Should you keep curtains closed in hot weather? Experts settle the debate

When the UK heatwaves hit, there's nothing we homeowners won't do to make our houses feel cooler and get a little respite from the overwhelming warmth. And yet sometimes even the simplest things, like closing our curtains, can stump us. Does it actually help?

Trying to cool down a room without AC in the UK is a consistent challenge, and one that often leaves us sweaty, panicked and questioning why insulation is even a thing. However, there are some rather common cooling mistakes that you can be making without even knowing, and they can have a huge impact on the temperature of your home.

One of them is what you do with your curtains when the hot weather hits. The mystery of whether it's best to have them open or closed and when to do it could have confused you for years, but luckily, we've got the answers direct from home and cooling experts.

Should you keep curtains closed in hot weather?

If the expert fan hacks aren't cutting it and you're still struggling with the heat in your home, then you might want to start by closing your curtains.

“Absolutely, keeping your curtains closed during the hottest parts of the day is one of the simplest and most effective ways to keep your home comfortable," says Victoria Robinson, product and trend expert at Hillarys. "Sunlight streaming through your windows doesn’t just brighten a room; it also brings in a significant amount of heat."

Especially if you're trying to keep your bedroom cool during a heatwave, you'll want to keep the sun out of the space for most of the day.

"By closing your curtains, especially on south- and west-facing windows, you’re essentially creating a barrier that stops that heat from building up indoors," she adds.

"That said, it’s all about timing. I’d recommend opening them again in the evening along with the windows, once the temperature drops to allow cooler air to circulate,” explains Victoria.

Shop cooling essentials

Does closing curtains make a room cooler?

Consider it an interior design mistake that is making your home warmer. But fear not, it is something you can do each day during the summer to reduce indoor temperatures.

"You're slowing down how quickly the room warms up and limiting how high the peak temperature gets later in the day, but how effective that is almost entirely depends on the curtain you have and how it's fitted," says Edward Simon, director at Direct Fabrics. "A thin, dark, unlined curtain can absorb sunlight and then radiate some of that heat inwards, which can feel stuffy."

"A curtain with a thermal or blackout lining, particularly with a light-facing surface towards the glass, performs better because it reflects more radiant heat out and adds an insulating layer," he continues.

It's one of the easiest cooling window hacks, but if you want to make it really effective, then choosing the right curtain will also make a huge difference.

"Curtains that are wider than the window, overlap the sides, and sit close to the wall or window recess reduce the warm air circulation that forms behind the fabric," explains Edward.

"If the top is left open, hot air can rise behind the curtain and spill into the room, so a close-fitting track and a pelmet can noticeably improve performance by reducing that chimney effect," he points out.

What can I put over my window to keep the heat out?

If you really struggle to keep cool in the summer, going the extra mile by changing your window dressings can be a great long-term solution. And there are a few options to consider for optimal heat blockage.

"External shading such as shutters, external blinds, or an awning is typically the strongest option in terms of heat rejection. Indoors, well-fitted systems that minimise gaps around the edges tend to outperform loose-hanging fabrics," says Edward.

"Cellular or honeycomb blinds are particularly effective because their air pockets slow heat transfer, and versions with reflective foil cores and side channels reduce both radiant heat and draughty edge leakage. For a similarly tight, clean finish, a roller blind in a cassette with side seals works well, especially when made in a solar-reflective or blackout fabric, since the cassette and guides cut down light and heat sneaking in around the edges," he adds.

In the same way you'd keep your home warm for less during the winter, there are certain things to do to ensure you're at a comfortable temperature no matter the weather.

"In practice, the best results often come from combining strategies. Keep shading fully closed whenever direct sun is on the window, then switch to ventilation only when the outdoor temperature drops below the indoor temperature, typically overnight and in the early morning," Edward finishes.

If you really struggle with hot sweats or your home gets particularly warm through the summer, it might be worth installing home air conditioning. While it's an expensive addition, it's a worthy investment and will be a saviour when the heatwaves arrive.