Sunlight Shading and Redirecting
Building shape and massing
The massing of a building determines the quality of light distribution. In general, narrow forms with greatest access to exterior openings will be easiest to illuminate with natural light. Before electric light was common, buildings were narrow, only as wide as they could be illuminated.
There are three basic forms for admitting natural light into a space: side lighting, top lighting or atria, as described below.
The term side sighting describes the location of the opening. However, effective use of natural light requires more than a window. Light-reflectingand light-receiving surfaces must be integrated into the architecture to avoid glare and excessive heat gain.
In most cases, the ceiling will be best surface to receive reflected light. It should be unobstructed, high-reflectance, and shoıld be able to seen by task areas in a space.
See the following graphics, how to use the ceiling best to advantage.
Locate openings carefully because location affects both light distribution and the perception of distribution. A window wall can be horizontally divided into an upper third, middle third, and lower third. Each section has its distinct characteristics.
The upper window sees brighter zenith of overcast sky and therefore has the best distribution of light on overcast days.For sunny conditions , the upper window does not provide the best light distribution. In any weather condition, an unbaffled upper window has great potential for sun and sky glare. Because the high window is often located above eye level, when properly baffled, the high window can admit very bright light without glare.
The middle window is not optimal for light distribution on sunny days or overcast days, yet it is the most commonly used location because of the view afforded. Be careful to avoid glare from bright window sills and reflections in video display terminal screens from middle windows.
The lower window provides optimal distribution of reflected sunlight. This is because it maximizes the distance between the light source and ceiling and provides greatest uniformity. Light levels will be lower near the window wall and higher deep in the space.
In practice, the upper, middle, and lower windows are often combined, and it is important to recognize that in the sunny condition, locating the opening as low as possible will result in most uniform distribution.
Locating the openings in more than one wall will enhance the distribution of light. With sidelighting in only one wall (unilateral), large amounts of light must be admitted to provide light deep in buildings. Because of this, there is a tendency for the area near the window to be underlit and perceived gloomy. Daylight openings on opposite or nearby walls of a space will provide more even distribution of light, brighten dark areas and allow usage of smaller windows with less over lighting.
Projecting lower sills form a large glazing area similar to a greenhouse. This configuration will maximize illumination from area sources such as overcast skies. It can be used at orientations aht do not require shading.
The reverse is the overbite configuration , in which the window header extends over the lower sill. Like overhangs, it is best for ground-reflected sunlight and shades direct sun and skylight.
Follow us on our next article “ Sunlight Shading & Redirecting devices ”.
Architectural Lighting by M. David Egan and Victor W. Olgyay
There is no universal answer to the question: “How deep can a room be effectively illuminated with natural light?” Room proportion determines light distribution, not size. For example, given the same proportion and opening, orientation, and reflectances these two rooms will have the same luminance distribution.
As ceiling height increases, the light distribution becomes more even for both toplighting and side lighting. Shown in the side lighting sections below, as the ceiling height increases from 8 to 16 m, the ratio of average light levels to minimum light levels decreases by a factor of 6. The flatter the illumination gradient, the more even the distribution of light.
Light distribution is highly dependent on room reflectance. In general, the ceiling is the most important light-reflecting surface. The IESNA guideline of 70/50/20 (ceiling/walls/floor) for minimum surface reflectance follows this principle. Because most tasks “see” light reflected from the ceiling, it will be a significant light source, especially in deep, wide, sidelit rooms. In toplighting and smaller rooms, the side walls become increasingly important.
In diagrams below, various combinations of flat black and matte white surfaces are placed opposite a window wall. The reduction of daylight on the desktop surface illustrates the relative importance of each surface for a space with this light source and proportion. The percentages show illuminance according to all white surface conditions rated at 100%.
Follow us on our next article “ Sidelighting & Openings ”.
Architectural Lighting by M. David Egan and Victor W. Olgyay
Planning for Solar Access
Master planning of an area or region is an ideal opportunity to provide solar access. Planning for solar access at the largest scale can very simplify the design for natural light at the building scale.
Topography may be used to provide shade or access sunlight. When properly oriented and located, circulation patterns can provide solar access between building and masses.
In urban design; large buildings often shade close by buildings or themselves. This can be an asset when cool courtyards are created or a liability when dark, huge urban streets are created. Zoning codes in many urban areas include daylight or solar access requirements to regulate building massing. Codes that specify access to daylight enhance views of the sky, whereas codes that specify access to sunlight must consider temporal orientation and sun angles.
Solar envelopes are three dimensional design tools used to maximize the buildable volume on particular site, while preserving access to sunlight for close by buildings. The basic elements used to design a solar envelope are: latitude, size, orientation and topography of the site; times of day solar access is desired and impact of shading on the site.
