Q: I'm thinking about insulating the basement of our unhistoric, early-1990s house, but I don't know whether it would be cheaper and easier to insulate the concrete walls or the joists of the floor above. Is it even worthwhile to put insulation in the basement? We don't use it for much more than storage, though it is home to the water heater and the furnace.

— Tim, Littleton, CO

A: Tom Silva replies: Insulating the basement of a drafty old house won't save much on heating costs. You'll get better results for less money by insulating and installing weatherstripping on upstairs doors and windows. If a house is "tight," however, and yours ought to be given how recently it was built, an uninsulated basement represents a fairly large proportion of its total heat loss, particularly in cold climates. So yes, even if you just use the basement for storage, insulation is worth considering. Plus you give yourself the option of someday turning the space into a rec room or a shop. You only need to insulate between the floor joists around the perimeter, using fiberglass batts; then insulate the walls. That way you'll use less material and you won't be covering up or working around the maze of wires and pipes that run through a typical basement ceiling. For your climate, the Department of Energy recommends R-10 insulation — either foam boards or fiberglass batts — and estimates savings of about $310 a year. Just be sure to protect the batts from dampness and the foam from fire (use drywall; for this location, moisture-resistant "greenboard" is best).
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