1. Assoc Prof Dr Noor Hanita Abdul Majid ARCH409
DAYLIGHTING
Assoc Prof Dr Noor Hanita Abdul Majid
ARCH409

2. Day Lighting a primary source of lighting in buildings,
supplemented originally with burned fuels and more recently with electrical energy.
Before daylight was supplemented or replaced with electric light in the late 19th-century, consideration of good daylight strategies was essential.
the mid-20th-century, electric light supplanted daylight in buildings in
during the last quarter of the 20th-century and early years of this century, architects and designers have recognized the importance and value of introducing natural light into buildings.

3. DEFINITIONS
Daylighting is the controlled admission of natural light into a space through windows to reduce or eliminate electric lighting. By providing a direct link to the dynamic and perpetually evolving patterns of outdoor illumination, daylighting helps create a visually stimulating and productive environment for building occupants, while reducing as much as one-third of total building energy costs.

4. Using Daylight
In large measure, the art and science of proper daylighting design is not so much how to provide enough daylight to an occupied space, but how to do so without any undesirable side effects.
It involves more than just adding windows or skylights to a space. It is the careful balancing of heat gain and loss, glare control, and variations in daylight availability. For example, successful daylighting designs will invariably pay close attention to the use of shading devices to reduce glare and excess contrast in the workspace. Additionally, window size and spacing, glass selection, the reflectance of interior finishes and the location of any interior partitions must all be evaluated.

5. Daylight can provide a welcome and dynamic contribution to the human experience in buildings and, as demonstrated in recent studies on schools and retail sales environments, can impact human performance (Heshong Mahone Group, 1999a & b).
Most people appreciate daylight and also enjoy the outside view that windows provide.
Good daylighting design can result in energy savings and can shift peak electrical demand during afternoon hours when daylight availability levels and utility rates are high.

6. Daylighting reduces the need for electric lighting by introducing daylight into a building.
Effective daylighting is achieved through the strategic placement of skylights and windows, as well as lighting controls that monitor available daylight and respond as needed to decrease or increase electric lighting.

7. Climate and Weather
Building types and site conditions vary widely for differentgeographic locations and from one climate type to another.
For design guidelines, consider four specific climate types, as discussed below.
example of a hot-humid climate.
reduction of heat gain is important, therefore solar gain should be controlled.
control or minimize direct sunlight. Extensive roof overhangs or external shading strategies are desirable. Windows should be sized and located to admit indirect daylight.
Buildings should generally be elongated on the eastwestaxis to minimize east-west exposure.

8. Hot-arid climate
design strategies that provide relief and protection from intense sunlight. Solar gain and glare, therefore, must be minimized.
Strategies that admit indirect light are appropriate on south elevations while larger glass areas may face north. Solar controls
should dominate on the east and west.
Enclosed courtyard spaces are frequently used in hot-arid locations

9. The temperate climate
benefit from building forms elongated on the eastwestaxis to maximize south-facing walls.
Larger glass areas may be considered, however glare conditions should be carefully studied.
solar heat gain needs to be balanced with shading on a seasonal basis.
Temperate climates allow greater flexibility in design due to modest temperature and seasonal changes.
Greater connections between indoors and outdoors should be considered.
Exterior horizontallouvers are effective for creating deep penetration of sunlight on south facades.

10. cool/cold climate.
This climate type experiences tremendous seasonal changes in temperature, precipitation, and sky conditions.
Sensible design combines daylight and passive solar light.
Daylight openings should be on the east, south, and west while glass on the north should be minimized.
Special effort may be required to control glare and contrast from direct solar gain and bounced daylight, especially in snowy winter conditions.
attempt to minimize building surface areas due to the temperature extremes.
Wind protection is often essential.

11. Sky Conditions
Season of the year, weather, and time of day combine with predictable movement patterns of the sun to create highly variable and dynamic daylighting conditions.
Atmospheric and pollution conditions vary depending on season, weather, and time of day.
Densely populated urban cities, have more pollutants than rural cities.
Daylighting design is usually based on the dominant sky condition and the micro-climate for the building site.
There are three common sky conditions: clear sky, overcast sky, and partly cloudy sky.

