqUid at a number of degrees the temperature In a the system (gas, electric, oil, etc.) which certain temperature and release energy space will vary during the course of a provides the non-solar portion of the when they tum solid at a certain sunny winter day without the furnace house's heating energy needs, referred to temperature, but some remain solid but operating; an indicator of the amount of as the "auxilary heat." undergo chemical changes which store thermal mass In the passive solar and release energy. Phase change system. British Thermal Unit (Btu): a unit used materials can be used as thermal mass to measure heat. One Btu is about equal but few products are commercially Thermallllaaa: material that stores to the heat released from burning one available at this time.. energy, although mass will also retain kitchen match. coolness. The thermal storage capacity Purcbued EDerlY: although the terms of a material is a measure of the Coaamvation: In addition to energy are often used interchangably, a house's material's ability to absorb and store conservation In the general sense, the "purchased energy" is generally greater heat. Thermal mass In passive solar term is used to refer to the non-solar, than its "auxilary heat" because heating buildings is usually dense material such energy-saving measures In a house systems are seldom 100% effiCient, and as brick or concrete masonry, but can which are primarily Involved with more energy is purchased than is also be tile, water, phase change improving the building envelope to guard actually delivered to the house. materials, etc. agaInst heat loss -- the insulation, the air inflltration reduction measures, and R-Value: a unit that measures the Thermal Storage WaUl a passive solar so forth. resistance to heat flow through a given system also sometimes called Trombe material. The higher the R-value, the Wall or indirect gain system; a south Direct Gain: a passive solar system In better insulating capability the material facing glazed wall, usually made of which the sunlight falls directly into the has. The R-value is the reciprocal of the masonry but can also be made of space where it is stored and used. U-value. (see below) containers of water.
GIulDg: often used Interchangeably with Radiant Burler: reflective material used Trombe WaD: a thermal storage wall, window or glass, the term actually refers In hot climates to block radiant heat, referred to by the name of its Inventor, to specifically just to the clear material particularly in a house's roof. Dr. Felix Trombe. which admits sunlight, and so can also be plastic. Double and triple glazing Sbadlq Coefllclent: a measure of how U-Value: a unit representing the heat refer to two or three panes. much solar heat will be transmitted by a loss per square foot of surface area per glazing material, as compared to a single degree OF of temperature difference (see Indirect Gain: a passive solar system in pane of clear uncoated glass, which has R-value above). which the sUnlight falls onto thermal a shading coefficient (SC) of 1. For mass which is positioned between the example, clear double-pane glass might glazing and the space to be heated, i.e. a have an SC in the range of .88. Thermal Storage Wall or Trombe Wall. Reflective glass might have SC's of .03- .06. In general, lower shading Low-Emlaslvlty: the term refers to a coefficients are desirable when heat gain surface's ability to absorb and re-radiate is a problem. heat. A material with a 10wemissMty absorbs and re-radiates relatively small SUDSpace: passive solar system amounts of heat. Low-emissMty or "low sometimes also referred to as an isolated e" glass sandwiches a thin layer of gain system. where sunlight is collected metallic film or coating between two and stored in a space separate from the panes of glass. The low-e glass blocks living space, and must be transferred radiant heat, so it will tend to keep heat there either by natural convection or by energy inside the house during the fans. winter, and keep heat energy outside the house during the summer.
BlrmlDgbam. Alabama 52 APPENDIX
References e. Glazings: The Design Considerations Insulation Aren't As Clear As Glass f. Ideas for Passive Solar Remodeling 10. NAHB Insulation Manual, National g. Passive Homes in the Marketplace Association of Home Builders, National General (Class C Studies) Research Center. Available from NAHB h. Daylighting in Commercial Bookstore, 15th and M Streets N.W., 1. A Sunbuilder's Primer, Solar Energy BuildingS Washington, D.C. 20005. (202) 822- Research Institute. i. Human Comfort and Passive Solar 0200. Design 2. Passive: It's a Natural, Solar Energy j. Passive Design for Commercial 11. Uschkoff. James K. The Airtight Research Institute. Buildings House: Using the Airtight DrywaU k. Passive Solar. Principles and Approach, Iowa State University 3. The Passive Solar Construction Products Research Foundation. Available for Handbook. Steven Winter 1. Increasing Design Flexibility $14.95; Attn: Sarah Terrones, EES AsSOCiates/Northeast Solar Energy m. Utilities and Passive: Predicting the Building, Iowa State University, Ames, Center/National Concrete Masoruy Pay-off IA. 50011 Association/Portland Cement AsSOCiation/Brick Institute of America. 12. Spears. John. Radon Reduction in Available for $29.95 plus $3.00 New Construction. Interim Guide, handling, from Steven Winter Associates, National Association of Home Builders, Attn: Publications, 6100 Empire State Environmental Protection Agency OPA Building. New York, N.Y. 10001 87-009. ,August 1987. Available from the EPA or the NAHB Bookstore, 15th 4. Suntemperlng in the Northeast, Steven and M Streets N.W., Washington, D.C. Winter Associates. Available from them 20005. (202) 822-0200. at the address above for $9.50.
5. Passive Solar Design HCUldbook. AppUances Volume I, II, m. Available from National 13. Saving Energy and Money Home Technical Information Service, U.S. Dept. with of Commerce, 5285 Port Royal Road, Appliances, Environmental Science Department. Massachusetts Audobon Springfield, Va, 22161. $32.00 each for I and n, $12.00 for Ill. Society/American Council for an Energy Efficient Economy. Available for $2.00 6. Balcomb, J.D., et al. Passive Solar apiece from ACEE, 1001 Connecticut Ave. N.W., Suite 535, Washington D.C. HeatIng Analysts. This volume supercedes and expands Volume III of 20036 the Passive Solar Design Handbook (Ref. 14. The Most Energy E.fftcfent Appliances. 5). Available from ASHRAE, 1988 Edition, ACEEE, $2.00 apiece at Publications. 1791 Tull1e Circle NE. address above. Atlanta, Ga, 30329, $30.00 for ASHRAE members. $60.00 for non-members.
7. LIving With the SWl (for consumers) and Building With the SWl (for builders). PPG Industries.
8. The Passive Solar lriformatton Guide, PSIC.
9. Passive Solar Trends. Technical briefs fromPSIC. a Infiltration in Passive Solar Construction b. The State of the Art in Passive Solar Construction c. Passive Solar in Factory-Built Housing d. Radiant Barriers: Top Performers in Hot Cl1mates
BlrmiDgbam, Alabama PASSIVE SOLAR DESIGN STRATEGIES 53
Site Plannlng SUDspaces More Information
15. Builder's Gut.de to Passive Solar 17. Jones, Robert W. and Robert D. CoaaervatioD and Reaewable Energy Home Design and Land Development, McFarland. The Sunspace Primer. A Inquiries and Referral Service National Fenestration Council. Available Gut.defor Passive Solar Heating, available (CAREIRS) 1-800-523-2929, Renewable for $12.00 from NFC, 3310 Hamson, for $32.50 from Van Nostrand Reinhold, Energy Information, Box 8900, Silver White Lakes Professional Building, 115 5th Avenue, New York, N.Y. 10003 Spring, Md. 20907 Topeka, KS. 66611 18. Greenhousesfor Living, from Steven National Auoolation of Home Builders 16. Site Planningfor Solar Access, U.S. Winter Associates, Attn: Publications, Attention: Technical Services Department of Housing and Urban 6100 Empire State Building, New York, 15th & M Streets N.W. Development/American Planning N.Y. 10001, $6.95. Washington, D.C. 20005 Association. Available for $6.50 from Superintendent of Documents, U.S. 19. Concept W, from Andersen National Concrete Maaolll')'" Government Printing Office, Washington Corporation, Bayport, MN. 55003, $6.95. Maoclatlon D.C. 20402 Attention: Energy Engineer 20. Passive Solar Greenhouse Design and 2302 Horse Pen Road Construction, Ohio Department of Herndon, Va. 22070 Energy/John Spears, 8821 Silver Spring, Md., 20910. BrIck laatitute of America Attention: Energy Engineer 11490·Commerce Park Drive Suite 300 Reston, Va. 22091
Solar Energy Retlearch Institute Attention: Solar Buildings 1617 Cole Boulevard Golden, Co. 80401
Paul" Solar Induatries CouncU 1090 Vermont Avenue, Suite 1200 Washington, DC 20005
Birmingham. Alabama 54 SUMMARY FOR BIRMINGHAM, ALABAMA Example Tables Examples of Heat Energy Savings Passive Solar-Direct Gain Examples of Heat Energy Savings 1,500 sf Single Story House Added Insulation Base 1,500 sf Single Story House Case 20% 40% 60% R-values Base Ceiling/Roof 27 25 32 42 Case 20% 40% 60% Walls 15 12 17 23 R-values Slab Edge 5 1 4 8 Ceiling/Roof 27 28 39 51 Glass .9 1.8 1.8 1.8 Walls 15 14 22 29 Slab Edge 5 2 8 11 Air Changes/Hour 0.75 0.70 0.71 0.60 Glass .9 1.8 1.8 1.8 Glass Area (percent of total floor area) Air ChangeslHour 0.75 0.67 0.70 0.46 West 3.0% 2.0% 2.0% 2.0% North 3.00/0 4.0% 4.0% 4.0% Glass Area (percent of total floor area) East 3.0% 4.0% 4.0% 4.0% West 3.0% 2.0% 2.00/0 2.00/0 South 3.0% 7.4% 9.3% 12.0% North 3.00/0 4.00/0 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% Added Thermal Ma.. South 3.0% 3.00/0 3.00/0 3.00/0 Percent of Floor Area 0.00/0 2.7% 14.0% 30.0%
