Our Bangor, Maine, home is a typical two-story saltbox with an attached one-story 22' x 22' garage. We'd like to extend the second floor out over the garage as a recreation area with an 8' x 16' hobby room. We have an asphalt shingle roof. The house is older, so framing is 2" x 4". Heating is by a fairly new boiler system. What type of heating do you recommend, and what's a ballpark price per square foot for these room additions?