Proposed Change 1923

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1923
Page: Last modified: 2024-02-18
Code Reference(s):
NBC20 Div.B 9.36.8.5. (first printing)
NBC20 Div.B 9.36.8.7. (first printing)
Subject:
Prescriptive Trade-off Path
Title:
Energy Conservation Points for the Building Envelope
Description:
This proposed change assigns energy conservation points for new building envelope measures.
This change could potentially affect the following topic areas:

Problem

The National Building Code of Canada (NBC) does not currently assign energy conservation points to ceilings below attics, cathedral ceilings or flat roofs, exposed floors or slabs-on-grade that exceed the minimum Code requirements.

Failure to assign energy conservation points to new conservation measures will not allow Code users to benefit from obtaining the associated energy savings when performance levels for these components exceed the minimum performance required by Energy Performance Tier 1, for the purposes of demonstrating compliance with the prescriptive trade-off path. These Code users would then need to demonstrate compliance using the energy performance path, which might necessitate hiring a professional energy advisor.

In order to accumulate the total energy conservation points required for compliance with higher tiers in the prescriptive trade-off path, Code users should have additional options for energy conservation measures than those currently provided in the Code.

Justification

This proposed change assigns energy conservation points for ceilings below attics, cathedral ceilings and flat roofs, exposed floors and slabs-on-grade for the purposes of compliance with the prescriptive trade-off path.

If energy conservation points are assigned to these building envelope measures that exceed the minimum energy performance required by Tier 1, the Code users who choose to install these measures will benefit from the additional options for demonstrating compliance with a higher energy performance tier.

This proposed change also assigns energy conservation points for combined roof systems consisting of ceilings below attics and cathedral ceilings or flat roofs to provide Code users with more options to receive a representative number of points based on roof design. For combined roof types, an average RSI of 5.80 is assumed for flat roofs, which is higher than the minimum for all climate zones. The thermal insulation of flat roofs becomes significantly cost inefficient beyond 5.80 RSI. Assigned energy conservation points gradually decrease as the climate zone becomes colder because the building envelope is required to meet a higher insulation baseline, which reduces the significance of the energy savings.

Additionally, this proposed change adds granularity for energy conservation points provided in tabulated form for ceilings below attics, cathedral ceilings and flat roofs, exposed floors and slabs-on-grade by allowing interpolation. If this proposed change did not permit interpolation, Code users would only be able to claim the lower of two point values when the energy conservation measure falls between two values listed in proposed Tables 9.36.8.5.-B to -E and 9.36.8.7.-B.

Failure to add additional energy conservation measures might prevent Code users from accumulating sufficient points to comply with higher tiers, as required by their respective jurisdictions.

PROPOSED CHANGE

[9.36.8.5.] 9.36.8.5.Energy Conservation Measures for Above-Ground Opaque Building Assemblies

