How to Install Roof Insulation

Written by c.l. rease
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How to Install Roof Insulation
Batt insulation provides the second layer of radiant heat protection. (Jupiterimages/Pixland/Getty Images)

Three layers of insulation provide the R-value required to protect your home from the heat generated by the sun's rays hitting the roof of your home. The first layer of protection comes from an air gap left between the roof sheathing and the first actual layer of insulation. An air gap allows air to circulate through the roof joists. The first layer of insulation provides the majority of the protection from radiant heat. Completing the protection is a layer of rigid insulation. Each layer must completely seal the previous layer to ensure you receive the highest amount of energy savings from the installed insulation.

Skill level:
Moderately Challenging

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Things you need

  • Fibreglass batt insulation
  • Straightedge
  • Insulation knife
  • Staple gun
  • Heavy staples
  • Rigid foam insulation
  • Drywall T-square
  • Pencil
  • Insulation nails
  • Claw hammer
  • Insulation tape

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  1. 1

    Unroll a bundle of fibreglass batt insulation. Unfold the paper tabs on both sides of the insulation batt. Measure the depth of a roof joist. Measure the thickness of the batt insulation. Remove fibreglass from the insulation -- if the batt is not 2 inches thinner than the joist depth -- by sliding an insulation knife down the length of the batt.

  2. 2

    Push the insulation batt between two roof joists. Pull the top of the insulation up to the peak of the roof. Load a staple gun with heavy staples. Hold the paper tabs of the batt against the front face of the roof joists. Place one staple 1 inch in from the end of a paper tab. Place one additional staple every 6 inches until you reach the end of the paper tab. Repeat the process with the paper tab located on the other side of the insulation batt.

  3. 3

    Install one insulation batt in each roof joist space using the described method. Ensure the paper tabs overlap to ensure a proper seal.

  4. 4

    Place one mark every 24 inches on a sheet of rigid foam insulation. Align the long leg of a drywall T-square with one of the marks. Pull a pencil along the aligned edge of the drywall square to create a reference line. Repeat the process to mark each joist location on the face of the insulation.

  5. 5

    Hold the marked sheet of insulation against the roof joist. Slide the sheet to the top far right side of the roof. Secure the sheet to the roof joist by running an insulation nail into a roof joist -- on a marked line -- with a claw hammer. Place one insulation nail every 12 inches on each marked line. Cover all roof joists with rigid insulation using the described method.

  6. 6

    Cover all seams between the installed pieces of rigid foam insulation with insulation tape to seal the insulation.

Tips and warnings

  • Wear a particulate respirator and loose clothing to keep fibreglass particles from irritating your lungs and skin.

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