Controlling Daylight to Optimize Light Quality

Alberto Rodriguez

Instructor Werner Lang

csd Center for Sustainable Development The University of Texas at Austin - School of Architecture - UTSoA

Controlling Daylight to Optimize Light Quality

Alberto Rodriguez

main picture of presentation

Kunsthaus: Bregenz, Austria

Introduction

Natural daylight is the key ingredient in allowing occupants to perceive their surroundings spatially as well as enhancing their optical comfort level. Daylight provides an essential element for experiencing architecture. Without daylight space would be void of any character and depth. Light also provides visual interest and character, which help shape our mental perceptions spatially. It is of the utmost importance that designers integrate daylight for occupant well being and quality of experience. This paper will examine basic concepts of how humans perceive light and strategies on how to achieve comfortable lighting levels. Two case studies will be analyzed in order to convey experiential daylight qualities of each building.

The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

Human Visual Perception Sensation of Vision

The image that the retina perceives The sensation of vision is caused and the way the brain interprets by light entering the eye. The light that image are critical in creating a can be thought of as a group of conscious perception of our world. convergent rays emanating from Light enters the eye through the different points in space thus pupil which is controlled by the carrying different levels of visual iris. The iris is the mechanism that information. The composite of these controls the amount of light entering rays comprises the entire visual the eye. This lens focuses the image image that the eye see’s and the on the retina which relays a visual brain comprehends. These rays of message to the brain via electrical light determine and describe the impulses. The retina is able to perceived brightness of an object or perceive light through two types of space. Basic visual tasks involve the light sensitive cells; rods and cones. use of the central foveal vision which The cones allow the eye and brain includes focusing and concentrating to discern detail and also gives us on small details. There are three our sense of color. The cones allow important factors when considering humans to detect luminances in the perception of simple visual tasks: the,”range of 3 to 1,000,000 cd/m2” (MEEB, p481). The rods are extremely • low contrast light sensitive cells that can detect • fine detail Fig. 01 The human eye luminances from 1/1000 cd/m2 to • brightness gradient 120 cd/m2 (MEEB, p481). A good lighting environment consists Our field of vision is also important of low glare, acceptable luminance in creating a three dimensional ratios, white light, and an observer image of our environment. Our with unfatigued eyes. central (foveal) vision is where acute perception of detail occurs. Transmittance Surrounding the foveal area is the binocular cone of vision where most Lighting design is possible because of the rough visual information is light has inherent predictable gathered. Beyond the binocular properties and obeys certain laws of vision cone is the farfield monocular physics. The luminous transmittance area of vision which is essentially our of a material such as a luminaire Fig. 02 Field of Vision peripheral vision. The peripheral lens or diffuser is a measure of its vision gives us our subjective context. capacity to transmit incident light. (Figure 01-03) The measurement of transmitted incident light is know as three various terms

• Transmittance • Transmission factor • Coefficient of transmission

These terms define the ratio of the total transmitted light to the

2

Fig. 03 Field of Vision The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

total incident light. In general, transmission factors should be used only when referring to materials displaying nonselective absorption. The following is a list of various types of glazing and transmittance percentages. (MEEB, 469)

• Clear glass: 80% - 90% • Frosted glass: 70% - 85%, • Solid opaque glass: 15% - 40%. Fig. 06 Specular and diffuse Reflection Fig. 04 Reflectance percentages Reflectance

Reflectance is a measurement of total light reflected. The light reflected may be specular or diffuse, or a combination of both. Diffuse transmission takes place through any translucent material such as frosted

glass, white glass, and translucent Fig. 07 Diffuse Reflection Plexiglas. This diffusing principle is widely employed to spread light Fig. 05 Reflectance Diagram throughout a space generated by a light source. Reflectance is the ratio Diffused and Directed Light of reflected light to incident light and is known as three various terms. Diffused light is emitted from large luminous surfaces. Diffusion • Reflectance creates an even soft light that • Reflectance factor illuminates a space evenly without • Reflectance coefficient creating hard shadows or causing reflections. Directed light is The amount of absorption and emitted from a single light source reflection depends on the type and creates shadows on objects of material and the angle of light and rough surfaces and reflects off incidence, because light impacts a of reflective surfaces. Brilliance surface at various angles it tends to effects are caused by reflection or be reflected rather than absorbed or refraction of directed light and they Fig. 08 Diffuse Transmission transmitted depend on the luminance of the light source. The optimum level of Recommended Reflectance: light is the balanced ratio of diffused Ceiling 60-90% and directed light. Daylight from a Walls 30-80% clear sky has a “ratio of directed to Working Surfaces 20-60% diffused light of between 5 to 1 and Floors 10-50% 10 to 1.” (Climatedesign p.21) c

