When guests step into Gopala Krishnan and Sangeetha’s ‘Midori’ Green home in Madipakkam, Chennai, their attention is drawn not to the decor or layout but to the floor-to-ceiling windows. The top halves have high ventilators that remain open day and night—a feature once common in traditional architecture but rare in modern homes.

This simple design floods the space with natural light while continuously expelling hot air. “It’s the first thing everyone mentions,” Sangeetha shares. “The rooms feel brighter, airier, and somehow cooler.” Visitors are often surprised to learn that the couple uses air conditioning for only a few hours during peak Chennai summers, if at all.

Built by the sustainable design firm Green Evolution, this two-storey home received the 2024 Nippon Paint A.C.E.D Award for Sustainable Residential Project. In fact, the climate-conscious design was driven by the homeowners. “We wanted a cool, minimalistic home that can reduce the heat island effect in our city,” says Gopala. With clay-based Porotherm blocks, heat-reflective tiles, water recycling, and solar panels, their house is a live demonstration of how climate-conscious design can coexist with comfort.

Why our cities are heating up

Their home stands in stark contrast to the increasing urban heat island effect in cities like Chennai and Bengaluru.

As of 2023, only 2.9% of Bengaluru’s green cover remains, according to an analysis from the Indian Institute of Science’s Bengaluru Urban Information System. Meanwhile, the study revealed that built-up areas and grey infrastructure made up 86.6% of the land cover. “You’re essentially replacing shade, breeze, and moisture with heat-trapping concrete,” says Vijay Narnapatti, Chief Architect at mayaPraxis, an architectural design studio.

The result? Warmer days, hotter nights, and unpredictable seasons. Concrete and glass absorb and radiate heat, while barren terraces and minimal ventilation trap it indoors. High-rise buildings squeeze out space for trees. “Even small commercial blocks now use glass facades, which let heat in, only to cool it with air conditioning. Which in turn pushes hot air back out,” adds Vijay.

Urban planner and architect, Arjun M Gowda, traces Bengaluru’s rising heat back to a specific moment in its growth story. “The IT boom brought economic gains, but it came at the cost of unregulated expansion. We lost lakes, tree cover, and open spaces. Everything that naturally cools a city,” he says. The result is an intensified urban heat island effect, where densely built-up zones can be 2–3°C hotter than surrounding areas. The traffic and air pollution add to the city’s burden.

Read more: Keeping it cool: How Mumbai’s building rules must address heat stress

Common mistakes that make homes hotter

Vijay points out that orientation errors, poor material choices, and one-size-fits-all designs have worsened the heat wave crisis. “Homes in Hyderabad, Bengaluru, and Chennai look the same, though their climates differ. That’s not sustainable,” he adds.

In the northern hemisphere, the Sun rises in the east, arcs slightly southward, and sets in the west. As a result, the north-facing side of a building remains shaded throughout the day, staying cooler than the southwest or southeast-facing areas. “If we don’t plan this orientation properly, we can end up having living spaces or bedrooms relatively hotter, where we spend a lot of time,” notes Arjun.

Anupama Mohanram, head and co-founder of Green Evolution, says that people rarely plan for vertical airflow, which makes for cooler homes. She points out that without high-level openings like Jaali (perforated screen) or clerestory vents, hot air gets trapped indoors.

She also highlights the mismatch between window placement and natural breeze directions: “In Chennai’s humid climate, aligning windows to capture the south-easterly winds and allowing a clear breeze path from one side of the room to the other can make a huge difference.” Instead, many modern homes end up with sealed layouts and randomly placed openings that block cross-ventilation.

Residents prefer flat roofs, which soak up heat. Aesthetics takes preference over climate functionality, as people retreat to air-conditioned silos. But ACs are not just energy-intensive; they worsen outdoor temperatures. The deeper issue, say experts, is a lack of awareness. “People don’t know that design choices can reduce indoor temperatures by 2–3°C,” says Vijay.

Sustainable design hacks that work

1. Smart material use

The ‘Midori’ Green home uses lightweight hollow Porotherm blocks for exterior walls. These large, hollow clay bricks are excellent insulators. “They look good, and the holes reduce heat transfer,” notes Sangeetha. Internal partition walls use Autoclaved Aerated Concrete (AAC) blocks, which reduce the load on the structure and help with thermal insulation. 

