Reducing indoor heat
There are simple ways to go about it, and air conditioners are not necessary.
In hot climatic zones like Rajasthan, people used to sleep on terraces. Even in places like Delhi, one can see many low income and middle class people sleeping outdoors, on pathways or verandahs. In slightly more humid regions like Kerala or Kolkata, traditional homes have perforated windows and doors with louvres which are kept open at night.
The principle behind these and more of such practices is simple – the night temperature is always much lower than the daytime in summer months. If we can ensure that the benefits of lower temperature are exploited, one can ensure a good night’s sleep. Our body works much on a comparative basis, where the reduced night temperature itself provides the relief we need, after exposure to a daylong heat. The emerging practice of sleeping at 22 degrees chilled air and then face the next day’s wrath at 40 degrees is neither healthy nor inevitable.
The accompanying picture is an apt example to show how we can manage indoor comforts through managing air. We need three kinds of air, first being cross ventilation, achieved through windows in differently oriented windward walls. Secondly, we need body-level breeze made possible by the ceiling fan. The third one, displacement ventilation, is the most important for indoor thermal comfort. It displaces the hot indoor air – air warmed up by solar heat gain on ceilings, heat conducted through the walls, heat dissipated by human bodies inside and any mechanical instruments – through roof-level openings and lets in cooler outside air.
Typically, most indoor spaces today do not have voids at ceiling level, hence the warmer indoor air gets stuck inside the room. In the picture too, the wall just below the roof has no ventilator, the idea cancelled due to provision of air conditioner, though elsewhere in the same building there are displacement ventilators. In the process, this particular room gets heated up during the summer months, so the AC steps in, while the whole year it stays nearly idle.
During the summer months, the real challenge is not to cool the indoor air, an idea which leads to installing an air conditioner, which is an energy guzzling, unsustainable and cost escalating practice. Simply throwing out hot air and letting in the cooler air from outside can make a notable difference in reducing indoor heat, though it may not be as effective as an air conditioner.
Among the temporary arrangements, turning the table fan towards the window is the simplest. After keeping a few windows open, turn on the fan with its face outside. It works like displacement ventilation cooling the indoors in a short time. Unlike the roof-level voids which work at a height, here the warmer air at body level gets thrown out. The ceiling fan can compliment the air circulation.
The case of the fan may be a makeshift solution for few