My DP doesn’t like to be hot at night, fair enough. But it’s -8°c outside and he has the window open, our bedroom is like an igloo. We still have the thin duvet on our bed so he doesn’t get hot, I have a blanket and a hot water bottle but I just don’t sleep well in a freezing bedroom.
So AIBU - it’s healthier to have the window open at night
Or AINBU - it’s winter!