Cooling options: Homes

What to build or change, what keeps it working, the traps to avoid and rough costs.

Protects. Sleep, care work, and the older people, young children and sick people who spend the hottest hours indoors.

Key caution. Check the roof type, fire safety, tenure and ventilation before any retrofit.

Options, and what keeps each working

Option	What it does	Keeps working with	Avoid	Rough cost
Reflective roof coating	A white, solar-reflective coat on the roof, so less of the sun’s heat passes into the room below.	Repainting every few years, and a thermometer to check it works.	Promising a fixed number of degrees before you have measured.	About US$2.6–US$3.7 per m² (₹250–₹350 at Indian prices)
Lime whitewash	A cheap seasonal white coat that households can apply themselves when a commercial coating is out of reach.	Recoating every season, by a named group.	Treating it as a lasting retrofit.	No solid range: get local quotes
Better roof panels	Replace or cover thin tin or asbestos sheets with an insulated roof panel.	A structural check, and secure enough tenure to make the investment safe.	Scaling up before checking structure and tenure.	No solid range: get local quotes
Insulation under the roof	A fire-safe layer or false ceiling that slows heat coming through the roof.	A fire-safety review of the material.	Flammable sheets near kitchens or wiring.	No solid range: get local quotes
Shade on walls and windows	Bamboo blinds, jute screens or awnings on the sunny side stop sunlight before it reaches the room.	Fixing and replacing screens each season.	Blocking airflow or all daylight.	No solid range: get local quotes
Let the air through	Higher vents and openings that let hot air out at night.	Security, rain protection and mosquito screens.	Openings that let in dust, rain or intruders.	No solid range: get local quotes

What the evidence says

In 16 homes in an Ahmedabad informal settlement, measured in September 2017, rooms under a modular roof averaged about 33.8 °C against 36.8 °C under asbestos sheets. White paint on tin did not beat asbestos or concrete in the same comparison: measure before you promise.
In a two-year trial in Burkina Faso, cool roofs lowered indoor temperatures by 1.2 °C in tin-and-mud homes and 1.7 °C in tin-roofed homes, and residents’ heart rates fell. The same team began a year-long trial in about 400 Ahmedabad homes in 2025.

How you will know it works. Indoor temperature at 3 p.m. in treated and untreated homes, logged through the season

Five traps that waste cooling money: Buying before diagnosing · Built, with no one to keep it · Green without water · Promising degrees you haven’t measured · A list of activities, not a model.

Kitchen heat. Cooking adds heat on top of the weather, often in the smallest room and usually for women; in Nepal’s Madhesh Province it falls hardest on women in the poorest single-room homes.

Ask: How much heat does the stove give off, and does anyone sit beside it for long? · Can hot air and smoke get out: a window, a vent, a gap under the roof? · Is there smoke from wood, dung or kerosene adding to the strain? · How long is cooking each day, and can some of it move to cooler hours? · Can the household afford cleaner fuel through the season, not only once? · Is the electricity reliable enough for a fan or an electric cooker when it is hottest?

Before you choose, ask: Does it need electricity, and is the supply reliable in the hottest weeks? · What happens in a power cut: does it stop, or keep cooling without power? · Does it need water, and where will that water come from in a dry spell? · Who services or repairs it, and how fast? · Who owns the running cost each year, and from which budget? · Who can use it: renters, women, older people, people with disabilities? Keep the outcomes apart: a cooler room, comfort, less heat strain, better health and kept income are different outcomes; measure the one you mean.

Costs are rough planning ranges for early budgeting, not quotes. They are Indian prices, from a practitioner’s planning workbook, shown in US dollars at about ₹95 to US$1 (mid-2026) with the rupee range alongside. India has some of the lowest building prices in Asia, so expect most Southeast Asian cities to pay more: see the regional prices below. Where a public figure exists, it is linked. Where no range is solid enough to share, the card says so: get local quotes.

Sources

Vellingiri et al., Indian Journal of Occupational and Environmental Medicine, 2020. pmc.ncbi.nlm.nih.gov/articles/PMC7227734
Reuters, via South China Morning Post, 2025. scmp.com/news/asia/south-asia/article/3301810/indian-slums-get-cool-roofs-beat-summer-heat
Ghimire and others, Frontiers in Public Health, 2025. frontiersin.org/journals/public-health/articles/10.3389/fpubh.2025.1657267/full
Telangana Cool Roof Policy coverage, 2023: about ₹300 per m². ap7am.com/en/63616/telangana-launches-cool-roof-policy-to-reduce-heat-stress
U.S. dollar–Indian rupee rates, 2026 (Pound Sterling Live). poundsterlinglive.com/history/USD-INR-2026