A few months back, I had to personally upgrade my driver’s license to include a permit to ride motorcycles. Unfortunately, this meant queuing at a land transportation office for at least three hours. I found myself in a windowless waiting area, approximately 60 square meters, with no air-conditioning, one among about a hundred other applicants. Surprisingly, it was comfortable. The secret (I had a lot of time to analyze this!) was the existence of two openings: a small stairwell leading to the ground floor and an opening through the ceiling to an upper level that was properly ventilated. There was no mechanical ventilation to induce or eject air, merely the use of the basic principles in passive cooling. This was adequate to push the collective body heat out of the room, making it relatively comfortable.
There were two principles successfully employed: That hot air goes up and that there must be cross ventilation. The opening through the ceiling acts as a vent shaft that releases the warm air accumulating inside the room. Meanwhile, fresh air enters through the other opening.
Air-conditioning is not the only solution to making rooms more comfortable. Especially now that energy costs have gone ballistic, alternatives to cooling must be tapped. Natural and less costly methods should now be adapted, particularly in homes. If you feel that your home is not cool enough, as compared, say, to being under the shade outdoors, then it is time to investigate and apply the basics of Passive Cooling.
Why is it hot inside? Where does the heat come from? Is your roofing made of metal sheets? Does it have a dark shade of paint? Is the interstitial ceiling space inadequate? Is it improperly vented? Is the ceiling space too small? Answering these questions will give you a clue to the proper solution to your home cooling problem.
Metal roofs, although good for shielding us from the rain, do not insulate us from the heat. There are less heat-conducting materials on the market to replace or insulate metal. However, it is not really the type or thickness of insulation materials that matter most, but where and how you install it. In truth, it is the empty space between your roof and the ceiling that provides the real insulation. So, it is more effective to put the insulating material above the ceiling, rather than right below the metal roof. Secondly, this empty space must be properly ventilated. Eaves vent would help, but it would be even more efficient to have the opening at the top. There are several ways of doing this without compromising your protection against the elements, something you can explore with your architect or builder.
The administrator of a retreat center once approached me with a similar problem, saying that their dormitories get uncomfortably warm but that their renovation budget is very limited. I recommended opening the eaves ceiling and replacing these with mesh. This simple approach ventilated the ceiling space and resulted in a pronounced cooling effect.
It is not how high the ceiling is that makes the room cooler but the empty space within the ceiling. However, if you are stuck with a room with an inclined ceiling, with no clerestory window or an escape hatch for the hot air, the room will still be uncomfortable. A quick fix would be to provide more openings at the sides and an opening somewhere near the top of the wall. In this case, exhaust fans might help too. No, you need not go to the extreme of using a rotating roof monitor, like what you see atop factories, although this option is very effective. Not everyone knows that those rotating monitors are propelled merely by escaping heat accumulating in the ceiling and not by electricity.
Above are some diagrams to explain the concept further.
To supplement the treatment of ceilings, improving the roof is likewise important. The use of clay or cement roof tiles would considerably lower your room temperature. However, this can only be done on existing roofs with adequate pitch of at least 23 degrees and if the structural framing can support it. In most cases it’s doable, again something your architect or builder can help you to analyze. It may be costly, initially, but well worth it and quite energy efficient. As with clothing, the lighter colors absorb less heat, so it is best to use a lighter shade of paint or even reflective silver on your roof.
As for the room itself, having two or more openings (doors, windows, or a combination) for every livable space would help enable the continuous flow of air.
Have you noticed that in two story houses, the ground floor is much cooler than the second floor?
That is obviously due to the “cooling space” of the first floor ceiling. However, some rooms directly below roof decks tend to be hot. The solution could be as simple as covering the deck floor with loose flat stones like araal or luna stones. This will shield the slab underneath from the scorching sun. I would like to emphasize that the stones should be loose and not cemented to the deck to avoid heat transfer from the stone to the slab. The less contact it has with the slab, the better. In some countries, flat roofs are protected from the heat using oyster shells, which is both inexpensive and highly effective. Others diffuse the heat by providing water features, such as fountains, waterfalls and water curtains, strategically placed where air passes through. These are used profusely in Bali, Indonesia.
Finally, we must not discount the importance of proper planning and house selection. The most comfortable areas are those facing north or east. A western or southern orientation is ideal for drying areas. Some designers place garage, toilets and kitchens on the west side to protect the living areas.
So, before buying an air-conditioner and conditioning your mind to the additional burden of higher electric bills, take the time to analyze your home. There just might be a better, more economical solution!
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