Brand new website coming soon. Learn MoreClose

Envelope Retrofit


Reduced Energy Consumption

  • Decreases heat loss through attics, walls and foundations.
  • Decreases heat loss through air leakage.
  • Reduces capacity requirements for space conditioning equipment.

Reduced Energy Costs

  • Better insulated, more airtight, building envelopes reduce space heating and cooling costs.
  • Can offers good returns from energy cost savings for the dollars spent on the retrofit work.
  • Improves energy affordability into the future as energy costs rise.

Reduced Environmental Impact

  • Lowers pollutant emissions.
  • Reduces consumption of non-renewable fuel resources.
  • Improves and preserves the existing housing stock.

Figure 1 — Retrofitting Spray Foam Insulation on Exterior Walls — Now House®

The exterior cladding has been removed from the outside wall of the home and a worker is spraying blue foam insulation between the studs.


The building envelope — ceiling, above grade walls, exposed floors and foundation walls and floors — of a house is only as energy efficient as the standards required when it was built. More than 85% of the houses in Canada are over 10 years old, many of them — especially in Eastern and Atlantic Canada — were built prior to the 1970 energy crisis when energy efficiency was of lessor concern. This means that a large proportion of Canadians are living in houses that could benefit from an energy retrofit.

Draftproofing, or air sealing, is often the least expensive but most effective energy efficiency measure that can be taken in an older house. Draftproofing helps to control airflow, moisture flow and heat flow. In some older houses, air leakage can account for 25 to 40% of the overall heat loss. Controlling air leakage is also a key way to improve the comfort level in a house and improve indoor air quality. Draftproofing starts with using a ‘blower door’ to test the house to see what the air change rate is and where the leaks are. Thermal imaging (infrared photography) is useful, as well, to identify un-insulated areas in older homes.

Reducing airflow through the cracks and holes in the envelope of the house results in energy savings, but at a certain point, can reduce indoor-outdoor air exchange to the point where stale air becomes a problem and increased humidity levels can result in moisture and mold problems for the structure and the occupants. The provision of controlled mechanical ventilation, such as that provided by a heat recovery ventilator, counteracts these issues, and the energy cost relating to fan use is minimal compared to the energy costs of uncontrolled air leakage.

The next biggest return on any dollar spent on energy efficiency is increased insulation. Attic spaces and wall cavities are most commonly insulated as part of a renovation or retrofit on older houses. Increasing attic insulation by RSI 3.53 (R20)  is relatively easy, but requires attention at the eaves to ensure there is good insulation value at the area most vulnerable to heat loss. Adequate ventilation of the attic space is required at the soffit and ridge. Above grade walls can be improved when siding is scheduled to be replaced. Installing 2 to 3 inches of rigid insulation board (RSI 1.761 – RSI 2.64) under new siding can double or even triple the insulation value of the walls, depending on what is already in the cavity.

Figure 2 — Adding Insulation to Exterior of Foundation Wall — Now House®

The exterior cladding has been removed from the outside wall of the home and a worker is spraying blue foam insulation between the studs.

Insulating areas such as finished basements by adding RSI 1.761 (R10) or more of rigid or semi-rigid board insulation applied to the interior or exterior of the basement walls can reduce heat loss and improve comfort. Basement renovations also provide an opportunity to correct any moisture problems.

Areas Prone to Air Leakage

Behind shower/tub
Behind fireplace
Sloped ceilings in attic rooms
Attic knee walls
Skylight shaft walls
Adjoining a porch roof
Staircase walls
Party, shared or double walls
Floor of ‘bonus room’ above garage
Cantilevered floor
Attic Access Panel
Attic Drop-Down Stair
Dropped Ceiling/Soffit
Recessed Lighting Fixtures

Figure 3 — Spray Foam Insulation Seals Between Joists — Now House®

A worker installs blue spray foam insulation between the ceiling joists in the basement of the Now House EQuilibrium demonstration home to reduce thermal bridging through the foundation wall.

Figure 4 — Loose-fill Insulation Added to Attic Space — Now House®

Loose – fill insulation has been spread over the attic floor in the Now House EQuilibrium demonstration home.