12. The clear sky
includes sunshine and is intense and brighter at the horizon than at the zenith, except in the area around the sun
Daylight received within a building is directly dependent upon the sun’s position
Easily used charts, diagrams, and software programs allow study of solar geometry for any geographic location and time of day.

13. The overcast sky
is characterized by diffuse and variable levels of light and has dense cloud cover over 90% of the sky.
It is generally three times brighter overhead (zenith) than at the horizon.
Because direct sun is not present, the brightness of this type of sky depends on sun position. Generally, higher daylight illuminance occurs at higher solar altitudes.

14. partly cloudy sky
may have cloud cover that ranges from heavy to light and is similar to the clear sky at one moment and the partly cloudy sky the
next.
Most designers do not base decisions on the partly cloudy sky because it is constantly changing and therefore, too variable.

15. Daylighting Concepts
It is important to appreciate that the daylighting design process involves the integration of many disciplines including architectural, mechanical, electrical, and lighting. These design team members need to be brought into the process early to ensure that daylighting concepts and ideas are carried throughout the project.

16. An awareness of basic visual acuity and performance issues is essential to an effective daylighting design.

17. Veiling Reflections:
Veiling reflections of high brightness light sources off specular (shiny) surfaces obscure details by reducing contract. They should be avoided, particularly where critical visual tasks occur.

18. Distribution:
Introduce as much controlled daylight as deep as possible into a building interior. The human eye can adjust to high levels of luminance as long as it is evenly distributed. In general, light which reaches a task indirectly (such as having bounced from a white wall) will provide better lighting quality than light which arrives directly from a natural or artificial source.

19. Glare:
The aim of an efficient daylighting design is not only to provide illuminance levels sufficient for good visual performance, but also to maintain a comfortable and pleasing atmosphere. Glare, or excessive brightness contrast within the field of view, is an aspect of lighting that can cause discomfort to occupants. The human eye can function quite well over a wide range of luminous environments, but does not function well if extreme levels of brightness are present in the same field of view.

20. Variety:
Some contrast in brightness levels may be desirable in a space for visual effectiveness. Dull uniformity in lighting can lead to tiredness and lack of attention—neither of which is compatible with a productive environment. Often times a good daylighting solution will integrate a "blast" of beam daylight in a circulation area for visual interest and to help lead occupants through a building. The human eye is naturally attracted to this bright area and can be useful in guiding people down an otherwise banal corridor.

21. Combined lighting techniques
Good daylighting requires attention to both qualitative and quantitative aspects of design. Make sure the combination of natural and artificial sources provides adequate light levels for the required task.
The Illuminating Engineering Society of North America publishes an industry-standard method for determining recommended illuminance levels (expressed in units of footcandles, or fc) for various tasks.
For office spaces, the U.S. General Services Administration has interpreted the IES method to recommend a minimum of 50 footcandles on an imaginary desk-height horizontal "work surface." Nevertheless, when used in conjunction with indirect an ambient lighting system and direct task lighting, a high-quality daylighting design can be achieved with ambient lighting levels of 30 footcandles or less.
To be effective, daylighting must be integrated with electric lighting design. In particular, daylighting must be coupled with efficient electric lighting controls if net energy savings are to be realized.
As part of a daylighting design, consider the use of continuously dimming fixtures controlled by luminous sensors.

22. Design Recommendations-understood and explored during the design process
These strategies are briefly described below.
Increase perimeter daylight zones—extend the perimeter footprint to maximize the usable daylighting area.
Allow daylight penetration high in a space. Windows located high in a wall or in roof monitors and clerestories will result in deeper light penetration and reduce the likelihood of excessive brightness.
Reflect daylight within a space to increase room brightness. A light shelf, if properly designed, has the potential to increase room brightness and decrease window brightness.
Slope ceilings to direct more light into a space. Sloping the ceiling away from the fenestration area will help increase the surface brightness of the ceiling further into a space.
Avoid direct beam daylight on critical visual tasks. Poor visibility and discomfort will result if excessive brightness differences occur in the vicinity of critical visual tasks.
Filter daylight. The harshness of direct light can be filtered with vegetation, curtains, louvers, or the like, and will help distribute light.
Understand that different building orientations will benefit from different daylighting strategies; for example light shelves which are effective on south façades are often ineffective on the east or west elevations of buildings.

