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Avoid Attic Insulation Mistakes

by Joseph Truini

A properly insulated attic will reduce energy consumption, lower your utility bills and make your home feel cozier throughout the year. However, to fully realize these savings and benefits, it's imperative that the insulation is installed correctly. Here are six common mistakes that do-it-yourselfers—and even some professional contractors—make when insulating attics. Avoid these mistakes, and you'll reap the benefits for years to come.

Leaving Gaps

The number one attic insulation mistake is leaving gaps and spaces between and around the insulation. Insulation can't do its job if it's not completely filling the voids between the joists. Even a small, seemingly insignificant gap allows warm air from the house to leak into the attic. That not only wastes energy, but also makes your heating appliance work harder, and it can even lead to destructive ice dams.

Cut attic  insulation to fill gaps and voids

Avoid this mistake by simply cutting and fitting the insulation to fill each and every void. It's also important that the insulation makes full contact with the drywall ceiling below. 

Blocking Vents

Every home should have vents that allow fresh air to enter and exit the attic. The constant airflow helps exhaust moisture and condensation and prevents the growth of mold and mildew. Attic vents are typically installed in the soffit, along the underside of the eave, along the ridge of the roof, or on the gable end of the house.

When insulating an attic, be careful not to lay any insulation over the vents. Even if you're not planning to add any more insulation, it's a good idea to confirm that the insulation already in place isn't blocking any vents. 

Covering Recessed Lights

If there are recessed light fixtures in the ceiling below the attic, be careful not to lay insulation on top of the fixtures. These lights create a tremendous amount of heat, which could ignite the insulation and set the house ablaze. Keep all insulation at least three inches away from recessed light fixtures.

With that said, it's important to note that the abovementioned warning relates only to standard Non-IC recessed fixtures. If the fixtures are labeled as IC-rated—which stands for Insulation Contact—then you can safely lay insulation right on top of the lights. If you're not sure which type of recessed fixtures are installed in your home, call in a home inspector or licensed electrician, and keep the insulation well away from the fixtures until a determination has been made.

Note from NH: Another solution would be to used a pre-manufactured recessed light cover (see graphic below) which is approved for use with any type of recessed light fixture. These covers allow enough of an air gap to prevent fixtures from overheating, while blocking air from passing through the fixture. As a bonus, they are easily removeable should the fixture need to be replaced/repaired.

Thermally-tested recessed light cover
Thermally-tested recessed light cover


Not Sealing Other Ceiling Penetrations

Look closely at the attic floor, and you'll likely see dozens of holes where wires, pipes, hoses, vents and other mechanical components poke up into the attic. The small gaps around these penetrations allow warm air to seep into the attic. Prevent this by sealing all gaps with fireproof caulk, which is often labeled as fire stop or fire barrier. Do not use regular caulk or sealant to seal these penetrations.

Compressing the Insulation

Another common mistake that DIYers make is tightly stuffing insulation into place, which actually makes the attic less energy efficient. Insulation is typically rather soft and fluffy because it's filled with air, and that trapped air helps insulate. If insulation is compressed too tightly, the air is forced out, and the insulation loses much of its insulating value. Avoid packing the insulation in tight during the installation process.

Not Insulating the Attic Entry

Most attics have an access panel, hatch, fold-back door or pull-down staircase. It's important to insulate these access openings to block the flow of warm air into the attic. Some of these openings can be pretty big—eight to 10 square feet—which would result in some serious heat loss.

Insulation cover over attic access hatches or stairs

Resembling a foil-lined teepee, this attic insulator seals the access opening and blocks
air from flowing into the attic from the room below.

You could simply lay insulation on top of the access opening, but for better results, go to the local home improvement store and buy a ready-to-install insulated attic door or attic stair cover. These products provide a quick, easy way to create an airtight seal over the attic access.

While you're up there anyway, add a second layer of insulation!

In the "old days", builders put insulaton between the ceiling joists and that was it. (Or in some cases poured it in.) But today most homes that don't use the attic for storage install a second layer of insulation. Since most of the heat loss in a home is through the ceiling, the energy-saving results can be incredible!

Attic Insulation

It is important to use unfaced batts so any moisture that might escape through air gaps in the ceiling can pass through the extra layer of insulation and not get trapped. Any moisture can dramatically lower the insulation value of your batts. Install the second layer of insulaton perpendicular to the ceiling joists. This will help seal any air leaks plus fully insulate the ceiling joists, which can transfer heat and bypass the insulation.

About the author: Joe Truini is a home improvement expert who writes about a variety of topics related to carpentry and plumbing. Joe is also the author of numerous DIY books, including the best-selling Building a Shed. To learn more about insulation and the right products for your home, please visit the Home Depot website.