Insulate a Basement?
Whether or not to do it depends on the age of your house
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
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).