Aluminium foil window treatments!

[RobertSmalls]

I just installed some. I used masking tape to affix Al-foil to the inside of my bedroom window, which was letting in a lot of unwanted light that was turning to heat inside my house. Metal foils have excellent optical properties: good reflectivity, nearly zero transmissivity (so it's almost black in my room with the window and door closed).

The objective was to reduce the temperature in my room, and it was definately successful. It reduced the temperature of my vinyl shade from 102°F to 82°F, and my desk thermometer hasn't exceeded 82°F while I've been home - A/C not yet required.

[UfoTofU]

I put this on my to-do list since I have trouble with lights in my room in general when I'm trying to sleep

[Ryland]

a space blanket would be cheaper and block around 90% of the light.

[Bicycle Bob]

Foil-backed foam shutters work even better, and also help on winter nights. The deluxe version has a soft foam edge to make a seal, and a fabric cover on the inside and over the soft edge. For easier installation and compact storage, some of mine are hinged in the middle by a slit on the outside, and a strip of duct tape inside.

[sn0w3n]

this is brilliant, can you just tape it to roll down shades??