How Do I Insulate a Basement Ceiling?

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Q: Would it be a good idea to insulate the ceiling of our unheated basement? I'm hoping that would make it easier to heat our living quarters.

—Frances Stout, Hillsdale, N.J.

A: Tom Silva replies: Any time you insulate, you're making your home more energy efficient and comfortable, but the gain may not be worth the expense and effort. Here's what's involved in this case.

First, you'll have to maneuver batts of insulation around the clutter of wires, pipes, and cross bracing in a typical basement ceiling. Hold the batts in place by stapling their paper-faced vapor retarders to the lower edges of the joists. Once the ceiling is buttoned up, insulate the rim joist—the floor framing around the perimeter of the house directly above the foundation wall. And now that your basement is going to be cold in the winter, you'll also need to insulate any ductwork and hot-water pipes that are below the ceiling, weatherstrip the basement door, and wrap a thick layer of fiberglass around the water-heater tank. In other words, you're in for a lot of work.

Not only that, research by the U.S. Department of Energy shows that there's not much to be gained by insulating a basement ceiling. So I suggest you put your time and money into improvements that have a bigger payback, such as adding more insulation in the attic, weatherstripping your windows and doors, sealing cracks, insulating the rim joist, and adding storm windows.

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