Journalist Alex Evans tested the viral tip of placing kitchen foil on windows to keep a house cool during a heatwave. The experiment, conducted during a 2022 UK heatwave when indoor temperatures reached 31°C in his home office, found that foil significantly reduced heat. After taping foil over a sun-facing window overnight, the room temperature dropped to 31°C by midday, while an unfoiled dining room downstairs reached 36°C within 30 minutes. The foil reflects sunlight rather than absorbing it, unlike curtains, and has a melting point of 660°C, making it safe for use.
How the Foil Works
The reflective surface of aluminium foil bounces sunlight away from the window, preventing the greenhouse effect that heats rooms through glass. This method is commonly used in hotter climates. Evans noted that the foil costs about £1.20 but gives the house an unsightly appearance, resembling a 'crack den'. He used fragile box tape to secure the foil, which added to the makeshift look.
Results and Practicality
The test showed a noticeable difference: the foiled office was the coolest part of the house. The temperature dropped instantly when the thermostat was moved from the dining room (36°C) to the office (31°C). Evans concluded that the foil works effectively but sacrifices aesthetics. He emphasized that the cost is minimal, but neighbours may question the appearance.
Context and Climate Change
The experiment was originally conducted in July 2022, but similar temperatures are now occurring in May, highlighting rapid climate change. The UK is increasingly experiencing unprecedented heatwaves, and such low-cost cooling methods may become more relevant. The Met Office forecasts continued heat before a break in weather.