[1] 1)Except as permitted by Articles 9.36.2.5. and 9.36.2.11., and Sentence 9.36.2.6.(3), the effective thermal resistance of above-ground opaque building assemblies or portions thereof shall be not less than that shown for the applicable heating degree-days of the building location in Table 9.36.2.6.-B.
[2] 2)Above-ground walls that comply with one of the energy conservation measures prescribed in Table 9.36.8.5. shall be credited with the corresponding energy conservation points stipulated therein.
[3] 3)The effective thermal resistance of rim joists shall be not less than that of the above-ground walls.
[4] 4)Where the top of a section of foundation wall is on average greater than or equal to 600 mm above the adjoining ground level, the effective thermal resistance of the above-ground portion of that section of wall shall be not less than that of the above-ground walls.
[5] 5)Except for tubular daylighting devices, the effective thermal resistance of skylight shafts shall be not less than that of the above-ground walls.
[6] 6)Except as provided in Sentence (7), where above-ground walls are constructed using two or more wall assemblies with different calculated effective thermal resistance values, the above-ground wall assembly with the lowest effective thermal resistance value shall be used to determine the applicable energy conservation points from Table 9.36.8.5.
[7] 7)The effective thermal resistance of one or more of the above-ground wall assemblies referred to in Sentence (6) is permitted to be less than that required to meet an energy conservation measure target listed in Table 9.36.8.5. for the wall or walls to be credited with the energy conservation points listed for that target, provided
[a] a)the effective thermal resistance of one or more of the other above-ground wall assemblies is increased to more than the energy conservation measure target listed in Table 9.36.8.5. to account for the wall assemblies that do not meet the target, and
[b] b)the sum of the results of each individual above-ground wall assembly area divided by its respective effective thermal resistance is less than or equal to the total area of all above-ground wall assemblies divided by the effective thermal resistance target listed in Table 9.36.8.5. that is to be credited.
(See also Note A-9.36.2.11.(2)PROPOSED CHANGE A-9.36.2.11.(2).)
Table [9.36.8.5.-A] 9.36.8.5.
Energy Conservation Measures and Points for Above-Ground WallsPROPOSED CHANGE Table 9.36.8.5. Footnote (1)
Forming Part of Sentences [9.36.8.5.] 9.36.8.5.([2] 2), ([6] 6) and ([7] 7)
Energy Conservation Measures for Above-Ground Walls – Minimum Effective RSI Values, (m2×K)/W Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
2.97 2.0 – – – – –
3.08 3.2 1.4 1.6 2.1 – –
3.69 7.4 5.4 6.2 6.7 5.4 5.2
3.85 8.2 6.0 6.9 7.4 6.2 6.0
3.96 8.9 6.8 7.7 8.2 7.0 6.8
4.29 10.2 8.1 9.2 9.7 8.6 8.4
4.40 10.8 8.7 9.9 10.3 9.3 9.1
4.57 11.4 9.3 10.6 11.1 10.1 9.9
4.73 11.9 9.7 11.1 11.5 10.6 10.4
4.84 12.3 10.2 11.6 12.1 11.2 10.9
5.01 12.9 10.7 12.2 12.7 11.8 11.6
5.45 14.0 11.9 13.6 14.0 13.3 13.1
[8] --)Roof systems consisting solely of ceilings below attics that comply with one of the energy conservation measures prescribed in Table 9.36.8.5.-B shall be credited with the corresponding energy conservation points stipulated therein.
Table [9.36.8.5.-B]
Energy Conservation Measures and Points for Ceilings Below Attics
Forming Part of Sentence 9.36.8.5.(9)
Energy Conservation Measures for Ceilings Below Attics – Minimum Effective RSI Values, (m2×K)/WPROPOSED CHANGE Table Footnote (1) Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
8.67 1.2 – – – – –
10.43 2.1 0.9 0.9 – – –
12.19 2.7 1.6 1.6 0.7 0.8 0.8
13.96 3.1 2.1 2.1 1.2 1.4 1.3
[9] --)Roof systems consisting solely of cathedral ceilings and flat roofs that comply with one of the energy conservation measures prescribed in Table 9.36.8.5.-C shall be credited with the corresponding energy conservation points stipulated therein.
Table [9.36.8.5.-C]
Energy Conservation Measures and Points for Cathedral Ceilings and Flat Roofs
Forming Part of Sentence 9.36.8.5.(10)
Energy Conservation Measures for Cathedral Ceilings and Flat Roofs – Minimum Effective RSI Values, (m2×K)/WPROPOSED CHANGE Table Footnote (1) Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
5.02 0.5 0.5 0.5 – – –
5.80 1.4 1.5 1.6 1.0 1.1 1.1
6.49 2.0 2.2 2.3 1.8 1.9 1.9
[10] --)Roof systems consisting of a combination of ceilings below attics and cathedral ceilings or flat roofs that comply with one of the energy conservation measures prescribed in Table 9.36.8.5.-D shall be credited with the corresponding energy conservation points stipulated therein.
Table [9.36.8.5.-D]
Energy Conservation Measures and Points for Combined Ceilings Below Attics and Cathedral Ceilings or Flat Roofs
Forming Part of Sentence 9.36.8.5.(11)
Energy Conservation Measures for Ceilings Below Attics– Minimum Effective RSI Values, (m2×K)/WPROPOSED CHANGE Table Footnote (1) Energy Conservation Measures for Cathedral Ceilings and Flat Roofs– Minimum Effective RSI Values, (m2×K)/W(1) Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
8.67 5.80 1.3 – – – – –
10.43 5.80 1.8 1.1 1.1 – – –
12.19 5.80 2.2 1.5 1.5 0.8 0.8 0.8
13.96 5.80 2.5 1.8 1.8 1.1 1.2 1.1
[11] --)Exposed floors not less than 30 m2 in total area that comply with one of the energy conservation measures prescribed in Table 9.36.8.5.-E shall be credited with the corresponding energy conservation points stipulated therein.
Table [9.36.8.5.-E]
Energy Conservation Measures and Points for Exposed Floors (≥ 30 m2)
Forming Part of Sentence 9.36.8.5.(12)
Energy Conservation Measures for Exposed Floors – Minimum Effective RSI Values, (m2×K)/WPROPOSED CHANGE Table Footnote (1) Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
5.02 0.2 0.2 0.2 – – –
5.42 0.5 0.5 0.5 0.2 0.3 0.3
6.77 1.1 1.1 1.1 0.9 1.0 0.9

