Since the Aluminum is a conductor of electricity, it forms a barrier often called a Faraday Cage, entirely stopping the radio waves. I do have blinds, but adding another light/heat blocking layer should help. I was just curious if aluminum foil could block the sun's UVA rays. Blackout shades will darken a room, but you (and your circadian rhythm) will still be very aware that it's daytime outside. Now try calling it, the phone won’t have any signal. I understand that standard glass blocks the majority of UVB rays, but it lets UVA rays in, so I need to find a way to block those as well. Here's what I'm planning so far. In a sense, your windows are no longer ‘windows.’ And, you have to keep them blocked whilst the sun’s up to achieve any heat reduction benefits. I have my home office and the sun always gets in and hits me. However, while foil may keep out unwanted heat, it is unsightly and essentially defeats the purpose of having a window to look outside. Putting aluminum foil on windows can keep heat out. Tin foil works effectively to block radiant heat. I will put Gila window film on the windows first. Aluminum foil does block, or shield, radio frequency waves. Because tin foil is resistant to heat, it prevents much of the sun's heat from entering the house. Aluminum is highly reflective, which makes it effective in keeping out the radiant heat of the sun. You can try this for yourself. I know sunlight can cause early photoaging and cancers, so I want to block out as much UVA rays as possible. Because of this, some people use it to block the heat of the sun by securing it over windows. It's cheap and easy to take down and put back up again when you need to. Ferne shared her tin foil hack after asking followers for help to block light out of her daughter's window Read More Related Articles. The foil is simply placed over the glass window panes -- on the inside of the house -- and secured with tape. I'm looking for a setup to block 100% of UV light from windows. Get a large sheet of aluminum foil, lay it out flat, set your cell phone on top and wrap it up. I've come upon some rumors stating that this would be bad for the windows, could cause them to be damaged. Is there any danger associated with taping aluminium foil to double-paned windows which will face the sun-side for pretty much the entire day? I do wear sunscreen, but I prefer blocking it another way while I'm in my home office. Up to 40 percent of undesired heat in a home comes in through the windows. They sell foam boards at craft shops, etc. The problem with this idea is that, first, just as with blackout film, you’re closing off your windows from natural light. cut it to size and tape it to the window frame, paint the inside black to darken the room but leave the outside white. Aluminum foil look GHETTO, use 1/4" white foam board instead, they insulate the heat and block out the sunlight. This film blocks around 98-99% of UV rays, or at least that's what it claims. Foil blocks 100% of the light. When I did shift work, I just covered the glass with aluminum foil.