HOW TO INSULATE AN INTERIOR BASEMENT WALL

INSULATION SOLUTION FOR DRY WALLS: INTERIOR WALL
INSULATION

As a general rule, avoid insulating the interior side of your basement walls.

It is best to leave breathing space for the concrete or block so moisture that

enters through the walls is not trapped. If your exterior basement walls

meet the definition of a dry wall  however, adding some

interior insulation can increase the comfort level in your basement. If you

are building a stud wall for hanging wallcovering materials, you can

insulate between the studs with rigid foam—do not use fiberglass batts and

do not install a vapor barrier. If you are building a stud wall, it’s a good

idea to keep the wall away from the basement wall so there is an air

channel between the two.

Interior insulation can be installed if your foundation walls meet the conditions for

dry walls . It is important to keep the framed wall isolated from the

basement wall with a seamless layer of rigid insulation board.

INSULATE AN INTERIOR BASEMENT WALL

Begin on the exterior wall by digging a trench and installing a 2"-thick rigid foam

insulation board up to the bottom of the siding and down at least 6" below grade. The

main purpose of this insulation is to inhibit convection and air transfer in the wall

above grade.

Insulate the rim joist with strips of 2"-thick isocyanurate rigid insulation with foil

facing. Be sure the insulation you purchase is rated for interior exposure (exterior

products can produce bad vapors). Use adhesive to bond the insulation to the rim

joist, and then caulk around all the edges with acoustic sealant.

Seal and insulate the top of the foundation wall, if it is exposed, with strips of 1/2"-

thick, foil-faced isocyanurate insulation. Install the strips using the same type of

adhesive and caulk you used for the rim joist insulation.

Attach sheets of 2"-thick extruded polystyrene insulation to the wall from the floor to
the top of the wall. Make sure to clean the wall thoroughly and let it dry completely
before installing the insulation.

Seal the gaps between the insulation boards with insulation vapor barrier tape. Do
not caulk gaps between the insulation boards and the floor.

Install a stud wall by fastening the cap plate to the ceiling joists and the sole plate to
the floor. If you have space, allow an air channel between the studs and the
insulation. Do not install a vapor barrier.