The article addresses an improvised solution that has been used in various countries during periods of intense heat: placing aluminum foil on windows. The trick serves two main purposes. First, the aluminum creates an almost immediate blackout, preventing the passage of natural light, which can be useful in bedrooms where you want to sleep during the day or in rooms without blinds or curtains. The British organization Which? states that this solution "completely blocks all natural light."
In addition to the light-blocking effect, aluminum foil also works as a reflective barrier against solar radiation. When placed on the exterior of the window, the material reflects part of the solar energy before it crosses the glass, preventing heat from entering the room. This solution is recognized by the Lawrence Berkeley National Laboratory, a laboratory linked to the United States Department of Energy, which includes it in a guide dedicated to cost-effective ways to protect windows during extreme heat episodes.
The use of this method has gained greater visibility during heat waves. The Argentine newspaper El Cronista noted that "more and more people" were covering the glass with this material during the summer. In cities like Paris, where thermometers exceeded 40 degrees, several windows with reflective surfaces were seen. French architect Vincent Parasie explained to La Vanguardia that the material works as a "thermal mirror" when placed on the exterior face of the window.
Which? recommends that the reflective barrier be preferably placed on the exterior of the window for maximum effectiveness. The organization also warns that the improper application of reflective materials on the interior of certain types of glass can cause thermal stress and increase the risk of cracking, especially on double-glazed windows, windows with low-emissivity coatings, or surfaces with special treatments. In these cases, it is advisable to verify compatibility with the existing type of glass before applying any permanent solution.
