Long before air conditioners, Indian builders shaped homes around sun, wind and water. From Rajasthani havelis to Kerala nalukettu, courtyards, jaalis, thick walls and stepwells created cooler microclimates tuned to local conditions. As summers worsen and energy use soars, this quiet, physics-based wisdom offers a vital vocabulary for truly sustainable modern design.
Think of yourself walking out in the Rajasthan sun, it dosn't shine but rather feels like it's pushing down on you and then go on to step into the courtyard of an old haveli. Straight away, something feels different. The light gets softer. The air feels cooler. Above you, a jaali is doing its job, just like it has for hundreds of years.
It's easy to think this is magic. It's not. It's just physics, figured out slowly, over a long time, by builders who had no thermostats and no ACs. They had to understand heat, air and water the hard way. Long before anyone talked about "sustainable design," India already had its own way of dealing with extreme weather. And it's worth irelearning this vocabulary, especially now that our summers are getting worse and our buildings are getting thirstier for power.
The essential thing to understand is that India doesn't have one climate. So it can't have one architectural answer either.
The Thar Desert is dry and scorching. The Kerala coast is wet and humid. The northern hill towns are cold. The Gangetic plains get a bit of everything and these are all very different conditions. So, a Rajasthani haveli and a Kerala nalukettu aren't two versions of the same house. They're two different answers to two different problems. Both Indian and both distinct in their ways.
Buildings in India didn't just sit in a place and put up with the weather. In many ways, the climate itself helped design the building. Strong sun meant people needed shade. Dry heat asked for thick walls and careful airflow. Humidity required open spaces and moving air. Scarce water meant storage, sometimes dug straight into the ground.
Once you start looking at buildings this way as answers to real problems, not just pretty patterns, the whole subject gets a lot more interesting.
Let's start with the jaali, the carved stone screen everyone photographs, but almost nobody really explains. A jaali isn't just "pretty latticework." It's a carefully worked-out filter as it controls sunlight, daylight, airflow and privacy, all at once.
The holes in a jaali are intentional, their size, how many there are, and where they sit on a wall all of this does real work. Make the holes smaller, and you block direct sun while still letting in enough soft light to see by. Angle them the right way and you speed up the breeze moving through a roomrather than just letting air drift in.
Kulbhushan Jain, the Indian architect and educator, who has studied desert buildings for years and remains one of the key voices on stepwell architecture, makes an important point here. He sees the jaali as part of a bigger system, working together with deep verandahs and thick walls to keep buildings cool.
The courtyard is another thing people are drawn to without really knowing why, and it deserves more credit than just being called "empty space in the middle." A well-designed courtyard actually works like a small cooling machine. Hot air rises and escapes through the open top, and cooler air gets pulled in from the shaded rooms around it to take its place, the same basic idea that green-building experts still use computer models to design today. At night, the courtyard lets go of all the heat it has stored through the day, releasing it up into the sky, so that by morning the rooms around it are noticeably cooler than the world outside.
What makes this really interesting is how the courtyard changes shape depending on the climate it's built for. In Rajasthan and Gujarat, courtyards are usually small and tightly enclosed, because in that harsh, dry heat, the less surface exposed to the sun, the better commonly seen in the pol houses of Ahmedabad. In the Chettinad region of Tamil Nadu, where the air carries moisture, the courtyard house opens up with long verandahs and deep, stretched-out plans designed to pull in cross-breezes. And in Kerala, the nalukettu opens up even further, staying loose and airy so that air keeps moving through the humidity. It's the same basic idea, just answered in completely different ways.
Underneath all the decoration, the real engineering happens in the walls themselves. Thick stone, mud, brick and lime slow down the heat. They soak up the sun's energy all through the day and then release it slowly, often much later, by which time people have moved to another room or the night has already cooled things off. Building scientists have a name for this now, they call it thermal lag but traditional Indian masons understood it by instinct, long before anyone had a word for it.
Roofs worked on the same principle. High ceilings let hot air rise up and away from people's heads. Domed or vaulted roofs gave the heat more surface area to escape from at night. And terraces, along with layered roof cavities, act like a buffer, breaking the sun's force before it ever reached the ceiling below.
If there's one structure that really shows off thinking, it's the stepwell. Those ancient, staircased reservoirs you find across western India, most famously in Gujarat and Rajasthan. Walk down into one, like Adalaj near Ahmedabad or the great Chand Baori in Abhaneri and you can actually feel the temperature drop with every level you go down, sometimes by several degrees compared to the surface above. Thanks to a mix of depth, shade, thick stone, and the slow cooling effect of standing water.
The American photographer and scholar Morna Livingston spent fifteen years studying these structures for her book Steps to Water: The Ancient Stepwells of India and she makes a point worth holding on to. A stepwell was never just a well. It was groundwater infrastructure, a place for people to gather, a religious site, a shelter from summer heat and a piece of architecture, all at the same time. That layering, all these different roles held together in one structure, is arguably even more impressive than the cooling itself.
It is important to note that none of this worked on its own. Which way a building faced, where the windows sat, where the courtyard was placed, how deep the verandah ran these were all decisions made together, not separate clever tricks used one at a time. And this is exactly what studies of climate-friendly buildings keep showing us even today, it's the combination of strategies that works, not any single feature by itself.
And behind all this physics, there were real people living their lives. Where a family slept in June wasn't where they slept in December. Courtyards weren't just there to keep things cool, people cooked in them, talked in them, spent their evenings in them. Privacy, gender, and the structure of the household all played a part in deciding which rooms opened where. The climate shaped how people actually lived inside it, day to day.
It's easy and a bit lazy, to end a piece like this by saying "our ancestors knew better." The truth is, they knew differently. They were working with what they had including the local materials, community labour, and skills passed down over generations. That doesn't translate neatly onto a modern tower block.
So the more useful question isn't whether we should go back to building the old way. It's about what we quietly handed over to the air conditioner along the way and whihc is a whole, hard-earned understanding of sun, air, mass and water.
And this understanding was never really lost. Through the twentieth century, architects like Charles Correa, Laurie Baker and B.V. Doshi kept proving the point, reworking jaalis, courtyards and thick walls into buildings that were unmistakably modern.
Clearly, the old vocabulary was never out of date. It was just waiting for someone to speak it again.