Installation Guide

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Insulating Ceilings:
How to Install Insulation In Ceilings
How to Insulate Your Cathedral Ceiling
Insulating Cathedral Ceilings:
Ceiling insulation provides essential sound control between floors in your home. Properly insulating the ceilings will make your
home a more peaceful and quiet place because it will ensure that footsteps and other sounds do not migrate to other rooms.
1. Seal around all penetrations in band joists. Any walls that
leak water must be repaired before insulating.
2. Caulk where wiring runs through the ceiling joists and
around the top of the wall.
3. Gently press the insulation between the joists. If you’re
using unfaced batts or rolls, allow friction to hold the
insulation in place (called “friction fit method”). If a
polyethylene vapor retarder is used, staple it across the
unfaced batts. Check to make sure there are no openings
where moisture can escape. If you’re using faced insulation,
install it with the vapor retarder positioned down toward the
room. Hold the insulation up with one hand, while stapling
the flange on both sides every 6" - 8" with the other hand.
Leave a little extra on each end to cover the top plate of the
outside wall. In attic installations, make sure the insulation
completely covers the top plate of the outside wall at the
end of each joist run. However, it should not block the flow
of air from the eave vents. If necessary, install baffles at the
inside of eaves.
4. Expand the insulation to its full thickness in the joist cavity to
insure complete coverage. Avoid compressing the insulation
material, because compression will reduce its R-value.
1. Caulk where wiring runs
through the ceiling joists and
around the top of the wall.
2. Staple prefabricated vent
chutes between joists with one
end over the wall top plate. Vent
chutes ensure there is at least
1" of space between the roof
sheathing and insulation, allowing vapor water to flow out
and to cool the roof. Depending on your house, vent chutes
may be placed only at the soffit areas or run all the way up
to the ridge line.
3. If you’re using unfaced insulation, place it between the joists
and gently press into position allowing friction to hold it in
place. Insulation should be expanded to its full thickness in
the cavity to extend over the top of the framing or trusses
to insure complete coverage. However, avoid compressing
the insulation material, because compression will reduce its
R-value.
4. If you’re using faced insulation, press it between the ceiling
joists with the vapor retarder face down toward the room,
unless building codes specify otherwise. Hold the insulation
up with one hand while stapling the flanges to the joists on
both sides every 6" - 8" with the other hand. Be sure to keep
insulation three inches away from recessed lighting fixtures,
unless the fixture is IC rated. Also, make sure the insulation
is installed at least 3" away from any metal chimneys, gas
water heater flues or other heat-generating sources.
Sloped, vaulted, and cathedral ceilings are different names for essentially the same ceiling
configuration. These ceilings are very popular in newer homes and remodeled homes, and they
certainly add dramatic visual interest to a room. But because there is little or no attic space
separating inside and outside air, proper insulation is especially important.
Many cathedral ceilings will require that insulation be installed around recessed light fixtures.
There are some important safety measures you should be aware of when working with insulation
around light fixtures. Be sure to review the Special Considerations for the information you need
to complete the installation without creating potential fire hazards.
To make your cathedral ceiling insulation job easier, Johns Manville makes special high-
performance R-value insulation designed specifically for cathedral ceilings.
CEILINGS AND ATTICS