Installing Rigid Insulation in the Attic

  • 4-40 hours
  • Beginner
  • 250-750
What You'll Need
Tape Measure
Rigid Insulation
Utility Knife
Straight Edge
1 x 3 Blocks 6 Inches Long
Furring Strips
2 1/2-inch Deck Screws
House Wrap Tape

With the use of rigid insulation homeowners in the northern areas of the country are able to combat heat loss through their attic. The rigid insulation is a foam polystyrene material that comes in various thickness to add to the current R-value of the fiberglass insulation between the rafters. One of the most common thicknesses of rigid foam insulation is 3/4 inches. The installation process is very straightforward and easily done by any do-it-yourselfer. Since the rigid insulation is the same dimensions of drywall, the installation is very much the same.

Step 1: Measure Attic for Rigid Insulation

In order to get the right amount of rigid insulation you will need you should take measurements for the total square footage. With this measurement, go to the home center and order the amount of insulation you will need.

Step 2: Prepare Attic for Rigid Insulation

Many attics have chimney bump outs and other obstacles that make it hard to install the rigid insulation. Prepare the attic by framing in these obstacles with lumber. The point is to create as much of a flat surface as possible, that is square, where you can easily install flat pieces of rigid insulation.

Step 3: Set First Piece of Rigid Insulation

Once the attic is prepared, then start to install the insulation. Start at one corner of the attic and lay the piece of insulation lengthwise like a piece of drywall. Mark the insulation where it lines up with the center of the rafter closest to the farthest edge. Cut the insulation with a utility knife.

Step 4: Cutting Rigid Insulation

Use a straight edge along the line where you want to cut the rigid insulation. Place a hard, flat surface under the insulation to give it some stability for a cleaner cut. Run a utility knife along the straight edge with several cuts.

Step 5: Screw Insulation to Rafters

Place the insulation back onto the rafters and screw it into place. Use 2 1/2-inch deck screws to secure the rigid insulation to the rafter. Place some 1 x 3 blocks along the insulation to keep it in place without any bowing or bending.

Step 6: Continue Installing Rigid Insulation

Following the same procedure, continue to install the insulation to the rest of the attic rafters and walls. Make sure that you cut each piece of the insulation so that it lands on the middle of a rafter. This is so you can attach another piece immediately after it.

Step 7: Apply Tape

After you have the rigid insulation installed along all the walls and rafters, go over all of the seams with some house wrap tape. This is important to keep any drafts from creeping in between the seams.

Step 8: Install Furring Strips

Once the tape has been attached to all of the seams, start to finish off your project by installing furring strips for attaching wall covering like drywall. The furring strips are installed running across the rafters and are attached with deck screws.