How to Insulate Exterior Brick Walls

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 minimize 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.

Insulate exterior brick walls with rigid foam board.

Step 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.

Step 2

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

Step 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. 

Step 4

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

Things You Will Need

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


  • 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.

About the Author

Jennifer Dawson is a Canadian researcher and writer who started freelancing in 2007. Specializing in environment and health topics, her work has appeared in “The Health Journal,” "Nutrition and Your Health," "Alternatives" and “Together Family.” Dawson has a Bachelor of Arts in English and a Master of Arts in anthropology from McMaster University.

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