Proposed Change 1536

From: National Research Council Canada

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Page: Last modified: 2020-02-18
Code Reference(s):
NECB17 Div.B 3.2.2.3.
NECB17 Div.B 3.2.2.4.
Subject:
Building Envelope - General
Title:
Thermal Characteristics of Fenestration and Doors
Description:
This proposed change reduces the maximum U-values for fenestration and doors.

PROPOSED CHANGE

[3.2.2.3.] 3.2.2.3.Thermal Characteristics of Fenestration

[1] 1)For the purposes of this Article, the term “fenestration” does not include doors, which are covered in Article 3.2.2.4.
[2] 2)Except as provided in Sentences (3) and 3.2.1.3.(1), the overall thermal transmittance of fenestration shall be not more than that shown in Table 3.2.2.3. for the applicable heating degree-day category taken at 18°C, as determined in accordance with Article 3.1.1.5.
[3] 3)Except as provided in Sentence 3.2.1.3.(1), the overall thermal transmittance of fenestration in semi-heated buildings, as defined in Sentence 1.2.1.2.(2), shall be not more than that shown in Table 3.2.2.3. for the applicable heating degree-day category taken at 15°C, as determined in accordance with Article 3.1.1.5.
Table [3.2.2.3.] 3.2.2.3.
Overall Thermal Transmittance of Fenestration
Forming Part of Sentences [3.2.2.3.] 3.2.2.3.([2] 2) and ([3] 3)
Component Heating Degree-Days of Building Location,PROPOSED CHANGE Table 3.2.2.3. Footnote (1) in Celsius Degree-Days
Zone 4:PROPOSED CHANGE Table 3.2.2.3. Footnote (2)
< 3000
Zone 5:PROPOSED CHANGE Table 3.2.2.3. Footnote (2)
3000 to 3999
Zone 6:PROPOSED CHANGE Table 3.2.2.3. Footnote (2)
4000 to 4999
Zone 7A:PROPOSED CHANGE Table 3.2.2.3. Footnote (2)
5000 to 5999
Zone 7B:PROPOSED CHANGE Table 3.2.2.3. Footnote (2)
6000 to 6999
Zone 8:PROPOSED CHANGE Table 3.2.2.3. Footnote (2)
≥ 7000
Maximum Overall Thermal Transmittance, W/(m2·K)
AllVertical fenestration 2.11.90 1.90 1.91.73 1.91.73 1.91.44 1.44
Skylights 2.69 2.69 2.41 2.41 2.01 2.01

[3.2.2.4.] 3.2.2.4.Thermal Characteristics of Doors and Access Hatches

[1] 1)Except as provided in Sentences (2), (3), (5) and 3.2.1.3.(1), the overall thermal transmittance of doors shall be not more than that shown in Table 3.2.2.4. for the applicable heating degree-day category taken at 18°C, as determined in accordance with Article 3.1.1.5.
[2] 2)Except as provided in Sentences (3) and (5), the overall thermal transmittance of doors in semi-heated buildings, as defined in Sentence 1.2.1.2.(2), shall be not more than that shown in Table 3.2.2.4. for the applicable heating degree-day category taken at 15°C, as determined in accordance with Article 3.1.1.5.
[3] 3)Doors need not comply with Sentence (1) or (2) where
[a] a)their total area does not exceed 2% of the gross wall area calculated in accordance with Article 3.1.1.6., and
[b] b)their overall thermal transmittance does not exceed 4.4 W/(m2·K).
[4] 4)Access hatches that are part of a building envelope shall be insulated to a nominal thermal transmittance of not more than 1.3 W/(m2·K), exclusive of stiffeners or edge construction.
[5] 5)Storm doors, automatic sliding glass doors, revolving doors, and fire shutters need not comply with Sentence (1) or (2). (See Note A-3.2.2.4.(5)PROPOSED CHANGE A-3.2.2.4.(5).)
Table [3.2.2.4.] 3.2.2.4.
Overall Thermal Transmittance of Doors
Forming Part of Sentences [3.2.2.4.] 3.2.2.4.([1] 1) and ([2] 2)
Component Heating Degree-Days of Building Location,PROPOSED CHANGE Table 3.2.2.4. Footnote (1) in Celsius Degree-Days
Zone 4:PROPOSED CHANGE Table 3.2.2.4. Footnote (2)
< 3000
Zone 5:PROPOSED CHANGE Table 3.2.2.4. Footnote (2)
3000 to 3999
Zone 6:PROPOSED CHANGE Table 3.2.2.4. Footnote (2)
4000 to 4999
Zone 7A:PROPOSED CHANGE Table 3.2.2.4. Footnote (2)
5000 to 5999
Zone 7B:PROPOSED CHANGE Table 3.2.2.4. Footnote (2)
6000 to 6999
Zone 8:PROPOSED CHANGE Table 3.2.2.4. Footnote (2)
≥ 7000
Maximum Overall Thermal Transmittance, W/(m2·K)
All doors 2.11.90 1.90 1.91.73 1.91.73 1.91.44 1.44

