I want to put in a through the wall dog door, DH thinks that our heating/cooling bills will skyrocket if we do. It would have a double flap and we could put insulation in the wall around the door. If you have a dog door do you notice hot/cold air coming in from it? We have a 10 lb dog so it would be a small door so I am not worried about people getting in.
). They also lock.

(Isn't that special!)