The Best Way to Insulate Older Homes

A poorly insulated house wastes energy.

If your old house is too cold, you need to insulate it. You could pad the walls with fiberglass batt insulation if they weren't already covered over with wallboard, but since they are, you need a different strategy. That strategy is to blow loose insulation into the wall bays with a rental blowing machine. You can do this from inside or outside the house, and the fuss is minimal when compared with removing the wallboard to install batt insulation or to blow foam.

Things You'll Need

• Plastic sheeting
• Pencil
• Drill
• Hole saw
• Blowing machine
• Loose cellulose or fiberglass insulation
• Goggles
• Protective clothing
• Can of spray foam insulation
• Utility knife
• Fiberglass drywall tape
• Drywall joint compound (mud)
• Drywall blade
• Wall primer

Instructions

1. Remove as much furniture as you can from the room, and cover any that remains with plastic sheeting.

2. Insulate one exterior wall at a time. Find the studs in the wall and make marks at top of the wall in the bay midway between each pair of studs.

3. Fit your drill with a hole saw attachment that has a diameter a bit larger than the nozzle of the insulation blower. Drill holes in the wallboard at every mark you made in step 2.

4. Fill the canister of the blower with loose insulation and insert the nozzle into one of the holes. Wrap a rag around the nozzle to control dust and turn on the machine.

5. Blow insulation into the bay until it fills. You'll be able to tell when it is full because the pressure on the blower will change and material will start blowing back out of the hole. Tap the wall as you are blowing to dislodge material from wires and pipes that may be in the wall. Fill each bay in the wall in this way.

6. Patch the holes by first spraying in foam insulation from a can. Let the foam expand to fill the hole, then cut it flush to the wallboard with a utility knife when it has dried.

7. Cover each hole with self-adhesive fiberglass drywall tape, then spread a coat of mud over the tape with a drywall blade. Scrape the mud flat with the blade, then let it dry overnight. When it has dried, top-coat it with two more coats of mud, feathering these into the wallboard with the blade. When the last coat has dried, paint it with wall primer in preparation for touch-up painting.

Tips & Warnings

• You can also blow insulation from outside by making holes in the siding or underneath it and covering them over when you are done. This works best with siding that can be removed a piece at a time and replaced when the hole is covered. It is not really an option if your house is made of brick.

• Wear goggles and protective clothing while you are blowing insulation, particularly if you blow fiberglass. Loose fiberglass is a skin and eye irritant.

References

• Bob Vila: Blow-In Insulation Options
• Ask the Builder: How to Insulate an Older Brick Home