Installation Guide

Insulating Exterior Walls:

How to Install Insulation in Exterior Walls

To apply a vapor retarder:

An exterior wall is any wall that faces outside or otherwise separates conditioned spaces from unconditioned spaces. These

walls should be thoroughly insulated in order to create the all-important thermal envelope around your living space. Properly

insulated exterior walls make all the difference between a comfortable, energy-efﬁcient home and a drafty one.

Take time to ﬁt the insulation carefully so heat cannot escape in the winter and the inside stays cool in the summer. A good, tight

insulation job saves energy, saves money, and protects your home for the future.

Since exterior walls may have plumbing and wiring running through them, review the Special Considerations for tips on installing

insulation around these obstacles.

1. If you are using faced batts, place the batts into the wall cavity and staple the ﬂanges of the batts to the

inside or face of the studs about every 12 inches. Kraft facing must not be left exposed. It must be covered

with gypsum board or another approved interior ﬁnish. Where an exposed application is required, use

FSK-25 ﬂame-resistant faced insulation. If you are using unfaced batts, place the insulation into the

cavity, making sure that it is the correct size and ﬁts snugly at the sides and ends and does not protrude

in the back.

2. If the insulation is too long, cut it to ﬁt properly. Don’t double it over or compress it. Use a sharp utility knife

and straightedge. Cut batts on a smooth, ﬂat surface, and cut them about 1" larger than the framing cavity.

If the material is too short, cut a piece to size to ﬁll the gap.

3. Fill in any narrow gaps between joists by forcing pieces of unfaced insulation into the gaps with a

screwdriver or putty knife.

4. To control air leakage, apply caulk or foam sealants around openings like window and door frames and

any openings where wires or pipes go through the exterior wall.

1. To apply the poly ﬁlm, start at the top plate in one corner

of the room.

2. Pull the ﬁlm tight and staple at least every 12 inches.

3. Drive staples at the center of every stud and around

openings, working around the room.

4. Overlap the sheets by one complete cavity to minimize

leakage. Then staple evenly through, fastening both sheets

to the studs at one- to two-foot intervals.

5. Pull the ﬁlm tight along the sole plate and staple in the same

manner, making sure the staples are driven ﬂat, ﬂush to the

stud surface.

6. Trim out the poly from over windows, doors and

electrical boxes.

WALLS

Insulation should be installed in all exterior walls that separate conditioned spaces from unconditioned spaces.

NOTE: In areas of the country where vapor retarders are not required, bathrooms would require unfaced insulation and no poly

ﬁlm covering to allow moisture to escape.