Himanshu Burte makes a case for lighting home and work spaces with natural light.
We are often blind to sunlight when we build. Artificial lighting rules our workspaces and sometimes our homes, even when the sun is shining brightly outside. If we harnessed natural light through design, we would be healthier, wealthier, and less of a burden on the environment. The challenge in daylighting — the lighting of spaces with sunlight — is to avoid the problems that come with sunlight, while maximising its benefits.
CHALLENGES OF DAYLIGHTING
Daylight is freely available, but getting it into interior spaces in the right way is important. Three things come with daylight which have to be controlled through design: glare, high contrast and heat.
In most of India, light is welcome indoors, but not heat. Glare causes discomfort and damage to the eyes over the long term. Windows in office buildings are usually not designed to control heat and glare. Often, expensive blinds block out free sunlight while fluorescent lights burn all day long. So we pay more for lighting, and the increased heat load on the airconditioning also adds to the capital and running costs — not to mention carbon dioxide emissions.
Direct and indirect sunlight
Daylight can be let in directly, through a window, or indirectly, after reflecting off some surface. Direct sunlight brings heat and glare. Indirect light is less sharp, more evenly distributed and more comfortable to work in. In regions with a harsh sun, like the Rajasthan desert, traditional architecture blocks direct sunlight, bouncing it off courtyard walls and floors first. This partly explains why the rooms are relatively dim and cool.
| DAYLIGHT FOR HEALTH Daylight is good for us. Without sunlight, our bodies can’t synthesise Vitamin D. Light affects mood and morale. Productivity in workspaces and patient recovery in hospitals improves with access to daylight. Even our eyes prefer it over artificial light. They have adjusted over millions of years to the rich mix of electromagnetic frequencies that the sun sends our way. Artificial light usually provides just one frequency. Sunlight also keeps us oriented in terms of time of day. Those working in enclosed, airconditioned spaces often experience shock at the change in daylight before and after a day in the office. |
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How much is enough?
Too much or too little light can cause eye fatigue. Since each region and site has a different intensity of light, design solutions for daylighting vary from place to place. There are standards for minimum and optimum intensity of light for different tasks, but most designers rely on experience.
The human eye needs a balance between homogeneous and variable light conditions. Too much sameness or contrast causes discomfort. Our eyes tire in the unchanging intensity of artificial light. They thrive on the changing intensity and quality of sunlight over the day, but are uncomfortable with the high contrast caused by direct sunlight.
HOW TO DESIGN FOR DAYLIGHT
Along the sun’s path
The science of the sun’s movement is not complex. There are easy-to-use tools like sun-path diagrams that allow architects to check how sunlight enters a room at different times of the day and year. Sun-path diagrams help architects control the light that enters a room. An architect can adjust the location, size and design of chhajjas (weathershades) and vertical fins to let in ‘good’ sun (the morning sun in winter in north India) and block out ‘bad’ sun (the afternoon sun in summer). This has been used to great effect in the shading grid over the open main courtyard of the India Habitat Centre, New Delhi, designed by Joseph Allen Stein.
Planning for daylight
The plan size of individual blocks or wings of a building is important. Very deep spaces are difficult to light naturally. The National Building Code does not allow any part of a room to be more than 25 feet from an external light source like a window — which ensures a minimum ambient lighting, but not necessarily enough for working. This means that no room with light from one side should be deeper than 25 feet if it is to be lit naturally. If a room can be lit from opposite sides, then its width can be doubled to 50 feet.
Even so, depending on window design and other factors like direction, there may not be enough light for work even 15 feet from the window. Architects committed to maximising daylight use it to decide the depth of a wing of an office building.
HOW THIS OFFICE WORKS
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Window design
How far daylight reaches into a room is determined by the location and design of a window. For instance, the higher up the window is placed on the wall (or roof), the farther it will throw light into the room.
Shading, reflecting
Chhajjas and fins that shade windows can be used to reflect light deeper into a building. One common way is to project the chhajja indoors, too, and have the window glazing continue above it. Light that enters through this upper glazing reflects off the top of this chhajja or ‘light shelf’ and onto the ceiling, from where it is reflected deeper into the room.
Picture windows
Most people like large glazed windows. In most parts of India, large windows let in more light and heat than is comfortable. Large windows make sense in cooler climates, or when they face away from the sun (for instance, north-facing windows in places north of Ahmedabad, which is about 23 degrees of latitude north of the Equator and close to the Tropic of Cancer).
The preference for large windows can be managed intelligently by shading the window glazing from outside, particularly in a way that cuts glare. One traditional device is the jali. Another is the perforated curtain, or the chik screen. Permanent architectural screens are easy to design. These simply block a certain amount of light from ever reaching the glazing. n
[Himanshu Burte is a Goa-based architect]