Bill writes from Adelanto, California: "I have a home built in 1991. It has an attached 3 car garage. The builder drywalled the lid of the garage with 5/8 firecode drywall and left the attic open throughout the floor plan, [garage and living space]. The living areas are well insulated, but with the garage section uninsulated I wonder if I'm wasting energy. Should I consider putting in r38 or is this okay?"

Answer: You do not say whether your garage is heated or cooled but I assume it is not conditioned space. My friends at Owens Corning would love to sell you some insulation but they do not recommend insulating an unconditioned space. Doing so will create a "hot box." When the sun, ambient air and hot car engines heat the garage in the summer, the insulation will cause that heat to be retained longer. On the other hand, if the space is conditioned and the attic is ventilated, you can add insulation to the ceiling and walls.