Walk into a Jaisalmer haveli at two in the afternoon in May. The lane outside is baking. Inside, the air is calmer and noticeably cooler, and nothing has been switched on.
That drop in temperature was designed. The passive cooling techniques in traditional Indian architecture were not decoration or habit. They were answers to specific climates, worked out over centuries by builders who had no fans, let alone compressors. Many of them still work.
One country, several climates, different cooling rules
India has more than one climate, and the old builders treated each differently. Rajasthan’s hot, dry heat calls for one set of answers. Kerala’s warm, humid air calls for another. Ahmedabad swings between the two.
A Jaisalmer house tries to keep heat out and hold on to coolness. A Kerala house tries to keep air moving. Copy a feature without its climate and you get a jaali that looks good and does nothing.
How narrow lanes and shared walls cut the heat
Cooling started at the city scale. Old Jaisalmer and Jodhpur have lanes only a few metres wide, with tall buildings facing each other. The buildings shade the street, so it stays cooler than a wide, open road would.
Ahmedabad’s pols go a step further. These clusters of houses share side walls, so each home exposes only its front and its roof to the sun. Less surface in the sun means less heat to deal with.
Why the courtyard works like a chimney
Almost every regional style has a courtyard. During the day, hot air rises out of the open top. At night, cool air sinks in and settles. By morning, the surrounding rooms are drawing on air that is cooler than the street.
You see this in Rajasthani havelis and in the large Chettinad mansions of Tamil Nadu. The Kerala nalukettu has one too. Its open nadumuttam lets in light, air and monsoon rain. Add a tulsi plant, a tree or a small water basin, and the courtyard cools further.
How thick walls delay the heat by hours
Stone, lime-mortared brick and rammed earth are slow to heat up. The sun warms the outer face of a thick wall through the afternoon. That heat takes many hours to reach the inside. By then it’s evening, the outside air has cooled, and people open the windows.
Architects call this thermal lag. The round bhunga houses of Kutch use it well. Their thick mud walls and conical thatch roofs keep interiors comfortable even when the desert outside is punishing.
Roofs got the same attention. In parts of Rajasthan and Gujarat, builders laid a thick layer of mud and straw, called phuska, over the roof structure to slow heat coming from above. Lime wash reflected sunlight off walls and terraces. Many Rajasthani houses also had a tehkhana, a basement room for the hottest hours.
What jaalis, jharokhas and chhajjas actually do
A jaali is a perforated screen, usually carved in stone or wood. It cuts glare and breaks direct sun into small patches. Breeze still passes through. The windows of the Sidi Saiyyed Mosque in Ahmedabad are the famous example.
Jharokhas, the projecting balconies, catch passing breeze and give people a shaded seat above the street. Jaipur’s Hawa Mahal has 953 of these small windows, and its upper floors were planned to stay airy through the summer.
Chhajjas, the deep overhanging eaves, are the simplest tool here. In hot-dry regions they block the high summer sun. In Kerala they keep rain out, so windows can stay open through the monsoon.
Stepwells and khus screens: cooling with water
Stepwells like Chand Baori in Abhaneri and Rani ki Vav in Patan were built to store water. They also became some of the coolest places around. Walk down the steps and the air cools, because you’re moving below ground into shade and damp stone. People gathered there in summer.
In north India, families hung wet khus screens, made of vetiver roots, across doorways and windows. Hot, dry wind passed through the damp mat and came out cooler, with a smell of wet earth.
There’s a catch. Evaporative cooling works in dry air and fails in humid air. A khus screen in Kerala would only make the room stickier.
What Laurie Baker and Doshi borrowed, and what you can too
Laurie Baker understood this better than most. His brick jaali walls at the Centre for Development Studies in Thiruvananthapuram let in air and filtered light at a fraction of the cost of a mechanical system. Balkrishna Doshi’s own studio, Sangath, in Ahmedabad, is partly sunken. It has vaulted roofs covered in reflective china mosaic and pools of water around it. It looks new, but every move has an old precedent.
Not everything transfers. A courtyard is hard to fit into a 2BHK flat. Mud roofs need upkeep that few owners will commit to. And when summer touches 45°C, passive methods alone may fall short.
The principles still scale. Spend on shade before you spend on better glass. Give hot air a way out through light wells, stairwells or high operable windows. Finish the roof in a light colour or ventilate it. Then plan for night ventilation, because heavy walls only help if you can open the building once the air cools.
Where to start on your next project
Begin with the sun path and the prevailing wind before you pick a facade. Decide where the shade comes from and where the air leaves. Mechanical cooling can then be sized for the heat that remains, which is usually far less than most buildings now plan for.
Old buildings in India got this order right. Following it today costs very little.
FAQs
How did people in India stay cool before air conditioning?
They relied on building form. Shaded lanes, courtyards, thick walls, jaalis and deep eaves kept heat out. Water, from stepwells to wet khus screens, cooled the air further.
Which traditional cooling method works best?
It depends on the climate. Thick walls and courtyards suit hot-dry regions like Rajasthan. Deep eaves and cross-ventilation suit humid regions like Kerala. No single method wins everywhere.
Does a courtyard really cool a house?
Yes, if it’s sized and shaded well. It pulls hot air up and out during the day and collects cool air at night. A courtyard open to full sun with no shade will mostly just heat up.
Do thick walls work in humid climates?
Not very well. In warm-humid places, heavy walls hold heat after sunset, when nights stay muggy. Lighter walls, large openings and constant airflow work better.
Can jaalis work in modern buildings?
They can. Brick, concrete and metal jaalis all cut glare and let air through. Orientation matters, so place them on the sides that take the harshest sun.
Can passive cooling replace air conditioning in Indian cities?
In most cases it can reduce the load, not remove it. Good shading, ventilation and roof design make a big difference. In extreme heat, a smaller AC running fewer hours is a realistic target.
What can homeowners do on a small plot?
Shade the west-facing windows first. Paint the terrace a light colour or add a ventilated roof layer. Open a high window or skylight so hot air escapes, and ventilate at night.