Properly insulating and air sealing your attic will help reduce your energy bills. Attics are often one of the easiest
places in a house to insulate, especially if you'd like to add insulation.
Warning: if you think you have vermiculite insulation in your attic, there's a chance it could contain asbestos. Don't
disturb it. Only insulation contractors certified to handle and remove asbestos
should deal with vermiculite insulation.
Loose-fill or batt insulation is typically installed in an attic. Although
installation costs may vary, loose-fill
insulation is usually less expensive to install than batt
insulation. When installed properly, loose-fill insulation also usually
provides better coverage.
Before installing any type of insulation in your attic, follow these steps:
Also insulate and air seal your attic
access if it's located in a conditioned part of the house.
Seal all attic-to-home air leaks. Most insulation does not stop
Duct exhaust fans to the outside. Use a tightly constructed box
to cover fan housing on attic side. Seal around the duct where it
exits the box. Seal the perimeter of the box to the drywall on attic
Cover openings – such as dropped ceilings, soffits, and bulkheads
– into attic area with plywood and seal to the attic side
of the ceiling.
Seal around chimney and framing with a high-temperature caulk or furnace cement.
At the tops of interior walls, use long-life caulk to seal the
smaller gaps and holes. Use expanding foam or strips of rigid
foam board insulation for the larger gaps.
Install blocking (metal flashing)
to maintain fire-safety clearance requirements (usually 3 inches)
for heat-producing equipment found in an attic, such as flues, chimneys,
exhaust fans, and light housings/fixtures unless the light fixtures
are IC (insulation contact) rated. IC-rated lights are airtight and
can be covered with insulation.
Make sure insulation doesn't block soffit vents to allow for attic
Check the attic ceiling for water stains or marks. They indicate
roof leaks or lack of ventilation. Make repairs before you insulate.
Wet insulation is ineffective and can damage your home.
You'll want to properly insulate and air seal any knee
walls – vertical walls with attic space directly behind them –
in your home as well.
Finally, if you're constructing a new home or remodeling, make sure any
attic decking, which provides additional storage space or a platform for
an HVAC unit or hot water tank, is raised above the ceiling joists to ensure
proper insulation depth. The decking then should be installed securely to
the top of the raised lumber after the insulation has been installed.
If you live in a hot or warm climate, you might consider installing a radiant
barrier in your attic along with the insulation.