I saw this in an article on this the Halloween issue of Living:
The editor wanted to make fire appear in his house so he took his camcorder and taped his fireplace. Most likely he did a closeup of just the flames alone. Then he had it looped on his dvd player and rear projected to his windows, which he covered up in paper (I forgot which but I'd rather use white shower curtains).
Voila! The room is on fire from the outside.
He showed a picture (looked photoshopped since the exterior appeared daylight and the flames looked too bright) of it but you pretty much get the idea after seeing Hallowindow and the other animations using rear projection.
I'll probably try this if I have time:
Items you need-
1. Camcorder/video recording device (sound optional)
2. Fire source, either a bonfire outside or in your fireplace, heck even the bbq pit would work.
3. A projector
4. Projection material (paper, spandex, shower curtain, etc) taped to the window
Chances are your projector from the distance you'll be placing it will end up too small an image for a overly large window, so I'd try a smaller window for a better effect. Also understand that you might take away the projector for other animated duties (ie Hallowindow) so consider either using the same window for both (I'd mixed them all on one dvd) or get a 2nd pj