Should windows be open or closed in a heatwave? Tin foil hack explained - when to close blinds in hot weather

In general, if it’s cooler outside than inside your home, you should open the windows

A heat health alert is coming into place across much of the country as temperatures are expected to climb to the mid-30s.

The UK Health Security Agency (UKHSA) has issued an amber heat health alert covering southern and central England from midday on Tuesday (9 August) until 6pm on Saturday (13 August).

The health alert comes following two water companies announcing hosepipes bans and others warning they may need to do the same - after the driest eight months from November to June since 1976.

With that in mind, many Brits have been left wondering, how exactly can we keep cool?

One tip that seems obvious is to open your windows. But with external temperatures so high, is that not just letting hot air in?

So what should you do? Is it windows open, or windows shut during a heatwave?

Here is everything you need to know.

Should I open or close my windows during a heatwave?

As the heat sets in, it can be tempting to open every window in the house, but this could actually make your home warmer.

Though it may appear that you are bringing fresh air into your home, persistent humidity might have the opposite effect on the temperature inside.

There is no set rule for keeping windows open or closed during a hot spell, but in general, if it’s cooler outside than inside, you should open them.

How can you know whether it’s hotter inside or outside? The best solution is to place a thermometer in both locations and act based on the reading.

But there are plenty of weather websites that can give accurate readings of the outside temperature for your local area too.

A cat sits on a window sill to stay cool (Photo: Hollie Adams/Getty Images)

Chris Nye, an international property specialist at Your Overseas Home, believes that in extremely hot weather, windows should be kept closed.

“It might seem counterintuitive,” he says, “but if the air outside is hotter than the air in your home, keeping your windows closed could help your home stay a little cooler.”

Another time when having your window could provide a noticeable benefit is when there is a definite breeze outside.

Having your windows closed during the day has the extra benefit of keeping pollen out of your home, which may improve your symptoms if you suffer from hay fever.

When the day begins to heat up, it may be preferable to use closed curtains and blinds; the NHS recommends keeping rooms that face the sun as shaded as possible.

At night, it is almost certain to be cooler outdoors than inside your house, so it’s best to leave your windows open to let the cool air in.

How can tin foil help?

One quick hack that has been doing the rounds on social media is to cover your window panes with inexpensive tin foil, the type that can be found at any supermarket.

By placing foil on windows that receive direct sunshine, you’ll direct the sun and heat away from your home.

Tin foil is non-toxic, and with a melting point of 230 degrees Celsius, even the uncomfortable temperatures of the next few days won’t phase it.