Planning for solar access includes more than direct solar access and shading. Urban planning e appropriate building orientation (typically elongated on the east-west axis) and thereby facilitate use of direct sunlight, shading and sunlight reflected from nearby ground and buildings.
Building orientation facilitates the use of natural light in buildings. Building orientation is critical for shading and redirecting sunlight, but less for non-directional daylight.
Long axis running North-South
Buildings oriented with the long axis running-north south usually have greatest exposure to the morning sun. The east and west facades receive more light during the summer than during the winter. Because of low -angle sunlight orientations it is hard to shade direct sunlight without also blocking the view. Openings on the east and west sides of buildings are less preferred for illumination, especially side lighting. However, toplighting with this orientation can give the best constancy of daylighting through the day.
Long axis running East-West
Buildings oriented with the long axis running east-west usually have greatest exposure to southern sunlight. This is generally the preferred building orientation. High summer sun has greatest impact on the roof and horizontal surfaces. The north-south faces are the easiest to shade, often by a simple device. The effects of the orientation are greatest at the northern latitudes where sun angle is lower. The higher-angle sunlight entering the openings on the north and south facades illuminates the horizontal surfaces well.
Follow us on our next article “ Room Proportion & Reflectances ”.
Book: Architectural Lighting by M. David Egan and Victor W. Olgyay
Daylight can be defined as diffuse light through clouds or partially cloudy skies. In a cloudy climate, the diffuse sky is often the main source of useful daylight.
For climate conditions in which cloud cover exists (no visible sun for a substantial percentage of the year), we should design to optimize daylight. In this case, the light source is the sky, not the sun or sunlit surfaces. Still, some of the sunlight strategies also apply to daylight, such as using light efficiently, controlling the amount of light, and integrating with architecture. Because the overcast sky not a point source it is an area source.
Here are the basic approach to the daylighting strategies;
1. Maximize solid angle of the sky seen from the task or light-reflecting surfaces. In practice, this means that tasks cannot be too far from the aperture. (windows and skylights). However apertures can be larger for daylighting than for sunlighting.
2. Shade to prevent glare. avoid direct views of overcast sky because it is a bright source of potential glare. Shading is not needed on the building exterior since heat gain is not a problem from overcast sky conditions.
3. Do not block light. Do not use solid light shelves or overhangs. They are not effective for redistributing light in overcast sky conditions and may reduce the amount of daylight reaching the task.
4. Locate openings high. Openings should see the brightest part of the sky. The overcast sky at the zenith is about 3 times brighter than at the horizon. High window locations and horizontal skylights will provide the best access to light
from overcast sky.
5. Shape space to minimize absorption of light. Use high-reflactance interior finishes. Maximize the ceiling height near windows to allow high windows and slope ceiling down toward the rear to minimize interior surface area.
Follow us on our next article “Planning for Solar Access ”.
Sources; Architectural Lighting by M. David Egan and Victor W. Olgyay
The sun is a powerful source of light. Properly used in building design, sunlight can be energy efficient and aesthetically pleasing. However, if not carefully designed, building may overheat, be too bright or have a poor distribution light.
For all designs, the preliminary goal is to provide illumination for visual activities and visual delight. With sunlight, the basic design strategy is to use the sunlight indirectly. Sunlighting design also should be integrated with architecture.
There are 5 design strategies to promote the effective use of sunlight.
1.Shade; Shade building openings to control to glare and excessive heat gain due to direct sunlight. North-south openings tend toward a lower, horizontal illumination which lights vertical surfaces well.
2.Redirect; Redirect sunlight to where it needs. The right distribution of illumination is the essence of good lighting, therefore it is even more important with sunlight. It is undesirable to have the area near the window over illuminated while the rest of the room is under illuminated.
The light from the sun, should be spread over a large area to optimize the balance of brightness. This has additional benefit minimizing the contrast in the room.
3.Efficiency, we can use light more efficiency by shaping the interior and using high-reflectance interior building surfaces.This will help better distribute light and will reduce the total amount of light that needs to be admitted.
4.Integrate; Integrate forms for sunlighting with architecture. When an opening for sunlight does not provide a view or fill an essential role in the architectural design, the opening is likely to be blocked with drapes or other obstructions.
5.Control; We must control the amount of light entering space. Provide the amount of light required, at the time it is desired. No more, no less.
So, what can be used to control natural light? With technological improvements everyday, we have many options. Such as; light shelves integrated to building control system, glass facade and blind/louvre systems, prismatic glass panels, spectral selective glazed glass and photochromic glass usage, also filtering alternatives can be used to balance the natural light indoors.