Percent Solar Savings Solar System Size (square feet) 9% 100/0 13% 16% South Glass 45 111 140 180 Added Thermal Mass 0 40 210 450 Performance (Btulyr-sf) Conservation 26,934 22,302 17,353 12,244 Percent Solar Savings Auxiliary Heat 24,472 19,978 15,081 10,178 9% 20% 27% 38% Cooling 12,373 7,421 5,423 3,384 Performance (Btulyr-sf) Conservation 26,934 25,044 20,689 16,401 Auxiliary Heat 24,472 20,007 15,055 10,137 Cooling 12,373 9,661 8,535 7,690
Examples of Heat E":?y Savings Summary: Insulation and tightness have been increased. South- SUntempe facing glazing has been substantially increased. For these 1,500 sf Single Story House examples, added mass area is assumed to be six times the added south glass area. Base Case 20% 400/0 60% R-Values Ceiling/Roof 27 25 35 46 Walls 15 12 19 26 Slab Edge 5 1 6 9 Glass .9 1.8 1.8 1.8
Air ChangeslHour 0.75 0.66 0.74 0.52
Glus Area (percent of total floor area) West 3.0% 2.0% 2.00/0 2.00/0 North 3.00/0 4.00/0 4.0% 4.00/0 East 3.0% 4.00/0 4.0% 4.0% South 3.0% 6.7% 6.7% 6.7%
Solar System Size (square feet) South Glass 45 100 100 100
Percent Solar Savings 9% 18% 22% 28%
Performance (Btulyr-sf) Conservation 26,934 24,503 19,428 14,208 Auxiliary Heat 24,472 19,928 15,070 10,169 Cooling 12,373 9,276 7,085 4,944
Summary: Insulation values and tightness of the house (as measured in ACH) have been increased. The window area has been slightly decreased on the west, increased slightly on the east and north, and increased significantly on the south. PASSIVE SOLAR DESIGN STRA TEGIES 55
Examples of Heat Energy Savings Examples of Heat Ener~y Savings Passive Solar-Sunspace Passive Solar-Thermal torage Wall 1,500 sf Single Story House 1,500 sf Single Story House
Base Base Case 20% 40% 60% Case 20% 40% 60% R·Value. R·Value. Ceiling/Roof 27 24 28 38 Ceiling/Roof 27 22 25 29 Walls 15 11 14 21 Walls 15 10 12 15 Slab Edge 5 1 2 7 Slab Edge 5 0 1 3 Glass .9 1.8 1.8 1.8 Glass .9 1.8 1.8 1.8
Air ChangealHour 0.75 0.74 0.67 0.74 Air ChangealHour 0.75 0.65 0.66 0.68
Gla•• Area (percent of total floor area) Gla•• Area (percent of total floor area) West 3.0% 2.0% 2.0% 2.0% West 3.0% 2.0% 2.0% 2.0% North 3.0% 4.0% 4.0% 4.0% North 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% East 3.0% 4.0% 4.0% 4.0% South (windows) 3.0% 3.0% 3.0% 3.0% South 3.0% 3.0% 3.0% 3.0% Sunspace 0.0% 6.8% 10.9% 17.0% Thermal Storage Wall 0.0% 6.8% 11.1% 17.0%
Solar Sy.tem Size (square feet) Solar System Size (square feet) South Glass 45 45 45 45 South Glass 45 45 45 45 Sun space Glass 0 102 164 255 Thermal Storage Wall 0 102 166 255 Sunspace Thermal Mass 0 306 492 765 Pwcant Solar Savings Pwcant Solar Savings 9% 27"/0 390/0 54% 9% 24% 34% 47% Performance (Btu/yr-sf) Performance (Btu/yr-sf) Conservation 26,934 27,627 25,001 22,119 Conservation 26,934 26,402 22,847 19,268 Auxiliary Heat 24,472 19,962 15,036 10,114 Auxiliary Heat 24,472 19,962 15,006 10,097 Cooling 12,373 8,867 7,419 6,004 Cooling 12,373 10,857 10,703 10,958 Summary: In the case of a Thermal Storage Wall, south-facing Summary: Insulation and tightness (for the 60% case) have been glazing and thermal mass are incorporated together. The estimates increased. North and east-facing glazing have been increased here assume a 12-inch thick concrete Thermal Storage Wall with a slightly. The sunspace assumed here is semi-enclosed selective surface and single glazing. (surrounded on three sides by conditioned rooms of the house, as in Figure SSCl of the worksheets), with vertical south glazing. The common wall is a thermal mass wall made of masonry. Sunspace glazing is assumed to be double. Cooling Potential Basecase 12,373 Btu/yr-sf
Energy Savings Percent Strategy (Btulyr-sf) Savings
No Night Ventilation 1 without ceiling fans 0 0% with ceiling fans 3,710 30
Night Ventilation 1 without ceiling fans 2,260 18 with ceiling fans 5,460 44
High Mass2 without ceiling fans 380 3 with ceiling fans 370 3
With night ventilation, the house is ventilated at night when temperature and humidity conditions are favorable.
2 A ·high mass· building is one with a thermal mass area at least equal to the house floor area.
Birmingham, Alabama 56 APPENDIX
Technical Basis for Los Alamos National Laboratory with Annual Auxiliary Heat funding from the U.S. Department of (Worksheet II) the BuDder Energy Solar Buildings Program. See the Guidelines references for more information. The tables of passive solar savings fractions are calculated using the solar Annual Heat Loss load ratio (SLR) method (references 1 and (Worksheet IJ 2). Monthly solar savings fraction (SS1'1 How the Builder values are determined using correlation fits to the results of hourly computer Guidelines Were The heat-loss calculation is based on a simulation calculations for a variety of straightforward summation of the Produced climates. These 12 values are converted traditional elements that make up the into an annual value and entered into building heat-loss coefficient (excluding The text of the Builder Guidelines book worksheet Tables FI-F4. The SLR the solar components). The worksheet is generated by merging two computer method gives answers that agree within procedure estimates the annual heat loss IDes. The first is a word-processor IDe about 5% of the hourly computer by multiplying the heat-loss coefficient conta1n1ng the text; it does not change simulations and within 11 % of the by annual degree days (times 24 to from location to location. The second measured passive solar perfonnance of convert from days to hours). Degree days contains numbers and text and is 55 bUildings monitored under the Solar for each month were determined using location dependent. This second me is Buildings Program. The SSF estimates an appropriate base temperature that produced by running a computer account properly for both solar gains accounts for an assumed thermostat program that calculates perfonnance and heat losses through the solar setting of 70 degrees, an assumed numbers based on long-term monthly aperture and, thus, correct for omitting internal heat generation of 36 Btu/day weather and solar data compiled by the the solar components from the per sq ft of floor area, and the total National Oceanic and Atmospheric calculation of annual heat loss. Administration for a particular location. building loss coefficient. This forms the The merge operation slots the numbers basis of the table of heating degree day and text in the second me into their multipUers. The result of the worksheet Temperature SWing correct locations in the first IDe. This is is an estimate of the annual heat (Worksheet Ill} then laser printed to produce the required to maintain comfort, excluding camera-ready manuscript. both positive and negative effects The temperature swing estimate on resulting from the solar components. In worksheet III is based on the diurnal this estimate, no solar heating credit is More than a Decade of heat capacity (dhc) method (reference 3). given to east, west, and north windows, The method is an analytic procedure in Experience because it is assumed that these will be which the total heat stored in the protected by vegetation or other shading building during one day is estimated by The concentrated effort of research, in accordance with the Builder Guideline summing the effective heat storage design, construction, mOnitoring, and recommendations. This is a conservative potential of the all the various materials evaluation of actual buildings that assumption because there will always be in the building for a 24-hour periodic started at the First Passive Solar some solar gain through these windows. cycle of solar input. Rooms with direct Conference in Albuquerque in 1976 has gain are assumed to have radiative continued up to the present. It is coupling of the solar heat to the mass. estimated that more than 200,000 Rooms connected to rooms with direct passive solar homes have been built in gain are assumed to have convective the United States during this time. This coupling, which is rather less effective, wealth of experience has been reviewed espec1ally for massive elements. The dhc by SERI, the Technical Committee of of the sheetrock, framing, and furniture PSIC, and by the Standing Committee on is approximated as 4.5 or 4.7 BtuFF per Energy of the National Association of sq ft of floor area. Worksheet Tables HI Home Builders and is distilled into these and H2 Ust the increased value of Guidelines. diurnal heat capacity for various conventional materials that are often Analysis Procedures used to provide extra heat storage, assuming these materials replace The analysis procedures used sheetrock. throughout the Guidelines were developed using simple, well-establtshed methods for estimating the perfonnance of passive solar heating and natural cooling strategies. These procedures (described below) were developed at the PASSIVE SOLAR DESIGN STRATEGIES 57
