When attic access is gained through pull-down stairs, the frame for the stairs fits in a rough opening and leaves a gap, much like a door or window, which must be sealed. If the gap is small (less than 1/2 inch), caulk can be used as the sealant. If a larger opening exists, then a non-expanding foam or a backing material (backer rod) is recommended in conjunction with the caulk. Expanding foam can be used, but care must be taken because of its highly expansive nature. It could potentially warp the frame and interfere with the ability of the stairs to open and close properly.
To ensure a tight fit between the stairs’ flat panel and the frame, weatherstripping or gasket material should be added either to the frame or panel. Latch bolts may be installed to help ensure a tighter seal.
To insulate attic stairs access, you can construct a lightweight, moveable box from rigid foam or fibrous ductboard to fit over the stairs from the attic side. Insulating kits are also available from weatherization suppliers or local hardware stores.