Human factors in daylighting design

3 Fig. 09 NondiffuseTransmission The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

Research has found daylight to be detracts from a comfortably lit space Glare is a difficult problem to an important factor influencing is glare. Glare is produced by bright overcome when balancing daylight human behavior, health,and surfaces within the field of vision and and view. Any window can produce productivity. Windows admitting can be experienced as discomfort problematic glare if the window is daylight provide occupants with glare or disabling glare. The within the field of view. High contrast a view and a connection with the difference between these two types ratios between a window and outdoor environment. The function of glare are: adjacent surfaces can occur unless of a window has an inherent task the window is designed to reduce to provide daylight and a view to • Discomfort glare: which is only luminance ratios through the use of the outdoors. The most preferred bothersome when viewing an sunshading devices, lightshelves, or views from a window include the object in space. high-reflectance interior surfaces. sky, the horizon, and the ground. • Disabling glare: reduces the There are certain strategies that help The connection to the temporal capacity of the eye to perceive is control daylight and reduce glare in qualities of daylight improves environment optically. interior spaces such as: our psychological well-being and productivity. In studies of Glare is created when excessive • Exterior fixed shades that exclude classrooms, researchers found luminance or luminance ratios are sunlight for all sun positions. that students with more daylighting perceived within the field of vision. • Use systems that diffuse the in their classrooms progressed There are two main types of glare: incident sunlight sufficiently to faster on math and reading tests direct and reflected. Direct glare eliminate glare potential. than students with less daylighting. is caused by too high of luminance • Occupant-controlled adjustable Also, glare negatively impacts a in the viewing field. Discomfort shades. student’s comprehension abilities, of direct glare stems from two and allowing the teacher or student conditions. to control the amount of sun 1. The eye adapts rapidly to the penetration can greatly increase a average brightness of the overall student’s ability to learn. visual scene In offices, people enjoy having 2. The eye is attracted to the windows in their work space because highest luminance within the they feel connected to the outdoors. field of vision. Windows also provide functional advantage where people can look Reflective glare is caused by too into the distance to reduce eye high a luminance contrast in the fatigue after doing close desk tasks. field of vision. Reflective glare Depending upon the type of building, depends on the reflectance and the

the designer should be aware of position of the reflecting surface in Fig. 10 Adjustable Shading device diagram the special circumstances that the relation to the glare light source by occupants will be confronted with the observed object or surrounding while inhabiting a building. environment. Glare decreases rapidly as the brightness source is Daylight and the Design Process Quality of Light and Glare moved away from the direct field of vision. Thus the glare produced Designing for the use of daylight is Quality of light is a term used to depends in the source’s location an integrated approach that spans describe all the factors in a lighting relative to the field of view. The all phases of the design process. scheme. Quality of light describes amount of the discomfort glare While priority of overall design the overall scene which takes produced is inversely proportional to goals change throughout the design into consideration the luminance, the adaptation level of the eye. process, maintaining a consist thread diffusion, uniformity and chromaticity for the treatment of daylight will of the lighting. One factor that provide a satisfactory result during