The only numbers in worksheet III underestimates very large cooling loads or minus 20%. the result could be that are location dependent are the in poorly designed buildings. adjusted. based on a mtio of cooling comfort factors. taken from Table I. The The adjustment factors for degree days. However. this adjustment is direct-gain comfort factor is 61% of the ventilation properly account for not done automatically within the solar gain transmitted through vertical. maintaining comfort in hot and humid worksheet. south-facing double glazing on a clear climates. Ventilation is restricted to January day. The driving effect of times when the outside dew-point sunspaces and vented Trombe walls ts tempemture is less than 62 OF. This Getting Data assumed to result in one-third this restriction avoids ventilation when high value. based on data from monitored humidity might cause discomfort. Heating and cooling degree-day data can be obtained from the National Climatic buildings. The origin of the 61% factor ts Center. Asheville. NC. Refer to described in the references. Notfor Sizing Equipment Climatogmphy of the United States No. 81 which lists monthly normals for the Annual Auxiliary Cooling All heating and cooling values given in period 1961-1980 on a state-by-state (Worksheet IV) the Builder Guidelines Tables and basts. More than 2400 locations are numbers calculated using the listed in this data base. The purpose of including the summer worksheets are for annual heat delivered cooling estimates in the Builder or removed by the mechanical heating or Guidelines ts to (1) determine if design cooling system. You cannot directly use elements added to promote passive solar these numbers for sizing the capacity of heating wfll cause excessive summer this equipment. The methods developed cooling loads and (2) provide a rough by the American Society of Heating. estimate of the effectiveness of solar Refrigerating. and AIr Conditioning shading and natural cooling strategies. Engineers for sizing equipment are well The analysts method ts based on a established and are recommended. The modified monthly degree-day procedure purpose of the guidance provided in in which the day ts dMded into day and these booklets ts to min1mfze the night periods (reference 4). All estimates operating time and resources consumed are derived from correlations based on by this eqUipment. hourly computer simulations. Solar. conduction. and internal gains are Using the Worksheets in estimated for each half-day period in each month. Delay factors are used to Nearby Locations account for heat canyover from day to The applicability of worksheets I and II night and night to day. The results are can be extended somewhat by using the estimates of annual sensible cooling base-65 OF degree-day value for a site delivered by the air conditioner and do which is close to the location for which not include latent loads. the worksheet tables were genemted. We Because the the original Los Alamos recommend limiting such applications to monthly procedure ts too complex to be sites where the annual heating degree implemented in a worksheet. a simplified days are within plus or minus 10% of the procedure is adopted on worksheet IV. parent location and where it is Heat Gain Factors arid Internal Gain reasonable to assume that the solar Factors in Tables L and N are the radiation ts about the same as in the calculated annual incremental cooling parent location. The procedure is simple: loads resulting from a one-unit Use the measured base-65 OF degree-day incremental change in the respective value in worksheet I. line F. instead of heat input parameter (that is. a one-unit the degree-day value for the parent change in UA, glazing area, or number of location. bedrooms). The combined heat load Worksheet III depends only slightly resulting from a1linputs is summed and on location. The only variables are the then adjusted for thermal mass and Comfort Factors in Table I. which only ventilation. This correction includes a change with latitude. Thus. this constant required to match the worksheet can be used anywhere within calculated cooling load of the base-case 4 degrees of latitude of the parent building. This linearized procedure gives location. accurate estimates for cooling loads that The cooling estimate obtained from are less than about 150% of the base worksheet IV ts specific to the location. case building; however. it Within the same vicinity and within plus
Blrmlagham. Alabama 58 APPENDIX References
1. J. Douglas Balcomb. Robert W. Jones. Robert D. McFarland. and William O. Wray• •~anding the SIR Method". Passive Solar Journal. Vol. 1. No.2. 1982. pp. 67-90. Available from the American Solar Energy Society. 2400 Central Ave. Unit B-1. Boulder. CO 80301.
2. J. Douglas Balcomb. Robert W. Jones. Robert D. McFarland. and William O. Wray. Paul"., Solar B_tlq AIlalJsR. American Society of Heating. Refrigerating. and Air-Conditioning Engineers. 1984. Available from ASHRAE. 1719 Tullie Circle. NE. Atlanta, GA30329.
3. J. Douglas Balcomb and William O. Wray. Paul"., Solar Beatlq ADaIpis. Supp1emeat ODe. Thena.allllau deets and Addltloaal SLR Correlatlon_. American Society of Heating. Refrigerating. and Air Conditioning Engineers. 1987. See ASHRAE address above.
4. Robert D. McFarland and Gloria Lazarus. Monthly AazlIluy CooUna z.tlmatlon for RHldentlal BuUdlq•. LA-11394-MS. Los Alamos National Laboratoty. Los Alamos. NM 87545. 1989.
5. J. Douglas Balcomb and Alexander B. Lekov. AJgorltluu for Builder GuldeUn_. SERI/TP-254-3492. Solar Energy Research Institute. Golden CO. Also contained in the Proceedings of the 14th Passive Solar Conference. Denver. June 19-23. 1989. See ASES address above.
Birmingham. Alabama PASSIVE SOLAR DESIGN STRATEGIES 59
Note: This is a generic example to explain how to fill out the worksheets. For an example specific to this book, refer to the worked example on the prior pages. The actual house design used for both examples is the same, but specific numerical values will be different.
Anytown , USA
Anytown, USA 60 INTRODUCTION Introduction A separate worksheet is The estimates from provided for each of four Worksheets I and II are based on Purpose separate performance levels a heating thermostat setting of perfo~ance level and 70°F. The .estimates from The purpose of the Any Town, associated target. These are Worksheet IV are based on a USA section is to explain how to deSCribed below: cooling thermostat setting of use the passive solar Worksheet I: Conservation 78°F with no ceiling fans and worksheets in the Passive Solar Performance Level: the 82°F with ceiling fans. Design Strategies: Guidelines for estimated heat energy needed by The worksheets are Home BUilding. Separate the building each year from both supported by a number of data Worksheets booklets are the solar and auxiliary heating tables. The data tables are given available for specific locations systems. The units are a letter deSignation and are throughout the continental Btu/yr-sf. referenced when applicable next USA. Each booklet contains Worksheet II: Auxiliary Heat to each worksheet entry. detailed technical data for a Performance Level: the A description and drawings specific location. Although the estimated heat that must be of the example building are example presented in this provided each year by the provided below, followed by booklet is for a moderate mid auxiliary heating system. This completed worksheets. Data Atlantic climate, the procedure worksheet accounts for the solar tables have also been included is presented in a general savings. The units are when appropriate. manner and is intended to be . Btu/yr-sf. Each step of the worksheets used for all locations. Worksheet III: Thermal is then explained in detail. Mass / Comfort: the temperature General Description swing expected on aclear winter day with the auxiliary heating of Worksheets system not operating. The units \ are OF. The Worksheets booklet for each location provides an easy-to-use Worksheet N: Summer Cooling calculation procedure, allowing Performance Level: the the designer to estimate the estimated annual cooling load of performance level of a particular the building. The units are building design and compare it Btu/yr-sf. against a base-case performance level or against the performance of the builder's more conventional house.
Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 61
Description of The building has an South facing windows attached sunspace. The provide direct gain solar heating Example Building ( sunspace floor has a four-inch to the dining area. kitchen and ) thick slab-on-grade with quarry master bedroom. The south A 1.504 square foot passive tile set in a mortar bed. The glazing in the kitchen and solar. single-family home with sunspace is separated from the dining area provides heat to an an 8.3 ft. average ceiling height conditioned portion of the house exposed slab-on-grade. is used to illustrate how to use by sliding glass doors and a The east portion of the the worksheets. A floor plan. masonry fireplace wall. Awning house is slab-on-grade building elevations. building windows located at the top and construction. The great room sections and details are shown bottom of the south wall provide and master bedroom suite are below. outside ventilation for the raised floor construction. The sunspace. slab-on-grade floor in the kitchen and dining area is finished with ceramic tile so that the floor may function as thermal mass. The exterior doors are metal with a foam core center.
