When the thermometer exceeds 35°C, it becomes difficult to maintain a bearable temperature indoors, especially when you do not have air conditioning. Close the shutters, ventilate at night, limit electrical appliances… the advice is well known. But a team of researchers from Loughborough University, specializing in building engineering, wanted to explore a much more original solution.
Their idea? Use… Greek yogurt to limit the heat penetrating through the windows.
Yogurt on the windows: an experience that surprised researchers
To carry out their work, the scientists used two perfectly identical test houses. One remained as is, while the windows most exposed to the sun of the other were covered, on the exterior side, with a thin layer of full-fat Greek yogurt with 10% fat.
As it dries, the yogurt forms a whitish veil which acts as a barrier against part of the solar radiation.
For a month, in May 2025, sensors measured the temperature inside the two homes. Result: according to data relayed by Homebuildingthe treated house remained on average 0.6°C cooler, with variations of up to 3.5°C on the hottest, sunniest days.
A difference that may seem small, but is sometimes enough to make a room much more comfortable during a heat wave.
Why does this funny trick work?
The explanation is ultimately quite simple.
Usually, the sun’s rays easily pass through a window and gradually heat up the interior of the house: this is what specialists call solar gain or the greenhouse effect.
As it dries, the yogurt creates a thin white layer capable of reflecting part of the radiation before it passes through the glazing. Result: less energy enters the home and the temperature rises a little more slowly.
For Dr Zoe De Grussa, head of research at the Chartered Institution of Building Services Engineers (CIBSE), this experience above all recalls a principle well known to specialists.
“It’s not an everyday tip, but anything you can place outside the windows will help keep the sun from coming in and warming up the interior.”
In other words, yogurt is just one example of an effective strategy: stopping the sun’s rays before they reach the windows.
It is undoubtedly no coincidence that this study is so talked about today. For several weeks, the French have been flocking to Meudon white, this white powder traditionally used to clean or whiten surfaces, but now applied to windows to limit the entry of heat. A victim of its success, the product is out of stock in many DIY stores in France, proof of the craze for simple solutions allowing you to keep your home cooler without air conditioning. The Greek yogurt tested by the researchers is based on the same physical principle: creating a clear layer on the outside of the windows in order to reflect part of the solar radiation before it enters the house.
A tip to try… but with some precautions
Researchers are the first to point out: this method does not constitute a miracle solution against heat waves.
As MétéoMédia points out, it does not replace the most effective actions, such as closing the shutters during the hottest hours, using blackout curtains, installing exterior solar protection or widely ventilating the home as soon as temperatures drop at night.
Another limitation: yogurt can attract insects, leave an unpleasant odor if it remains damp or require cleaning the windows once the heat wave has passed.
The researchers therefore recommend, if you wish to try it, to test the technique on a small area very exposed to the sun, before cleaning the windows as soon as the hot weather ends.
At the same time, Loughborough University is continuing its research into more sustainable solutions, in particular exterior solar protection capable of effectively limiting the overheating of homes without resorting to air conditioning.