4 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

building occupancy. Daylighting cooling loads. Daylighting is a critical easily. The south facade is the design begins with the initial siting of design factor to those concerned most desirable because daylight is a building which directly affects the about global warming, carbon distributed in a uniform manner and subsequent phases of design. emissions, and sustainable design. direct solar gain can be controlled Now that we have entered what to prevent overheating. The north During the Schematic Design phase, Thomas Friedman calls the “Energy facade can be treated with skylights establishing orientation, building Climate Era” designers must to allow constant diffused light to form, floor plan, and fenestration confront the rising cost of energy and penetrate interior spaces. Since the are key elements to drive the rapid depletion of natural resources. ideal building orientation lends itself design into the next phases. Design To obtain lighting energy savings the to a long narrow building form much Development consists of specifying Illuminating Engineering Society of of the floor area will have access to materials and finishes that would North America (IESNA) have provided daylight. The following list provides compliment the decisions made six essential recommendations for perimeter dimension for daylight during schematic design. Also daylighting design. (MEEB, p.588) penetration integrating building systems such as electrical and mechanical equipment 1. Plan interior space for access to • Full daylight: 15 ft. to optimize building performance daylight. • Partial daylight: 15-30 ft. should be established in accordance 2. Minimize sunlight in the vicinity • Artificial light: Beyond 30 ft. with occupancy schedules. During of critical visual tasks. (MEEB, p.590) the Construction Document phase 3. Design spaces to minimize glare. it is critical that the detail drawings 4. Zone electric lighting for clearly explain how the tectonics of daylight-responsive control. Aperture Strategies: the building are assembled in order 5. Provide for daylight-responsive Sidelighting to for the general contractor to bid control of electric lighting. the correct materials and ensure 6. Provide for commissioning and Sidelighting systems provide light that they are installed correctly. maintenance of any automatic from apertures in window walls Once the building is occupied, it is controls. where daylight penetrates the important to track the buildings space from one or more sides. The performance in order to understand Site Strategies for Daylighting distance to which usable daylight how to maintain and fine tune the illuminates a space and is reflected building systems. Finally the last To achieve optimal daylighting levels onto a work surface is the challenge important phase of the building and the designer must first consider the for designers. Sidelighting is best design process is to provide a post- buildings site orientation relative for desk tasks because there are no occupancy evaluation (POE). The to the path of the sun, horizontal veiling reflections. There are various POE is critical in determining overall obstructions, and building form. sidelighting strategies that provide occupant satisfaction, visual comfort, Neighboring buildings, existing greater illuminance farther into a and daylighting performance. It trees, and topography can determine space and improve visual comfort. allows the designers to gain a the amount of natural daylight a Below is a list of strategies when better understanding of how there space will receive, therefore the developing a sidelighting system decisions actually perform in reality designer must develop strategies and what changes need to be made that will maximize daylight within • Bilateral lighting: When a in future projects. the space while considering adjacent space is lit from two walls and properties access to daylight. distributes daylight evenly Energy Savings with Daylighting • Place windows high on a wall. The ideal orientation for buildings Daylight will penetrate farther Designing with daylight can improve is along a east-west axis which into a space and have a uniform energy efficiency by minimizing the provides the south and north facade distribution. use of electricity for lighting as well with the maximum solar exposure • Use the ceiling as a reflecting as reducing associated heating and and ability to control daylight surface by placing window

5 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

heads as close as possible to the Toplighting advanced systems use reflectors ceiling. and lens to concentrate light into a • Use adjacent interior walls as Skylights, heliostats, and conductor device that can disperse reflectors, which reduces the clerestories are suitable apertures light more effectively and evenly. contrasting edge around the for allowing daylight to penetrate the Though these systems can be quite window. roof plane of a building and allowing costly due to the materials used and • Provide daylight filters such light to enter interior spaces. the time to develop such products, as trees, vines, and trellises to These strategies are helpful when their viability is proven through diffuse daylight. perimeter windows cannot allow the reduction of artificial lighting • Provide summer shading with daylight into deep interior areas. To needed during daytime hours. These exterior louvers, overhangs, and prevent veiling reflections or direct specialized lighting systems reduce lightshelves that can block direct glare situations with toplighting overall energy consumption while sunlight, and reflect diffused apertures, and interior reflectors increasing the mental well being of sunlight into a space should be used to diffuse and building occupants. • Provide light-colored materials control daylight. The following are or finishes on shading elements a few toplighting strategies that will that will reduce contrast and enhance overhead daylight. reflect light deeper into a space. • Splaying the sides of a skylight washes light along a larger surface area and reflects diffuse light into the space. It also reduces glare. • Place toplights high in a space, this allows for more surface area for light to diffuse upon. • Use interior devices to block, or diffuse light that can be redirected by a reflector below a Fig. 13 Light harvesting blind Fig. 11 Rendering depicting bilateral lighting roof aperture Light harvesting blinds redirect daylight into interior spaces while reducing glare. When sunlight hits the blind, the specular upper side of the slat turns toward the exterior and provides perfect sun shading due to the reflection of the sunrays.