~r--~2~O~' --.....;*~i~ __ ..!:2=2-'--~r· ...... ·.... ·...... g4.'...... :...... \
Garage
4040
Bedroom
Great Room
Master Bedroom ;...,... Suns pace
8088 8088 14' o 2 4 8 12 FLOOR PLAN ----
AnytOWD, USA 62 INTRODUCTION
SOUTH ELEVATION
024 B 12 NORTH ELEVATION
'...... ---- ...... ::::::::::::::J
"r ABOVE GRADE SECTION ) 02...... 4 B 12
Insulation,.---i''ti"*t:=;::::::l I . ., ...... ' : .r'''<:'.:l.-m~'-'-:! """"!1rf"'_'11IT'nl-.LA .' .' • § 1111 § III I;, : .....: . ini~),i~, §1I11 § 1111 ., ..•• ". 1I11§1Il1t=' •.• ' :." .•• 1I11§1II" .• : .' ~'. 1111" ", ....• "II .~. ", . ....111' . .'" .•.... . " . ",'.' . . . -... '. -. .' ... ", .. ' ... " . ,' . • ' II' .' II'
SLAB-ON-GRADE CRAWLSPACE FULL BASEMENT
\ TYPES OF FOUNDATIONS /
Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 63
General pro~ect Information
~:Area 1504 sf
Worksheet I: Conservation Performance Level
A. Envelope Heat Loss Construction R-value Heat Description Area [Table A] Loss
Q!!iliog~L[QQt~ B-;36 io 8!liQ ]Q64 + ;3f2!:! = ;3Q B-;3Q io Qrull!!Qml Q!!iliog 42Q + 24f2 = ]I ..,... WiillI~ B-l!:!± B-Z SIl!!iillIliog io BigiQ IO~!JliiI!iQO !:!!:!2 24Z = 4Q B-1!:! io ~iilmg!! 14Q + lZZ 6 IO~!JliiI!!!Q EIQQ[~ B-1!:! io EIQQ[ Qll!![ ~!!ois!Q Q[5nIl1~I2ii1Q!! Z64 + 2f26 = ;3Q + = ~Qo-~QliiI[ ~Iiili:iog OQ!Jbl!! !:aliilZ!!Q WQQQ E[iillD!! liZ' iili[ giill2 f22 + 16 2!:! - L.QY:l-i; (!!:;;- 4Q) + OQQ[~ M!!!iilllI:li!1l EQiillD QQ[!! 4Q + f2!:! = Z + = 1121 Btu/OF-h Total B. Foundation Perimeter Heat.Loss Heat Loss Factor Heat Description Perimeter [Table B] Loss
Sliilb~-QO-!:a[iilQ!! B-Z 62 X Q;3Q 2f2 ~ H!!iilis!Q BiilS!!ID!!O!S X = I Uoll!!ru!!Q Eliil~!!ID!!O!~ X = E!![iID!!t!![ IO~!Jliilt!!Q Qmll:ll~I2ii1Q!!~ X = 2f2 Btu/oF-h Total
C. Infiltration Heat Loss 1246;3 X Qf2Q X .018 112 Btu/OF-h Building Air Changes Volume per Hour
D. Total Heat Loss per Square Foot
24 X 2~6 + lf2Q4 = 4Z!2 Btu/DD-sf Total Heat Loss Floor Area (A+B+C)
E. Conservation Performance Level
H!2 X nQ;3 X Qn = lZQn Btu/yr-sf Total Heat Heating Degree Heating Degree Loss per Days [Table C] Day Multiplier Square Foot [Table C]
F. Comparison Conservation Performance (From Previous Calculation or from Table O) 2f2 ;3!2Q Btu/yr-sf Com are Line E to Line F
Anytown, USA 64 CONSERVATION PERFORMANCE LEVEL
Worksheet I: Step A. Envelope Heat Loss Ceilings/Roofs Conservation The first step is to calculate the There are two types of Performance Level heat loss through the building ceiling/roof construction in the) Worksheet I is essentially a heat envelope. The building envelope example building. R-38 mineral \ loss calculation, similar to the consists of all walls, roofs, insulation is located in an attic type of calculation made to size floors, non-solar windows and space, and R-30 insulation is heating and cooling equipment. doors that enclose the located in the framed cathedral The major difference is that the conditioned space of the house. ceiling. The total R-value is calculation does not consider Heat loss for each envelope selected from Table Al for each heat loss through any of the component is calculated by ceiling/ roof component. The passive solar systems. The dividing the surface area of the values in Table Al account for following building corriponents component by the total R-value. the buffering effect of the attic in the example building are not The total envelope heat loss is (when applicable), the ceiling considered in the calculation: the sum of the heat loss for all material (sheetrock) and the • Heat loss through direct gain of the envelope components. effect of framing. solar glazing. Table A in the Worksheets • Heat loss through walls and booklet contains R-values that A 1-Ceilings/Roofs Attic Insulation R-value windows that separate the may be used in the calculation. Construction R-30 I!1J R-49 R-60 house from the sunspace. There are actually five separate 27.9 35 46.9 57.9 Framed Insulation R-value If the example building had tables labeled AI, A2, A3, A4 Construction R-19 R-22 R-30 R-38 2x6 at 16"oc 14.7 15.8 16.3 - Trombe walls or water walls, and A5. A separate table is 2x6 at 24'oc 15.3 16.5 17.1 - heat loss through these passive provided fQr ceilings/roofs, 2x8 at 16"oc 17.0 18.9 20.6 21.1 2x8 at 24"oc 17.6 19.6~ 22.2 solar systems would also be walls, floors, windows and 2x10 at 16"oc 18.1 20.1 24. 25.7 2x10 at 24"oc 18.4 20.7 . 26.8 excluded from the calculation. doors. The R-values' in these 2x12 at 16"oc 18.8 21.0 25.5 30.1 Heat loss from the passive tables include the thermal 2x12 at 24 'oc 19.0 21.4 27.3 31.4 solar energy systems is excluded resistance of both the insulation The area and R-value of the ) since the solar savings fractions and other materials that two different types of in Worksheet II take these losses typically make up the construction are entered on two into account. construction assembly such as lines of the table under exterior sheathing and "ceilings/roofs" and the heat sheetrock. They also account loss is calculated by dividing the for framing members that surface area by the total . penetrate the insulation and R-value. Note that the ceiling reduce the effectiveness. over the sunspace is not included in this calculation.
Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 65
Walls The R-value of each wall The total R-value is selected There are two types of wall type is detennined from Table from Table A3, which considers '\ construction in the example A2 in the Worksheets booklet. the buffering effect of the ) building. The typical exterior The R-value of both wall types is crawlspace as well as framing wall is of 2x6 wood frame 17.7 from the table, but since and the floor materials. The construction with R-19 mineral the first wall type has R-7 area and R-value is entered on insulation in the cavity. An insulating sheathing, this is one line of the table and the insulating sheathing with an R- added to the value from the heat loss is calculated by . 7 rating is attached to the table so that 24.7 is used in the dividing the area by the R-value. exterior surface of the framing. calculations. These R-values The wall is finished with 1/2 along with the associated areas A3-lnsulated Floors Insulation R·value inch sheetrock on the inside are entered on two lines of the Framing R-11 R-19 R-30 R-38 2x6s at 16"oc 18.2 23.8 29.9 and a brick veneer on the table and the heat loss is 2x6s at 24"oc 18.4 24.5 31.5 outside. calculated by dividing each 2x8s at 16"oc 18.8 24.9 31.7 36.0 2x8s at 24"oc 18.9 33.1 37.9 The second type of wall surface area by the 2x10 at 16"oc 19.3 4W25.8 33.4 38.1 2x10 at 24"oc 19.3 .1 34.4 39.8 construction separates the corresponding R-value. 2x12 at 16"oc 19.7 26.5 34.7 39.8 house from the garage. This 2x12 at 24"oc 19.6 26.7 35.5 41.2 These R·values include the buffering effect of a wall is also of 2x6 wood frame A2-Framed Walls ventilated crawlspace or unconditioned basement. Single Wall Insulation R·value construction With R-19 in the Framing R-11 R-13 R-19 R-25 Had there been different cavity, but it does not have the 2x4 at 16"oc 12.0 13.6 insulation conditions for the 2x4 at 24"oc 12.7 13.9 ~ - insulating sheathing or the 2x6 at 16"oc 14.1 15.4 17. 19.2 raised floor, an additional line of 2x6 at 24"oc 14.3 15.6 . 19.8 brick veneer. Note that the Double the table would be completed for Wall Total Thickness (inches) walls that separate the house Framing 8 10 12 14 each condition. from the sunspace are not 25.0 31.3 37.5 43.8 If the example building had included...... The R·value of insulating. sheathing should be insulated floors over a garage or \ added to the values in this table. / It is necessary to measure unheated basement, these the surface area of each type of components would also be wall construction. The surface Floors included in this step. area may be determined by Only the raised floor is As an alternative to multiplying the length of wall by considered in this step of the insulating between the floor the average height and heat loss calculation; heat loss joists, the perimeter walls of the subtracting the area of doors from the slab-on-grade floor is crawlspace could have b~en and windows. conSidered in Step B. There is insulated and floor insulation one type of raised floor eliminated. When this construction in the example technique is used, the perimeter building. R-19 mineral heat loss method in Step B insulation is placed between should be used. Step A only 2xlO floor joists at 16 inches on includes floors when insulation center; the crawlspace beneath is placed in the floor assembly. is ventilated.
