Aluminum foil on windows serves as emergency heat protection

During heatwaves, many people use aluminum foil on windows as an emergency measure to combat rising indoor temperatures. According to ADEME, approximately two-thirds of summer heat enters a home through glass surfaces. Aluminum foil acts as a thermal shield by increasing the window's albedo, reflecting solar radiation back outside.

However, architects warn that this is a superficial, short-term solution rather than a long-term strategy. A critical mistake is placing the foil on the inside of the glass; this can create a greenhouse effect between the pane and the foil, potentially worsening the heat. Experts emphasize that external solar protections, such as shutters or panels placed outside the window, are significantly more effective, capable of reducing indoor temperatures by 3 to 5 degrees Celsius.