Fig. 12a Toplighting Diagram: Bartenbach LichtLabor Light pipes operate through Innovative Daylight Strategies channeling light from a heliostat Fig. 12 Rendering depicting bilateral lighting with shade device into a highly reflective tube made of There are a number of innovative prismatic glass, aluminum film, or daylighting systems that allow mirrors. Light pipes can transport natural light to penetrate interior light 65 ft. from a single light source spaces and enhance the quality and is able to diffuse the direct of light. These systems include sunlight at the end of the pipe prismatic panels, solar tubes, resulting in an even distribution of heliostats, and fiber optics. Some light.

6 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

Fig. 15a: Daylight Pipe Diagram: Bartenbach LichtLabor

Advantages of daylight pipes: • Savings on artificial lighting due to sufficient daylighting Fig. 14 Light tube • No solar protection necessary • A lower proportion of openings in Daylight Pipes are light shafts that the roof due to utilization of the sun have highly reflective surfaces and are • A positive effect on the people due capped by a clear skylight to daylight The amount of light transmitted into the interior depends on the diameter of the shaft. This system is convenient and economical for supplemental illumination. Tublar skylights are able to diffuse direct sunlight through a stratified layer of reflective material, which softens and evenly distributes daylight.

Fig. 15 Daylight Tube

7 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

Case Studies about 2,000 sf on the ground floor.

Within this section of the paper I will This museum has an frosted glass transition from a technical approach exterior skin that diffuses direct to a perceptual approach of analyzing sunlight and allows it to penetrate daylight within buildings I have along the edges of the interior visited during my time in Europe. spaces. This treatment of daylight I hope to convey an experiential allows the occupant to be connected qualities through the treatment of with the exterior without having daylight. any visual access to the outdoor environment. The bright edges in the Kunsthaus museum are extremely apparent and

Architect: Peter Zumthor the architect uses this edge condition Fig. 16 Kunsthaus exterior Location: Bregenz, Austria. to create a soft gradient of light throughout the gallery spaces The The facade consists of frosted glass diffused light that floods the gallery panels that serve multiple functions. spaces is optimal for displaying and They give the building an inherent viewing art. Zumthor employs a lightness with the translucency frosted glass suspended ceiling on of the panels and insulates the the inside of gallery spaces which are concrete core of the building against backlit with artificial light that mimic varying weather conditions. The a natural daylighting effect. He panels essential role is diffusing uses this type of glazing to conceal the incoming daylight for the overall the artificial lighting above and to interior lighting scheme. trick the user into thinking that the Fig. 17 Kunsthaus suspended glass ceiling The frosted glass envelope was gallery is completely lit by daylight. designed as a self-supporting The stairwells are completely lit structure independent from the with diffused daylight through a concrete core of the building. It frosted glass ceiling. The glazing completely encases the core of the encourages the user to walk up the building with glass on the interior stairs towards the next gallery space as well as the exterior. Between the as if the gallery space is emitting the two layers of glass is a three foot light for the stairwell. wide gap that allows daylight to enter the first subterranean level and also All the gallery spaces have the houses the light installation which same floor plan and detailing but illuminates the Kunsthaus at night. the artwork in each gallery has the ability to affect the overall ambiance Three vertical concrete slabs support of the space. Another interesting

the floors and ceilings of the interior aspect are the reflections created Fig. 18 Kunsthaus stairwell core of the building. These slabs and within the polished concrete floor. walls delineate the interior space The soft diffused light creates timid and divide the vertical arrangement reflections that give the floor the of the building. The service functions quality of walking on ice. for the building have been placed outside the main structure, in order Through the treatment of daylight to allow for three large span gallery and the uniterupted gallery space, spaces The Kunsthaus offers 1500 the elements of art and architecture sf of exhibition space per floor, and begin a dialogue with each other so Fig. 19 Kunsthaus gallery space

