Check your insulation situation

To check for wall insulation, cut the power to a few outlets on exterior walls, then unscrew and look behind the cover plates. Use a wood ruler to push aside loose insulation and look for gaps.

A more high-tech solution is to have a professional energy audit. For $400 to $600, a professional energy auditor will use thermal or infrared scanning tools to look for temperature variations on walls that indicate failed or missing insulation.

Adding wall insulation

To add wall insulation, a contractor drills small holes through the inside or outside wall and blows loose-fill material between studs. Costs range from around $1.25 per square foot for loose-fill fiberglass, cellulose, or rock wool to $4.40 for polyurethane foam, which insulates about twice as well.

Drawbacks of adding wall insulation

Despite the obvious advantages, such as a cozier interior, there are several drawbacks:

  • It’s not necessarily cost-effective. Figure it costs $3,000 to $4,000 to fully insulate the walls of a 2,200 square-foot home. If energy savings are $130 per year, then the payback period on your investment would be more than 23 years.
  • Framing blocking, pipes, ducts, and wiring can prevent blown-in insulation from completely filling stud cavities, creating voids with no insulating value.
  • Dozens of holes are needed to fill all the stud cavities in an average house, leaving you with the problem of filling or patching all those holes.

Best strategy for wall insulation

If your walls already have some insulation, you probably can’t add more without tearing into the drywall or plaster. That’s not cost effective unless you’re remodeling, so the best strategy is to wait until you need to replace siding. Then you can add insulating sheathing underneath it.