We recently moved into a 1970 split entry house near Binghamton, NY. Our 3 bedrooms are over our unheated garage. The bedrooms have hardwood floors and they are very cold even with socks on. The garage ceiling is finished with plaster, so I can't tell for sure, but I think there's little - if any - insulation in it. A little of the ceiling is exposed along the back wall of the garage and I don't see much insulation there. The joists are 2x10 spaced 16" on center. I've been thinking about having foam insulation sprayed into each ceiling joist cavity through a series of access holes the contractor would drill in the ceiling (since it's the garage I don't care much about the holes). Is spray foam insulation the way to go? Should I consider some other time of insulation?
ALSO, the windows in the house are the original 1970 aluminum ones. There's a total of 5 windows in the 3 bedrooms. Needless to say they are a big heat loss and act as a cold radiator.
My question is: since I can't afford to do both the insulation and windows at the same time, which should I do first?