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Reducing indoor heat

There are simple ways to go about it, and air conditioners are not necessary. 

20bgp-greensensGM81OS5VP3jpgjpgIn 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.

Crucial factors

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


Options for hot water

Energy consumed in heating water may not appear like a major problem, compared to industries, but thousands of homes each with 2 or 3 heaters may surpass many industries in energy consumption.

28PP-greensense_28_2325243eIt is easy to get an instant answer to the question “what’s the single major reason for high electricity bills in homes.” It is electric geysers. Yes we know, yet we have no single solution acceptable to all to get our daily supply of hot water. The last decade has produced a few viable alternatives, but they have not yet replaced the age-old geyser.

The challenge of hot water lies in the very nature of its need and this challenge can only be met with by using cold water! Unfortunately such a suggestion would get laughed at as impractical, for hot water bath has been part of our civilisation, biologically or culturally.

Though we need hot water mostly during the morning hours, it could also be needed at any time depending on the family lifestyle and guest arrival, with varying water quantity each time. Therefore, electric geyser comes to stay as an anytime, any quantity solution. On a quick look, energy consumed in heating the water may not appear like a major problem at all, compared to say some industry; but thousands of homes each with 2 or 3 heaters may surpass many industries in energy consumption. The problem is getting critical even in rural areas, with firewood getting depleted at rapid rate.

Solar water heaters have emerged as an effective alternative to the electric geyser, with 300 sunny days in a year in most areas of India. Roof-top installations, panel facing south, could be seen everywhere today, both on flat roofs and of late, sloping roofs too. The water storage tank comes with a built-in electricity geyser, an option which is not very desirable. In case of water not being hot enough, we end up heating all of 100 or 200 litres of cold water, consuming much more energy.

If really hot water is expected, we can route the solar water through a conventional electric geyser, thus reducing the power needed to heat up already warmed-up water.

Keep it simple

There have been complaints about lower water pressure if water is so routed, which can be resolved by the plumber. However, bringing solar water directly to the bathroom saves on extra connections, besides the confusing method of providing both fresh and solar water inlets for the geyser. One back-up electric geyser can be provided in the upper floor, with gravity flow to the ground floor baths.

Providing long piping for solar hot water is not advisable, considering the amount of cold water that flows first, before we get warm water. For this reason, avoid it in kitchens and wash basins. A larger family can save by staggering the bath timings, instead of installing higher capacity units. Also, locating it to get best sunlight hours is very important and so is occasional cleaning of the panel surface.

Most plumbers today know how to get the best from solar water heater connections, so it is time to look for other lesser known options.