Hi, I'm doing a science project... Help?

I think your idea is pretty much what I would come up with, but you should also put a door flap on it to keep the cold from coming in. I put one on my dogs house every winter and it helps insulate it because there is no longer a huge opening to let the cold in. I don't know how big your project is going to be, but you could probably use an old lid from a plastic container, and key chain rings to put it on the house. Just drill some holes in the wood over the opening to your dog house, and drill holes on the plastic lid that will match up to the holes on the dog house and attach it with the key rings. It would make a big difference.