Anytown, USA 66 CONSERVATION PERFORMANCE LEVEL
Non-solar Glazing Windows in the example These values are entered in Next, heat loss from the non building are all double-pane the table and the heat loss is solar glazing is calculated. Note wood windows with a 1/2 inch calculated by dividing the door that the passive solar direct gain air space between the panes. areas by the R-value. If the glazing is not included. Also the The R-value for this window example building had more than windows that separate the type is 2.1, selected from Table one door type (different house from the sunspace are A4. R-values), then additional lines not included. The non-solar window area of the table would be completed. The rough frame opening of is taken from the building plans. each window is generally used These values are entered in the Total for the window area. This is table and the heat loss is The heat loss of all components because the R-values presented calculated by dividing the of the building envelope is in Table A4 and most heat loss window area by the window summed at the bottom of the data presented by window R-value. If the example building table and this completes Step A manufacturers is for the rough had more than one window type of the worksheet. frame opening. Using the rough (different R-values), then frame opening also makes it additional lines of the table easier to estimate window areas would be completed. since windows are usually specified on the plans in terms Doors of the rough frame dimensions. The doors are the last component of the envelope to A4-Windows Air Gap consider. The example building 1/4 in. 1/2 in. 1/2 in. argon has two exterior doors: the main Slandar'd Metal Frame Single .9 entrance and an additional door Double 1.1 1.2 1.2 Low-e (e<=0:40) 1.2 1.3 1.3 to the garage. These have a Metal frame with thermal break total surface area of 40 square Double 1.5
Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 67
Table B-Perimeter Heat Loss Factors Step B. Foundation for Slabs·on·Grade and Unheated The building volume is Perimeter Heat Loss . Basements (Btuth·F·ft) calculated by multiplying the Heated Unheated Insulated ) Foundation heat loss from Perimeter Siabs-on- Base· Base- Crawl· average ceiling height by the slabs-on-grade. basements and Insulation Grade ments ments spaces conditioned floor area. In this None 0.8 1.3 1.1 1.1 insulated crawispaces is R 5 ~ 0.8 0.7 0.6 example the average ceiling R:7 0.3 0.7 0.6 0.5 estimated by multiplying the R·11 . 0.6 0.5 0.4 height is 8.3 ft. The conditioned R-19 0.2· 0.4 0.5 0.3 length of perimeter times an R-30 0.1 0.3 0.4 0.2 floor area is 1,504 sf which does appropriate heat loss factor When a raised floor assembly is not include the garage or the taken from Table B. not insulated, for instance, over sunspace. The resulting The dining area, kitchen and crawlspaces insulated at the building volume is 12,483 cubic secondary bedrooms in the perimeter or basements, heat feet. example house have slab-on loss occurs primarily at the The units of infiltration heat grade construction. R-7 perimeter. loss are Btu;oF-h, the same as insulation is installed around The example house does not for the building envelope and the perimeter. have a basement or a heated the foundation perimeter. The heat loss factor for the crawlspace, but if it did, the Step D. Total Heat Loss per slab edge is 0.3, selected from foundation heat loss would be Square Foot Table B. The heat loss factor is calculated by multip1ying the The total building heat loss is multiplied by the perimeter to perimeter of these elements by a the sum of the heat loss for the calculate the heat loss. The heat loss factor selected from building envelope (Step A), the units of heat loss, using the Table B. foundation perimeter (Step B) perimeter method, are the same When houses have heated and infiltration (Step C). For as for the building envelope basements, heat loss from , residences this value will range calculated in the previous step. basement walls located above between 200 and 500. It Note that sunspace slab is not grade would be included in represents the Btu of heat loss included in this calculation. Step A. The slab edge perimeter from the building envelope over adjacent to the crawlspace and Step C. Infiltration Heat Loss the period of an hour when it is the sunspace is also excluded. The heat loss from infiltration or one OF colder outside than air leakage is estimated by inside. This total heat loss, of multiplying the building volume course, does not include heat times the air changes per hour loss from the solar systems, times a heat loss factor of 0.018. including direct gain glazing. The example building is The result of Step D, estimated to have an infiltration however, is the annual heat loss rate of 0.50 based on local per degree day per square foot. building experience. This value is calculated by mUltiplying the total heat loss by 24 hours/ day and dividing by the conditioned floor area.
Anytown, USA 68 CONSERVATION PERFORMANCE LEVEL
Step E. Conservation The heating degree days are Step F. Comparison Performance Level selected from Table C 1 and Conservation Performance Once the total heat loss per based on specific locations. The The conservation performance square foot is calculated, the heating degree day multiplier is level for the proposed design conservation perfonnance level selected from Table C2 and is may be compared to the base may be calculated by based on the total heat loss per case perfonnance level for the multiplying the total heat loss square foot (Step D) and the area, given in Table D. per square foot (Step D) by the passive solar glazing area per Table D-Base Case Conservation heating degree days times the square foot of floor area Performance (Btu/v. • heating degree day multiplier. (Worksheet II, Step A). Base Case 25,38 Alternatively, the C1-Heating Degree Days ~ 65°F) C2-Heating Degree Day Multiplier conservation perfonnance level Raleigh·Durham ~ Passive Solar Heat Loss Glazing Area per may be compared to other This value is from TMY weather tapes and per Square per Square Foot should be used for Worksheet Calculations. Foot .00 .05 .10 .15 .20 building designs considered by It will vary from long term averages. 8.00 1.03 1.05 1.07 1.09 1.11 7.50 1.01 1.04 1.06 1.07 1.10 the builder to be typical of the 7.00 0.99 1.02 1.04 1.06 1.08 6.50 0.97 1.00 1.02 1.04 1.06 area. In this case, the 6.00 0.94 0.97 1.00 1.03 1.05 worksheets would first be 0.90 0.94 0.98~. 1.03 .00 0.86 0.91 0.95 . 1.01 completed for the typical design ~5 Q~ Q~ Q~ Q9 Q~ ~. 0 0.77 0.83 0.88 . 2 0.96 and the results of these 3.50 0.72 0.78 0.83 0.88 0.93 calculations would be entered in The conservation Step F. perfonnance level for the If the conservation example building is compared to per.(onnance level of the the base case conservation proposed building (Step E) is perfonnance level in the next greater than the base case or ) step. typical-design conservation perfonnance level. the designer should conSider additional building insulation or reduced non-solar glass area.
