You can also rolled insulation in the ceiling. I also strongly recommend
ceiling fans- a few cheap ones from Home Depot will do wonders to help
circulate the air. Do you have gas available for heat in your hangar? A
Modine heater is relatively inexpensive, and in my previous hangar I had an
office buildout with baseboard electric heat. It makes tinkering on the
plane in the winter a lot more pleasant. I generally kept it at 40-45
degrees, but when needing to work on the plane jacked it up to 60. I found
that I flew a lot more in the winter when the hangar was more comfortable.

Now, all I need to do is figure out is how to get an electrically heated
ramp, and put a hot tub in the hangar.