These Notes are included for explanatory purposes only and do not form part of the requirements. The number that introduces each Note corresponds to the applicable requirement in this Part.

A-9.36.1.1.(1) Energy Used by the Building.

Energy used by the building

= space-heating energy lost and gained through building envelope + losses due to inefficiencies of heating equipment + energy necessary to heat outdoor air to ventilate the building + energy used to heat service water

A-9.36.1.2.(2) Overall Thermal Transmittance.

The U-value represents the amount of heat transferred through a unit area in a unit of time induced under steady-state conditions by a unit temperature difference between the environments on its two faces. The U-value reflects the capacity of all elements to transfer heat through the thickness of the assembly, as well as, for instance, through air films on both faces of above-ground components. Where heat is not transferred homogeneously across the area being considered, the thermal transmittance of each component is determined: for example, the thermal transmittance values of the glazing and the frame of a window are combined to determine the overall thermal transmittance (U-value) of the window.

A-9.36.1.2.(3) Conversion of Metric Values to Imperial Values.

To convert a metric RSI value to an imperial R-value, use 1 (m²·K)/W = 5.678263 h · ft² · °F/Btu. "R-value," or simply the prefix "R" (e.g. R20 insulation), is often used in the housing industry to refer to the imperial equivalent of "RSI value." Note that R-values in Section 9.36. are provided for information purposes only; the stated metric RSI values are in fact the legally binding requirements.

A-9.36.1.2.(4) Fenestration.

The term "fenestration" is intentionally used in Articles 9.36.2.3. (prescriptive provisions) and 9.36.2.11. (trade-off provisions), and in Subsection 9.36.5. (performance provisions) as opposed to the terms "window," "door" and "skylight," which are used in the prescriptive provisions in Subsections 9.36.2. to 9.36.4. that address these components individually. The term "fenestration" is sometimes used in conjunction with the term "doors" depending on the context and the intent of the requirement.

A-9.36.1.3. Compliance Options According to Building Type and Size.

Table A-9.36.1.3. describes the types and sizes of Part 9 buildings to which Section 9.36. and the NECB apply.

Table A-9.36.1.3.
Energy Efficiency Compliance Options for Part 9 Buildings
Forming Part of Note A-9.36.1.3.

Notes to Table A-9.36.1.3.:
(1) The walls that enclose a common space are excluded from the calculation of floor area of that common space.

A-9.36.1.3.(3) Houses and Common Spaces.

Houses

For the purpose of Sentence 9.36.1.3.(3), the term "houses" includes detached houses, semi-detached houses, duplexes, triplexes, townhouses, row houses and boarding houses.

Common spaces

The walls that enclose a common space are excluded from the calculation of floor area of that common space.

A-9.36.1.3.(5) Exemptions.

Examples of buildings and spaces that are exempted from the requirements of Section 9.36. include seasonally heated buildings, storage and parking garages, small service buildings or service rooms and unconditioned spaces in buildings. However, note that, where a building envelope assembly of an exempted building is adjacent to a conditioned space, this assembly must meet the requirements of Section 9.36.

A-9.36.2.1.(2) Wall or Floor between a Garage and a Conditioned Space.

A wall or a floor between a conditioned space and a residential garage must be airtight and insulated because, even if the garage is equipped with space-heating equipment, it may in fact be kept unheated most of the time.

A-9.36.2.2.(3) Calculation Tools.

The thermal characteristics of windows, doors and skylights can be calculated using software tools such as THERM and WINDOW.

A-9.36.2.2.(5) Calculating Effective Thermal Resistance of Log Walls.

ICC 400, "Design and Construction of Log Structures," defines log wall thickness as the "average cross sectional area divided by the stack height." This approach equalizes all log profiles regardless of their size or shape by eliminating the need to vary, average or round out log thickness measurements, which would otherwise be necessary to determine applicable profile factors for different log shapes. The ICC 400 standard lists R-values for log walls, including the exterior and interior air film coefficients, based on wall thickness and wood species' specific gravity.

A-9.36.2.3.(2) and (3) Calculating Gross Wall Area.

Where the structure of the lowest floor and rim joist assembly is above the finished ground level or where the above-grade portion of foundation walls separates conditioned space from unconditioned space, they should be included in the calculation of gross wall area. Figure A-9.36.2.3.(2) and (3) shows the intended measurements for the most common type of housing construction.

Figure A-9.36.2.3.(2) and (3)
Example of interior wall height to be used in the calculation of gross wall area

A-9.36.2.3.(5) Areas of Other Fenestration.

Figure A-9.36.2.3.(5) illustrates how to measure the area of glass panes as described in Sentence 9.36.2.3.(5).

Figure A-9.36.2.3.(5)
Measuring the area of glazing that is not in the same plane

A-9.36.2.4.(1) Calculating the Effective Thermal Resistance of Building Envelope Assemblies.

The general theory of heat transfer is based on the concept of the thermal transmittance through an element over a given surface area under the temperature difference across the element (see Sentence 9.36.1.2.(2)). As such, the NECB requires all building envelope assemblies and components to comply with the maximum U-values (overall thermal transmittance) stated therein. However, the requirements in Subsection 9.36.2. are stated in RSI values (effective thermal resistance values), which are the reciprocal of U-values.