[9.36.8.7.] 9.36.8.7.Energy Conservation Measures for Opaque Building Assemblies Below-Grade or in Contact with the Ground

[1] 1)Opaque building assemblies below-grade or in contact with the ground shall be designed and constructed in accordance with Sentences 9.36.2.8.(2) to (10) and this Article.
[2] 2)Except as permitted by Article 9.36.2.5., the effective thermal resistance of foundation walls shall be not less than that shown for the applicable heating degree-days of the building location in Table 9.36.2.8.-B.
[3] 3)Foundation walls that comply with one of the energy conservation measures prescribed in Table 9.36.8.7. shall be credited with the corresponding energy conservation points stipulated therein.
[4] 4)Where foundation walls are constructed with more than one effective thermal resistance (RSI) value, the lowest effective RSI value of any of these walls shall be used to determine the applicable energy conservation points from Table 9.36.8.7.
Table [9.36.8.7.-A] 9.36.8.7.
Energy Conservation Measures and Points for Opaque Building Assemblies Below-Grade or In Contact with Ground
Forming Part of Sentences [9.36.8.7.] 9.36.8.7.([3] 3) and ([4] 4)
Energy Conservation Measures for Foundation Walls – Minimum Effective RSI Values, (m2×K)/W Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
2.98 1.7 – – – – –
3.09 1.8 0.2 0.2 0.2 0.2 –
3.46 2.2 0.6 0.8 0.6 0.7 –
3.90 2.6 1.2 1.4 1.1 1.3 –
[5] --)Slabs-on-grade that comply with one of the energy conservation measures prescribed in Table 9.36.8.7.-B shall be credited with the corresponding energy conservation points stipulated therein.
Table [9.36.8.7.-B] 9.36.8.7.
Energy Conservation Measures and Points for Slabs-on-Grade
Forming Part of Sentence 9.36.8.7.(5)
Energy Conservation Measures for Slabs-on-Grade – Minimum Effective RSI Values, (m2×K)/WPROPOSED CHANGE Table 9.36.8.7. Footnote (1) Heating Degree-Days of Building Location, in Celsius Degree-Days
Zone 4
< 3000		 Zone 5
3000 to 3999		 Zone 6
4000 to 4999		 Zone 7A
5000 to 5999		 Zone 7B
6000 to 6999		 Zone 8
≥ 7000
Energy Conservation Points
2.84 1.0 0.8 0.9 – – –
3.72 1.6 1.3 1.4 – – –
4.62 2.0 1.7 1.8 0.5 0.5 –

Impact analysis

This proposed change would improve the affordability of complying with the energy performance tiers through the prescriptive trade-off path by providing additional options for energy conservation measures, which are eligible for energy conservation points. These additional measures included in the proposed change allow Code users to obtain credit for the energy savings associated with building envelope measures that exceed the minimum energy performance of tier 1. Accumulating the appropriate number of energy conservation points in the prescriptive trade-off path is one of the compliance options for Code users. The estimated costs of each option are listed below.

It should be noted that the costs listed in the analysis are estimates that depend on various factors. One method used to conduct the analysis was obtaining cost data for a specific region and adjusting for other regions using the location factors provided by RSMeans. The location factors in Table 1 were used for cost estimation based on 2023 values.

