Page: Last modified: 2024-02-20
Code Reference(s):
NECB20 Div.B (first printing)
Building Envelope - General
Use of the Term "Grade" in the NECB
This proposed change clarifies Note A- by using “ground” instead of “grade” to refer to the finished ground level.
This change could potentially affect the following topic areas:


In the National Building Code of Canada (NBC), “grade” is a defined term used to determine a building’s height in storeys, which in turn determines requirements for the construction and protection of that building. The NBC defines “grade” as the lowest of the average levels of finished ground adjoining each exterior wall of a building. Therefore, at any point along the length of a wall, grade may be above or below the adjacent ground level. As such, the defined term “grade” does not necessarily refer to the finished ground level.

If Code users determine the requirements for the insulation of a building component based on the definition of grade provided in the NBC, which is reproduced in the National Energy Code of Canada for Buildings (NECB), this could lead to the installation of thermal insulation that is insufficient to minimize heat loss.


In the NECB, the main purpose for references to “grade” is to establish requirements to reduce heat loss. In most instances, rather than using the defined term “grade,” the NECB should refer instead to “ground,” which more accurately describes the building level intended to be used to determine the required thermal resistance of the building element. The use of the defined term “grade” to determine thermal insulation requirements may lead to building elements having a thermal resistance that does not meet the objectives of the NECB.

Using the non-defined term “ground” instead of “grade” to determine the required thermal resistance of a building component will minimize heat loss and better meet the objectives of the NECB.


[] of Insulation Materials

[1] 1)Except as provided in Sentence (2), the building envelope shall be designed to avoid increasing the overall thermal transmittance of the insulation material due to
[a] a)air leakage or convection,
[b] b)wetting, or
[c] c)moisture bypassing the plane of thermal resistance.

Note A- Protection of Insulation Materials.

Sentence is not intended to preclude the use of building envelope systems such as protected membrane roofing systems, vegetative roofing systems, EIFS in rainscreen applications, and exterior insulation on below-groundgrade walls.

Impact analysis

The proposed change has no cost implications, as it is not a change to the Code requirement. The change would have the benefit of clarifying the explanatory Note.

Enforcement implications

This change can be enforced by the infrastructure currently available to enforce the NECB.

Who is affected

Designers, engineers, architects, builders and building officials.


[] ([1] 1) [F92-OE1.1]
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