Cambridge professor and BBC regular Hannah Fry has advised UK residents to cover their windows with tin foil to combat rising temperatures as the country braces for its third heatwave of the year. Parts of the UK are expected to reach 30°C from Monday, July 6, following a historic heatwave last week that broke multiple June temperature records.
Why Homes Feel 'Insanely Hot'
Fry, who has 2.2 million followers, explained the science behind the greenhouse effect in homes. Sunlight passes through glass window panes easily, but once inside, the light waves bounce around and change to shorter wavelengths, becoming trapped. This creates a one-way filter that lets energy in but prevents it from escaping, causing rooms to heat up rapidly.
"As soon as [the light waves] get inside, they bounce around and they change to much shorter wavelengths - and they're then trapped," Fry said. "It's sort of like you've got this one-way filter to the outside, letting in loads of energy but not letting any of it escape, which is why your room ends up heating up."
The Tin Foil Trick
Fry, who will appear on BBC's Celebrity Traitors, acknowledged that many people close curtains during hot weather, but described this as trying to "stop the invaders once they're already inside the room." She recommended a more effective method: attaching tin foil to the outside of windows.
"If you really want to minimise the amount of extra energy that is coming in when it's absolutely boiling outside, you should get some tinfoil and basically copy what they do in space," she said. "Get some tinfoil and then attach it to the outside of your window."
Does the Tin Foil Trick Work?
Tinfoil acts as a reflective surface for infrared radiation. Aluminium foil deflects up to 90% of the sun's radiant heat, redirecting solar energy back outdoors before it penetrates the room. However, Fry stressed that the foil must be attached to the outside of the glass. Placing foil on the inside allows heat to pass through the window pane, but it becomes trapped between the glass and the foil. This concentrated heat can cause the window to become excessively hot, potentially leading to cracks or complete breakage.
