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Proposed Change 1840

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1840
Page: Last modified: 2023-11-17
Code Reference(s):
NECB20 Div.C 2.2.2.3.(1) (first printing)
Subject:
Building Envelope - General
Title:
Use of the Term "Grade" in the NECB
Description:
This proposed change clarifies the documentation on the building envelope required by Sentence 2.2.2.3.(1) by using “ground” instead of “grade” to refer to the finished ground level.
Related Code Change Request(s):
CCR 1391
Related Proposed Change(s):
PCF 1653, PCF 1962
This change could potentially affect the following topic areas:

Problem

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.

Justification

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.

The proposed change would replace the term “grade” with “ground” in Clause 2.2.2.3.(1)(i) of Division C, such that the Clause describes the required documentation for opaque walls that are above ground or in contact with the ground rather than opaque walls that are strictly above or below grade. This proposed change would clarify the documentation on the building envelope required by Sentence 2.2.2.3.(1).

PROPOSED CHANGE

[2.2.2.3.] 2.2.2.3.Documentation on the Building Envelope

[1] 1)The following documentation on the building envelope shall be provided for the proposed building and, if Section 3.3. of Division B is applied, for the reference building as well:
[a] a)gross wall area,
[b] b)total window area,
[c] c)total exterior door area,
[d] d)gross roof area,
[e] e)total skylight area,
[f] f)ratio of total skylight area to gross roof area,
[g] g)exposed floor areas,
[h] h)ratio of total vertical fenestration and door area to gross wall area,
[i] i)overall thermal transmittance of
[i] i)opaque walls (above and below gradeabove-ground walls and walls in contact with the ground),
[ii] ii)roofs (above and below gradeabove-ground roofs and roofs in contact with the ground),
[iii] iii)floors (exposed floors and floors in contact with the ground)
[iv] iv)fenestration,
[v] v)doors forming part of the building envelope, and
[vi] vi)skylights,
[j] j)description and location of air barrier assemblies in opaque building assemblies,
[k] k)air leakage characteristics of fenestration and doors that act as environmental separators,
[l] l)heat loss coefficient for the building, determined as the sum of the products of area and overall thermal transmittance for all above-ground building envelope components, and
[m] m)heat loss coefficient for the building, normalized by dividing the value from Clause (l) by the total floor area.

Impact analysis

The proposed change has no cost implications, as it is not a change to the Code requirement. The change would clarify the intended meaning of the provision.

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.

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