Anytown; USA PASSIVE SOLAR DESIGN STRATEGIES 69
Worksheet II: Auxili Heat Performance Level / A. Projected Area of Passive Solar Glazing I. ) Solar System Rough Frame Net Area Adjustment Projected Reference Code Area Factor Factor [Table E] Area
Q~QI ee X 0.80 X ~e fl~ SSQI 2Qe X 0.80 X ~e jfl~ X 0.80 X X 0.80 X = X 0.80 X = X 0.80 X = X 0.80 X = 2~fl 2~2 sf Total Area Total Projected Area
2~2 -;- jf!Q4 = jf! Total Floor Total Projected Projected Area Area per Area Square Foot
B. Load Collector Ratio
24 X 2~a + 2~2 = ~Q e~ Total Total Heat Loss Projected [Worksheet I] Area
C. Solar Savings Fraction ) System / Solar Savings Solar System Projected Fraction Reference Code Area [Table F]
Q~Qj fl~ X 44 ~Q ~fl SSQl jfl~ X 4f! = Z~~f! X = X = X = X = X =
jQ~ Zj + 2~2 Q4f! Total Total Solar Projected Savings Area Fraction D. Auxiliary Heat Performance Level
[1 - Q4f! jx 1ZQ~Z = ~Q4~ Btu/yr-sf Solar Conservation Savings Performance Fraction Level [Worksheet I, Step E]
E. Comparative Auxiliary Heat Performance (From Previous Calculation or from Table G) 23 Q99 Btu/yr-sf Com are Line D to Line E ,
Anytown, USA 70 AUXILIARY HEA T PERFORMANCE LEVEL
Worksheet II: The reference codes are shown Auxiliary Heat on Tables FI through F4 for Performance Level various types of solar systems. Worksheet II is used to estimate More information about the the savings from passive solar system types is provided in the systems and to estimate the discussion under Step C of this auxiliary heat performance level.. worksheet. The reference code This is the amount of heat that for the direct gain system is must be provided to the building "DGC 1" because night each year after the solar savings insulation is not proposed. The have been accounted for. reference code for the sunspace The example building has is "ssc 1" since all the sunspace two solar systems: direct gain glazing is vertical. south glazing and a sunspace. The south wall of the
South example building actually faces Step A. Projected Area of Projection 10° east of south because of site Passive Solar Glazing Projected Area of Passive Solar Glazing conditions. The adjustment The solar savings fraction is based on the The first step is to calculate the projected area of solar glazing. factor is therefore 0.98 for both projected area of the solar The worksheet allows the solar systems as selected from glazing. The proj ected area of user to enter the rough frame Table E. Each solar system area passive solar glazing is the area area of solar glazing. since it is is multiplied by the net area projected on a plane facing true generally easier to measure this. factor and the appropriate south (the actual glazing may be The rough frame area is adj ustment factor to calculate oriented slightly east or west of multiplied by a net area factor of the projected area. Both the true south). The projected solar 0.80 to account for window total projected area and the total . glazing also accounts for sloped framing and mullions. If the net area are summed at the bottom glazing in certain types of glass area is entered. the net of the table. sunspaces. area factor is 1.00. For most solar systems the Table E-ProJected Area The example building has Adjustment Factors projected area may be calculated two separate passive solar Degrees off ~solar System Type True D SSA SSB, by multiplying the actual glazing systems: direct gain and a South ,S SSD SSE area times an adjustment factor sunspace. This means that two o 1.00 0.77 0.75 5 c$? 0.76 0.75 taken from Table E. lines of the table must be 10 0.98 0.75 0.74 15 . 0.74 0.73 Alternatively. the projected completed. If the example 20 0.94 0.72 0.70 25 0.91 0.69 0.68 area may be determined by building had other types of solar 30 0.87 0.66 0.65 making a scaled elevation systems. for instance Trombe The last part of Step A is to drawing of the building. looking walls or water walls. additional divide the total projected area by exactly north. Surface areas lines in the table would be the conditioned floor area. giving may then be measured from the completed. the total projected area per scaled elevation drawing. This In the first column. the square foot. This value is used concept is illustrated in the reference code for each type of in Worksheet I. Step E to figure below. solar system is entered along determine the heating degree with a description of the system. day multiplier.
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Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 71
Step B. Load Collector Ratio A reference code, for The solar savings fraction for The load collector ratio is instance "DGC 1", is also each system is multiplied by the calculated by taking the total provided for each solar system projected area and totaled at the heat loss from Worksheet I, Step variation. These references are bottom of the table. This total is D and multiplying this value entered on the worksheet "Solar then divided by the total times 24 (hours/ day) and System Reference Code". They projected area from Step A to dividing by the total projected are also a key to additional calculate the weighted average area of the solar glazing information about each solar solar savings fraction for the calculated in the previous step. system as provided in Passive whole building. Solar Heating Analysis and The solar savings fractions Step C. Solar Savings Fraction other reference manuals. are based on reference designs. The next step is to calculate the The assumptions made about solar savings fraction for the F1-Direct Gain these reference designs are Load DGCI DGC2 DGC3 building. This is calculated as a Collector Double Low-e R-9 Night summarized below. weighted average of the solar Ratio Glazing Glazing Insulation 200 0.10 0.11 0.13 savings fraction for the separate 155 0.13 0.14 0.17 Direct Gain 100 0.18 0.20 0.24 passive solar systems. The 80 0.22 0.25 0.30 The direct gain reference 60 0.28 0.31 0.38 weightings are based on 50 0.32 0.36 0.44 designs are all assumed to have projected area. 45 0.34 0.39 0.47 40 0.37 0.43 0.51 double-pane glass and sufficient The solar systems used in 0.47 0.56 heat storage to limit the clear 0.52 0.62 this step should be identical to ar ~. 9 0.58 0.69 day temperature swing to 13°F. 20 0.55 0.65 0.77 those used above in Step A. The 15 0.62 0.74 0.85 For the case with night first two columns are simply insulation, the thermal carried down from the first and F4-Sunspaces resistance is assumed to be R-9. Load last columns in· Step A. Collector sunsEace Type ) The solar savings fraction for Ratio SSAI SSBI SCI SSDI SSEI Trombe Walls 200 '0.17 0.14 0.11 0.19 0.15 e9-ch individual system is taken 155 0.20 0.17 0.14 0.23 0.19 The Trombe wall reference 100 0.26 0.22 0.19 0.30 0.26 from Tables F1 through F4 80 0.30 0.25 0.23 0.35 0.30 designs are all assumed to have based on the load collector ratio 60 0.35 0.30 0.28 0.42 0.36 50 0.39 0.34 0.32 0.46 0.40 double-pane glass. The mass calculated in Step B and the 45 0.42 0.36 0.35 0.49 0.43 wall is assumed to be 12 inches 40 0.44 0.39 0.38 0.52 0.46 type of solar system. Table F1 is 0.48 0.42 0.56 0.49 thick and constructed of for direct gain systems, Table F2 0.52 0.46 0.60 0.54 ~ 0.56 0.50 ~.0 0.65 0.59 masonry or concrete. for thermal storage walls, Table 20 0.62 0.56 0.57 0.72 0.65 15 0.70 0.64 0.65 0.79 0.73 F3 for water walls and Table F4 Water Walls for sunspaces. There are The water wall reference designs multiple columns in each table are all assumed to have double that account for system design pane glass. The water tank is features such as night assumed to be nine inches insulation or selective surfaces. thick, extending continuously in front of the glazing surface. The space between the water tank and the glazing is assumed to be sealed.
Anytownl USA 72 AUXILIARY HEA T PERFORMANCE LEVEL
Sunspaces Step D. Auxiliary Heat Data is provided for five Performance Level sunspace reference designs as The auxiliary heat performance illustrated on the following level is calculated by multiplying figure. Double glazing is the conservation performance assumed for all reference level from Worksheet I, Step E, designs. Reference designs times one minus the solar SSAl, SSB 1 and SSD 1 are savings fraction, calculated in assumed to have opaque end the previous step. This value walls. All are assumed to have a represents the amount of heat concrete or masonry floor about that must be provided to the six inches thick and a masonry building by the auxiliary heating or concrete common wall system(s). separating the sunspace from the living areas of the house. Step E. Comparative Auxiliary The glazing for designs SSAI Heat Performance and SSD 1 is assumed to be The calculated auxiliary heat sloped at an angle of 50° from performance level may be the horizon. The sloped glazing compared to the performance in designs B and E is assumed level for a typical basecase to be at an angle of 30°. building in the area. This may be taken from Table G and is 23,099 Btu/yr-sf.
\ ) I Alternatively, the performance level may be compared to a previous worksheet calculation made for a typical builder house. If the auxiliary heat performance level calculated in Step D were larger than the base case auxiliary heat performance, the designer should conSider increasing the size of the solar
Sunspace Reference Designs systems, adding additional solar Data is provided for five types of sunspaces. systems or increasing insulation levels.
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Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 73
Worksheet III: Thermal Mass/Comfort ( \ A. Heat Capacity of Sheetrock and Interior Furnishings '\ ) Unit Total Heat Heat Floor Area Capacity Capacity
BQQIDl! lIlli!b Qi[~Q! !:aiilie 424 X 4.7 2H~1 QRiilQ~l! QQee~Q!~g !Q Qi~Q! !:aiilie QRiilQ~l! ~4~ X 4.5 = 42Z1 2452 Btu/OF Total B. Heat Capacity of Mass Surfaces Enclosing Direct Gain Spaces Unit Heat Mass Description capaci~ Total Heat (include thickness) Area [Table ] Capacity
nQIDb~ WslIIl! X 8.8 , wm~[Wiillll! X 10.4 = E~RQl!~g Qliilb ie Que lQa X 13.4 = laaQ E~RQl!~g Qliilb IlIQ! ie Que laZ X 1.8 = 24Z X = X = X = 122Z Btu/OF Total
C. Heat Capacity of Mass Surfaces Enclosing Spaces Connected to Direct Gain Spaces Unit Heat Mass Description Capacity Total Heat (include thickness) Area [Table H] Capacity I[QIDb~ WslIIl! . X 3.8 W~[WiillIl! X 4.2 = ) EiilQ~ 6[iQis 4" III X 3,Z = 4ll X = X = 4ll Btu/OF Total
D. Total Heat Capacity a4~Q Btu/OF (A+B+C)
E. Total Heat Capacity per Square Foot
a4~Q + 15Q4 = 52 Btu/OF-sf Total Heat Conditioned Capacity Floor Area
F. Clear Winter Day Temperature Swing Total Comfort Projected Area Factor [Worksheet II] [Table I]
Qi~Q! !:aiilie 2~ X a22 = 5~Z54 Quel!RiilQ~l! Q[ 12a X 2~~ = 4a zaz ~e!~g nQIDb~ WslIIl! lQa 4~1 + a4~Q = 12 a OF Total Total Heat Capacity G. Recommended Maximum Temperature Swing 13 OF ) Com are Line F to Line G
Anytown, USA 74 COMFORT PERFORMANCE LEVEL
Worksheet III: Step A. Heat Capacity of In the example building, the Thermal Sheetrock and Interior master bedroom, dining area Mass/Comfort Furnishings and kitchen are all direct gain This worksheet is used to The first step is to estimate the space.s. The secondary calculate the thermal effective heat capacity bedrooms, bathrooms and mass/comfort performance level, associated with low-mass master bedroom closet are which is the temperature swing construction and interior directly connected to the direct expected on a clear winter day furnishings. To complete this gain spaces. The utility room with the auxiliary heating step it is necessary that two and entry foyer are not system not operating. A high sub-areas be identified within conSidered in this calculation temperature swing would the building: those areas that since they are not connected to indicate that inadequate thermal receive direct solar gains and a direct gain space. These areas mass is provided in the building those areas that are connected are illustrated for the example design, which not only creates to rooms that receive direct solar building. discomfort but decreases solar gains. This is because the mass The direct gain space is heating performance. of sheetrock and furnishings multiplied by 4.7 and the spaces The general procedure of the located in direct gain rooms is connected to direct gain spaces worksheet is to calculate the more effective. Rooms that are are multiplied by 4.5. These effective heat capacity of mass separated from direct gain products are summed and elements located within the spaces by more than one door represent the effective heat conditioned space of the should not be included in either capacity associated with the building. The total effective heat category. sheetrock and interior capacity is then combined with furnishings. the direct gain projected area to estimate the clear winter day temperature swing. Note that ) thermal mass elements located within unconditioned spaces such as the sunspace are not included in this calculation.
