By Kunwar Rana
LEED Green Associate
Sustainable Investment Group (SIG)
Daylight is a combination of all the indirect and direct sunlight available during the day. Daylight can transform an internal space from an uninspiring atmosphere to a psychologically uplifting experience. This ability to irradiate the area and fill it with energy inspires the architect to include daylighting into a building wherever it is possible.
However, introducing daylight into the building is not as simple as it looks. It does not mean using a lot of transparent glass on the building façade. If architects and building owners fail to understand how daylight works, they could run the risk of failing the building occupants. An architect should be wise enough to know what is the right amount of daylight, its intensity, distribution, and penetration and should be able to incorporate it in the building. Glare is another factor which is known to be a large impediment to visual comfort and work performance. Proper daylighting design strategies, integration between daylighting and the design and operation of other building systems, and a careful consideration of occupant perception and behavior are all necessary to realize the potential energy savings from daylighting and to support the comfort, health, and performance of building occupants.
The following are basic principles that address the daylighting opportunities in a building:
- Start the planning of the building in such a way that every regularly occupied space and living rooms have access to the windows, skylight and other sources of natural light. Windows that provides better views should be given high priorities. In doing so, one must keep in mind that effective daylighting extends into the building only about two times the width of the window and about 2 to 2.5 times its height.
- Since the path of the sun varies seasonally, it is difficult to design the east-west facing windows. So, it is better to maximize the size of the building on the north and south side. In the northern hemisphere, north facing windows will not have any solar heating problems while south facing windows will be easiest to protect with overhangs, awnings and light shelves.
- It will be futile to investigate top-light skylights in one-story buildings or the top floor of multi-story buildings if a large area of a building is not near a window. Simple top light only occupies 3% to 5% of the total roof surface area and it is sufficient to provide the adequate level of interior lighting.
- It is also important to protect the interior from too much natural light. If the natural light is more than 2.5 times or more than the average electric light, it will have a negative impact on the occupants. In such situations measures like exterior shading devices, interior shading devices, window glass, or a combination of these is effective.
- Providing an electric lighting system/ or automatic lighting control will help in overall energy saving. Dimming the electric lights rather than switching them off is the best way to save energy. Modern fluorescent dimming systems allow daylighting controls, and fundamentally compact and energy efficient fluorescent lighting.
The overall objective of daylighting is to minimize the amount of artificial light and reduce electricity costs, but it can also lower HVAC costs as well. Electrical lighting produces a lot of heat, whereas, if properly controlled, natural lighting generates hardly any heat at all.
For most buildings incorporating daylighting, the overall energy savings ranges from 15 to 40 percent. Although energy savings and sustainability may be the reasons companies initially opt for daylighting, it can also have an impact on the productivity and satisfaction of employees, students, clients and retail customers.
People have a natural attraction and need for daylight. Studies suggest that daylighting has a direct impact on well-being, productivity and overall sense of satisfaction. Even retail stores like Wal-Mart have seen the environmental and monetary benefits of daylighting for both employees and consumers. In an experiment, stores that included skylights over certain departments found that overall sales per square foot were higher in the departments lit by natural light.
Students with the most daylight in their classrooms were found to progress 20 percent faster on math tests and 26 percent faster on reading tests over the course of a year.
A high-performance daylighting system may initially require a significant investment. However, if the project team uses an integrated, strategic design approach, a company’s overall long-term savings make up for any initial dollars spent on daylighting.
Daylighting also calls for controlling the amount of heat that enters a building. Because the sun is such a powerful source to light buildings, it can also produce tremendous amounts of heat. If not planned properly, using natural lighting can result in undesirable heat gains.
One important point is controlling glare. Direct sunlight penetration in classrooms and office spaces often produces an unpleasant glare on work surfaces, making it difficult to work or view a computer screen.
Provide manual or automatic (with manual override) glare-control devices for all regularly occupied spaces. Select one of the following three options.
Option 1. Simulation: Spatial Daylight Autonomy (2-3 points, 1-2 points Healthcare)
Option 2. Simulation: Illuminance Calculations (1-2 points)
Option 3. Measurement (2-3 points, 1-2 points Healthcare)
RADIANCE, Autodesk’s ECOTECT, SPOT and DAYSIM
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