Sunlight is a must in architecture. We should try to find the balance, make sure to get the maximum use out of it, practice these strategies so design process can benefit from it in the best way possible.
Follow us on our next article “Light Distribution of Luminaires”.
An another source of natural light is Reflected light, which can be defined as light reflected from natural and man made surfaces.
The sun illuminates surfaces, creating secondary sources of light. Light-colored surfaces reflecting sunlight are typically the second-brightest sources of light in the environment. On a sunny day they can be dominant light sources in the field of view.
Reflected sunlight is normally is more diffuse than direct light, reflected sunlight may be less intense and maybe have a different color or direction. The qualities of reflected sunlight are largely dependent on properties of the reflecting material.
Reflected light effects architecture in two very distinctive ways, it can be studied as reflectance on horizontal and vertical surfaces.
Horizontal reflected light is most abundant on the sunny sides of buildings. Light reflected from horizontals surface such as un shaded light colored ground cover can be significant source of natural light, especially in low buildings.
In tall buildings, a much greater extent of sunny foreground is required. Light may also be reflected from horizontal surfaces attached to or integral with the building facade. Examples are wide sills or light shelves. Even small amount of horizontal surfaces receive greatest solar impact at high sun angles.
Vertical reflected light is most abundant on the shady side of buildings, where light is reflected from unshaded light-colored walls or facades of adjacent buildings in the sun. vertical surfaces receive their greatest solar impact at low sun angles, such as in winter time and at high latitudes. Light reflected from vertical surfaces is often relatively horizontal and may be a source of glare. For this reason, luminous surfaces should be of visual interest or locate openings above eye level.
Good interior lighting can simply be defined as lighting that enables people to perform visual tasks and to be comfortable while performing them. Daylighting design is inseparable from electric lighting design and must consider issues such as: Brightness balance, Distribution of light in space and time (time of day and season), Appropriateness of illumination levels , Energy saving techniques.
For interior spaces in which sunlight and daylight are an integral part of the luminous environment, special care must be taken early in the design process to ensure proper orientation, massing, space planning, and sizing and shaping of apertures, since these early decisions will have the biggest effects on the overall building performance.
Follow us on our next article “Sources of Natural Light; Sunlighting Strategies”.
As we mentioned on our previous article to effectively use natural light, first we must try and understand its abilities. Sunlight can be defined as direct-beam light through clear or partially cloudy skies.
Partially cloudy skies are also partially clear. Clear sky and sunlight together act very differently from a diffuse overcast sky. In clear, sunny condition, sun is the brightest source of light, virtually a point source coherent, parallel rays producing sharp shadows.
The light intensity of sun varies with many factors such as latitude,solar altitude and atmospheric conditions. The solar illumination at sea level can exceed to can exceed 100,000 Lux perpendicular to the sun’s rays, the color temperature of sunlight changes also, from 1000 to 1800K at sunrise to approximately 5000K at noon. This is considerably lower than a clear blue sky at greater than 10000K.
Atmosfere of the clear blue sky filters and diffuses light, but provides low illumination. Near the sun the sky is bright, but majority of the blue sky provides less bright illumination than overcast skies. The allure of northern skylight for artists is due to its consistency of intensity and color temperature.
To find out more about Natural light, follow us on our next article “Sources of Natural Light; Reflected Light”.
To use natural light effectively, first we need to understand its abilities. Available daylight patterns are modified by factors such as close by landforms, vegetation, and structures. the variety light conditions create dramatically different perceptual environments and architectural responses.
The three basic sources of natural light are;
Daylight, Sunlight, Reflected light.
Let’s start from Daylight with a basic definition.
We can define Daylight as diffuse light through clouds or partially cloudy skies.
We can describe daylight such as the combination of all direct and indirect light originating from the sun during daytime. In a cloudy climate, the diffuse sky is often the main source of useful daylight.
When the cloud cover completely obscured sun, the sky is considered totally overcast. An overcast sky produces diffuse light. The sky is brightest at the zenith and decreases at the horizon to approximately one third of its maximum brightness.
In totally overcast condition, the sky is generally the brightest element in an outdoor scene; light reflected off other surfaces has a much lower luminescence.
The totally diffuse diffuse area of the sky indistinctly renders shadows. Filtering of the light by the clouds also significantly raises the color temperature of the transmitted light.
The totally overcast sky is actually quite uncommon. It is much more common to have less dense cloud cover with uneven luminous distributions revealing the sun.Thin, hazy clouds can be very bright, usually brighter than the fully overcast sky or a clear sky.