1i)))1 Direct Gain Spaces Unconditioned Garage I,l@ililm Spaces Connected to Direct Gain Spaces moo Spaces Not Connected to Direct Gain Spaces
Suns pace
Building Sub-areas for Calculating Effective Heat Capacity Worksheet 11/ requires that the building be divided into sub-areas.
Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 75
Step B. Heat Capacity of Mass Exposed slabs-on-grade Step C. Heat Capacity of Mass Surfaces Enclosing include those with a surface of Surfaces Enclosing Spaces () Direct Gain Spaces vinyl tile. ceramic tile or other Connected to Direct Gain The heat capacity of thermal materials that are highly Spaces mass elements (other than conductive. Slabs that are The same type of calculation is sheetrock and furnishings) that covered with carpet should not performed for mass surfaces enclose the direct gain spaces is be considered to be exposed. that enclose spaces connected conSidered in this step. The The exposed slab area should be to direct gain spaces. The surface area of each element is further reduced. when primary difference is the unit measured from the building appropriate. to account for heat capacity figures taken from plans and multiplied by the unit throw rugs and furnishings. Table H2 instead of Table H 1. heat capacity. The unit heat The exposed slab area is In the example building. the capacity is printed directly in then subdivided into two areas: fireplace wall and hearth are the table for Trombe walls. water that which is expected to be in considered in this category. walls. and exposed slabs-on the sun and that which is not. This area and the unit heat grade. The unit heat capacity As a rule-of-thumb. slab area capacity is entered in the table for other mass elements is should be considered in the sun and multiplied by each other. selected from Table H 1. Note only when it is located directly This represents the total that thermal mass located in the behind south glazing. In any effective heat capacity of mass sunspace is not included in this event. the slab area assumed to elements that enclose the calculation. be in the sun should not exceed spaces connected to direct gain 1.5 times the south glass area. spaces. H1-Mass Surfaces Enclosing Direct Gain Spaces . In the example building. the Thickness (inches) slabs-on-grade located in the H2-Rooms with no Direct Solar Gain Material 1 2 3' 4 6 8 12 Thickness (inches) Poured Conc. 1.8 4.3 6.7 8.8 11.311.5 10.3 kitchen and dining room are Material 1 2 ~ 4 6 8 12 ) Conc. Masonry 1.8 4.2 6.5 8.4 10.210.0 9.0 located within direct gain Poured Conc. 1.7 3.0 3.6 3.8 3.7 3.6 3.4 Face Brick 2.0 4.7 7.1 9.0 10.49.9 9.0 Conc. Masonry 1.6 2.9 3.5 ~.6 3.4 3.2 Flag Stone 2.1 4.8 7.1 8.5 8.6 8.0 7.6 spaces. Some of this area is Face Brick 1.8 3.1 3.6 3.7 .5 3.4 3.2 Builder Brick 1.5 3.7 5.4 6.5 6.6 6.0 5.8 Fla~Stone 1.9 3.1 3.4 . 3.2 3.1 3.0 Adobe 1.3 3.2 4.8 5.5 5.4 4.9 4.8 considered to De in the sun and Builder Brick 1.4 2.6 3.0 3.1 2.9 2.7 2.7 Hardwood 0.4 1.4 1.8 1.7 1.5 1.5 1.5 Adobe 1.2 2.4 2.8 2.8 2.6 2.4 2.4 Water 5.2 10.415.6 20.8 31.241.6 62.4 the remainder not. These Hardwood 0.5 1.1 1.3 1.2 1.1 1.0 1.1 surface areas are entered in the table and multiplied by the appropriate unit heat capacity. The products are then summed at the bottom of the table.
Anytown, USA 76 COMFORT PERFORMANCE LEVEL
Step D. Total Heat Capacity Step F. Clear Winter Day Step G. Recommended The total heat capacity is the Temperature Swing Maximum Temperature Swing sum of the heat capacity from The clear winter day The comfort performance target '\ Steps A, B and C. This temperature swing is calculated for all locations is 13°F. If the ) represents the effective heat in Step F. The projected area of comfort performance level capacity of all thermal mass all direct gain glazing is entered calculated in Step F had been within the building. in the first row. This includes greater than 13°F, additional all direct gain systems either thermal mass should be added Step E. Total Heat Capacity with or without night insulation. to the building or direct gain per Square Foot In the second row, the projected glazing should be reduced. The total heat capacity area of sunspace glazing and calculated in Step D is divided Trombe walls vented to the by the total floor area of the indoors is entered. Unvented building to get the total heat Trombe walls and water walls capacity per square foot. The are not included in this floor area used in this calculation since solar gain from calculation should not include these systems does not the sunspace or other contribute to the temperature unconditioned spaces. This swing of the conditioned space. value is calculated here for The appropriate comfort convenience, but it is not used factor is entered in the second until Worksheet IV is completed. column, selected from Table I. ,(he projected areas are multiplied by the appropriate comfort factors and summed. '\ This sum is then divided by the ! total heat capacity from Step D to yield the clear winter day temperature Swing.
