How much heat does your house need? Is this seasonal? I assume youre more up north and still heating your house. Jodamon is on the right track. Your seem to be continuously heating the room the tent is in with the house heat pump etc and the exhaust from the tent going back into this room. Run exhaust ducting to some where else if you can. Intake air not much you can do other than run an AC unit which i have done in some set ups. Find a cool place to pull air from