• In this how-to video, This Old House general contractor Tom Silva explains how to retrofit cellulose insulation.


    1 Locate two adjacent wall studs on an exterior wall.
    2 Use utility knife to remove a shingle from the bottom of the wall; be sure the shingle falls between the two studs.
    3 Use a 1 1/8-inch-diameter spade bit to drill a hole through the wall sheathing where the shingle was removed.
    4 Check for studs using a straightened wire coat hanger.
    5 Remove a shingle at the top of the wall and drill 1 1/8-inch-diameter hole into the stud bay.
    6 Fill hopper on the insulation blower with cellulose insulation.
    7 Force the nozzle on end of blower hose into the lower hole in wall.
    8 Turn on blower to force insulation up into space between the two studs.
    9 Use a rag to plug upper hole, if necessary, to prevent insulation from blowing out.
    10 Once you hear the blower motor start to strain, turn it off and move the nozzle to the top hole.
    11 Turn the blower back on and force insulation down into the wall.
    12 Once the stud bay is completely filled, turn off the blower.
    13 Apply silicone caulk around the holes in the wall, and along the top seam of the shingle.
    14 Nail the shingles back to their original spaces with 4d galvanized finishing nails.
    15 Measure over 16 inches from first set of holes to locate the next stud bay.
    16 Continue to drill holes and fill the stud bays with insulation.
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    • Difficulty: Moderate to hard
      Requires at least two people and quite a bit of climbing up and down ladders
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      Video Directory

      Selected Topic/Section

      Tools List

      • utility knife
        Utility knife
      • drill
        Drill and 1 1/8-inch-diameter spade bit
      • hammer
      • Insulation Blower
        Insulation blower
      • 100-foot tape measure
        Measuring tape
      • extension ladder
      • caulk gun
        Caulking gun

      Shopping List

      1. Cellulose insulation

      2. Silicone caulk,

      used to seal shingle to wall

      3. 4d galvanized finishing nails,

      used to re-attach shingles