How to insulate an attic-access opening

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SMART, MONEY-SAVING GREEN CHOICES

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Question: I just discovered my new house has no insulation on the attic opening cover. Shouldn’t the cover be insulated and sealed? If I add folding stairs, how can I insulate them?  

Answer: Builders don’t always insulate and seal the attic-access opening cover. Often just a scrap piece of plywood or drywall is cut somewhat close to the correct size and placed in the opening, resting on a strip of molding. That type of cover’s insulation value is less than R-1, and it leaks air like a sieve.

Attic opening covers should be insulated and sealed for energy savings. Because the attic access is often in the ceiling of a bedroom closet or a hallway, the air leakage and heat loss/gain are less noticeable. In a well-insulated house, even just several square feet of uninsulated space can lose a considerable amount of heat.

The simplest fix is to attach insulation to the top of the cover and add weatherstripping underneath where the cover rests on the lip of the opening. The insulation on the top of the cover should be up to the recommended code ceiling R-value for your area—that’s R-38 for South Carolina attics.

Measure the cover to make sure it fits the opening well, with the cover overlapping the molding lip so the weatherstripping will seal it. If you have to make a new cover, a piece of half-inch drywall works well and is fire resistant.

In my own house, I first nailed a piece of half-inch drywall to the front of the plywood cover to give it some additional weight. Next, I glued four layers of three-quarter-inch polyurethane foam sheets to the back, to get three inches of foam insulation. I used foil-faced insulation that will reflect heat from a hot roof back up.

The next step is to attach adhesive-backed foam weatherstripping to the top edge of the lip around the opening. Before you start, place the cover on the lip to make sure it’s even. The lip often consists of molding pieces nailed to the sides of the opening. If they aren’t level, you may have to pry pieces loose and reattach them. An uneven fit makes it difficult to get a good seal under the cover.

Use as thick a foam as you can find to accommodate any out-of-level edges. The weight of the plywood and drywall should be adequate to compress the foam weatherstripping.

If you want to install pull-down stairs or a ladder, or if your attic currently has one, buy a special insulated cover for the attic-access opening.

One of the least expensive options is basically a three-sided, heavy-duty cardboard box. It’s easy to open and assemble, and then you can attach your own insulation to the top and sides. It’s lightweight and easy to lift when you enter the attic on the stairs.

Another option is a lightweight, large, rigid-foam domed device that covers the folded stairs or ladder from above. It’s strong, and the foam provides adequate insulation. Another design uses a flexible, zippered, insulated cover that is permanently attached to the attic floor for an airtight seal. The zipper provides a large opening for easy access to the attic.

Get More

TogetherWeSave.com, an energy-efficiency website from the nation’s electric cooperatives, has two videos on this subject as part of its Watch & Learn series; visit energysavings.togetherwesave.com/watch-and-learn and click on the Sealing and Insulation tab, then scroll down to find how-to videos on insulating attic hatches and attic pull-down stairs. 

Download do-it-yourself instructions for sealing attic hatches.  

The following companies offer attic entrance products:  

Send questions to Energy Q&A.