Page: Last modified: 2024-02-16
Code Reference(s):
NBC20 Div.B 10.9.36. (first printing)
Alteration of Existing Buildings
Alteration of HVAC Systems
This proposed change introduces requirements for HVAC systems subjected to alteration.
This change could potentially affect the following topic areas:

General information

See the summary for subject Alteration of Existing Buildings.


See the "Problem" section of the summary for the subject Alteration of Existing Buildings.

The energy performance requirements for the HVAC systems described in Subsection 9.36.3. of Division B of the National Building Code of Canada (NBC) theoretically already apply to the alteration of existing buildings. However, the enforcement of the application of these requirements depends on the interpretation of the authority having jurisdiction, which balances the implementation costs against the relative importance of achieving the Code’s environment objective.

Applying the requirements for the minimum energy performance of HVAC systems to all voluntary alterations could result in alterations that exceed their original scope.

If voluntary alterations include upgrades to existing HVAC systems, not upgrading these systems to reasonable performance levels of energy efficiency might waste an opportunity for future energy benefits and cost savings through reduced energy bills and reduced construction costs.


The voluntary alteration of an HVAC system in an existing building represents an opportunity to upgrade the energy performance of the system.

To address the alteration of existing buildings, a guiding principle of the development of provisions is that the provision should be reasonable, pragmatic and avoid placing an undue burden on building owners. Providing exemptions for cases of maintenance, repair or replacement with similar parts or components allows the flexible continued use of existing functional equipment by extending its service life and deferring system replacement costs.

This proposed change aims to clarify the requirements for authorities having jurisdiction, designers and building professionals. The enhanced clarity would ensure that building owners could benefit from energy performance upgrades while avoiding an undue burden, ultimately promoting energy efficiency and reducing the incremental cost of the upgrade.


[10.9.36.] -- Energy Efficiency

[] ---Alteration of HVAC Systems

(See Note A- (PCF 1825))
[1] --)Except for maintenance and repair, and except as provided in Sentences (2) to (5), HVAC systems and equipment shall conform to Subsection 9.36.3.
[2] --)Where the alteration is an addition, newly installed ducts and plenums shall conform to Article
[3] --)Where portions of existing HVAC ducts or plenums are exposed within the extent of the alteration, the joints of those portions of ducts or plenums shall be sealed in conformance with Sentence and Articles and, as applicable.
[4] --)Except as provided in Sentence (5), where a previously unconditioned space in a residential building is converted to a habitable, conditioned space, HVAC systems serving the space shall comply with Sections 9.32. and 9.33.
[5] --)Where the capacity of existing HVAC equipment is determined to be adequate to serve the existing building and addition, the HVAC equipment need not comply with Table

Impact analysis

There is no associated cost increase with the replacement of heating or air-conditioning equipment, since any new equipment on the market meets the minimum Code requirements. The cost associated with sealing the existing portions of ducts or plenums that can be accessed is expected to be minimal. However, an assessment of costs is provided below for general information.

Assessment of Costs

The following representative conditions were selected for assessment purposes.

  • Household size: four occupants (energy use: ~130 GJ/year)
  • House: 2 000 ft.2 detached, built prior to 1980 (HVAC system demand: 65 000 BTU/h heating capacity, 2.5-ton cooling capacity). (See Table 1.)

 Table 1. Size of Furnace and Air Conditioner for a Detached, Two-Storey House

Detached House, ft.2(1) Furnace Output, BTU/hr Air Conditioner Size, ton
Built after 1980 Built before 1980 Built after 1980 Built before 1980
< 1 300 40 000 50 000 1.5 < 2
1 300 to 1 700 45 000 < 55 000 1.5 2
1 700 to 2 500 55 000 < 65 000 2 to 2.5 2.5
2 500 to 3 500 < 65 000 < 80 000 2.5 to 3 3 to 3.5
3 500 to 4 500 < 80 000 < 100 000 3.5 to 4 4 to 5

Note to Table 1:

(1) The above square footages do not include the area of the basement.

Different energy sources are available for both heating and cooling equipment, e.g., gas, electric, oil, air-source and geothermal (for heat pumps) or a combination of these energy sources. This analysis determines the associated costs and benefits of replacing existing equipment while maintaining the existing energy source. Therefore, the associated costs and benefits of replacing existing equipment with higher energy-efficiency HVAC equipment are also captured. Gas-fired heating equipment and electric cooling equipment are selected as representative energy sources. Note that energy cost savings based on different energy sources is assumed to be similar to that of the representative energy source.

The typical cost of heating equipment with a capacity of up to 65 000 BTU/h that is available at big box stores, such as Home Depot, is around $3 500 to $5 000. The typical cost of cooling equipment with a capacity of up to 2.5 tons that is available at big box stores is around $2 000 to $3 000.

Typically, the installation of new HVAC equipment is provided by professionals, and the costs associated with such service include labour and materials (required to replace the accessible portions of ducts or plenums that form part of the HVAC system to be insulated). According to the resources available for Canadian consumers, the average cost of labour for the installation of an HVAC system is between $2 000 and $3 000.
The estimated total cost of the replacement of heating equipment is between $3 500 and $8 000 including installation or between $2 000 and $6 000 without installation. [3]

Assessment of Benefits

The benefits of this proposed change are measurable due to the direct energy savings associated with using higher energy-efficiency HVAC equipment. Energy savings that result from applying a small section of thermal insulation to supply and return plenums are considered negligible for this particular installation.

According to Natural Resources Canada, space heating accounts for 64% of the energy used in the average Canadian house as a result of Canada’s cold climate [1]. Annual average energy use is 130 GJ, which implies 83 GJ is used for annual space heating. Average cooling accounts for 1.6% of the energy used in the average Canadian home. Annual average energy use is 130 GJ, which implies 2 GJ is used for space cooling.

According to the ENERGY STAR guide, typical annual energy savings of around 10% to around 30% are expected where higher efficiency HVAC equipment is properly installed. It follows that annual average energy savings of 20% delivers 17 GJ and 0.4 GJ would result with the use of higher efficiency heating and cooling, respectively. Average energy cost in Canada is around $0.179/kWh (1 GJ is 277.79 kWh) [3]. Annual average energy cost savings generated upon installation of higher efficiency heating and cooling equipment is expected to be around $845 and $20, respectively.

Applying thermal insulation to ducts and plenums in the HVAC system may minimize thermal transfer from the ducts and plenums to the surrounding environment and reduce the extra consumption of energy required for HVAC equipment.


(1) Natural Resources Canada guide,

(2) Statistics Canada (2011). Average energy use data. 

(3) National average pricing for HVAC equipment from big box stores such as Home Depot.

(4) Energy Rates Canada, accessed in July 2023.

Enforcement implications

It is expected that a consistent set of provisions that apply to the alteration of existing buildings would help reduce the administrative and enforcement work of assessing the degree to which any particular requirement could be relaxed without affecting the level of performance of the building with respect to the Code objectives.

This proposed change would aid enforcement by identifying the work necessary to improve the energy performance of an alteration.

Who is affected

Designers, engineers, architects, building officials, manufacturers, suppliers and energy advisors.


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