Roof down approach to staying cool

 
















Source:DIVYA KUMAR,The Hinhu,Chennai,1 st May 2010
 

You can do a lot to keep the interiors of your home cool by focussing on keeping the sun out, instead of turning up the AC and worrying about your electricity bills. Divya Kumar reports

It's blistering hot outside and it's only going to get hotter still. You turn up the air-conditioning inside your home and worry about your electricity bills. 

What else could you possibly do?

A whole lot more, it turns out. All based on one very simple idea — keeping the heat out of your home, as far as possible, rather than running up astronomical bills trying to beat it once it's inside.

To do that, you get down to the basics, says architect Kapil Chitale of Chitale and Son, and “protect your roof, your walls and your windows from the sun.”

Many measures

The measures can run from the very simple and inexpensive to the cutting edge and hi-tech, depending on how much you want to shell out. Let's take it from the top — the roof.

“The simplest thing you can do is whitewash your roof at the start of every summer – that way it reflects more heat,” says architect Benny Kuriakose.

“Another very easy, almost crude measure is just dumping coconut leaves on your terrace (if it isn't used much). The leaves don't conduct heat and insulate your roof.”

There are a whole lot of new technologies available that function on the same two principles — reflection of the sun's rays and providing insulation.

“You have insulating tiles for the roof, such as Thermatek, that are made of materials with very low thermal conductivity and in light colours to reflect heat,” says Chitale.

“Then you have reflective coatings that can be used on roofs without much traffic. They can reduce the temperature in your home by four or five degrees.”

If you want to get more creative, says Kuriakose, you can go in for a ‘false roof' on top of your existing one, perhaps a sloping tile roof. “This creates an air gap that brings down the temperature in your home,” he says.

This concept of the ‘air gap' was used a lot in traditional buildings — for instance, the timber ceiling beneath the tiled roof in old buildings is one of the reasons why they're so much cooler.

Use of sunshades

The other thing they got right — the ubiquitous sunshade that ran around the circumference of the building, protecting walls and windows from the direct rays of the sun.

“Nowadays they provide sunshades only for windows — but what about the large area of your walls, absorbing heat and transmitting it inside?” he says.

One option is giving your roof an ‘overhang', providing a shade for the walls.

You might also consider adding an insulating layer to your walls during construction.

“We've attempted to use hollow clay tiles on external walls, creating an air cavity,” says Chitale.

And then there's the paint. Keeping the exterior wall colours light, of course, is common sense.

But companies in India are also beginning to offer new varieties of ‘sun-block' paint for exterior walls that reflect as much heat as possible, allowing less into your home.

“We've just recently launched an acrylic emulsion paint for concrete walls, Weatherbond SolarReflect, that reflects up to 90 per cent of solar heat, as opposed to regular paint that reflects just 10 per cent,” says Ramakanth Akula, president – decoratives, Nippon Paints. “The beauty of this new formulation is that your walls don't have to be white to reduce heat – we have over 200 shades available.”

For windows too

Similar technology has been available for windows for some time, and has been extensively used in large corporate ‘green buildings'. Now, products such as St. Gobain's Sun Ban range are becoming popular with individual homeowners and high-rise apartment construction companies such as Ceebros, says Dinesh Kumar N., marketing manager, St. Gobain.

“What this high-performance metal-oxide coating for your glass does is cut off the sun's heat (from 50 per cent to 80 percent, depending on quality) while letting in the light,” he says.

“Earlier, film on glass meant that your interiors got dark and you were spending more on lighting.”

Other simple measures during construction can include reducing the size of West-facing windows, says Chitale.

And at all times, try and ensure cross-ventilation is possible, especially in the evening when the sea breeze sets in.

“In humid climates such as Chennai's, more than temperature, it is movement of air that gives relief,” says Kuriakose.

So get those roofs, walls and windows prepped for the heat wave.

And maybe you won't need to worry quite as much about your air-conditioning bills this summer.