How to Blow in Insulation From Outside

If you need to insulate a house that doesn't have the walls open, the common approach is to blow in loose insulation. You will have to cut holes in the walls to do it. You can go from the inside, but that requires extensive wall repair afterward. Or, if your siding is horizontal and can be easily removed and reinstalled, you can blow it in from the outside under the siding, so the holes will be hidden.

Pry bar
Hammer
Electronic stud finder
Pencil
Rented insulation blower
Jigsaw
Cellulose insulation
Spray foam insulation
Siding nails

Instructions

- 1
  Use a hammer and pry bar to pry off a horizontal strip of the siding across the exterior wall, at a level equal to about 6 inches below the ceiling of the room inside. Keep the siding intact as you take it off.
- 2
  Use your electronic stud finder to locate each stud in the wall. Put a pencil mark midway between each pair of studs, marking on the exposed sheathing where you took off the siding. The marks should be 16 inches apart.
- 3
  Hold the end of your insulation blower against the wall at each of the marks you made. Trace around the end of the hose, leaving a circle.
- 4
  Cut out the traced circles with a jig saw.
- 5
  Load your insulation blower with cellulose insulation. Feed the blower hose into one of the holes, pushing it all the way to the bottom of the wall space inside.
- 6
  Start the blower. Let it fill the space inside with loose insulation from the bottom up. Withdraw the hose as it fills the cavity. Repeat for each hole.
- 7
  Spray foam insulation into the mouth of each hole, letting it fill the opening. Allow it to set for an hour.
- 8
  Nail the siding back in, using your hammer and siding nails, to cover the sealed holes.

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