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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


Try to shade the surface with wooden pallets, which is a frame of wood planks with gaps in between.

06bgp-greensensGN01MOLE03jpgjpg.jpegFor reasons more than one, the summer season in India is a popular topic of discussion. It is possibly comparable to the British often talking about their rains.

Imagine the book titled ‘Indian Summer- Lutyens, Baker and Imperial Delhi’ which has little to do with climatic data on India, being the story of how New Delhi was planned and made, written by Robert Grant Irving. Another book by the same title ‘Indian Summer’ is on ‘The Secret History of the End of an Empire’ written by Alex von Tunzelmann, even more remotely connected to the idea of a season. Even the film ‘Heat and Dust’ directed by James Ivory attempts to refer to our summer, even if it is metaphorical. Summer is the talk of town.

Nowadays, Indian summer is in the headlines for the more direct climatic reasons – every year new records are being set for the highest temperature of the decade or so. How we the people and our consumptive patterns are among the creators of this record is rarely discussed, but the soaring temperatures are always debated intensely. As a fall out, sale of air conditioners is also soaring, paradoxically pushing the outdoor temperatures further up.

It appears like temperatures have crossed the limits of passive cooling and we have given up hopes on simple measures. Partly yes, but in many cities like Bengaluru which witness the extremes only for few weeks in an year, there is no real need to switch over to air conditioners. Shading the roof during the high summer can reduce indoor temperature to bearable levels, if not as low as AC can achieve.

Terrace gets direct solar incidence, hence has high solar heat gain, which is transferred to inside surface by conduction. Imagine we try to shade the surface with wooden pallets, which is a frame of wood planks with gaps in between, used in packaging especially across ships and such others. Google search can show up many images. Once unpacked, these are discarded for sale in the seconds market.

No heat transfer

Placed on the terrace, they let in direct light between the gaps for a short time span, which does not let the surface gain much heat. Of course, the air under pellet gets heated up but hot air moves out letting in cooler air from outside the pellet, so very little heat would transfer through convection.

These pellets, often made abroad with pine and such types of timber, can withstand sun and rain for a long period, if treated well. The gaps between them can be maintained fairly narrow; as such anyone can walk over them without any discomfort. In case of any unexpected summer showers, the rain water drains out without any hindrance. Once the scorching summer is over, the pellets can be safely stored for reuse the next season.

The theory behind this idea is rooted in a big sounding term ‘ventilated cavity roof’, but can be achieved in a small budget.

Salute the sun, and build

Orientation of structures to bring in natural light and avoid glare and heat is crucial.

01bgp-greensens_01_1740129eAsk any elderly person from any village – what is among the most important criteria to be followed in locating a building? How would they decide the location of specific rooms? How are the windows positioned? We can ask many more questions, but to get one single answer – respect the directions of the sun.

Commonly termed as orientation, humans learnt the importance of effective orientations towards a good home possibly as the nomadic way of life gave way to settled life! Among the earliest principles of eco-friendly buildings to be discovered, orientation continues to be valid even today, helping those who follow the sun and punishing those who disregard it.

The exact location of the sun varies depending on the place and time of the year. Also, the height to which it rises and the angle it creates in comparison to the position of the earth is a matter of great implication.

All these data have now been precisely documented under solar charts, altitudes, azimuths, shadow angles and such others for each location on earth. We know that the sun not only brings in light, but also heat and glare; as such, solar heat gains, sky glare and other factors affecting their impacts on our buildings have been quantified to precision.

Technology helps

During the last few decades they were available in printed version, but now with the advent of computer applications varied kinds of softwares are available which assist in applying our knowledge of orientation to design better buildings.

From mere data for design incorporation to real time simulation exercises, today a building can be pre-checked for natural air, day light, window protection, shading patterns, sky glare, heat gain and such others.

Such advanced applications would of course demand guidance by experts with high-end equipment, which all of us cannot afford to have. Incidentally, IGBC, TERI, BEE and such institutions with all their knowledge of research and data also suggest orientation as a safe starting point for design.

Keeping such technological skills aside, there are many common sense approaches that could be applied on an everyday basis. Our past generations have been a large repository of time-tested knowledge systems which can take care of a majority of basic design sensibilities.

Stating this is not to negate the relevance or importance of modern research-based data, but only to admit that we can manage basic climate confirming designs just by being sensible to our contexts.