23. Materials and Methods of Construction
Exterior Shading and Control Devices: In hot climates, exterior shading devices often work well to both reduce heat gain and diffuse natural light before entering the work space. Examples of such devices include light shelves, overhangs, horizontal louvers, vertical louvers, and dynamic tracking or reflecting systems.
Glazing Materials: The simplest method to maximize daylight within a space is to increase the glazing area. However, three glass characteristics need to be understood in order to optimize a fenestration system: U-value, Shading Coefficient, and Visible Transmittance.

24. glass characteristics
U-value represents the rate of heat transfer due to temperature difference through a particular glazing material.
Shading Coefficient (SC) is a ratio of solar heat gain of a given glazing assembly compared to double-strength, single glazing. [NB: A related term, Solar Heat Gain Factor (SHGF), is beginning to replace the term Shading Coefficient.]
Visible Transmittance (Tvis) is a measure of how much visible light is transmitted through a given glazing material.

25. Glazings
inexpensively altered to increase both thermal and optical performance. Glazing manufacturers have a wide variety of tints, metallic and low-emissivity coatings, and fritting available. Multi-paned lites of glass are also readily available with inert-gas fills, such as argon or krypton, which improve U-values.
For daylighting large buildings in most climates, consider the use of glass with a moderate-to-low SC and relatively high Visible Transmittance.
Aperture Location: Simple sidelighting strategies allow daylight to enter a space and can also serve to facilitate views and ventilation. A rule-of-thumb is that the depth of daylight penetration is about two and one-half times the distance between the top of a window and the sill.

27. Reflectances of Room Surfaces
Reflectance values for room surfaces will significantly impact daylight performance and should be kept as high as possible. It is desirable to keep ceiling reflectances over 80%, walls over 50%, and floors around 20%. Of the various room surfaces, floor reflectance has the least impact on daylighting penetration.

28. Integration with Electric Lighting Controls: A successful daylighting design not only optimizes architectural features, but is also integrated with the electric lighting system. With advanced lighting controls, it is now possible to adjust the level of electric light when sufficient daylight is available. Three types of controls are commercially available:
Switching controls—on/off controls simply turn the electric lights off when there is ample daylight.
Stepped controls—provide intermediate levels of electric lighting by controlling individual lamps within a luminaire.
Dimming controls—continuously adjust electric lighting by modulating the power input to lamps to complement the illumination level provided by daylight.

29. To take full advantage of available daylight and avoid dark zones, it is critical that the lighting designer plan lighting circuits and switching schemes in relation to fenestration.
In addition to daylight controls, other electric lighting control strategies should be incorporated where they are cost effective, including the use of:
Occupancy controls—Using infrared, ultrasonic or micro-wave technology, occupancy sensors respond to movement or object surface temperature and automatically turn off or dim down luminaires when rooms are left unoccupied. Typical savings have been reported to be in the 10 to 50 percent range depending on the application.
Timers—these devices are simply time clocks that are scheduled to turn lamps or lighting circuits off on a set schedule. If spaces are known to be unoccupied during certain periods of time, timers are extremely cost effective devices.

30. Design strategies for thermal comfort.
—Avoid direct sunlight and skylight unless needed
for thermal comfort.
—Bounce daylight to create indirect daylight.
—Bring daylight in from above to obtain deeper penetration.
—Filter daylight into buildings.
—Use sustainable design principles.
—Maximize ceiling height to gain better light distribution.
—When appropriate, separate view glass from daylight
glass.

31. Cont…
—Determine whether daylight is primary or supplementary in lighting design. —External control strategies offer best light and heat control. Combined strategies of external and internal controls are also practical and are becoming more common. —Building geometry and interior space planning should promote, rather than preclude, distribution of daylight. —Locate the maximum number of spaces near daylight through building massing and configuration. —Create low contrast between window frame and adjacent walls to reduce glare and improve the vision experience. Splaying openings inward can increase distribution of daylight into rooms. —Integrate building systems, including artificial lighting with daylighting through control systems.

32. Lighting strategies

33. Single side lighting
—from one direction provides a strong directional quality of light with rapid deprecation of light quantity away from the window.

