Check clearances before assembling the Therma-Dome® cover

If your attic has low overhead clearance (such as a ranch home), make sure there will be adequate room to maneuver the assembled Therma-Dome cover into the attic. This is particularly important for the larger covers, such as the Pull-Down Attic Stair Cover. If clearances are limited, the cover should be sent up into the attic in pieces and assembled in the attic.

Ensure a flat deck for the Therma-Dome cover's gasket to rest on

If your attic floor does not have decking, you will need to create a "landing zone" for the Therma-Dome cover. Cut strips of plywood or OSB to surround the attic door opening on all four sides, and attach them to the attic joists.

Additional blocking may also be required to support the strips of flooring material.

Make certain that there is a tight air seal around your attic stair opening

The Therma-Dome cover will provide an excellent air seal between the Pull-Down Attic Staircase and the unconditioned attic space. However, the effectiveness of this seal can be compromised if air can move between the attic stair opening and the space under the attic decking. To prevent this, use a minimal expansion foam filler for any large gaps, and caulk filler to seal any small gaps around the attic stair unit. Fill the area between the casing and the rough opening. The decking should come all the way to the edge of the attic stair opening. Caulk the seam between the decking and the joist. Make sure there are no gaps that would allow air passage under the attic decking from the area under the Therma-Dome cover.

The "dead" air trapped between the stairs and the Therma-Dome cover will serve as an additional insulating medium. To maximize the effectiveness of this air pocket, install gasket around the edges of the pull-down attic stair door, where it closes against the casing. Self-adhesive gasket would work well for this application.

Repair any damage that occurs to the Therma-Dome cover

The Therma-Dome cover is constructed of polyisocyanurate foam board that has been sandwiched between two layers of reflective foil. Rough handling of the Therma-Dome product could cause damage. Any damage that occurs should be repaired to ensure maximum effectiveness of the Therma-Dome cover.

For any clean breaks that occur, use adhesive (such as the adhesive included with the Therma-Dome kit) to glue the pieces back together. To ensure a good bond, keep pressure on the glued pieces overnight. Foil tape (such as the tape included with the kit) may be used to cover any breaks that damage the foil of the polyiso panel. Small punctures can be repaired the same way.

Larger punctures or gouges will need to be filled with spray foam before a foil tape patch is applied. After the spray foam dries, cut it down to be even with the surface of the Therma-Dome cover, clean any dust from the area, and apply the foil tape over the foam patch.

Protect Versa-Dome sidewalls during insulation blow-in

If using the Versa-Dome™ in the insulation dam configuration, be sure to protect the sidewalls from potential damage caused by rubbing from the blowing hose. A simple way to do this is to make use of the cardboard carton that the cover came in. Cut it into sections and fold it over the sidewall. Duct tape of thumb tacks can be used to hold the cardboard in place temporarily. The cardboard can be removed as you descend the ladder and blow in the last bit of attic floor immediately surrounding the attic opening.