When architect Monish Siripurapu was growing up in southern India, air-conditioning was a rarity in middle-class homes. He recalls sprinkling water on the floor or on the roof to cool the house. 

Now Siripurapu, now 39 years old, tries to wean people off of air-conditioners using natural materials. His design and architectural firm Ant Studio makes installations made mostly of clay and water for everything from factories to schools to sports complexes. The designs are not only functional, they’re beautiful. An installation for a temple in the city of Pune is designed in the shape of a lotus leaf. Another installation for an auto parts factory, also in Pune, is arranged in squares, where tiles can be tilted to let fresh air and light through. 

What’s more, they support local livelihoods: Siripurapu sources clay pots and tiles for the installations from small artisans. 

As heatwaves intensify and strain day to day life in Indian society, increasing people’s access to air conditioning can’t be the solution, Siripurapu says. He hopes his demonstration installations will help “reduce the amount of space you’re filling with air-conditioning,” as the need for cooling solutions grows, Siripurapu says. 

Second skin

Hot summers are the standard for southern Asia’s tropical countries, but each year, the temperatures rise and extreme heat stretches for longer spans. In some cities, temperatures are hitting 50 degrees Celsius multiple times a summer. 

The burden of extreme heat most often falls on those who are least equipped to deal with it, including the urban and rural poor, the elderly, those working in outdoor jobs. Extreme heat could cost India 2% of the country’s economic output every year, according to new research from the International Institute for Environment and Development.

A range of new cooling technologies are in development. Even when those commercialize, however, they’re unlikely to immediately reach the individuals and communities who need them most urgently. 

Siripurapu sees the opportunity to use a low-cost technology on a large scale: terracotta. The baked clay is a long-standing staple in Indian households for keeping drinking water cool. The science behind it is evaporative cooling: when hot air passes over wet clay, the water evaporates, pulling the heat out.

Siripurapu’s solution is a structure composed of a large frame of stainless steel on which many terracotta pots or tiles are placed. The wall-sized structures are set up several feet away from the outside walls of a building. Water is then dripped through pipes at the top of the frame over the tiles or pots. As hot air passes over the wet terracotta, it cools before entering the building. 

“It acts like a second skin” for the building, Siripurapu says. He estimates that CoolAnt can reduce a building’s electricity bills by 15% to 30%, depending on how much area is covered by the installation.

The density of the tiles and where they’re placed depends on the space to be cooled. Heat typically enters from the south or west walls of a building, so Ant Studio suggests to clients that they begin there. At the auto parts factory in Pune, CoolAnt was installed on three sides of the building, covering a total area of 25,000 square-feet. 

Artistic origin

Siripurapu built the first version of CoolAnt in 2015 as an art installation. He placed hundreds of handmade terracotta pots together in the shape of a beehive, and flowed water across the beehive to demonstrate the cooling effect. Pots for the installation were sourced locally to support local potters. 

In 2018, Siripurapu made the first commercial version of the beehive for an electronics factory in the northern Indian city of Noida. The project got global attention. Siripurapu received a grant and mentorship from the UN Environment Programme to develop the idea. It brought more attention than he was ready for at the time. 

“I struggled badly,” he recalls.

The global slowdown during the pandemic, ironically, gave him an opportunity to hire a team and develop his materials supply chain. 

Other Indian architects and building designers are gravitating to natural materials to address the growing need for cooler spaces in India’s built environment. 

The company A Threshold used terracotta and other materials to cool a residential building in a dense neighborhood in Bangalore. Earthen Studio, a sustainable architecture practice in the south Indian city of Chennai, uses locally available materials such as rammed earth, adobe bricks and grass to build the walls and roofs for homes. 

“A lot of architects are trying to revive the traditional techniques,” Earthen Studio’s Krithika Venkatesh says. 

Her studio has also used “pantile” roofs made of clay tiles, or the “madras terrace roof” made of clay bricks or tiles, placed on wooden rafters and set in lime mortar – techniques found in old homes.

“We have 200 to 300 year-old roofs,” says Venkatesh. “These are time tested.”

As natural materials were substituted with reinforced cement and concrete, knowledge of how to use them has dropped. These otherwise frugal cooling tools have in turn become more expensive to build with and maintain.

Capital, Venkatesh says, is needed to “help us document and revive more practices.”

What’s scalable

Most projects in India that are reviving natural materials for cooling are being financed by clients, not investors. Aid and grant funding is being used for projects supporting very low-income populations. 

For example, UNEP and Mahila Housing Trust, a nonprofit in western India, are undertaking projects to apply  heat-reflective paint on rooftops in low-income housing and slums. The paint can bring down indoor temperatures by five to eight degrees Celsius.

In the western state of Rajasthan and in the northern city of Jammu, Mahila Housing Trust has set up “cooling stations” for street vendors, rickshaw drivers and anyone else who works outdoors and needs to escape the scorching heat for a while. These are typically one-room structures with walls made of vetiver grass or “khus”, which absorbs heat, and when sprayed with water, can lower inside temperatures through evaporative cooling. The room has ceiling fans, and in some cases a sprinkler to sprinkle water in the room. 

Ant Studio has commissions from Indian conglomerates Godrej Group and ITC Group; ITW Automotive, a unit of the US manufacturer Illinois Tool Works; as well as for community buildings, like the temple in Pune. Siripurapu says that amid Europe’s record heat waves this summer, he fielded inquiries from France for a business collaboration, and to bring CoolAnt to residential properties.

There’s a lot of demand, Siripurapu says. The company earned about 60,000,000 rupees ($630,000) for the first half of the year. But the model isn’t set up for easy replicability or scale. All of its projects are customized and Ant Studio itself handles maintenance. 

One of the changes it has already made concerns the sources of its terracotta. The company now uses a mix of handmade and factory-made pots and tiles, the latter of which can be made faster and in different shapes for efficiency and aesthetics. 

It’s also grappling with the natural limitations of its natural materials. Ant Studio uses only CoolAnt and indoor fans to cool its office in Noida. But during the rainy season, the space gets very humid, which can cause its electronics to malfunction. Siripurapu installed dehumidifiers. 

“In peak humidity conditions, you need something mechanical to counter that,” he says. 

Expansions plan

With interest for new use cases and markets, Siripurapu is thinking about how to scale the roll-out of its systems. One avenue for substantial growth is specific designs for air chillers, a type of appliance used for equipment or factory cooling. On hot days, when the temperature outside is 45 degrees Celsius or hotter, keeping the inside of large factories cool is extremely energy-intensive and expensive. CoolAnt terracotta envelopes can be used to mitigate the heat that air coolers throw off, reducing the chillers’ energy consumption and improving their performance, Siripurapu says. 

Ant Studio is also now designing cooling towers for use in the middle of a space, and it continues to design art installations. 

One of the studio’s most ambitious projects is a sports complex without any air-conditioning in the southern city of Vijaywada. The company is using CoolAnt terracotta envelopes, but also plans to use earth air tunnels, an ancient system in which air from outside is passed through a pipe underground where it cools naturally before it is released upward into the building.