34. —Bilateral lighting
occurs when light enters rooms from two side directions, thus improving uniformity of distribution depending on widtof room, height, and location of glass.
Figure 1: BTV Building in Wolfurt, Austria. Layered façade elements are combined to control daylight and sunlight in bank offices and apartments. (Source: Baumschlager & Eberle Architects, Lochau, Austria. Pictures by Arch Photo)

35. Multilateral lighting
—enters from several directions and can reduce contrast and glare, improveuniformity of light on horizontal and vertical surfaces, and provide more than one primary daylighting zone.
Daylighting study of the Wainright Building rendered in RADIANCE by VISARC

36. —Clerestories
are high windows with sill heights greater than seven feet above the floor and are excellent strategies for task illumination on horizontal and vertical surfaces.
Glass higher on a wall generally provides deeper penetration into a room.

37. Light shelves
provide shading for middle window positions and re-direct sunlight from high position windows.
Light shelves, which separate view glass from daylight glass, are most effective on a building's southern exposure and under clear skies.
Light shelves may be external, internal, or a combination of external and internal. Depth of shelves depends on visual needs, orientation, latitude, and window height.

38. Borrowed light
as a concept allows sharing of light to adjacent spaces when the geometry and depth of perimeter spaces permit.
Corridor lighting gained through translucent partitions, glass block, or glass transoms represents a viable concept.
Usually borrowed light will supplement or replace electric light during daylight hours when illuminance requirements are low
Security and fire safety influence feasibility of borrowed light.

39. top lighting
When daylight penetrates a building from above the ceiling plane or is concentrated in the roof
greater freedom of source placement to achieve more uniform illumination, takes advantage of high wall surfaces and other architectural elements to distribute light where needed, and increases security and privacy.
Splayed openings, for example, can spread the horizontal distribution of daylight over a wider area and reduce contrast associated with glare.
The major restrictions for top lighting are the structural design, mechanical system, electrical system, and fire safety layouts. Top lighting is of limited use in tall buildings because it can only illuminate upper floors

40. Skylights
placed horizontally in flat or sloped roofs can provide a uniform level of illumination throughout a space when skylights are spaced on a ratio of 1.5 times ceiling height.
Skylights are generally effective for lighting horizontal tasks and function best for one-story buildings.
The performance of skylights differs under clear versus overcast skies. Thermal gain is an issue in hotter climates.

41. Roof monitors
are in raised or elevated roof planes. The higher plane contains the monitor which illuminates task areas under each monitor bay.
Glazing may be vertical or sloped. North facing monitors perform differently from south facing monitors.
Monitors should be avoided on east and west orientations.

42. Sawtooths
are apertures with vertical or angled glazing installed in a slopped roof plane.
Sawtooths are most effective when used in series of three and were historically used in industrial and manufacturing buildings as the primary light source.
Sawtooth slope is generally at a 45 degree angle.

43. Courtyards
outdoor areas open to the sky and are partially or totally enclosed by the building.
In partly enclosed courtyards, the north orientation should be the open segment to reduce glare and to reduce the need for sun control.
Façade and ground materials should reflect daylight and sunlight without increasing glare for building users.

44. Lightwells
openings in the ceiling or floor of a room that allow daylight penetration to the floor, or floors, below.
Lightwells are generally utilitarian shafts for daylight and ventilation and are not occupied space.
Performance of lightwells depends on depth and the aspect ratio of the shaft. It is best to consider a lightwell as a source of supplementary light.

45. Atria central areas of multi-storied buildings open to the sky.
Atria can be glazed to create acontrolled environment. Short and wide atria perform better than tall and narrow atria.
Performance of atria, like lightwells, is dependent on aspect ratio.
Aalto’s Academic Bookstore, Helsinki, Finland (skylighting from
top floor)

46. Ø Atrium and greenhouse -Optical systems
Daylight strategies
-Common options
Ø Side lighting (e.g. side wall windows)
Ø Top lighting (e.g. roof skylights)
Ø Courtyards and light wells
Ø Atrium and greenhouse
-Optical systems
To collect, transport and distribute daylight, e.g. light
pipes and light shelves.
-Electric lamp control systems