Partially cloudy skies are even more common, constantly changing between direct sunlight and hazy daylight and fluctuating in intensity, distribution and color temperature, as all of us experience the most in our daily routine.
To find out more about Natural light, follow us on our next article “Sources of Natural Light; Sunlight”
Lighting designer’s main source is natural light. Sun is a
natural source and it has sustainable unlimited energy. In this article series, we want you to inform about natural light more. Let’s begin with ‘What is Natural Light’.
Light inspires us and enriches the spaces. The
ever changing presence of natural light in a building is delightful and inspiring. Natural light tells us about the weather, the time of day, and satisfies other deeply rooted in our psychological needs. Simply ‘Natural light can enhance architecture, improve the way people feel.’
Please read about how leCorbusier has played masterfully with orientation, openings and textures to create kinetic architecture with daylight.
The benefits of natural light are so valuable that we often have to discuss the health and economic related aspects. Some searches in
2000’s in numerous schools and retail stores in USA indicated that quality daylight does enhance the learning (measured by academic test scores) and shopping (yearly growth in scales). As lighting designers we often ‘try’ to mimic these feelings with artificial light.
Nowadays with the development of light sources,
high end control systems powered with connected technologies, we can easily and more ‘economically’ focus on some applications such as color temperature, light colors and intensity changes in our built environments. But we have strong doubt because we realise how little we really know about light and how we perceive it, we behave accordingly. This is a discomforting topic; A way of using ‘latest’ technology in both artificial and natural lighting systems has become a ‘necessity’.
Lets focus on the natural and learn more about how we can benefit from daylight more.
Natural light in buildings can provide ambient illumination which will reduce the usage of electric light. This lowers energy consumption and reduces the generation of ‘pollution’. These benefits alone often are sufficient justification to include natural light in a building’s design. Great lighting design also relies on using natural light effectively.
Unfortunately, there are many unsuccessful buildings which are designed with misapplication of natural light. Sometimes, natural light can be difficult to control. It can cause
of result as excessive heat gain, uncomfortable glare, and degradation of artwork and materials. Building orientation is too often ignored, facades and openings are designed without regard to daylight.
To successfully design with natural light, place the light where needed. Avoiding disturbing contrasts, glare, unwanted heat gain is possible with focusing on the design considering natural light. The integration of natural light and artificial light into buildings can create delightful luminous environments.
The primary objective of natural light where we will define as ‘daylight systems’ is to maximize use of daylight for buildings. To use daylight effectively first assess its availability. The quantity and quality of light available for illumination in a building are determined by the regional climatic conditions. Available daylight patterns are modified by factors such as adjacent landforms, vegetation and structures.The varying light conditions different perceptual environments and architectural responses.
Three basic sources of natural light are:
Next article: “Sources of Natural Light; Daylight”.
Book: Architectural by M. David EgLighting an and Victor W. Olgyay (2nd Edition)
If we want to know more about light, we should start know the basic metrics to describe ‘light’. Let’s make it as simple as wecan.
There are different units for measuring quantity of light and it sometimes can get complicated.
Luminous flux is defined as the time rate of flow of light. The amount of total luminous energy – light emitted from a source in unit time is measured in lumen. It does not imply direction, distance, or intensity. Simply the total light output of a source. The more lumens the fixture or the source gives off, more light it emits.
The force of the luminous flux in a specified direction is luminous intensity. Luminous intensity measures the strength or (we rather to called it as) “punch” of a light source in a specific direction Very often, a light source will have different intensities when measured at different directions.
Measured in candelas (lumen / stredian), the luminous intensity of a light source is commonly shown on a candlepower distribution curve. The polar axis on this chart graphically indicates the luminous intensity in any given direction from the source position.
Clue: You can find most of the successful luminaire producers share their products candlepower distribution curves for you to understand the basic light distribution characteristics of the luminaire you are planning to use. An experienced eye can understand how light will behave with looking to these polar distribution intensities.
The intensity of light falling to a surface in unit time is called Lux, in which is also called as illuminance. Illuminance is the density of incident on a surface. Simply how much light is hitting a surface. It changes according to the distance and angle of the surface. It can be measured inexpensively by a lightmeter called luxmeter.
We can easily measure amount of light falling to a surface.
Density of light varies according to the distance and the angle to the square of the distance.
That is called inverse square law.
We do not see illuminance when a surface is illuminated we see its brightness defined as Luminance. Luminance, is measured brightness which is defined as the intensity of visible brightness of a source or surface in the direction of the observer, divided by the area of the source or surface seen. The specific way the light comes off of a surface. It allows us to see things. The unit is candela/squaremeter .