How to Insulate an Attic When Finishing

Maximize headroom when insulating an attic.

Next Project


Are you finishing your attic? Here's how to save the most headroom when installing insulation.

Materials Required

  • Fiberglass batt insulation
  • Plastic air chutes
  • Rigid foam sheet insulation

Knowing how to insulate an attic while leaving adequate clearance can be tricky. That’s because insulating it to the proper R-value can cause a dramatic loss of headroom if you limit yourself to fiberglass batts. To maximize headroom, while properly insulating your attic and ventilating the roof, use a combination of dense batt insulation, rigid foam sheeting and air chutes.

Attic suppliesFamily Handyman

Most building codes require a specified minimum amount of headroom. It’s often tough to meet this requirement when insulating a finished attic, especially since most codes require insulation equal to R-38 or more. However, most inspectors I’ve spoken with will lower the insulation requirement if it means that the finished attic will have the required headroom. To get the most R-value with the least thickness, use batt insulation with higher R-value per inch in combination with rigid foam insulation. Rigid foam sheeting has an R-value ranging from R-5 to R-10 per inch of thickness. This means you can have a combined R-value ranging from R-23 to R-31 with only 5-1/2 inches of combined fiberglass and foam insulation.

Project step-by-step (2)

Step 1

Why Your Roof Needs Air Chutes

  • To effectively ventilate your roof, create a 1-inch airspace from the soffit to the ridge by installing a continuous air chute in each rafter bay.
    • Note: Air chutes, when combined with soffit vents and a ridge vent, will help prevent problems with condensation and ice dams.

Attic diagramFamily Handyman

Step 2

Air Chute Installation is Easy

    • Note: Air chutes come in 4-foot lengths and 14-1/2 and 22-1/2 inch widths.
  • Staple them directly to the roof decking for better insulating roof rafters.
    • Note: Air chutes work only when the rafter spaces run from the soffit to the ridge. This method won’t work where rafter spaces stop short, such as in a valley, or in the corner of a hip roof.

Attic insulationFamily Handyman

Additional Information