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How to insulate basement rim joists?

· Cut the rigid foam insulation in strips with your table or circular saw. Alternatively, a handsaw or knife will do. Normally 2 x 10 joists have a width of 9 ¼ or 9 ½ inches. Cut the strips narrower than the measurement.

· If you have many engineered joist which resemble small wooden I-beams, you will need to notch every piece between the joists. Perhaps cut out the foam corners.

· With the long foam sections, cover the rim parallel joists.

· Do not glue the parts.

· Caulk around openings

· Run a coat of acrylic caulk near each foam section and make an airtight barrier. For larger gaps use expanding foam sealant.

· With a box cutter cut your insulation to length – a tighter fit.

Call the local building inspection department before begining this project. Some locales require you to cover a new insulation using drywall in order to create a fire block and leave some areas bare to allow for insect inspections. Unfortunately, you cannot insulate the second-floor rim joists using the same technique unless you by chance tore out a ceiling while remodeling. You might want to contact an insulation professional and determine if you have the insulation in place and if they could inject foam insulation in the bays. You will need to spackle a few small ¾-inch holes when this is done.