To calculate effective thermal resistance, Section 9.36. requires that contributions from all portions of an assembly-including heat flow through studs and insulation-be taken into account because the same insulation product (nominal insulation value) can produce different effective thermal resistance values in different framing configurations. The resulting effective thermal resistance of an assembly also depends on the thermal properties and thickness of the building materials used and their respective location. The following paragraphs provide the calculations to determine the effective thermal resistance values for certain assemblies and the thermal characteristics of common building materials. The Tables in Notes A-9.36.2.6.(1) and A-9.36.2.8.(1) confirm the compliance of common building assemblies. Calculating the Effective Thermal Resistance of an Assembly with Continuous Insulation:

IsothermalPlanes Method

To calculate the effective thermal resistance of a building envelope assembly containing only continuous materials-for example, a fully insulated floor slab- simply add up the RSI values for each material. This procedure is described as the "isothermal-planes method" in the "ASHRAE Handbook - Fundamentals." Calculating the Effective Thermal Resistance of a Wood-frame Assembly: Isothermal-Planes and

Parallel-Path Flow Methods

To calculate the effective thermal resistance of a building envelope assembly containing wood framing, RSIeff, add up the results of the following calculations: A. calculate the effective thermal resistance of all layers with continuous materials using the isothermal-planes method, and B. calculate the effective thermal resistance of the framing portion, RSIparallel, using the following equation, which is taken from the parallel-path flow method described in the "ASHRAE Handbook - Fundamentals":

where
RSIF = thermal resistance of the framing member obtained from Table A-9.36.2.4.(1)-D,
RSIC = thermal resistance of the cavity (usually filled with insulation) obtained from Table A-9.36.2.4.(1)-D,
% area of framing = value between 0 and 100 obtained from Table 9.36.2.4.(1)-A or by calculation, and
% area of cavity = value between 0 and 100 obtained from Table 9.36.2.4.(1)-A or by calculation.

When the values in Table A-9.36.2.4.(1)-D are used in the calculation of effective thermal resistance of assemblies, they must not be rounded; only the final result, RSIeff, can be rounded to the nearest significant digit.

Example of Calculation of RSIeff for a Typical 38 x 140 mm Wood-frame Wall Assembly
Using the Isothermal Planes and Parallel-Path Flow Methods

Table 9.36.2.4.(1)-A
Framing and Cavity Percentages for Typical Wood-frame Assemblies⁽¹⁾

Notes to Table 9.36.2.4.(1)-A:
(1) The framing percentages given in this Table account not just for the repetitive framing components but also for common framing practices, such as lintels, double top plates, cripple studs, etc., and include an allowance for typical mixes of studs, lintels and plates. The values listed represent the percentage of wall area taken up by framing and are based on the net wall area (i.e. gross wall area minus fenestration and door area). If the actual % areas of framing and cavity are known, those should be used rather than the ones in this Table. Rim joists are not accounted for in this Table because they are addressed separately in Sentence 9.36.2.6.(2).
(2) "Advanced framing" refers to a variety of framing techniques designed to reduce the thermal bridging and therefore increase the energy efficiency of a building. Some advanced framing solutions require that some framing components be insulated or eliminated; in such cases, it may be appropriate to calculate the actual % area of framing. Note that using an advanced framing technique may require additional engineering of the framing system.

The framing percentage values listed in this Table for advanced framing are based on constructions with insulated lintels or framing designed without lintels, corners with one or two studs, no cripple or jack studs, and double top plates.

Calculating the Effective Thermal Resistance of a Steel-frame Assembly

The parallel-path flow method described above for wood-frame assemblies involves simple one-dimensional heat flow calculations based on two assumptions:

• that the heat flow through the thermal bridge (the stud) is parallel to the heat flow through the insulation, and
• that the temperature at each plane is constant.

Tests performed on steel-frame walls have shown that neither of these assumptions properly represents the highly two-dimensional heat flow that actually occurs. The difference between what is assumed and what actually occurs is even more significant in steel-frame assemblies. The results achieved using the calculation method below compare well with those achieved from actual tests. The method provides a good approximation if a thermal resistance value of 0.0000161 (m²·K)/W per mm (or a conductivity of 62 (W·m)/(m²·°C)) is used (this value is associated with galvanized steel with a carbon content of 0.14%). To calculate the effective thermal resistance of a building envelope assembly consisting of steel framing, RSI_eff, use the following equation:

where

RSI_T1 = effective thermal resistance of building envelope assembly determined using parallel-path flow method for wood-frame assemblies (use framing and cavity percentages in Table A-9.36.2.4.(1)-C), RSI_T3 = RSI_T2 + thermal resistance values of all other components except steel studs and insulation, where RSI_T2 = effective thermal resistance of steel studs and insulation determined using parallel-path flow method for wood-frame assemblies,
K₁ = applicable value from Table A-9.36.2.4.(1)-B, and
K₂ = applicable value from Table A-9.36.2.4.(1)-B.

Table A-9.36.2.4.(1)-B
Values for K₁ and K₂

Example of Calculation of RSI_eff for a 41 x 152 mm Steel-frame Wall Assembly
with Studs 406 mm o.c.

Table A-9.36.2.4.(1)-C
Framing and Cavity Percentages for Typical Steel-frame Assemblies⁽¹⁾

Notes to Table A-9.36.2.4.(1)-C:
(1) The framing percentages given in this Table are based on common framing practices and not simply on the width of the studs and cavity. They are based on 18-gauge (1.2 mm) ste