We have a friend over and whenever he gets hot he opens the window all night while we are sleeping…

We have a friend over and whenever he gets hot he opens the window all night while we are sleeping AND he doesn't turn off the heat! You can't be that stupid.. so earlier this morning when I went to go lay in bed I heard a bang.. I waited for him to go to sleep and sure enough the window is open and with the heat on.. it's just gonna make the heaters use more power and our electric bill will be through the roof.. he is lucky Leo's room stays warm when his door is closed.. it looks like I'm gonna have to go out there and shut the heat off -.-