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| What's your orientation? |
| Himanshu Burte / Feb 13, 2010, 00:10 IST |
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Among the easiest ways of ensuring that a building is ‘green’ is by orienting it right. It is also a way to ensure comfort at lower cost. Himanshu Burte tells you how to make it work.
More than half the energy an ordinary building will consume in its lifetime is already consumed in its construction. But a significant amount is consumed over its lifecycle, usually as electricity for air conditioning, heating, fans and lighting. How a building is oriented decides how hot, cold, dark or stuffy it gets inside, which decides how much electricity must be consumed to make it comfortable to live in. Since electricity in India is largely made from non-renewable coal, the more we consume the less of it we have for the future. In addition, the burning coal also releases carbon dioxide into the air which heats up the earth’s atmosphere and can hasten climate change. So it helps to know about orientation and not just when building your own house or other facility. Knowing about orientation helps even when selecting an apartment or office.
Right light and sun
The basics of orientation are simple for large parts of India where the summer or daytime heat is the bigger problem (and where airconditioning is a sought after luxury). The sun impacts buildings in two ways. First, it heats up the physical mass of the building — its walls and roofs in particular — which releases heat into the indoor spaces. Second, it heats up the interiors of the building directly by smuggling heat in through the windows and glazing along with light. Orientation affects both impacts.
The less a building directly faces the morning or afternoon sun, the less hot its walls and roof get. This is because the low-angle morning or afternoon sun hits the walls of buildings straight on and heats them up most. The higher midday sun, by contrast, hits the walls at a downward angle and heats the walls less. Moreover, the smallest of continuous projections (like a cornice or a continuous chhajja or weathershade) can cut off this sun because of its high angle, and further reduce the heat absorbed by the wall.
Thus, in most situations, a long building broadly aligned east-west is a good way of orienting buildings to minimise heat gain. That way only the shorter sides get the direct heat of the low sun. If you position all the “service” spaces (toilets, staircases, stores, for example) on these shorter sides, then they further insulate the main living spaces.
Of course, peculiar conditions of a site (say, a great view to the east or west) always have to be accounted for. This is particularly true of the placement of windows, fixed glazing and other openings. Ideally, the mid-morning and afternoon sun should not enter spaces directly. Weathershades over windows ( or chhajjas), which many architects think are design nuisances, are extremely useful and interesting devices, to achieve this. In a building oriented east-west, vertical baffles can be oriented to cut off just the low sun from the sides of a window, while the horizontal chhajja cuts of the high midday sun and ultraviolet radiation from the sky. Only reflected and ambient light is thus allowed to enter the rooms, reducing the amount of heat that enters indoors.
Selecting ready units
These and related principles are regularly flouted in design, sometimes because of genuine constraints of site, access, functional requirements and what have you. But remember, in most cases, apartments or office units, which have longer walls facing west are likely to get unbearably hot by evening, especially in summer. Of course, in places like New Delhi that get pretty cold too, indoor spaces warmed up by evening might be a great amenity in winter. While making a choice of apartment or office unit, remember that the right orientation can mean the difference between comfort and discomfort, and between low and high electricity bills. The great thing is, high comfort and low bills, in this case, also mean a “greener” solution.n
The writer is a Goa-based architect
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