According to scientists, you only need two things for good cooling: Transparent tape and aluminum foil. The reason this works is primarily due to the wavelength of heat.
The phenomenon of passive radiative cooling is a method for lowering temperatures by directly dissipating heat into space. The key to efficiency lies in the so-called atmospheric window, which is the infrared range with wavelengths of 8 to 13 micrometers.
Researchers have found that this method can also be applied on Earth using surprisingly simple materials. You only need aluminum foil and clear tape. This is reported by the magazine Photonics.com, and the study itself was published in the Journal of Photonics for Energy.
Aluminum foil and tape send heat back into space
How does the trick work? Two layers of clear tape are applied to a highly sun-reflective surface, such as common aluminum foil. It is also important to apply the aluminum foil outside the window and not inside the room, as this can potentially shatter the window glass.
Such a configuration has high emissivity and is effective even at large angles of incidence of sunlight.
The chemical structure of acrylic and polypropylene in the tape absorbs and consequently also releases heat energy precisely in the required wavelength range. This is because the material structure works in the appropriate wavelength range of thermal radiation.
In this range, the atmosphere absorbs little; therefore, heat can escape more easily into space without warming the surrounding air. This results in a noticeable cooling effect in the apartment.
Are there also disadvantages? On one hand, the cooling is not as fast as with an air conditioner, and on the other, adhesive residue may remain on surfaces. Some experts therefore recommend changing the tape regularly.
Particularly, attention must be paid to the condition of the window frame: wood, painted surfaces, and some plastics are more sensitive than glass and can subsequently be difficult to clean (via radiosaw.de).
Another disadvantage pointed out by some: The highly glossy foil surface reflects sunlight so strongly that neighbors or street traffic can be extremely dazzled. Therefore, you should not place such foil on a heavily trafficked street, as you could otherwise endanger people.
If it gets hotter outside, many people ventilate at night. However, in very high temperatures, this is hardly sufficient. Because your apartment stores heat in the walls and furniture. Those who really want to prepare against the heat must take other measures nowadays: Experts say that opening windows at night and closing them during the day is no longer the best strategy against heat.
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