Wall Insulation

Your walls may be letting warm or cool air escape from your home. Use our guide to insulating your walls to improve energy efficiency and lower your power bills.


Heat flows naturally from warmer spaces to cooler ones—even through your home’s walls if they aren’t properly insulated. That means the summer heat intrudes on your air-conditioned air, and the air you heat in the winter escapes outside, wasting energy and money.

Wall insulation works in conjunction with attic insulation and sealing air leaks to form the “thermal envelope” that keeps your home cool in summer and warm in winter. While many newer homes are built with adequate wall insulation, you may want to consider installing or adding to it if:

  • You have an older home, most of which were not built with wall insulation.
  • You are finishing an unfinished space such as a bonus room or basement.
  • You are replacing exterior siding.


Benefits of Wall Insulation

  • Slows heat loss and gain, conserves energy, reduces utility bills and improves temperature control and comfort
  • Decreases the workload on your HVAC system

What You Should Know

Insulation is measured by R-values, which indicate its ability to resist heat flow. Higher values represent better performance. Exterior walls should be insulated to about R-13, though your needs will vary depending on the size of your walls and the type of insulation you use.

Before Beginning Work

  • Seal air leaks, including structural, mechanical and other penetrations.
  • Address any moisture problems.
  • In older homes, have an electrician check wiring near the insulation to ensure it’s not degraded or overloaded.
  • If your home has an attached garage or gas appliances, install a carbon monoxide monitor.

General Guidelines

  • Use high-quality, long-lasting insulation appropriate to the area you are insulating.
  • If you are replacing exterior siding, add R-5 thermal insulating sheathing beneath the new siding.
  • Use an infrared camera to identify voids in the insulation that need to be filled.

Maintenance + Upkeep

  • Use an ENERGY STAR dehumidifier to keep basement humidity under 45 percent.