WHEN temperatures soar, many people reach for the fan remote or dream of central air.

But a surprisingly simple trick can help keep your house cooler and improve your sleep, without touching the thermostat.

Door and window expert Joseph Holman calls it the “caveman method.”

Holman, the CEO of Green Doors, is based in the UK but says this method can help anyone struggling through a heatwave.

The idea is to treat your home like a cave: dark, shut tight, and sealed off from the outside heat.

“A cave is cool in heatwaves because it is dark and doesn’t have direct sunlight or a direct entrance for the heat,” Holman said.

“You want to probably mimic that.”

That means no more flinging open windows at the first sign of a breeze.

While it might feel instinctual to crack open doors and windows, Holman told Tom’s Guide that it could backfire.

“You should be treating your home like you’re hiding in a cave. Keep the warm air outside, and make sure you’re not inviting it in,” he said.

Even shaded parts of the home aren’t safe from the heat creeping in.

“By opening a window or door, you’re still bringing hot air into the house regardless of how much shade is outside,” Holman added.

The key is to shut it all – doors, windows and even blinds – for the hottest parts of the day.

“You want to reduce sunlight and stop the movement of the outside air inside. Even switching off the lights will help you with that,” he said.

If you had air conditioning, Holman notes, you would never dream of leaving a window open.

In the same way, even without AC, it makes sense to seal things off to avoid heat sneaking inside.

That’s the short-term fix, but Holman also recommends a few long-term upgrades.

“If you want to protect your home from the heat longer term, I would recommend investing in tinted film for windows to reflect the heat,” he said.

He also suggests installing integral blinds, which can be fitted without replacing your existing windows or doors.

“They are a great space saver and will last longer than external blinds, which can be damaged much more easily,” Holman explained.

Modern glass can also help with heat reflection, he said.

And roller blind canopies are another option to block out the sun before it hits your doors and windows.

The caveman method might sound extreme, but it could be your best defense on scorching days.

With more heatwaves expected this summer, a little preparation now could mean better sleep later.