Beating the Heat
It has been incredibly hot these past few days in Karachi. The sun has been shining at its extra-scorching brightest and today there was almost not a single cloud in the sky. The heat in this city is usually at its extremes during this time of the year. It does not leave you alone even inside your house unless you have been running your airconditioners 24/7.
I happen to live on the top floor of my house and I have been noticing that my floor gets much warmer than the lower floors during the daytime. Even at night, the heat does not abate to comfortable levels as the roof radiates all the sun’s energy it absorbed during the day. If you are a resident of the top floor of your house / apartment, you would also have noticed that your home often gets too warm for comfort as your rooftop gets baked to oven hot temperatures every day. You would have been getting high electricity bills as your airconditioner works overtime in order to pump all the extra heat out. But is there any solution to this problem?
There are different insulation materials available on the market these days which can help to insulate your roof from the scorching sun. Most products being offered by foam manufacturing companies utilize the application of polyurethane/polystyrene foam in the form of a spray-on application or pre-manufactured boards. These foams are costly however — around Rs. 35 per sq ft, and you need to overlay them with a cover of mortar or cement in order to protect the foams themselves from the sun. Then afterwards, utilization of your roof also gets reduced due to the fact that the foam cannot support great loads. This sounded incredibly cumbersome, expensive and inefficient to me. Do you really need to do so much on your roof to keep it cool?
I began experimenting with different ideas. The objective was to cool the roof cheaply and in an efficient way without using any cement or second roofing which would have been labour intensive and cumbersome to carry out. How could I effectively shade my roof from the heat of the sun? First trial was with pottery. A few hundered small earthen gamlas were bought which I placed inverted on my roof. This cost about Rs. 15-20 per sq ft… much lesser than the foam insulation, and no overlay of cement required. How would they work? The sun would fall on the gamlas instead of my roof, which would stay shaded underneath with an insulating region of air in between the two surfaces.
How did it work? Well, my roof was cooler then it was without anything on it. However it still seemed inefficient. The coverage of the gamlas was not very good since they were round in shape, and left gaps in between where the sun could still scorch. And once they themselves got heated, they slowly started transferring the heat to the roof. Moreover, a tremendous amount of dust and dirt accumulated underneath them and around them in a few seasons. A large portion of my roof also became inaccessible because of coverage with gamlas. Another disadvantage of this method was the difficutly in buying such a large number of pots and transporting and positioning them on the roof. A pretty labour intensive job. So this method mostly failed. Something even simpler was the need of the hour.
After a little brainstorming, I hit on just the right idea — something so simple that I had studied about it in the eighth grade. If the idea of blocking the sun proves so difficult, why not reflect it instead? To this effect, I remembered a small science experiment I read about in grade school… the brighter the color, the less amount of heat it absorbes. What is the brightest color? white. Why do the Greeks whitewash their houses? to keep them cool… yes, this seemed too simple to be very useful. But worth a try.
I got my roof cleaned and washed, then got it coated with two layers of pure white enamel paint. Why enamel? well, enamel is shiny and in addition to absorbing less heat it would also reflect a majority of the sun’s light, back skywards. Since enamel is also oil-based, it would also waterproof my roof, keeping it seepage free in the rainy months.
How did it work? Presto. Instant heat control. I think the method was a resounding success. And for a fraction of the cost that insulation would have required. In the daytime now, my roof is so bright you need sunglasses to look at it. But it stays so cool that you can walk around on it bare-footed. Since it reflects so much of the sun’s light, it does not absorb much of its heat and temperatures inside stay in the comfortable range. I am sure I will see a reduction in my electricity bill very soon as well. This method was the clear winner. If you have been bothered by the heat on your roof, I would suggest – try it out! You would be making your house more energy efficient, comfortable, and reducing electricity usage. All in the same go.