When I stored some items up in the attic recently, I realized there is no insulation on the access door in the ceiling and it did not seal well. Is there much energy lost through there and what can I do about it? —Dan W.
An attic access opening can account for a significant loss of heat during the winter.
During the summer, heat from the roof radiates down into your home through the uninsulated access cover. With adequate attic ventilation, during the summer, a slightly negative pressure exists inside the attic area. If you air-condition, a leaky access cover draws cool air from your house and forces your air conditioner to run longer. If you do not air-condition, the air leakage can actually help ventilate your home naturally by effectively creating a solar chimney.
When I moved into my home, the attic cover was just a 20- by 22-inch piece of thin plywood resting on uneven wood molding around the access opening. To correct this gap, I first stuck thick adhesive-backed closed-cell foam weatherstripping on the top of the molding. I cut each of the four lengths slightly longer than each side of the molding because it may shrink over time.
Next, I nailed a layer of old drywall over the plywood to give it enough weight so the cover would compress the weatherstripping for a tighter seal. Drywall is better to use than lumber because the drywall creates a fire-resistant barrier.
I glued several layers of rigid foam insulation on top of the drywall to provide an insulation level as high as the rest of the attic floor. Finally, I covered the rigid foam insulation with a layer of aluminum foil to help block the radiant heat transfer from the hot roof during the summer.
The above method works well for a small access opening, but not necessarily for a large one. It may be dangerous trying to lift a large heavy cover while you are standing at the top of a ladder.
There are several products designed specifically for large access openings or ones with folding stairs. For any of these, install plywood on the attic floor around the opening. This provides a flat surface so a cover seals well and is a safe place to step when you enter the attic.
Battic Door offers a reasonably priced simple design that is basically a very strong cardboard box sized to fit over the opening and the stairs. You attach your own fiberglass batt insulation to the top and sides.
Another option is an insulated zippered opening cover by InsulSure. This cover is flexible and is attached to plywood on the attic floor around the opening for a good seal. To enter the attic, use a stepladder or pull down folding stairs, climb up, unzip the top of the cover, and fold it back. The cover is made of a flexible material filled with one-half inch of microfiber urethane insulation for R-3.2 insulation value. There is an optional reflective-foil top to block the radiant heat from the hot roof during the summer.
The third option, by Atticap, is a domed, molded foam cover made of expanded polystyrene (similar to a foam cooler), designed to fit over the stairs and opening. It is 60 by 30 by 9 inches high and weighs only about 8 pounds, yet has an insulation value of R-12. You can easily lift and move it to the side when you enter the attic.