How to insulate exterior brick walls

Written by jennifer dawson
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How to insulate exterior brick walls
Insulate exterior brick walls with rigid foam board. (brick image by radiobryan from

Rising energy costs and the threat of climate change mean that owners of older homes are looking for ways to save money and shrink their ecological footprint. A brick wall, on its own, has an insulating value of only R-0.2 per inch. Insulate brick walls on the exterior to minimise the mess and work of tearing out and insulating from the inside. Adding 2 inches of polyurethane foam board insulation to the exterior of your home, then covering the insulation with siding or stucco, can add R-14 to your walls.

Skill level:
Moderately Challenging

Things you need

  • Polyurethane foam insulation board (1-inch or 2-inch thickness)
  • Spray foam insulation
  • Fasteners
  • Caulk
  • Ladder or scaffolding

Show MoreHide


  1. 1

    Seal any possible air leaks from the exterior of the house, using spray foam insulation. Look for gaps at the eaves and any penetrations in the wall, such as places where pipes and other services enter your home.

  2. 2

    Caulk any spots on the interior walls where air may leak in. Focus on window and door frames and baseboards.

  3. 3

    Attach the polystyrene board insulation to the outside face of your exterior brick walls, using fasteners recommended by the supplier. A total depth of 2 inches is optimal, as it allows you to screw far enough into the brick to secure the insulation properly, but you can achieve this depth using two sheets of 1-inch foam board. This allows you to use the second layer of insulation to overlap the joins in the first layer of insulation.

  4. 4

    Apply a new exterior surface to your house, such as stucco or siding.

Tips and warnings

  • Reduce your energy costs and environmental impact further by installing a programmable thermostat and replacing single-glazed windows with low-E, argon-filled double-glazed windows.
  • If your basement is not already insulated, consider extending the insulation below ground level over the foundation wall.
  • Your house needs to be considered "a system" with interrelated and interdependent parts. Moisture balance and ventilation are two things that can be impacted by an insulation retrofit. Installing exterior insulation is a job for an experienced handyman or professional.
  • Polyurethane foam board insulation degrades when exposed to sunlight and water.

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