RATIONALE

Problem

The building envelope’s performance is a key contributor to the energy performance of a building. The code specifies maximum U-values for envelope components such as fenestration and doors. One method of improving overall building energy performance is to increase the levels of thermal performance of the building envelope, i.e. reduce maximum permitted U-values. This is a potential path towards reaching the CCBFC’s long term energy efficiency goals.

Justification - Explanation

The reduction in U-values of fenestration and doors reduces the excessive loss of energy leading to smaller heating and cooling loads of the building. This results in smaller HVAC equipment capacities and reduced HVAC capital costs. This capital cost savings will partially offset the incremental building envelope first costs due to additional insulation.

The relaxation of the skylight U-values from vertical fenestration is to recognize that the physics of the heat transfer in a skylight is different than a vertical fenestration due to the slope of the skylight. Skylights are heated from below and the convection inside the glass unit increases due to the turbulence that is introduced. The proposed skylight U-values will result in a skylight with the same physical components (i.e. low-e coatings, gas fills, and warm edge spacers) as a window that complies with the lower U-values. 

Furthermore, this reduction in U-values of vertical fenestration and doors meets the Standing Committee on Energy Efficiency’s (SC-EE) goal of 15-20% improvement over NECB 2017 for tier 1 as well as CCBFC’s long term energy efficiency goal.

Impact analysis

The results from a simulation study, conducted by the NRC, on adopting the proposed changes to the allowable window thermal transmittances are presented. A set of 16 NECB 2017 compliant archetypes, generated using CANMETEnergy’s building technology assessment platform (BTAP) located in six climate zones were used to estimate the energy savings. The climate zone average (average of the 16 archetypes for each climate zone) annual energy savings, associated annual fuel cost savings, and building envelope (window) cost increases are presented in Table 1. These items are presented as a percentage change and in terms of magnitude (energy and dollars), relative to NECB 2017 baselines (the archetypes without the proposed changes); negative values infer the opposite of the associated trend (i.e. additional fuel cost increase instead of savings). The fuel savings presented are rounded to the nearest $10 and the envelope costs are rounded to the nearest $100. The average envelope cost increment for each archetype is presented in Table 2, to provide an insight into the range of cost increments a builder would see in their projects. Lastly, the detailed energy savings, fuel cost savings, and envelope cost increase for each archetype in each of the six climate zones studied are presented in Tables 3, 4 and 5, respectively.

Table 1 Summary of climate zone averaged energy savings and cost increases

Associated Change Climate Zone
4 5 6 7A 7B 8
Total Annual Energy Savings (%/GJ) 0.9% 29 GJ 0.5% 19 GJ 1.0% 36 GJ 2.4% 94 GJ 2.8% 114 GJ 0.6% 27 GJ
Total Annual Fuel (Energy Cost) Savings ($/year) - $110 $20 $1030 - $280 - $160 $880
Envelope Cost Increment ($) 1.0% $6,200 0.4% $2,600 1.0% $5,900 2.0% $12,900 2.2% $14,000 0.7% $4,200

The proposed reduction in window thermal transmittance results in reduced heating but increased cooling (reduction/increase to auxiliary equipment energy e.g. fans, pumps, are mixed because they depend on the building loads). The better insulated windows reduce heat loss during the winter, but prevent cooling during cool summer nights/mornings. A balance of the changes to the heating and cooling energy forms the majority of the energy savings for the archetypes in the six climate zones.

The envelope cost increments were estimated using data from RSMeans 2017 and comprise a multitude of construction costs (labour, equipment, material etc.). Table 2 shows that the large office envelope cost increment, averaged across the six climate zones, is the greatest at $25,900 (2.0% increase). The highrise shows the greatest average percentage increase at 2.1% ($8,700 increase). Only three archetypes have average costs increments greater than $10,000: large office ($25,900), secondary school ($16,300), and hospital ($14,500).