The floors for bedrooms and living spaces are laid with handmade Athangudi tiles from Tamil Nadu. These are not just artisanal but also cool on the feet. “They’re far better than energy-intensive vitrified tiles,” she adds. Natural stone is used for flooring in balconies and staircases.

2. Thoughtful roofing

The home’s terrace is coated with white Solar Reflective Index (SRI) tiles that reflect solar radiation. “There’s a 1–2°C temperature difference between the indoors and outdoors,” says Sangeetha. Green Evolution also avoids false ceilings, which trap heat, and prefers sloped or shaded roofs that cast self-shadows.

Other options include Mangalore tiles and thatch. These traditional materials are making a comeback for their natural insulating properties. Mosaic tiles, which are more popular in Gujarat and Rajasthan, have high reflective properties. “Mosaic tiles are not required in Bengaluru. Heat reflective paints are ideal in terms of cost,” says Arjun. Also, mosaic tiles usually require more labour and time to set up.

3. Passive cooling and ventilation

Cross-ventilation is non-negotiable in climate-responsive design. Each room in the Madipakkam home has large, tall windows with ventilators.

The home’s orientation and window placement were mapped based on wind directions and sun exposure. “We avoided large windows on the west, planted trees strategically, and ensured every room had proper ventilation,” says Anupama.

4. Low-toxicity and low-waste choices

Exposed bricks reduced the need for plaster and paint. Where paint was necessary, the couple used low-VOC (Volatile Organic Compound) options that are better for health and the environment. Most of their woodwork is repurposed from scrap timber.

Another climate-responsive building material is Compressed Stabilised Earth Blocks (CSEBs), made from the home’s excavated mud and stabilised with a small amount of cement. Eco-friendly and effective in reducing indoor heat, they offer a sustainable alternative. “They’re a modern engineering material that keeps homes cooler,” explains Vijay. When combined with the rat-trap bond technique—creating air cavities for insulation—CSEB walls significantly reduce heat transfer, unlike non-biodegradable styrofoam insulation.

5. Systems that reduce energy and water use

The ‘Midori’ house also utilises solar power effectively. “Our electricity bill rarely exceeds ₹170,” says Gopala. A biodigester (a system to manage organic waste) treats black water, and grey water is filtered using a canna bed and carbon filters for gardening and flushing. Fixtures include low-flow sensor taps and dual-flush toilets.

6. Green cover

Vertical planters on balconies, a terrace vegetable garden, and creepers on exterior walls insulate and reduce the building’s heat absorption.

Meanwhile, the mayaPraxis Home Office in Panduranga Nagar, Bengaluru, has an expansive terrace garden, which reduces the heat load while offering fresh, organic produce. 

Rooftop gardens are becoming a popular urban design trend, not just for aesthetics or leisure, but for cooling. They add a layer of shade that protects the rooms below from direct sunlight. “With more people using terraces as weekend sit-outs or party spaces, these green rooftops are blending function with comfort,” Arjun said.

Are sustainable homes expensive?

Not significantly. Experts say the civil cost of sustainable construction is either equal to or only 5–10% higher than conventional methods. “Where you spend on insulation or solar panels, you save on plastering and electricity,” notes Vijay.

Gopala says that mass-produced tiles are cheaper, but the long-term cost of sustainable living is lower when considering utility savings. Anupama points out, “Civil material costs are on par now. The only extra comes from systems like water treatment and solar. But they pay back quickly.”

Scaling sustainable design

The Madipakkam house inspired Sangeetha’s parents to adopt similar upgrades during the renovation of their Velachery home. Yet, the bigger change must come from the industry and community. “Every street can be cooler if residents plant trees, paint terraces white, and share resources,” Vijay says.

Urban planners argue for an “urban vernacular” which communicates designs tailored to local climates, not copied from global templates.

Designing homes for passive cooling is not a luxury; it’s a necessity. With the right materials, orientation, and systems, residents can drastically reduce AC use, cut emissions, and still stay comfortable. As Sangeetha puts it, “It’s not just better for the Earth. It’s better for us, too.”

Also read:

• Co-creating cooling solutions for the homes of Bengaluru’s poor
• Heat insurance: The missing piece in India’s heat action plans
• Climate laws must enforce heat mitigation measures: Professor Vidhya Venugopal