Design/Installation/Operation/Maintenance Considerations

  • Many aspects of draftproofing and insulating can be carried out by the homeowner.
  • Some materials require specially trained installers.
  • A blower door test is crucial to determine whether or not mechanical ventilation is required.
  • An energy audit, such as those provided through Natural Resources Canada’s EnerGuide for Houses Rating System (ERS) program and other energy assessment programs are very helpful in determining the best locations and levels of insulation and draftproofing for a house, as well as the amount of additional mechanical ventilation required (if any).
  • ‘Keeping the Heat In’, a publication of the Office of Energy Efficiency of Natural Resources Canada is a useful resource as is the renovation-related material from Canada Mortgage and Housing Corporation (see online links below).
  • Some tight urban lots may require variances for exterior insulation or thickened walls.
  • Its important to correct any pre-existing moisture problems with the building envelope prior to undertaking energy efficiency retrofits.
  • Energy retrofits make more economic sense when done with other home renovation work such as siding and roofing replacement, window upgrades, basement renovations.

What Does it Save?

The cost savings associated with improving the draftproofing and insulation levels in a house are dependent upon a number of factors including the existing insulation and airtightness levels, the climatic region and energy prices.

Here is an example of the possible savings a family of four living in a 2-storey house built in 1973 could see by carrying out an expanded building envelope energy retrofit. The air leakage rates range from 4.4 to 10 ACH @ 50 Pa. The original house has RSI 2.1 (R-12) in the exterior walls, RSI 3.5 to 4.6 (R-20 to R-28) in the ceiling, RSI 0.8 to 1.4 (R- 5 to R-8) in the basement walls and no insulation in the foundation floor.

Retrofit measures include:

  • Reducing the air leakage rate to 1.5 air changes per hour (ACH) @ 50 Pa
  • Increasing the attic insulation to RSI 8.8 (R-50) (Vancouver, Toronto and Halifax) or RSI 10.6 (R-60) (Montreal, Calgary and Whitehorse)
  • Adding RSI 2.1 (R-12)  for Vancouver, Toronto and Halifax -or — RSI 3.2 (R-18)  for Montreal, Calgary and Whitehorse to the exterior above grade walls
  • Improving the basement wall insulation value to RSI 3.2 (R-18) (all cities)
  • Adding RSI 1.8 (R-10) to top of basement slab (all cities)

Envelope Retrofit — Annual Energy Savings

  Vancouver Calgary Toronto Montreal Halifax Whitehorse
MJ/Year Before Envelope Retrofit 92,115 98,871 87,895 94,693 113,755 164,146
MJ/Year After Envelope Retrofit 44,662 61,634 55,178 53,206 74,478 90,936
Annual Cost Savings 2,991 251 349 795 1,158 2,568
% Energy Savings 52 35 37 44 34 45

The chart shows cost savings associated with a mid-efficiency gas furnace in Vancouver, Calgary and Toronto, an electric furnace in Montreal, a mid-efficiency oil boiler in Halifax and a mid-efficiency oil-fired furnace in Whitehorse. Cost savings will vary according to the price of the energy source for space heating, the energy efficiency of the space heating equipment, the amount of insulation added, and air tightness level attained.

Note that although all cities show a 35 to 52% reduction in energy use, where energy prices are low, as in Calgary, the annual space heating cost saving is as low as $251/year.

For More Information

The information contained in this publication represents current research results available to CMHC. Readers are advised to evaluate the information, materials and techniques cautiously for themselves and to consult appropriate professional resources to determine whether information, materials and techniques are suitable in their case. The text is intended as general information only and project and site-specific factors of climate, cost, aesthetics, practicality, utility and compliance with applicable building codes and standards must be taken into consideration. A number of assumptions were applied with respect to fuel prices, water rates, costs of materials, equipment and labour, planning horizons, etc. Actual reductions in energy consumption and fuel savings will vary. Any reliance or action taken based on the information, materials and techniques described are the responsibility of the user. CMHC accepts no responsibility for consequences arising from the reader’s use of the information, materials and techniques herein.

Last revised: 2013



Print(opens in a new window)