Surviving summer with sustainable solutions

CHENNAI: This year, Chennai’s day temperature breached the 400C mark on April 2, over a month before the kathiri period set in. The city had its higher-than-usual bout of heat waves too, all month long. We’ve reached that broiling point when even staying indoors does little to escape the heat; especially when you don’t have the luxury of an air-conditioner.

You find that there’s little you can rely on when your primary place of shelter fails against the increasingly extreme vagaries of climate, insulation paint notwithstanding. Stuck at home safely amid the pandemic, if you find yourself Googling “How to keep the house cool?”, well, you wouldn’t be alone. Priya Rajnarayanan from Tirupur found herself relying on tricks that had been passed down from one generation to another. Instead of the mosquito net draped around your bed, if you were to use a wet cotton sari held up by a four-poster framework, you’d find so much relief, she says.

“The air that descends from the ceiling when you have the fan on would be hot. But, when it passes through these wet (not dripping wet) saris, it’ll turn cooler. You can do the same with cotton curtains by the windows and door. I’ve used jute sacks wetted and wrung out against the window to filter out the stark heat of the air coming in from the outside; jute can retain that moisture for hours,” she details.

Time-tested techniques
Besides these DIY remedies, more and more people have started to rely on reflective paint on the terrace floor and perhaps, even reflective tiles. For better results, there’s wisdom in returning to traditional architectural techniques that are slowly making a comeback, suggest architects and engineers in the sustainable construction space. “There can be a small opening on the wall, eight-nine feet from the ground. They are called vent shafts and measure about 15x5 cm (length vs height).

It’s the small slit that doesn’t affect the load. Basically, the hot air which is light in weight will be present only in the upper part of the room. The moment you turn the fan on, it will descend. You have to allow the hot air to leave the building. Even in old buildings, these shafts were put in. This can be incorporated into any house. Make sure the shaft doesn’t affect any sunshade and it’s better when there’s cross-ventilation (shafts on opposite walls),” suggests Krithika Venkatesh, architect at DTD Studio.

A central courtyard in oldenday houses did the same job, notes Aravind, a planning engineer at Magizh Builders. “If not for this, there would be provisions in the slate roof raised blocks that allow hot air to escape. Modern architecture, too, allows for these devices; the ceiling is higher,” he says.

Good old green cover
But, what’s sure to make a huge difference is vegetation, especially terrace gardens, he offers. “Especially for houses in the city. The green cover would prevent hot air from being absorbed by the roof,” he says. Krithika, too, agrees. “The nature of concrete is to absorb heat and radiate it. So, it’s possible to live in a concrete building during the day but difficult at night, when the re-radiation is high. Covering the building from radiation is the first solution. This way, the terrace garden can help,” she explains. Priya can attest to this modifier.

Living in a rented house where an air-conditioner was not an option then, it was her extensive terrace garden that saved the day all through summer. “I’ve had the garden for ten years. Everything there is wet — the bags, the soil in it, and greenery above it. So, the house also remains cool. Not only did I get something healthy for my family (in the form of fruits and vegetables), we got this benefit too. There is a small patch above the sit-out where there are no plants on the terrace. Even in that small space, the air is hotter than elsewhere.

Such is the difference. Even when you go up to the terrace, the green cover makes the open space much cooler,” she vouches. For those with the luxury of space around the house, leaving it open or better yet, having mud and vegetation as cover would help too, says Krithika. “Another way re-radiation happens (other than the roof and walls) is the ground. We concrete every piece of the house, we don’t allow water to penetrate; so, there will be a lot of heat radiation from the concrete floor.

There is an open space rule that every plot has to have. People usually allow for that space but concrete it. But, open space means allowing soil, allowing plants to grow,” she details. Besides these major changes, simple things like curtains from natural materials vettiver, bamboo and such can help too. A layer of lime mortar on the roof would offer immense relief, says Krithika.

Starting from scratch
While there are many modifications one can try, there is only so much we can do in an existing house. With a new building, however, there’s plenty you can do with the basics, says Goutam Seetharaman, principal architect at Centre for Vernacular Architecture. “If you see old houses, they will have thick walls. Now, we cannot afford it because of the cost but we can make the walls on just the south and west side thick.

If not that, you can make cavity walls or ensure that it is in the shade by planting a line of Ashoka trees perhaps,” he explains. High ceilings and big windows can also go a long way to help. And the mother of all rules is, perhaps, cross-ventilation, he says. While these norms do matter, there’s plenty more you can do with natural, ecofriendly and vernacular techniques and practices, it seems. The materials that you use matter, says Goutam and offers clay, exposed brick, hollow blocks, laterite and lime.

Lime lessons
Krithika vouches for the benefits of lime and offers a small comparison between this material and cement. “Urban Heat Island Effect is a study that was done worldwide; it found the temperature to be increasing every year. It is all because of the materials that are present on earth — be it the roads or buildings. All the production materials we use are heat absorbers. The heat they absorb is going to stay in the atmosphere and this phenomenon is very high in the city, where the use of concrete is extensive. We think concrete and cement are stronger.

Yet, cement came into use only after the industrial revolution. And all studies point to the life of concrete buildings to just 60 plus years. Lime mortar that comes from the same raw material is much stronger. The heritage buildings that we see have used lime and survived for over 200 years,” she explains. And the thermal comfort it offers is one of the best, she says. Paul Jacob, who has the rare privilege of living in a Britishera garden house that once belonged to his grandfather, attests to this.

What amazed him when he moved into the house was how little he needed to add to the house in terms of airconditioning or lighting. The tall windows and the high ceiling ensured that the house always had plenty of light. The lime-mortar walls offered perfect insulation against heat even in high summers; even after this many years, he says. Krithika resorts to a study they have done to prove the point. “Four years back, we constructed a building in Guduvanchery. It’s a complete lime building with Madras terrace. The temperature last summer was 7.9 degrees cooler than the outside and 8.65 degrees cooler than a concrete building,” she reveals.

Mud matters
Coming up as an equally viable and eco-friendly alternative is the humble mud. “Mud walls do two things when it’s hot outside, it keep the inside cool; when it’s cold outside, it keeps the inside warm. That’s why you see mud walls in houses in the Himalayan region, as well as in hot regions like the Middle East and here. VPR Thangamani, one of Aravind’s clients, decided to go for mud walls in the house he’s building at his farm in Perundurai, Erode.

The eco-friendly aspect of the material that it comes from the earth and returns to it appealed to him. While the building is close to being done, he’s getting the personal experience of its thermal comfort properties too. Just the site visits have proven much the walls affect the temperature on the inside as opposed to the outside temperature, he says. While traditional techniques often don’t get the mainstream spotlight, thanks to its cost or the lack of ready access to skilled artisans, there are plenty of options for one to choose from.

From lime to rammed earth constructions, cow dung floors to terracotta tiles, there’s something for everyone. If not the entire house, one can always pick the elements that fit their need and budget and reap benefits, while also being environmentally responsible. “With climate change and rising temperatures, it’s only with these old techniques that we can find balance,” remarks Aravind. Perhaps, you should find out for yourself.

Architects suggest that there is much wisdom in falling back on traditional techniques and practices that make our homes more livable in summers