For double-pane glass, does it matter whether the heat rejecting film is on the inside or outside? Outside it can get damaged, but inside it might reflect heat back through the glass and cause the seals to fail, leading to fogging.
I have a couple skylights in my garage workshop that are 30 years old and are fine, but transmit a lot of heat through them. I was thinking of adding film to them, but worried about the double pane seals failing. In my house, with a dozen skylights also 30 years old, one skylight seal as failed and is fogging. Since we need a new roof this summer anyway, we're also replacing all of the skylights. The new skylights have a heat rating of 0.26, which means they let only 25% of the heat through (I can look up the exact term if anyone's interested) since they're both tinted and argon gas filled - so I'm expecting it won't be as warm inside as currently.
But, I'm cheap and didn't want to replace the skylights in the garage (at a couple grand each) so thinking about films and shades. I do like having more natural light in the shop, though, and opening them to vent hot air out is nice, too.