You can use this on windows, ceilings, walls, any area you want to be cooler. To install, roll out the amount you want, cut it, and then tack it/nail it to the area you want.
Promising review: “I have a couple of sets of French doors and a skylight where even on a normal day, a ton of late afternoon heat comes in because they get sustained direct sun. Northern California normally has mild summers, but this week a heat wave is coming and we’ll be close to 100 (even 104) for a week to 10 days. I’ve put this up behind my shades using clear 3M dual lock tape. It was super simple and has made an IMMEDIATE difference to how cool the house feels — now the AC has a fighting chance to do its job, and it will be easy enough to take down and store once the heat wave is over. I ordered the 3mm, 24” width for my doors, and 48” width for my skylight. It’s super lightweight, and REALLY works!” —Amazon Customer
Get it from Amazon for $15.95+ (available in10 roll size options, from 16″x10 ft to 48″x100 ft).
