At my house, we have had a heat wave the last couple of weeks. About 95 degrees every day.
I have shades on the south-facing windows that I keep down to keep the hot sunlight out. However, I also have two large skylights, one in the kitchen (up real high, vaulted ceiling) and one in the upstairs bedroom.
Neither has any kind of blind on them. Both face west, and get a LOT of light through them the entire afternoon.
Special blinds for these types of skylights get expensive fast, and I just wanted a cheap, quick fix.
Digging through my camping equipment, I found I had a "space blanket". Those are thin sheets of folded plastic with a reflective silver surface. I unfolded the space blanket, and pinned it up against the upstairs skylight with a couple bits of tape. Then I trimmed off the extra with a razor blade against the glass.
After that, I filled a spray bottle with water, pulled back the space blanket, and spritzed a mist in there. Pressed the blanket against the glass, and sort of squeegeed with my hands from the middle to the outside.
The space blanket sticks right on the glass!
The other thing to keep in mind is that the space blanket IS NOT opaque! Rather, it's almost like a really dark mirror tint. The window is now reflective AND much darker, but I can still see out through it!
My house should now stay cooler because of less solar energy coming in.
Not bad for just a few minutes time and use of materials I already had!