Exterior Insulation

Installing exterior insulation
Installing exterior insulation. Image source: JLC


Exterior retrofitting, or house wrapping, is an important step in reducing the carbon footprint of your home and achieving Net Zero. It will significantly increase your comfort level and reduce your heating and cooling needs. With many converting to electric energy with air source heat pumps for heating, cooling and hot water, it is a smart choice in reducing overall energy costs. As such, it remains a popular method used throughout Europe and North America to reduce energy consumption and our reliance on gas.


As the name suggests, it involves adding insulation to the outside of a house. Typically, the following layers are applied on top of the existing siding or a brick wall: an air barrier, Rockwool Comfortboard insulation, wood strapping and then new siding. Preferably, the materials used in an exterior retrofit should have a low carbon footprint. For example, Rockwool insulation has a much lower footprint than spray foam or rigid foam boards. Similarly, wood siding has a lower footprint than aluminum and vinyl siding.


Since most Harbord Village houses are heritage homes, the front walls of those houses should be insulated from the inside. But the sides and backs can be insulated from the outside with much less disruption to the occupants. Our Net Zero committee interviewed 3 contractors who were knowledgeable with Passive House practises and came up with the following cost estimate for an exterior retrofit in the spring of 2022.

The cost came to approximately $40/sq.ft. (or $53/sq.ft. if the existing siding is removed and the existing insulation is replaced before adding the “wrap”. Both prices include HST.) An exterior retrofit of a house with brick veneer would cost approximately 10% more due to a different procedure used to attach the insulation to the brick. Please consider this as a rough estimate to help determine if this is a project within your budget. Bear in mind the complexity and costing are dependent on a number of factors, such as the number of windows and corners.


The federal Greener Homes program provides a rebate of up to $5,000 if significant levels of new insulation are added to a house. For semi-detached houses, the maximum rebate is $3,750. In the quote below, the retrofit of a 740 sq.ft wall would cost $28,000, plus $11,000 for new siding, but it would only earn the homeowner a $1,300 rebate. However, the City of Toronto now offers interest-free loans of up to $125,000 which can be amortized for up to 20 years and repaid through your property taxes. As such, if the house is sold, the new owner would repay the remaining cost of the loan.

For additional information about the rebate and loan programs—as well as the required home energy assessment—visit the Net Zero Project’s Home Retrofit Programs page.


If you are interested in joining other homeowners in a “bulk buy” of exterior retrofits, please contact us. If at least 10 homeowners are interested, they will each benefit from the cost savings of a contractor being able to purchase the needed materials in bulk and work on properties located near each other.

If this is a project you would like to explore, please start by estimating the square footage of the exterior walls you would like to insulate. Then multiply that number by the estimated cost per square foot of an exterior retrofit. If the total amount is within your budget, contact us at netzero@harbordvillage.com. Once enough homeowners have expressed interest, we will share the list of names with the contractor.

Alternatively, if you are keen to start sooner rather than later—and not wait until there is sufficient interest to enjoy the cost savings of a bulk purchase—please let us know. We will be happy to share with you the name of the contractor who prepared the cost estimate and who comes highly recommended.

While this bulk purchase opportunity is mainly intended for Harbord Village residents, those in other neighbourhoods are welcome to contact us to have their names added to our list. If there are 5 interested homeowners in another neighbourhood, our contractor will likely be willing to include them.