I have used film like this around my house and even on my vehicle (extra tint for the back seat when kids were little and watched the TVs on the headrest). The tint is easy to install with a little spray bottle and some soapy water. Easy to remove too. Stays up, even without the adhesive of other films. However, I have noticed that the reflective material seems to fade. It just goes away and you are left with a nearly transparent film. Granted, it takes years of being in the sun, but I wouldn’t use this on windows that you can’t get to easily. I wouldn’t see this as a once-and-done type permanent fix. Based on my experience, I would expect to have to replace it every few years. But it does work! My son’s room has a window facing East and it would get noticeably warmer in the mornings than the rest of the house. Put this up, inside and outside, and it fixed the heat issue in the summer. Careful using this on the inside of double pane windows- it reflects the sun/heat back through the glass, so the window could still get really warm and radiate heat. Best to try and reflect the sun/heat before it gets to the glass (outside application is ideal, but used it on the inside of my vehicle windows).