I live in NY state and store several vintage cars in unheated garages on my property. The outside temperature and humidity varies a lot during the winter here. Any unheated building will tend to breathe this changing outside air causing condensation in the building, especially on cars, that tend to resist sudden temperature changes. I have found that an inexpensive ceiling fan, or freestanding floor fan running constantly at a low setting will reduce condensation, and help evaporate any that forms.
On that first warm day after a long cold stretch. Your first instinct is to check on the cars. When you open the garage door and that warm air rushes in you can see the cold cars glaze over with condensation. Better to check them on a cold day, and keep that fan going to help dry them out.
As for keeping mice out, dryer sheets work good for me. But buy a good brand name, not the dollar store sheets that stop working in a few weeks. … Gary