How to Insulate Behind Drywall

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A hole saw allows you to blow insulation behind drywall.
A hole saw allows you to blow insulation behind drywall. (Image: circular saw image by Albert Lozano from Fotolia.com)

If your home does not have insulation, you can hire an insulation contractor or address the problem yourself. Either way, the solution is to blow cellulose insulation between the wall studs. Because cellulose insulation is made of 85 percent recycled paper and cardboard, it is an environmentally friendly material. It also has a high R-factor, which means that it has good insulating qualities. In addition, it is treated with borates, a Class 1 fire retardant. If you can use a hole saw and patch drywall, you can save money by tackling the job yourself.

Things You'll Need

  • Stud finder
  • Masking tape
  • Stepladder
  • 3-inch hole saw
  • Cordless drill/driver
  • Insulation blower
  • Cellulose insulation
  • String
  • 1/2-inch-thick plywood strips
  • 1/16-inch drill bit
  • Drywall screws
  • Phillips head bit
  • Drywall mesh
  • Drywall compound
  • Sanding block
  • 120-grit sandpaper
  • Interior wall paint

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Use a stud finder to locate all the exterior wall studs. Mark each location with a small piece of masking tape.

Place a stepladder midway between the first two studs and have a helper steady it while you work. Cut a hole into the drywall close to the ceiling with a 3-inch hole saw mounted in a cordless drill/driver. Save the drywall plug; you will use it to patch the hole after insulating the walls. Repeat by drilling a hole close to the ceiling midway between each set of exterior wall studs.

Thread the insulation blower hose through the first hole and feed it down as far as it will go. Wrap a rag around the hose and plug the hole to prevent blowback as you work. Ask your helper to switch on the blower. Pull the hose up a few feet each time you feel resistance. Fill the cavity with as much insulation as it can take before turning the blower off.

Repeat until all exterior wall cavities are filled with insulation.

Tie a piece of string around the midpoint of a 5-inch by 2-inch strip of 1/2-inch-thick plywood. Insert the supporting piece through the first round hole and draw the string tight, centered in the middle of the hole. Drill four 1/16th-inch pilot holes through the drywall and into this support strip near each corner. Secure with four drywall screws, using the drill/driver and a Phillips head bit. Sink the screws 1/16th of an inch into the drywall. Take care not to tear the drywall paper.

Insert the drywall plug into the hole and secure with four drywall screws. Place a 4-inch square patch of drywall mesh over the hole. Apply several coats of drywall compound to the patch -- letting each coat dry before applying the next coat -- until you’ve built up a smooth surface flush with the wall.

Use a sanding block and lightly sand the surface flush and smooth with 120-grit sandpaper. Paint the patch to match the wall. Repeat with each hole around the perimeter walls.

Tips & Warnings

  • According to the U.S. Department of Energy, blown cellulose insulation can save between 30 percent and 50 percent of the heating expenses for an average-size home.
  • Wear safety goggles and a respirator mask when blowing insulation into drywall.

References

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