Table I-Comfort Fact~rBtu/sf) Direct Gain Suns paces and 99 Vented Trombe Walls
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Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 77
Worksheet IV: Summer Coolin Performance Level A. Opaque Surfaces '\ Radiant Barrier Absorp- Heat Gain j Heat Loss Factor tance Factor Description [Worksheet I] [Table J] [Table K] [table L] Load
Q!2i1iDg:!lrQQf:! ~Q X j QQ X Q!lZ X !lZQ = !2!2~ lZ X j QQ X Q!I:Z X !lZQ = ~Z!2 X X X = W§II:! !lQ X na QZQ X 2!2~ = Z~!2 X na X = OQQ[:! ~fi X na Q~Q X 2!2~ = 2a jaQ~ kBtu/yr Total B. Non-solar Glazing Rough Frame Net Area Shade Factor Heat Gain Description Area Factor [Table M] Factor [Table L] Load
t!/Q[tb !:al~:!:! !lQ X 0.80 X Q!2Z X ~ZQ = ~~fi X 0.80 X X = ESI:!t !:a lSi:!:! !2 X 0.80 X QaQ X !2a ~ = ~~j X 0.80 X X = W!2:!t!:aI~:!:! !2 X 0.80 X QaQ X Z~2 = ~fij X 0.80 X X = Slsllligbt:! X 0.80 X X = X 0.80 X X = j!2ZZ kBtu/yr Total C. Solar Glazing Solar System Rough Frame Net Area Shade Factor Heat Gain \ Description Area Factor [Table M] Factor [Table L] Load ) Oi[!2Qt !:a~iD aa X 0.80 X Qa~ X fifiQ = ~2g X 0.80 X X = StQ[~g!2 llll~lI~ X 0.80 X X X 0.80 X X = S!.ID:!J2~Q!2 2Qa X 0.80 X Qa~ X j22 = j!2afi X 0.80 X X = !la~~ kBtu/yr Total D. Internal Gain
22fiQ +( ~!lQ X ~ = fiQZQ kBtu/yr Constant Variable Number of Component Component Bedrooms [Table N] [Table N] E. Cooling Load per Square Foot
1,000 X j~ !I!I~ + jfiQ!I a~!l2 Btu/yr-sf (A+B+C+D) Floor Area F. Adjustment for Thermal Mass and Ventilation No night vent with no ceiling fan Z~!2 Btu/yr-sf [Table 0] G. Cooling Performance Level a2Q!2 Btu/yr-sf (E -F) H. Comparison Cooling Performance (From Previous Calculation or from Table P) 9Z!2!2 Btu/yr-sf Com are Line G to Line H
Anytown, USA 78 SUMMER COOLING PERFORMANCE LEVEL
Worksheet IV: Table J-Radiant Barrier Factors The heat loss from each of Radiant Barrier Summer Cooling No Radiant Barrier .0 these elements is carried over Performance Level from Worksheet I. Note that the Worksheet IV is used to Table K-Solar Absorptances door heat loss is reduced by half . Color Absorptance calculate the summer cooling Gloss White since one of the two doors does performance level. This is the Semi-gloss White not receive sunlight. The Light Green heat that would need to be Kelly Green I proposed building does not have Medium Blue 0.51 removed from the bUilding by an Medium Yellow 0.57 a radiant barrier in the attic, so Medium Orange 0.5B air conditioner in order to Medium Green 0.59 the radiant barrier factor is 1.00. maintain comfort during the Light Buff Brick 0.60 Absorptances are selected based Bare Concrete summer. Red Brick on the exterior building colors Medium Red ~ The worksheet accounts for Medium Brown 0.B4 and the heat gain factors are Dark Blue-Grey O.BB four sources of cooling load: Dark Brown O.BB from Table L. opaque surfaces exposed to the sun, non-solar windows, passive Step B. Non-solar Glazing solar systems, and internal gain. Ceiling/roofs Cooling load associated with the Walls and Doors These loads are then adjusted to North Glass windows that do not face south, East Glass account for ventilation and West Glass i.e. those that are not part of one Skylights of the solar systems, is thermal mass .. Direct Gain Glazing Trombe Walls and calculated by multiplying the Water Walls Step A. Opaque Surfaces Sunspaces surface area in each orientation SSAl 39.3 Not all opaque surfaces SSBl times the net area factor, a contribute to the cooling load of SSCl .~ shade factor (from Table M) and SSDl the building: only those surfaces SSEl 39.3 a heat gain factor (from Table L). exposed to sunlight In the example building, four This calculation gives the (ceilings/roofs and walls) are lines of the table are completed, annual cooling load for each ) included in the calculation. For two for the ceiling/roof types, non-solar glazed surface. The each ceiling and wall surface one for the exterior walls with total for the building is the sum listed on Worksheet I and brick veneer and one for the of the cooling load for each exposed to the sun, the heat entrance door. The wall that surface. loss should be carried over to separates the house from the Table M-Shading Factors this worksheet along with a garage and the door in this wall Projection consistent description. This are not included, since they are Factor South st North 21 0.00 ~ . 1.00 . heat loss is then multiplied by a not exposed to sunlight. 0.20 . .93 ~ .93 . 4I1o,~ 0.40 . 3 ~0.B1 O.Bl • 1 9' c;1JC7 radiant barrier factor when 0.60 0.49 0.71 0.7 '67 0.6B O.BO 0.35 0.60 0.6f 0.56 appropriate (from Table J), the 1.00 0.30 0.50 0.54 0.45 absorptance (from Table K) and 1.20 0.24 0.40 0.46 0.3B a heat gain factor (from Table L). -... Multiply by O.B for low-e glass, 0.7 for tinted glass and 0.6 for low-e tinted Qlass. The end product of this The rough frame area is calculation is an estimate of the generally entered in the table annual cooling load that is and adjusted by the net area associated with each suIface in factor. If the net glazing area is thousands of Btu per year entered instead, then the net (kBtu/yr). area factor is 1.00.
Anytown, USA PASSIVE SOLAR DESIGN STRATEGIES 79
Table M gives the shade If the example building had Step C. Solar Glazing factor for overhangs. The tinted glazing. glazing films or The solar systems addressed on overhang shade factor depends external shading devices. the Worksheet II reduce heating on the orientation of the window shade factors from Table M energy. but they also can and the projection factor. The should not be used. Sunscreen increase cooling energy. The proj ection factor is the overhang and glass manufacturers cooling energy impact of the projection divided by the usually rate the shading effect of solar systems is calculated in distance from the bottom of the their devices by publishing a this step. Each solar system window to the bottom of the shading coefficient. The listed on Worksheet II should be overhang. as illustrated below. shading coefficient is a number carried over to this worksheet. between zero and one that The cooling energy for each A indicates how much solar heat system is calculated by makes it through the window multiplying the total surface compared to an unshaded 1/8 area (not the projected area) inch clear pane. This shading times the net area factor. the coefficient may be used in the appropriate shade factor (as calculation instead of the value discussed above) and a heat from Table M. gain factor (from Table L). This The overhang on the east calculation gives the annual and west is at the eave. well cooling load for each passive above the window. and does not solar system. Overhang Projection Factor provide any useful shading. For A shade factor of 0.83 is The projection factor is the overhang projection divided by the distance between the these windows. the shade factor used because of south bottom of the window and the bottom of the is 1.00. overhangs. This is based on a overhang. Each glazing area is projection factor of about 0.2 as \ The north windows have a multiplied by the net area factor discussed above. height of four feet and the and the appropriate shade The annual cooling load bottom of the overhang is about factor. The products are associated with all the passive six inches above the window summed at the bottom of the solar systems is summed at the head. The overhang projection table. bottom of the table. is 1.5 feet. The projection factor is calculated by dividing the overhang projection by the distance from the bottom of the window to the bottom of the overhang. This is about 0.33. A shade factor of 0.84 is used in the calculations. which is interpolated between the values for a projection factor of 0.2 and 0.4
Anytown, USA 80 SUMMER COOLING PERFORMANCE LEVEL
Step D. Internal Gains Step F. Adjustment for Step G. Cooling The last component of cooling Thermal Mass and Ventilation Performance Level load is from internal gain. The total cooling load calculated The summer cooling \ Internal gain is heat given off by in Step E is adjusted in this step performance level is calculated' ) lights, appliances and people. to account for the effects of by subtracting the adjustment Some of the cooling load thermal mass and ventilation. in Step F from the cooling load associated with internal gain is The adjustment depends on per square foot calculated in considered to be constant for all the total heat capacity per Step E. This is an estimate of houses regardless of the number square foot calculated on the amount of heat that must be of bedrooms or size. This is Worksheet III, Step E, but also removed from the building each because all houses have a depends on whether or not the year by the air conditioner. refrigerator and at least one building has night ventilation or occupant. Another component ceiling fans. The adjustment is Step H. Comparison Cooling of cooling load from internal entered in the blank in Step F. Performance gain is considered to be variable The cooling performance level Table 0-Thermal Mass and Ventilation for the proposed design may be and depends on the number of Adjustment (Btu/yr-sf) bedrooms. These components Total Heat Night Night No Night No Night compared to the base case Capacity Vent wI Vent wI No Vent wI Vent wI N are accounted for separately in per SF Ceil. Fan Ceil. Fan Ceil. Fan Ceil. Fan cooling performance level for the 0.0 4,250 400 2,320 -1,600 the calculation. 1.0 5,550 1,480 3,620 -520 area, given in Table P. 2.0 6,240 2,080 4,310 080 Both the constant 3.0 6,610 2,420 4,680 410 component and the variable 6,800 2,600 4,8 600 . 6,910 2,700 ,0 700 component are taken from Table 6.0 6,960 2,760 5,0 760 dP. 6,990 2,790 , 60 790 N. The variable component is 8.0 7,010 2,810 5,080 810 Alternatively, the cooling 9.0 7,010 2,820 5,080 820 multiplied by the number of 10.0 7,020 2,820 5,090 820 performance level may be compared to other building bedrooms in the house and Total heat capacity per square foot is calculated on added to the constant Worksheet III Ste E. designs conSidered by the ) component to yield the total The example building has a builder to be typical of the area. cooling load from internal gain. total heat capacity per square In this case, the worksheets foot of 5.6. It has neither night would first be completed for the ventilation nor ceiling fans. typical design and the results of Constant Component Variable Component Night ventilation is a these calculations would be building operation strategy entered in Step H. Step E. Cooling Load per where windows are opened at If the cooling performance Square Foot night when the air is cooler. level of the proposed building This step sums the cooling load The cool night air allows heat to (Step G) is greater than the base associated with opaque escape from the thermal mass case or typical-design surfaces, non-solar glazing, elements in the building. The conservation performance level, passive solar systems and cooler thermal mass elements the designer should conSider internal gain (Steps A, B, C and help keep the building measures to reduce the cooling D). The sum is then divided by comfortable the following day performance leveL Such the floor area of the building when air temperatures rise. measures might include and multiplied by 1,000 to reducing non-solar glass, convert the cooling energy into providing additional shading or terms consistent with the base increasing thermal mass. case cooling performance.
Anytown, USA