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Heatwave advice: Should we keep our windows open or closed in hot weather?

Windows open or closed in hot weather? (Getty Images)
Is it better to have windows open or closed in hot weather? (Getty Images)

We know reaching for the fan, an ice lolly and drinking plenty of water are surefire ways to stay cool indoors, but the question of whether to keep windows open or closed in hot weather still baffles us.

And with the heat finally picking up in the UK, we don't want to make any mistakes in the measures we take to reduce our body temperature.

You might think that flinging open as many windows as you can and letting in the 'breeze' is a safer bet than sweltering inside with no air, right? Luckily, the NHS' George’s, Epsom and St Helier Hospitals Group has helped to clear things up, with some advice on staying safe in the sun.

Should windows be open or closed when hot?

Window open hot day. (Getty Images)
Is your go-to method only making you hotter? (Getty Images)

While some advice says to shut windows, and some says to open them, it seems getting the balance just right is key.

"Keep windows closed when the room is cooler than outside, but open them at night when the temperature has dropped," the hospital group says.

So, when the air is hotter outside, having windows shut is a safer bet, followed by opening them in the evening and when you sleep for some ventilation.

NI Direct government services agrees with this hot weather advice but adds "close ground floor windows when you leave the house or go to bed".

How can I know if it's hotter outside or inside?

Thermometer in garden. (Getty Images)
How sweaty you are coupled with some thermometers can help you know when to adjust your windows. (Getty Images)

When stuck indoors working or looking after children during a heatwave, it's tricky to tell for sure by just sticking your arm out the window whether 'out or in' is cooler.

If you really want to know, then place a thermostat or thermometer both inside and outside your home, whether in your garden, on your balcony, or just on your window ledge, to help you be sure of the difference, and act accordingly.

You can also refer to our useful guide on what temperature your home should be this summer.

Should curtains be open or closed in hot weather?

Man closing curtains. (Getty Images)
Some curtains should be closed, and some should be left open. (Getty Images)

It seems just shutting the windows when it's hotter outside might not be enough.

"Close curtains on rooms that face the sun to keep indoor spaces cooler and remember it may be cooler outdoors than indoors," advises the NHS Hospitals Group.

Hopefully, not all your windows face the sun and you'll still be able to have some natural light coming in...

However, NI Direct has the answer to this too. "Close pale-coloured curtains – closing dark curtains and metal blinds can make rooms hotter," it urges. So there's no need to shut every sun-facing window.

Now you know whether it's better to have windows open or closed when hot, hopefully you'll feel that couple of degrees cooler...

Staying safe in the sun

The full list of tips from the Hospitals Group include:

  • Look out for people who may struggle to keep cool and hydrated, such as elderly relatives or neighbours.

  • Keep windows closed when the room is cooler than outside, but open them at night when the temperatures has dropped.

  • Close curtains on rooms that face the sun and remember it may be cooler outdoors than inside.

  • Drink plenty of fluids and avoid excess alcohol. Take water with you, if travelling.

  • Try to avoid the sun between 11am and 3pm.

  • Stay in the shade.

  • Apply suncream regularly, and wear a hat.

  • Don’t exercise during the hottest parts of the day.

  • Have cool showers or baths; put a loose, cotton, damp cloth or scarf on the back of the neck, and spray or splash your face with cold water frequently to help keep your body cool.