Rooftop Harvesting

by 

Riya Vazirani Laheja

Cities are growing faster than most people can keep track of. Buildings are going up on every empty patch of land, contractors are advertising “green buildings” that don’t really feel that green, and construction is happening everywhere at once. Most of the time, nobody stops to think about it because that’s just how things have always been done. But maybe that is the problem. Maybe it is worth thinking twice about, whether the choice is buying a new pen or building on a square foot of land. In Puducherry, India, a group of architects is doing exactly that, and their project might be one of the most creative rethinks of what a home even is.

The project is called Humanscapes Habitat, and it was designed by an architect named Ramya Prasad along with her team led by Suhasini Ayer, the head of Auroville Design Consultants.. Suhasini is an architect and urban planner working on a housing project in Auroville, and their whole idea is that with the right technology and planning, homes can be built very differently from the way they usually are. Homes where people can genuinely live well without damaging the land underneath them. The project was recognized with the Green Solutions Award at the COP26 climate summit in Glasgow in 2021.

The first thing the team thought about was the ground itself. When rain falls on a piece of land, it takes a specific path. Over thousands of years, water carves the landscape into a shape, and every drop that falls kind of knows where to go. When land gets covered with concrete and its shape gets changed, the water has nowhere to go, and that is exactly why cities like Chennai flood every monsoon. Water rushes into homes, and ironically, in the middle of all that flooding, many people still don’t have clean drinking water. The whole thing is a mess that has been created by ignoring how water actually moves.

So at Humanscapes, the design starts with the rain. Water from the rooftops flows down through pipes that connect to channels around the building. Older Indian homes used to have chain systems where water would trickle down chains instead of pouring straight down, so the ground around the base didn’t get hit too hard. If water falls too fast from a roof, it just erodes the soil. To slow it down further, the team placed pebbles in the ground where the water lands. Between cement blocks around the building, bricks were laid with gaps in them so rainwater seeps through instead of running off. In the middle of it all sits a borewell. So even during a heavy downpour, the water slowly makes its way into the earth instead of flooding the surface. That is rainwater harvesting done properly.

The next thing to figure out was heat. Puducherry has hot and humid weather, and when those two things combine, people sweat, which usually means more fans and more air conditioners and more electricity. So the team designed every home with cross ventilation. The doors and windows are placed so that air flows through naturally, which cuts down on how much artificial cooling anyone actually needs. They also tracked the sun. They noted which part of the building would get hit by direct sunlight at which time of day, so they could design shade in exactly the right spots.

The walls themselves are made of red earth from the land nearby, and this is honestly one of the coolest parts. Mud walls don’t let heat in easily. Even when the sun beats down and the heat starts pushing through, by the time it gets four or five centimeters into the wall, the sun has already moved and the wall stays cool. So the house stays comfortable without needing a machine to fight the heat. It is the kind of design that works with the weather instead of against it.

Now here is a statistic that is genuinely surprising. In 2020, the construction industry was responsible for 36% of the world’s total energy use and 37% of energy-related emissions. That is more than a third of everything, coming just from how buildings get made. Which means changing how construction is done could actually change how much energy the whole planet uses. The Humanscapes team took this seriously by asking which materials they could cut back on and which ones they could replace with something better.

For starters, they didn’t use much steel, cement, or plaster. A lot of what they used was construction waste that would have otherwise ended up in a landfill. They ground up old construction debris and used it on the mud walls. They put third-grade white ceramic tiles on the roof to reflect heat away from the building. Limestone pieces were used along the walls to keep the interior cool. All of this stuff was basically free because it was considered garbage by everyone else. Every couple of weeks, the team would visit local shops to collect whatever waste materials were available, since finding these things wasn’t easy and required going back over and over.

But the design is not only about the building. It is also about how people live inside it. Humanscapes was designed for single people, couples, and small families to live together and share things. There is common space, common washing machines, and shared cooking. One resident said that she moved in during February and has never felt lonely since, because there are always people around to talk to. When she doesn’t feel like making dinner, someone else is cooking and shares with her. That kind of setup takes what could be a bunch of isolated apartments and turns it into something closer to a community.

The building also recycles its own water. Grey water from drains gets treated and used for the gardens, so nothing gets wasted. Solar panels on the roof provide electricity, which makes sense because Tamil Nadu is one of the most reliable places for solar power in India. The team set a goal of 45 kilowatt hours per person per day, which is about 30% less than the standard energy usage for middle income group housing. And they are actually hitting that number.

The obvious question is whether this could be done elsewhere. The answer is yes, but with a big caveat. This design cannot just be copied and dropped into a different city. Humanscapes works in Puducherry because the team used red earth that was locally available and designed around the specific climate there. If the exact same building went up in a different region with different weather and different soil, it wouldn’t work the same way. The idea is not to replicate the design, but to replicate the approach. Wherever a building goes up, someone should look at what materials the land already offers, look at how the sun and wind move, and design something that fits that specific place.

Suhasini and her team are hoping this model can be used on college campuses in the future, and honestly that would be a big deal. Sustainable buildings alone won’t solve climate change, but they can make cities way more prepared for what’s coming. Floods, heatwaves, energy shortages, all of it. And even if this is just one small project in one part of India, it shows that a different way of building is possible. It just has to start.

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Riya Vazirani Laheja is a student at Ridge High School. She loves writing, reading, STEM, and playing soccer. She is very passionate about her studies, helping people, and working with kids. She is a hardworking and dedicated volunteer and has leadership experience in increasing awareness regarding South Asian Mental Health and teaching STEM topics to younger children. She also loves to try new things and visit new places whenever she gets the chance.