Thanks everyone for your input. To address some of the questions that have been raised:
1) The roof is actually solar gray and is supposed to cut about 80% of the sunlight. It does look clear in photos, though--don't blame you for thinking it was!
2.. There will be (actually there is now, we just did it today) hardware cloth over the top of the "box," right below the rafters--I'm not relying on the plastic roof to keep raccoons out.
3. Good point about taking advantage of solar heating. The only two possibilities on this coop are west and south, and it gets SO hot in the summer that I'm afraid I'd cook the poor chooks if I put it in the south. The window as my DH is holding it in the photo is on the west side.
I went ahead and installed it today. It is hinged at the top, and I'm going to weatherstrip it and then have hardware cloth behind it. It's super cute, I think--I'm really happy with it. Thank you so much for your advice!
Oh . . .
4. KatyTheChickenLady--thanks for the cautionary tale! Wow. There will be hardware cloth between the roost and the window, and hopefully that will keep any confused little chickies from flying into the window!