As summer temperatures reach record highs across India, our homes are increasingly turning into heat traps. While air conditioning offers immediate relief, relying heavily on high energy-consuming cooling methods cannot be a long-term solution. These are not sustainable and contribute to carbon emissions. On the other hand, many quick DIY fixes may not work, and heavy architectural changes may not be an option for those living in rented homes or in budget-conscious households.
So, how can we make our homes more liveable as cities heat up? What are some sustainable, affordable yet durable options available for cooling? We brought together architects, urban planners, and cool home owners for a Citizen Clinic on Sustainable Cooling.
FAQs: Expert advice on cooling solutions
The experts — Deepak Gupta, Architect and Managing Director, D R Design Consultant Pvt Ltd, Sangeetha, Analytics Manager and owner of Midori Green Home and Deepak Kumar, Partner at Mindwagon Sustainable Design — gave valuable insights on the topic. Here is a clear breakdown of their practical, eco-friendly strategies for keeping homes and neighbourhoods cool without breaking the bank or harming the environment.
1: How do I use natural ventilation to my advantage? I live in a rented apartment facing the backwaters of the Arabian Sea. During the day, there is a cool sea breeze until 1 pm, after which the sun becomes too harsh to keep the windows and curtains open. We currently use an AC, but I want to use it less to save on electricity costs and environmental impact, and to avoid keeping the windows shut (which defeats the purpose of a sea-facing view). I live in a humid area, so a traditional evaporative cooler only makes the humidity worse.
Deepak Gupta: In places with high humidity like Chennai and Mumbai, you require cross-ventilation. In many of our projects, we introduce ventilators that touch the ceiling. To handle the harsh afternoon sun, you can install bamboo roller blinds for shading. You can also use dehumidifiers or install small wall grilles, even as small as 1 foot by 2 feet. Creating an inlet at the bottom and an outlet at the top helps reduce indoor heat because it forces the air to move.
One crucial rule of ventilation is that whatever air comes in must go out. Even bedroom doors should always allow for airflow; traditionally, doors were built with angled slats to facilitate this. Think of architecture as a “third skin”; even at night, you should not sleep in a completely closed room. You can also install stepped glass to allow trapped hot air to escape from various parts of the house. A stepped glass setup is an Insulated Glass Unit (IGU), where one of the panes is larger than the other, giving a step-like effect, to enhance ventilation of air.
Why ventilation is important
2. How have you approached ventilation in your home, Sangeetha?
Sangeetha: In our home, we incorporated massive 6-foot-tall, floor-to-ceiling windows in every room. It’s the first thing visitors notice. Our architects made sure the orientation of the windows is aligned to the wind direction. We keep these windows open so hot air can naturally escape. Even when we do turn on the AC, we close the lower vents and leave the upper vents open to let hot air exhaust out. Many people don’t even open their windows these days, but simply letting your home breathe by opening curtains and windows is the easiest step you can take.
Deepak Kumar: For glass and opaque doors, it’s far better to use a louvered door or a mosquito-mesh door. This enables continuous cross-ventilation through natural atmospheric pressure differences. Additionally, keep your bathroom and balcony doors cracked open. The plumbing shafts in bathrooms act as natural chimneys for air movement, especially in high-rise apartments. You can also add an acoustic louvre or a simple ventilation slit to the bottom of bathroom doors to encourage airflow.
Tackling trapped heat in small homes
3. Independent homes are often built very close to each other nowadays, which exacerbates heat. How should this be tackled?
Deepak Gupta: There must be at least a 5-foot gap between neighboring buildings to allow a sufficient air inlet. While this building rule is frequently violated, I make it a mandatory requirement for all my client projects.
4. In urban informal settlements (slums), families live in into 10 by 10 and 10 by 15 square feet homes that trap intense heat due to asbestos or cement sheet roofing. What are some viable solutions?
Deepak Kumar: A very cost-effective solution links directly to urban agriculture: place metal sheets with crates of soil on top of the existing roof ledges to grow vegetables. The soil and vegetation act as a natural heat barrier while also dampening the loud tapping sound of heavy rain. You can also use PUF (Polyurethane Foam) insulation panels sandwiched beneath or between the roofing sheets.
Deepak Gupta: If constructing a new low-cost structure from scratch, the side walls should be built using hollow concrete blocks, and the roof should be made of sandwich PUF panels. Compressed earth or soil blocks are ideal for walls, as they require zero energy to produce and offer high thermal mass.
Read more:Informal settlements try out new cool roof solutions to beat the heat
Moving away from glass for sustainable design
5. What can be done about the heat and glare generated by glass-heavy buildings?
Deepak Kumar: Glass facades cause severe solar glare alongside heat, often making interior spaces uncomfortable to use. For offices with standard glass, retrofitting them with spectrally selective window films allows natural light inside while blocking radiant heat. If glare remains an issue, tinted films can be added.
For residential units with glass balconies, always opt for external shading (like exterior blinds or louvres) rather than internal curtains, as internal blinds trap heat after it has already entered through the glass. Design shading angles according to the movement of the sun to maximize energy efficiency.
Deepak Gupta: You must create a buffer zone (like a deep balcony or double skin) to prevent direct sunlight from heating up the glass surface.
Deepak Kumar: Earlier, builders used “rat-trap bonds” for brickwork (—arranging bricks to leave an insulating air cavity inside the wall. This significantly reduces heat inflow and prevents water seepage in high-rainfall regions. We need to move away from using glass! Bigger windows do not automatically mean better ventilation. What matters most is having an inlet and outlet for air to flow through.
Bringing greenery home
6. What retrofitting steps can residents take regarding indoor and outdoor greening? Does it genuinely reduce heat?
Sangeetha: Fill your living space with soil, potted plants, and local flora instead of hard concrete surfaces. The primary goal is to intercept heat before it enters the home. Use tall indoor plants on balconies or grow money plants vertically up wall trellises to create green thermal buffers. If you have access to a flat roof, establish a terrace garden; the soil layer cools the living spaces directly underneath.
Deepak Kumar: Urban landscaping is becoming essential. Roofs and terraces are usually wasted spaces; transforming them into terrace vegetable gardens (which can be fed using home vermicomposting) cools the structure while producing fresh food.
7. Residents often worry about water seepage when setting up terrace gardens. How should they address this?
Deepak Gupta: Seepage is indeed a common risk if ignored. You should never place soil directly on top of the concrete floor slab. Always install proper waterproofing layers, drainage mats, and raised planting beds or containers with adequate clearance underneath.
Watch this video to get more insights from the discussion:
Policy interventions for cooling solutions
8. Are there policy-level interventions that cities should incorporate to tackle urban heat systematically?
Deepak Kumar: We need mandatory Energy Performance Benchmarks (EPB) starting right at the design phase. Unless energy consumption thresholds for cooling and water usage are strictly mandated, people won’t take them seriously. Existing building standards, like the Energy Conservation Building Code (ECBC) currently apply mainly to government and large commercial buildings. These codes must be made mandatory across all residential developments, and architects must actively guide clients to follow them.
Deepak Gupta: The GRIHA (Green Rating for Integrated Habitat Assessment) framework already provides comprehensive guidelines for evaluating a building’s environmental footprint. Raising awareness among clients and homebuilders about these ratings is essential.
Sangeetha: Municipal authorities should provide financial incentives or tax rebates for property owners who maintain green spaces, alongside soft mandates that require a minimum percentage of greenery over concrete paving.