June 16, 2025, 10:00 am | Read time: 3 minutes
When the temperature rises indoors, quick cooling is needed. A simple trick using aluminum foil is suggested as a solution. However, experts warn against it, as the supposed trick can do more harm than good.
Aluminum foil on the window is supposed to keep the heat out of the apartment. In some places, you see the silver foil on windows in the summer, and this supposed trick is also recommended online. However, experts explain to myHOMEBOOK that it is not advisable. In the worst case, the windows could break.
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 meant to be reflected by the shimmering foil, preventing them from entering the apartment. While this sounds plausible and straightforward at first, it can negatively affect the window panes.
“Basically, you shouldn’t stick anything to the inside of windows,” explains Felix Ernst from the Window + Façade Association (VFF) upon inquiry from myHOMEBOOK. “The aluminum foil is intended to add an internal sunshade, but without sufficient ventilation, it causes high thermal stress on the glass, which can lead to glass breakage.”
Related: When you should never ventilate in the heat
And What If You Stick the Foil 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 windows leads to similar problems if the foil only covers parts of the glass,” says the association spokesperson. “This results in thermal stress 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, and that’s not a good solution either.
Which Methods Really Help Against Heat in the Apartment
It’s advisable to avoid the aluminum foil trick on windows. But how can you protect yourself from the heat instead? “Products for external and internal sun protection are generally recommended,” says the association. Specifically, this means awnings, indoor blinds, or roller shades. An external sunshade is more efficient, “as most of the sunlight is blocked before it reaches the glass.”
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More Tips Against Heat in the Apartment
Especially in attic apartments, the heat is often unbearable. Find out what cooling options are available here. Whether drying wet laundry in the apartment helps lower the room temperature is discussed in this article. And here you can learn how to keep your garden and plants thriving over the summer.