A project you can do yourself to improve your home's energy efficiency

Put a Lid on One of the Most Inefficient Spots In Your Home

Download instructions and diagram (PDF file)

Materials

• One 4'x8' sheet of 1/2 foam board
• 22 to 25 8d nails
• Tube of latex or silicon caulk
• Tools
• Utility knife
• Pencil or marker
• 6' straight edge
• Tape measure

Pull-down attic stairs inside a house provide convenient access to the attic space above. From an energy point of view, however, it is like having a multi-lane freeway between the inside conditioned space and the attic unconditioned space on which heat moves in and out of your home.

The only material insulating you from extreme attic temperatures above a pull-down attic stair is a ¼ inch piece of plywood that has virtually no insulative value. This is a great contrast to the insulation that is all around the attic stair opening. The result is a hot or cold spot underneath your stairs that will affect your comfort and your heating and cooling bills.

One way to make this freeway limited-access is to construct an attic hatch cover, which fits over the attic side of the opening and reduces the transfer of heat without limiting access to the attic. The following step-by-step guide will walk you through the process.

Instructions for Assembling an Attic Hatch Cover
Measure the outside edges of the wooden frame of your attic stair assembly. You should have two measurements. A shorter measurement for the END piece of your hatch cover and a longer measurement for the SIDE piece. These measurements will be the outside dimensions for your attic stair hatch cover.

You are now ready to cut out two 8 inch by 8 foot strips of foam board for the SIDE and END pieces (see foam board layout on drawing). Lay the 4 foot by 8 foot sheet of ½-inch foam board on a flat surface. Starting with the long edge, measure out an 8 inch by 8 foot strip of foam board. Adjust your straight edge and carefully cut out the foam board.

Repeat step #2 so that you have two pieces of foam 8 inches by 8 foot.

To cut out your END piece, take one 8 inch by 8 foot strip of foam board. Measure the length of the END piece longways from one end. (This is the shorter measurement you acquired from the attic stair opening in step #1). Mark the foam board in two places to use as a guide for your straightedge. Cut out the END piece.

After you cut out the END piece, take the leftover piece of foam and use it to cut out the SIDE of the hatch cover. Take the length you measured for the long side of the attic stairs in Step #1 and subtract 1 inch. Using your new SIDE measurement, measure down the length of the leftover strip of foam board and cut out the SIDE. You should now have one SIDE and one END piece.

Repeat steps #4 and #5 with the other 8 inch by 8 foot strip of foam board. You can use the END and SIDE pieces you just cut as patterns so you will not have to measure again.

Take the four sides of your box and "dry fit" them in the attic hatch opening to see if they are going to fit properly. You can tape them together temporarily at this stage.

NOTE: It is very important in this step that you install these pieces accurately. Review the drawing for the correct assembly.

The hatch cover BOX FRAME should fit to the outside of the metal arms and line up with the wood frame that holds your attic stairs in place. If not, you may want to adjust the BOX FRAME to fit before you go any further. Once you feel confident that the BOX FRAME will fit the opening, you are now ready to assemble it. Place a line of caulk on the narrow, short edge of one SIDE piece. Remember to view the drawing so that the ENDS and SIDES are fitted properly. Make sure to line up the outside edges flush with each other.

Install three 8d nails through the END piece into the SIDE to hold the box together. Make sure to push your nails straight in. If the nails start to stick out, back the nail up and push it in straight. Repeat this process for the remaining pieces.

Measure the outside dimensions of your four-sided BOX FRAME you just assembled. Transfer these measurements to the remaining piece of foam board and cut out the TOP using your straight edge and utility knife. Apply a line of caulk to the top edges of the BOX FRAME. Lay the foam TOP on the BOX FRAME being careful to line up the SIDE and END pieces with the TOP.

Install the 8d nails through the TOP into the BOX FRAME to hold the hatch cover together. You may want to move the SIDE and END pieces in or out as you install the nails so that the TOP is flush with the outside of the BOX FRAME.

Reinforce the inside of the hatch cover by running a line of caulk on all inside seams.

Going the Extra Mile

Now that your attic hatch cover is built and installed, why not go ahead and perform some simple air sealing to your stair opening? Purchase some ½-inch self-sticking foam tape from your local hardware store. Apply the foam tape around the attic stair opening so that when you close the door to your pull-down stairs, the plywood cover will press against the foam. You will have the advantage of a fairly tight air seal and an insulated opening.