The heatwave is officially back, and households are being urged to use a simple trick to keep their homes cool - and it's cheap too.Alex Evans Deputy Audience Editor and Nicola Roy Multimedia content creator12:34, 22 Jun 2026The heatwave is well and truly back. Following a very grey start to June, there's set to be an onset of sweltering weather about to leave the nation feeling muggy, stuffy and humid, while making our homes unbearably hot.‌Conditions could peak as high as 38C this week, prompting the Met Office to place certain parts of the UK under a red alert for hot weather. Areas like London, the Midlands, the South East and Cardiff are covered by the warning, set to come into place on Wednesday June 24 .‌The heat could end up posing a health risk, especially for vulnerable people, so it's important to do all you can to keep cool. British Gas has recommended that everyone grabs a roll of tin foil and puts it on their windows, reports the Express.‌This little-known method for keeping your home cool requires nothing more than a £1.20 roll of tin foil or kitchen foil - available at Asda and other major supermarkets including Tesco, Morrisons, Sainsbury's and Aldi, though superior results can be achieved with more advanced reflective foils found in homeware stores.Those desperately seeking relief from the heat have been urging others to unroll kitchen tin foil and place it across their windows, particularly those in direct sunlight.‌Jessica Rawstron, a British Gas Smart Energy Engineer, has explained exactly how this method works. She said: "This is an affordable and super effective tool for keeping your house cool in summer by keeping the sun's rays at bay. It's not very expensive and widely used in hotter climates, and it can reduce heat and glare by up to 99%."While you can have it installed professionally, it's not a tricky DIY project. It can give you a bit more privacy without sacrificing any natural light, and another bonus is that reflective window film can help to protect your furniture and flooring over time by blocking harmful UV rays and so preventing sun damage."Ordinarily, when direct sunlight streams through a window, it amplifies the sun's heat and makes your home even warmer — this is the same principle greenhouses use to keep plants warm inside. Foil, however, works by bouncing the sun's rays back off the window, deflecting them outside rather than letting them in.‌Adam Pawson, Head of Digital at Safestyle, told Ideal Home: "Blocking your windows with tin foil will help to keep your rooms cooler in the heat as it reflects the heat back outside."He did warn, though, that the trick works best when applied to the outside of the window: "However, one mistake people make is by placing the foil on the inside of the window. It is really important to be careful to place the tin foil on the outside of your windows rather than the inside to prevent the glass from getting too hot."Another alternative is to keep your windows open while your curtains remain drawn, preventing direct sunlight from streaming in. Bear in mind, however, that this will still cause your room to warm up slightly through the curtains, whereas foil is far more effective at reflecting the sun's rays.‌Ways to keep your house cool in a heatwaveYou should only open windows and doors during the evenings, allowing cooler air to flow through the house, while keeping any windows and curtains that face direct sunlight firmly shut during the daytime.You can also position bowls of water in various rooms throughout the house, which will evaporate and help maintain a cooler air temperature. Houseplants are another great way to keep a home cool, acting as natural air conditioners by regulating room temperature through releasing moisture into the air in a process known as transpiration.‌You can also switch off appliances that aren't in use. Every appliance, from an oven or toaster to a laptop or PlayStation, generates small amounts of heat even on standby, which all adds to the overall temperature inside your home.The same applies when charging items like your phone — the modest amount of heat produced could contribute to warming a room slightly, so it's better to charge overnight.Energy-saving LED light bulbs will also help keep your house cooler. Traditional light bulbs such as Halogen produce a tremendous amount of heat as they illuminate a room, and multiple Halogen lights or spotlights can warm up a space rapidly at night.Article continues belowConsider switching to energy-saving LEDs and keeping lights turned off whenever possible — which will also help you save money.