How to Keep Your Home Cool in Extreme Heat

Global temperatures have reached alarmingly high levels across the U.S., Europe, and Asia as heat waves set record highs this week.

Parts of European countries including most of Italy, eastern Croatia, southern Spain, southern Bosnia and Herzegovina, and Montenegro are under red alert, the European Union’s Emergency Response Coordination Centre said on Wednesday. Meanwhile, as of July 18, Phoenix had experienced 19 consecutive days of 110°F temperatures or higher. And Beijing is also experiencing a record stretch of 95°F heat.

The extreme heat comes as weather phenomenon El Niño, which occurs every two to seven years and brings higher global temperatures along the northern hemisphere, takes place. It also arrives at a critical point in global warming.

“Extreme heat events in the United States are already occurring and expected to become more common, more severe and longer lasting due to climate change,” said Claudia Brown, a health scientist at the Centers for Disease Control and Prevention.

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Some scientists say that 2023 could be the warmest year on record, posing a problem for millions across Europe where air-conditioning is relatively rare. Only about 3% of homes in Germany and less than 5% of homes in France have an air cooling unit in their home, according to the Washington Post. That’s compared to 90% of homes in the U.S.

TIME spoke to experts about how to keep cool in your home. Here’s what they said.

Block out sunlight

The main thing to do when attempting to keep your house cool, is to block sunlight from entering the home.

“What you want to do is stop the heat before it gets through the glass or any other wall,” David Wright, a solar environmental architect, says. “You can use outside shading techniques or shades that go up and down and block sunlight at certain times of the day, or horizontal shading devices like arbors, trellises, and awnings.” Any sort of plant life that can absorb sunlight before it hits a wall is helpful, he adds.

While blocking sunlight and heat from the outside before it has a chance to enter the home—such as by having trees around your house—is the most efficient way to keep your home cool, there are tricks for people living in apartments too, says Wright, pointing to blackout curtains as a good option.

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“If sunlight is allowed to come through glass into the house, once it gets inside and strikes an object,” explains Wright, “the wavelength goes from long wave to shortwave. And the short waves don’t go back through the glass. That’s what traps heat.”

Homeowners can opt for insulated glass or low-e glass—which has a thin coating that reflects heat—to prevent heat from entering the home. Applying a tint to windows in your home may also be beneficial, Miami Chief Heat Officer Jane Gilbert writes to TIME in an email statement.

Gilbert adds that residents can paint their roof a reflective white to help block out sunlight, while Wright suggests people invest in a heat pump or air conditioner to help with additional cooling.

Improving insulation in ceilings, attics, crawl spaces and even walls, will also reduce heat, according to Gilbert. Residents can also get a deal when fixing their homes as “utilities offer rebates and the IRS provides tax credits for insulation,” Gilbert tells TIME.

Use the nighttime to your advantage

If you live in a house with thermal mass (meaning it’s made of brick or concrete and retains heat well), Wright says that you can try to cool your home at night without air conditioning. He suggests homeowners take note when the outside temperature drops below the interior temperature, and then open all the windows and doors that you can.

Of course, Wright mentions, this should only be done if safety is not a concern. Low lying windows or doors are especially beneficial when doing this technique because hot air rises.

Wright also mentions that any part of your house that is built into the ground, like a basement, is going to be much cooler than other parts of your house because it is touching the surrounding earth, which is likely cooler than the air temperature. Spending time there may be optimal for cooling.

Know when a fan is efficient

Wright says that ceiling fans with large paddles, or Casablanca fans, are most helpful. “It pushes the heat up toward the ceiling and provides evaporative cooling around the body of the person,” Wright tells TIME.

Sonia Singh is the marketing communications supervisor for Maricopa County, Ariz., where Phoenix is located. There, it can get so hot that simply slipping on the concrete can lead to second-degree burns. Singh says that fans “become insufficient for cooling the air at a safe temperature” when its hotter than 90°F. At that temperature, residents without air conditioning should move to a space with air conditioning.

Know when to move to a cooling center

Brown emphasizes that air conditioning is the most efficient way of staying cool when temperatures are particularly high.

Read more: Air-Conditioning Is Rare in the U.K. Could Heat Waves Change That?

“When it’s extremely hot, spending time in locations with air conditioning, particularly during the hottest hours of the day, is going to be your best line,” Brown says. “If you do not have air conditioning in your home, we do recommend going to public places where there is air conditioning such as shopping malls, public libraries, or public health sponsored heat relief shelters (sometimes these are referred to as cooling centers). Gilbert adds that anytime there is a heat advisory or heat warning and you do not have air conditioning, you should move to a cooling center.

Brown adds that staying cool should be a community effort, and asks that residents check on their neighbors who may not have any family members nearby or live alone.

If you or someone you know is feeling confusion, headache, or dizziness, they may be facing a heat-related illness. People should also watch out for muscle spasms, nausea, or profuse sweating.