Table 1. Location Factors by Region

Region Location Factor
BC 0.98–1.05
AB 1.02–1.09
SK and MB 0.88–1.07
ON 1.01–1.15
QC 1.06–1.17
Atlantic Canada 0.88–1.05
Northern Canada 1.03–1.12

 

Table 2. Cost Analysis for Ceilings Below Attics (Impact of Proposed Table 9.36.8.5-B)

 

Effective RSI

 

Energy Savings (%)

 Incremental Costs of Insulation(1) ($/m2)
 BC  AB SK and MB  ON   QC Atlantic Canada Northern Canada
8.67 1.2 1.93–2.05 2.04–2.15 1.72–2.15 2.05–2.26 2.15–2.37 1.72–2.05 2.05–2.26
10.43 0.9–2.1 1.93–2.05 2.04–2.15 1.72–2.15 2.05–2.26 2.15–2.37 1.72–2.05 2.05–2.26
12.19 0.7–2.7 2.90–3.12 3.01–3.23 2.58–3.23 3.01–3.44 3.12–3.55 2.58–3.12 3.12–3.34
13.96 1.2–3.1 2.90–3.12 3.01–3.23 2.58–3.23 3.01–3.44 3.12–3.55 2.58–3.12 3.12–3.34

Source: Task Group on Prescriptive Trade-off Path in Section 9.36.

Note to Table 2:

(1) Insulation type: blown cellulose.

The incremental insulation costs listed in Table 2 represent incremental material costs. The costs obtained from a reputed builder in Ontario are for that province. Costs for other regions are calculated by adjusting the Ontario cost using the location factors provided. The costs gradually increase with an increase in effective RSI values.
 
Table 3. Cost Analysis for Cathedral Ceilings and Flat Roofs (Impact of Proposed Table 9.36.8.5-C)

 

Effective RSI(2)

 

Energy Savings (%)

 Incremental Costs of Insulation(1) ($/m2)
 BC  AB SK and MB  ON  QC Atlantic Canada Northern Canada
5.02 0.5 7.75–7.86 7.42–7.75 6.57–7.86 6.99–7.43 4.84–6.57 6.03–7.64 8.07–8.29
5.80 1.0–1.6 15.71–15.82 14.74–15.61 13.13–15.61 13.89–14.96 13.13–14.21 12.16–15.29 16.14–16.58
6.49 1.8–2.3 23.57–23.68 22.17–23.36 19.59–23.36 20.88–22.39 19.59–21.42 18.19–23.04 24.21–24.87

Source: RSMeans

Notes to Table 3:
(1) Insulation type: closed cell, spray polyurethane foam. 
(2) Insulation thickness: 4.5 in. for RSI 5.02, 5 in. for RSI 5.8, 5.5 in. for RSI 6.49.
 
The incremental insulation costs listed in Table 3 represent incremental material costs. The costs gradually increase with an increase in effective RSI values.
 
Table 4. Cost Analysis for Combined Ceiling Below Attics and Cathedral Ceilings or Flat Roofs (Impact of Proposed Table 9.36.8.5-D)

 

 Effective RSI

 

 

Energy Savings (%)

 Incremental Costs of Insulation(1) ($/m2)
Attics Cathedral Ceilings or Flat Roofs  BC  AB SK and MB  ON  QC Atlantic Canada Northern Canada
8.67 5.80 1.3 8.88 8.63 8.10 8.26 7.98 7.78 9.23
10.43 5.80 1.1–1.8 8.88 8.63 8.10 8.26 7.98 7.78 9.23
12.19 5.80 0.8–2.2 9.38 9.13 8.55 8.81 8.50 8.25 9.76
13.96 5.80 1.1–2.5 9.38 9.13 8.55 8.81 8.50 8.25 9.76

Source: RSMeans

Note to Table 4:

(1) Insulation type: blown cellulose (for ceilings below attic); closed cell, spray polyurethane foam (for cathedral ceilings and flat roofs).

The tabulated cost is an approximation for combined roof types assuming an area comprised of 50% ceiling below attic and 50% cathedral ceiling or flat roof. The incremental insulation costs listed in Table 4 represent incremental material costs. The costs gradually increase with an increase in effective RSI values.

