How to Install Rafter Insulation

Robert Sylvus

A properly insulated home has insulation above the top floor's ceiling and a ventilation chute between the insulation and the roof deck. Most homes have an attic area, and builders place the insulation between the ceiling trusses and use short chutes at the roof's eaves.

Always insulate a roof's rafters before installing drywall.

Certain rooms, such as finished attics and rooms with a cathedral ceiling, do not have an attic area above the ceiling. In this case, builders install the insulation and ventilation chutes between a home's rafters prior to installing drywall.

  1. Slip one end of an attic ventilation chute, sometimes called an insulation baffle or rafter baffle, 4 to 6 inches into the attic's eave. Center the chute between the rafters, and secure the chute's lips to the roof deck with a hand-held staple gun and insulation staples. Place a staple near the top of the chute and every 8 to 12 inches along each side. Repeat this step for each set of rafters.

  2. Extend the rafter's ventilation chutes from the pieces entering the attic's eaves to the roof's peak. Secure the chutes to the deck every 8 to 12 inches, using the staple gun and insulation staples. Cut the last piece to size, using a utility knife.

  3. Measure the rafter from the roof's eave to its peak with a tape measure.

  4. Put on a dust mask.

  5. Stretch out a roll of code-approved batt-style insulation. Local building codes state the proper insulation R-rating needed for the geographic area. Batt insulation uses a paper backing with installation flaps on each side and a fiberglass insulating material.

  6. Transfer the rafter's length measurement to the batt insulation. Compress the fiberglass with one hand and cut the insulation to size with the utility knife.

  7. Hold one end of a piece of insulation to the rafter's peak, with the fiberglass facing the ventilation chute and the paper backing facing down. Attach the installation flaps on each side of the insulation to the bottom of the rafters, using the staple gun and insulation staples. Tack the insulation's installation flaps to the bottom of the rafter every 3 feet from the peak to the eave.

  8. Tack each piece of insulation to its set of rafters.

  9. Drive a staple every 8 to 12 inches along each rafter from the roof's peak to its eave, using the staple gun. This row of staples should hold the flaps from the insulation on both sides of the rafter.