"Bob M" wrote in message
news
I have a raised ranch which has two bedrooms over a garage.
However, the following site:

http://www.clarkpublicutilities.com/...es2001/12-01-4

says that if you're not going to heat the garage, insulation may actually
make the garage cooler in the winter and not warmer.

The cave effect is interesting. For a free standing building, the loss of
solar may be a real factor, but the garage under the house is already a cave
and probably have little sun exposure. I'd insulate.

The only heat, of course is going to be what you introduce from the heated
house, and possibly from bringing in a car with a hot engine. I don't know
the balance between a hot engine and a cold mass of metal though. Right
now, the garage is acting as a big vestibule like older houses had.
Ed