How to keep your home cool

Bloomberg Green ends its Heat Week coverage today with a look at how to keep your home cool this summer. You can also read and share this story on Bloomberg.com. For unlimited access to climate and energy news, please subscribe.

Tips to temperature-proof your house

By Todd Woody

To protect your home from floods and fire, you can raise the house out of harm's way or establish an ember-resistance zone around the dwelling. But how do you safeguard your home against extreme heat, an increasingly frequent climate-driven threat that now strikes historically temperate regions?

"Even here, it's definitely a leading concern," says Chris Magwood, who's an Ontario, Canada-based sustainable construction expert for RMI, a nonprofit that promotes decarbonization.

If you're building a new house, you can bake heat-resilience into the structure, while existing homes can be retrofitted with temperature-reducing features. Here are some of the most effective steps you can take to keep your home cool.

Cool down roofs and walls

A lighter color is better when it comes to a home's roof and walls. The material doesn't matter – a "cool roof" (1) can be made of asphalt shingles, metal or tile — as long as it's light-colored so it reflects solar radiation away from the house. Such roofs can lower indoor temperatures from 2.2F to 5.9F (1.2–3.3C), according to the US Environmental Protection Agency.

Cool walls (2) are painted a light color or are covered by light-colored siding. Some paints are made with ingredients that reflect non-visible infrared radiation, which allows homeowners to use darker or more vibrant colors.

"A solar-reflective wall can go a long way to preventing heat from entering the building," says Audrey McGarrell, communications manager for the Cool Roof Rating Council, a nonprofit in Portland, Oregon. "Cool roofs and cool building exteriors are really low-hanging fruit in terms of something that you can do to instantly improve the resilience of your home."

Insulate the walls

Magwood lives in a straw-bale house he built. "It's 38 degrees Celsius [100F] outside right now, but I'm really nice and cool," he says from Ontario. Traditional straw-bale homes (3) are built by plastering stacked straw bales. It's more common now, though, for straw to be the insulating material in prefabricated wall panels.

The thick straw and plaster keep heat at bay. "It actually takes a fair bit of thermal energy to warm up that plaster skin to the point where heat is starting to transfer through the insulation and into the building, and, by then it's night," says Magwood. On really hot days, Magwood's heat pump, which also cools the home, will kick on, but not until the late afternoon, as the house stays at a comfortable temperature for most of the day.

Throw some shade

New construction should feature oversized eaves (4) to shield south and west-facing windows from the sun in the summer. Installing double-or-triple-paned glass and reducing the size of windows (5) that face the afternoon sun also will help lower temperatures

Adding a simple awning over sun-blasted windows also is effective, according to Magwood. "The house I grew up in New Hampshire was very uninsulated and the windows were terrible, but because of an awning we were able to keep the rooms a lot cooler," he says. New windows are expensive so adding a solar-reflective coating to existing ones can help lower interior temperatures.

While shade trees and other landscaping (10) surrounding a home have cooling effects, in wildfire-prone areas, there may be restrictions on vegetation close to a house.

Have a backup plan

Heat pumps (6) are highly efficient electrical devices that ease demand on the power grid. However, in a widespread heat wave, utility blackouts can happen. A home battery (7) connected to rooftop solar panels can keep the electricity flowing to heat pumps and air conditioners. If you don't have solar panels or a stationary energy-storage system, portable lithium-ion batteries can power fans and other devices.

Don't forget the inside of your house

Putting up blackout curtains (8) or shades on sun-struck sides of a home can ease interior temperatures. Ceiling fans (9) keep air circulating and lower the strain on air conditioners and heat pumps.

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This week we learned

Trump's new tax and spending law creates a climate safety net for chickens. This is according to one US senator who notes the law has a provision allowing contract growers of laying hens "to receive index-based insurance from extreme-weather related risk resulting in increased utility costs."
Few Texas homeowners hit by recent extreme rains have flood insurance. In Kerr County, where the Guadalupe River swelled, killing more than 90 people, only 2% of homeowners hold federal flood insurance. In neighboring Kendall, another hard-hit county, that share is less than 5%.
Global banks channeled more than $385 billion to the coal power industry over the past three years. Annual flows increased last year from 2023, according to analysis by a group of nonprofits. Chinese banks are the top providers of coal-related financing, allocating almost $250 billion to the industry between 2022 and 2024.
Soot from wildfires is a potent short-term warming agent. Black carbon, the technical name for soot, absorbs copious heat from the sun and, when it coats a layer of ice or snow, reduces its ability to reflect solar energy back into space. Scientists are revising their view of the role it may play in endangering glaciers and ice sheets.
The planet cannot get as hot as 500 degrees. This much we know for sure, but scientists are still trying to determine what the Earth's temperature limit is with implications for humanity as climate change makes heat more intense and frequent.

Power transmission lines during high temperatures in June 2025. Photographer: Sam Wolfe/Bloomberg

Worth your time

People who work outside are among the most exposed to dangerous levels of heat and European countries are moving fast to protect them. Spain and Greece already limit work outside on hot days, while France and some Italian regions passed similar legislation this year. Yet even some of the world's most advanced regulations are not enough, and the problem is getting worse as climate change makes heat waves more frequent and intense. Read more on how heat deaths are becoming an increasing concern for Europe during an unusually hot start to summer.

A worker drinks water in a fountain during the first heatwave of the summer in Ronda, southern Spain, on July 2. Photographer: Jorge Guerrero/AFP/Getty Images

Weekend listening

The world's militaries are incredibly polluting, collectively accounting for some 5.5% of global emissions. Western economies are now gearing up for a big expansion of their militaries, with members of the North Atlantic Treaty Organization (NATO) agreeing to increase defense spending to 5% of their gross domestic product by 2035. That will commit trillions of dollars more to an enormously carbon intensive industry, unless militaries can find a way to reduce their emissions. This week on Zero, Akshat Rathi asks retired Lieutenant General Richard Nugee, author of the UK Ministry of Defence's climate change report: Can warfare go green? Listen now, and subscribe on Apple, Spotify, or YouTube to get new episodes of Zero every Thursday.