One viral hack that’s currently doing the rounds is putting tinfoil on windows to keep the heat out. We can definitely see the appeal – it’s cheap, easy to access, and when it’s sweltering inside most of us will give anything a go to bring the temperature down a few degrees. So, does putting foil on your windows really work, or is there a better window hack?
How foil works to block out heat
The thinking behind this hack is that foil is reflective, so can ward off incoming rays. As sunlight contains invisible infrared radiation (heat), when this hits standard glass windows it passes straight through them. The heat then gets trapped inside the room, warming it up.
However, because of the reflective properties of the foil, as well as its low emissivity – aluminium can reflect a significant amount of radiant heat – it can bounce the infrared rays away from the window, minimising the amount of heat that can get inside a building.
Does foil on windows actually work to keep a room cool?
Anecdotally, some people do find that it can drop the temperature by a few degrees. However, one key mistake is putting foil on the inside of the window, which we’ve seen a lot of people doing. Putting it on the inside of a window can trap solar heat, which can create extreme thermal stress between the glass and the foil. As this will heat up the glass unevenly across the window pane, the risk of the glass breaking is significantly higher.
Double or triple-glazed windows are at particular risk, as it can cause the internal pane to expand and potentially even shatter. Sticking foil to the outside of a window can prevent this from happening, and in a pinch might make a hot day indoors feel a bit easier.
What can be used instead of aluminum foil on a window?
Foil may offer some temporary relief, but it’s not an ideal solution in the long run – especially not for commercial properties. For properties with a lot of windows, or windows above ground floor level where applying foil to the outside can be risky, using foil won’t be as effective. Plus, foil-covered windows make a room much darker, and for a business especially, don’t give off the most professional appearance. Blackout blinds or curtains can offer similar properties, but again, come at the expense of natural light.
For a long-term solution, we would recommend solar control window film. Sometimes referred to as heat rejection window film, it is designed to better regulate the transmission of heat and light through glass windows.
Solar control film is a lightweight film that comprises layers of polyester that reflect and absorb certain wavelengths of sunlight before it has a chance to penetrate the glass. This means that excess heat is kept out of the property, keeping the temperature more stable. One of the major benefits of solar window film is that you can still see through them, and they don’t block out natural light.
It’s a simple and effective way to regulate the temperature inside a commercial property. Naturally, it costs more than a roll of tin foil, but many people find that it can save them money on energy costs as they have less need to rely on expensive cooling systems. In the winter, the film has the opposite effect – it can conserve heat to keep it cosier, reducing the need for central heating. With more hot summers on the horizon, solar film makes an excellent long-term investment for commercial properties that want to make working conditions more comfortable for employees.
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