What do you use to winterize?

My garage is not heated but heat from my basement does get in there. Recently we have tried to turn our indoor cat into an outdoor cat. I think things are going great. I found 2 dead mice in my yard and I'm hoping the cat finally is earning his keep. I will let him into the garage for mouse duty now too. I'm sure moth balls cannot be could for cats either. Might not be able to go that route.