June 25, 2026, 12:11 pm | Read time: 3 minutes
When temperatures rise in the apartment, quick cooling is needed. A supposed heat trick with aluminum foil is currently going viral on social media: It is said to block sunlight and keep rooms pleasantly cool. However, experts advise against this method. myHOMEBOOK consulted an expert. She explains why the trick can do more harm than good and, in the worst case, even cause glass damage to the window. What’s behind the viral trend?
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Aluminum Foil Against Heat? Experts Advise Against the Trick
A bit of aluminum foil stuck to the window–and the apartment is supposed to stay pleasantly cool even in summer temperatures. The sun’s rays are supposed to be reflected by the shimmering foil and thus not penetrate the apartment. What initially sounds quite plausible and straightforward can, however, negatively affect the window panes.
“Basically, you should not stick anything to the inside of windows,” explains Pantea Khaledpour from the Window + Façade Association (VFF) at the request of myHOMEBOOK. “The aluminum foil is intended to add an internal sunshade, but without sufficient ventilation, it causes a high thermal load on the glass, which can lead to glass breakage.”
About the Person: Pantea Khaledpour is a press, communication, and marketing officer at the Window + Façade Association (VFF) in Frankfurt/Main. The association represents the interests of manufacturing and installation companies as well as industry and trade partners.
Related: When you should never ventilate in the heat
And What if You Stick the Foil on the Outside?
In many cases, the aluminum foil is applied to the inside of the window–probably for simplicity’s sake. Is it better to attach it outside? “Sticking aluminum foil to the outside of the windows leads to similar problems if the foil only covers parts of the glass,” says the association spokesperson. “This results in thermal stresses on the glass, similar to a shadow, which can lead to glass breakage.” You would have to cover the entire outside, which would make the room dark, which is also not a good solution.
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Which Methods Really Help Against Heat in the Apartment
So, the aluminum foil trick on the window is not recommended. But how can you protect yourself from the heat instead? “Basically, products for external and internal sun protection are recommended,” says the association. Specifically, this refers to awnings, indoor blinds, or roller shades. An external sunshade is more efficient, “as most of the sunlight is already blocked before it reaches the glass.”
More Tips Against Heat in the Apartment
Especially in attic apartments, the heat is often unbearable. Find out what options are available for cooling here. Whether it helps to dry damp laundry in the apartment to lower the room temperature can be read in this article. And here you can learn how to get the garden and plants through the summer.