You may have a well insulated attic, but chances are that the attic hatch is under insulated or not insulated at all, which is equivalent to having hole in the ceiling for heat to escape through. This stair cover is an effective insulating cover for folding attic stair door. It is constructed of an R-13 laminated 1.5" thick foil-faced Thermax board, and incorporates foam gaskets around the edge and Velcro tie-downs to provide a tight seal. The inside dimensions are 27 inches wide x 57 inches long. It is 10.5 inches deep.