8 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

they are seen not as isolated objects lecture hall. The large movable but as one subject matter coexisting panels inside the lecture hall control in a single space. and diffuse daylight through the application of the micro-perforated Case Study II fabric. This allows the lecture to create a controlled environment in The Oskar von Miller Forum terms of light quantity and quality. Architect: Thomas Herzog + The lecture hall has a dual nature Partners where it can be opened and closed Location: Munich, Germany depending on the type of event taking place. Fig. 24 OvMF Sawtooth double skin facade The sawtooth double skin facade is located on the prominent south facade of the building, which integrates several strategies in controlling daylight. The southwest glazing of the sawtooth is transparent and allows direct daylight to penetrate the first layer of the facade which is then diffused by the wooden louvers in the second Fig. 21 OvMF Lecture Hall layer of the double skin. The southeast glazing is translucent and immediately diffuses the daylight Fig. 20 Oskar von Miller Forum Exterior upon entering the southeastern The Oskar von Miller Forum direction of the facade. The is a prime example of German transparent panels allow for views engineering and design in terms towards the southwest which would of daylight. The major component not be possible if the entire facade for manipulating daylight is its consisted only of translucent panels. double skin facade which acts as This creates a connection between the mediator between indoor and the occupant and the outdoor

outdoor conditions. Its ability to Fig. 22 OvMF Lecture Hall with panels open environment which is important for diffuse daylight while maintaining mental well-being. a connection with the changing outdoor environment increases the quality space and well being of its inhabitants. This building has integrated many different approaches in how to manipulate daylight.

The ground level has large expanses of glass that open towards the public realm of the street and conveys a Fig. 23 OvMF Lecture Hall with panels closed Fig. 25 OvMF Sawtooth double skin facade daylight diagram sense of openness to the community. The large glazing panels allow daylight to penetrate deep into the

9 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

The wooden louvers within bilateral lighting effect which the second layer of the double reduces glare and visual contrast. skin facade allow occupants to manipulate its position according to The Oskar von Miller Forum employs their specific daylight needs. This different daylight strategies that factor is important because it allows directly reflects the specific use of the occupant to become an active certain spaces. The careful attention participant within the overall building to detail allows the interior spaces system. It allows them to control to become visually comfortable as their environment instead of the wells as aesthetically pleasing. The Fig. 26 OvMF Sawtooth double skin facade with wooden louvers building automation system dictating integration of building automation what the indoor environmental and occupant driven manipulation quality should be. produces indoor environments that are continually changing thus adding to the overall dynamism of the The metal perforated panels on the interior space. east facade were designed to control light levels in the stairwell which Conclusion would prevent overheating. These panels supposedly are opened and Daylight has numerous strategies closed according to the building which designers can employ to affect automation system. These panels the overall quality of architectural Fig. 27 OvMF East facade perforated metal panels could be more successful if the space. In order for daylight to be occupants had the ability to change a critical element of a building it their configuration similar to the must be fully integrated throughout wooden louver panels on the south the design process and the building facade. If the occupants could systems. It cannot be treated as a control the exterior metal panels the trivial aspect of nature because of stairwell would have varying levels its abundance. Rather it is the one of light instead of having a monotone resource that architects can rely on light level. This would increase the to help shape their buildings. By character of the space visually as allowing daylight to enter interior well as experientially. The occupant space it creates numerous benefits driven configurations would give the that are both psychological and facade a sense of vitality and would experiential. produce various aesthetic qualities Fig. 28 OvMF East facade perforated metal panels diagram on the interior as well as the exterior.

The glazing on the east facade of the building has embedded micro-louvers that reflect direct sunlight towards the exterior, which reduces glare and decreases the light level in the hallway adjacent to the professor’s apartments. The translucent glass panels that separate the apartment from the hallway allows diffused light to Fig. 29 OvMF East facade micro-louver glass panels enter the apartment thus creating a

10 The University of Texas at Austin - School of Architecture - UTSoA Subject heading of presentation (DIN OT 8 regular)

Figures

Figures 1-9: Mechanical and Electrical Equipment of Buildings

Figure 10-12: Created by Alberto Rodriguez

Figure 13, 15-20: Photos taken by Alberto Rodriguez

Figure 14: http://cache.wists.com/ thumbnails

Figure 21-29: Oskar von Miller Forum Presentation by Roland Schneider

References

Hausladen, Gerhard. ClimateDesign - Solutions for Buildings that Can Do More with Less Technology. München: Birkhäuser, 2005.

Grondzik, Walter T. Mechanical and Electrical Equipment of Buildings Hoboken : John Wiley & Sons, Inc., 2009. 11th ed.

11