How to Insulate Attic Drop Down Access Stairs

Drop down attic staircase

Even if your attic is well insulated, the folding stairs that provides access can be a major source of heat loss. They often are poorly sealed and provide only a thin piece of plywood to keep the heated air from escaping.

Begin by checking to see if the attic stairs close tightly then apply self-adhesive foam weather stripping around the perimeter where the plywood door meets the frame, except on the hinge end.

Apply foam weather stripping around attic staircase opening

Once the opening has been sealed, it can be further insulated by building a foam box in the attic to enclose the stairs.

DIY insulating foam box for attic staircase

Materials for the project cost around $30. Here’s what you’ll need:

Materials List:

  • 1 – ¾” x 4’ x 8’ sheet rigid foam board
  • 1 – 2” x 30’ roll foil duct tape
  • 2 – ¾” x 17’ roll foam tape weather stripping
  • 1 – tube caulking (optional)

Be sure to use foil tape since regular duct tape won’t hold up to the heat in the attic.

Start by measuring the dimensions of the opening.

Measuring width for insulating foam box

And the height the stairs protrude above the attic floor.

Measuring the height of the stairs in the attic

Using a utility knife with a straight edge as a guide, cut strips from the sheet of foam to form the sides of the box. For best results use a new blade so it will cut the foam cleanly. Make the strips an inch or two wider than the stairs extend above the attic floor.

Cutting foam board to size

Finish the cuts by bending the piece and cutting from the other side.

Finishing the cut on the other side

Cut the strips to length to form the box using a framing square as a guide then join the corners with foil tape. A bead of caulking can be applied as well to form a better seal.

Taping insulating box together

Attach foam tape weather stripping to the top edge of the box to form a tighter seal. Cut a piece of foam the size of the exterior dimensions of the box for the lid. Tape the lid to the top of the box along one of the long edges with foil tape.

Taping lid to insulating box

Clean the floor around the attic stairs so the tape will adhere well. Position the box over the opening, making sure it is square.

Position insulating foam box over attic opening

Attach the box to the floor around the outside with strips of foil tape then run tape along the entire edge.

Tape insulating foam box to attic floor

A bead of caulking can be applied around the inside of the opening to provide a better seal.

Finally, remember to close the lid when you leave the attic.

Ckompleted foam insulated attic box

For those who would prefer to purchase a premade cover, the Attic Tent and Attic LadderMate are available in several sizes to fit different openings.

Premade insulation attic staircase cover