 

Table 5. Cost Analysis for Exposed Floors (Impact of Proposed Table 9.36.8.5-E)

 

Effective RSI(2)

 

Energy Savings (%)

 Incremental Cost of Insulation(1) ($/m2)
BC  AB SK and MB  ON  QC Atlantic Canada Northern Canada
5.02 0.2 7.75–7.86 7.42–7.75 6.57–7.86 6.99–7.43 4.84–6.57 6.03–7.64 8.07–8.29
5.42 0.2–0.5 15.71–15.82 14.74–15.61 13.13–15.61 13.88–14.96 13.13–14.21 12.16–15.29 16.14–16.58
6.77 0.9–1.1 31.86–32.08 30.14–31.75 26.59–31.75 28.31–30.36 26.59–29.06 24.75–31.22 32.83–33.69

Source: RSMeans

Notes to Table 5:

(1) Insulation type: closed cell, spray polyurethane foam.

(2) Insulation thickness: 4.5 in. for RSI 5.02, 5 in. for RSI 5.42, 6 in. for RSI 6.77.

The incremental insulation costs listed in Table 5 represent incremental material costs. The costs gradually increase with an increase in effective RSI values.

 

Table 6. Cost Analysis for Slabs-on-Grade (Impact of Proposed Table 9.36.8.7-B)

 

Effective RSI(2)

 

Energy Savings

(%)

 Incremental Cost of Insulation(1) ($/m2)
 BC  AB  SK and MB  ON  QC  Atlantic Canada  Northern Canada
2.84 0.8–1.0 20.77–20.88 19.69–20.67 17.33–20.67 18.40–18.62 17.33–18.95 16.14–20.34 21.42–21.96
3.72 1.3–1.6 43.70–43.92 41.87–43.49 36.49–43.49 38.85–39.19 36.49–39.94 34.01–42.84 45.10–46.18
4.62 0.5–2.0 55.54–55.87 52.63–54.25 46.28–55.22 49.40–49.84 46.28–50.70 43.16–54.47 57.26–58.77

Source: RSMeans

Notes to Table 6:
(1) Assumption: rigid insulation, extruded polystyrene (XPS). 
(2) Thickness of assumed insulation: 3 in. for RSI 2.84, 4 in. for RSI 3.72, 5 in. for RSI 4.62.
 
The incremental insulation costs listed in Table 6 represent incremental material costs. The costs gradually increase with an increase in effective RSI values.

Enforcement implications

This proposed change could be enforced by the existing Code enforcement infrastructure.

Who is affected

Designers, engineers, architects, builders and building officials.

OBJECTIVE-BASED ANALYSIS OF NEW OR CHANGED PROVISIONS

[9.36.8.5.] 9.36.8.5. ([1] 1) no attributions
[9.36.8.5.] 9.36.8.5. ([2] 2) [F92-OE1.1]
[9.36.8.5.] 9.36.8.5. ([3] 3) [F92-OE1.1]
[9.36.8.5.] 9.36.8.5. ([4] 4) no attributions
[9.36.8.5.] 9.36.8.5. ([4] 4) [F92-OE1.1]
[9.36.8.5.] 9.36.8.5. ([5] 5) no attributions
[9.36.8.5.] 9.36.8.5. ([5] 5) [F92-OE1.1]
[9.36.8.5.] 9.36.8.5. ([6] 6) [F92-OE1.1]
[9.36.8.5.] 9.36.8.5. ([7] 7) [F92-OE1.1]
[9.36.8.5.] -- ([8] --) [F92-OE1.1]
[9.36.8.5.] -- ([9] --) [F92-OE1.1]
[9.36.8.5.] -- ([10] --) [F92-OE1.1]
[9.36.8.5.] -- ([11] --) [F92-OE1.1]
[9.36.8.7.] 9.36.8.7. ([1] 1) no attributions
[9.36.8.7.] 9.36.8.7. ([2] 2) [F92-OE1.1]
[9.36.8.7.] 9.36.8.7. ([3] 3) [F92-OE1.1]
[9.36.8.7.] 9.36.8.7. ([4] 4) no attributions
[9.36.8.7.] -- ([5] --) [F92-OE1.1]
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