Although the overall building energy usage decreases for the vast majority of each archetype-location pair, the fuel costs don’t necessarily reflect this because electricity generally costs more than heating fuel. In Table 1, zone 5 averages $20 savings in fuel costs and is negligible compared to its average envelope cost increment. Archetypes in zones 4, 7A, and 7B, on average, see an increase in its fuel cost, due to the greater cost of electricity compared to natural gas. Lastly, zone 6 and zone 8 see reasonable rates of return because zone 6 (Montreal) only uses electricity for heating and cooling, and the difference between electricity and heating oil costs per GJ in zone 8 (Yellowknife) is smaller than in the other zones.

Table 2 Average archetype envelope cost and incremental cost across climate zones

Archetype Rounded Incremental Cost Incremental cost in percentage
Secondary School $16,300 0.6%
Primary School $9,800 0.7%
Small Office $1,000 0.9%
Medium Office $4,400 1.1%
Large Office $25,900 2.0%
Small Hotel $4,100 1.5%
Large Hotel $9,900 1.5%
Warehouse $9,900 1.0%
Retail Standalone $4,000 0.8%
Retail Strip mall $3,600 0.8%
Quick Service Restaurant $700 1.2%
Full Service Restaurant $1,000 0.9%
Midrise Apartment $2,900 1.4%
Highrise Apartment $8,700 2.1%
Hospital $14,500 1.5%
Outpatient $5,300 1.6%

 Table 3 Energy savings from proposed thermal transmittances

Archetype Climate Zone Archetype average
4 5 6 7A 7B 8
Secondary School 0.8% 82 GJ 0.5% 51 GJ 0.9% 91 GJ 2.2% 272 GJ 2.2% 307 GJ 0.5% 65 GJ 1.2% 145 GJ
Primary School 1.1% 41 GJ 0.5% 22 GJ 1.1% 42 GJ 2.9% 132 GJ 3.1% 149 GJ 0.6% 33 GJ 1.6% 70 GJ
Small Office 0.7% 2 GJ 0.5% 1 GJ 1.2% 3 GJ 2.9% 8 GJ 3.5% 10 GJ 0.6% 2 GJ 1.6% 4 GJ
Medium Office 1.3% 30 GJ 0.6% 16 GJ 1.5% 34 GJ 2.8% 74 GJ 4.1% 101 GJ 0.8% 18 GJ 1.8% 45 GJ
Large Office 0.6% 96 GJ 0.4% 73 GJ 0.7% 117 GJ 1.6% 297 GJ 2.2% 396 GJ 0.5% 89 GJ 1.0% 178 GJ
Small Hotel 0.5% 13 GJ 0.4% 10 GJ 0.9% 22 GJ 1.7% 53 GJ 2.2% 68 GJ 0.5% 16 GJ 1.0% 30 GJ
Large Hotel 0.4% 29 GJ 0.3% 23 GJ 0.7% 48 GJ 0.9% 85 GJ 1.0% 97 GJ 0.4% 39 GJ 0.6% 53 GJ
Warehouse 2.3% 35 GJ 1.1% 20 GJ 2.2% 40 GJ 5.8% 117 GJ 6.7% 134 GJ 1.3% 28 GJ 3.2% 62 GJ
Retail Standalone 1.5% 19 GJ 0.7% 9 GJ 1.3% 17 GJ 3.8% 55 GJ 4.2% 62 GJ 0.8% 13 GJ 2.1% 29 GJ
Retail Strip mall 1.4% 18 GJ 0.7% 10 GJ 1.4% 19 GJ 4.0% 59 GJ 4.2% 64 GJ 0.8% 14 GJ 2.1% 31 GJ
Quick Service Restaurant 1.1% 2 GJ 0.6% 1 GJ 1.2% 3 GJ 2.8% 7 GJ 2.8% 8 GJ 0.7% 2 GJ 1.6% 4 GJ
Full Service Restaurant 0.9% 4 GJ 0.4% 2 GJ 0.9% 4 GJ 2.0% 13 GJ 1.9% 14 GJ 0.3% 3 GJ 1.1% 7 GJ
Midrise Apartment 0.4% 7 GJ 0.3% 6 GJ 0.7% 14 GJ 1.3% 32 GJ 2.1% 44 GJ 0.5% 12 GJ 0.9% 19 GJ
Highrise Apartment -0.1% -3 GJ 0.2% 10 GJ 0.5% 23 GJ 0.2% 14 GJ 0.8% 53 GJ 0.4% 24 GJ 0.3% 20 GJ
Hospital 0.4% 62 GJ 0.2% 39 GJ 0.4% 74 GJ 1.1% 215 GJ 1.2% 249 GJ 0.2% 51 GJ 0.6% 115 GJ
Outpatient 0.7% 19 GJ 0.4% 13 GJ 0.8% 24 GJ 2.0% 64 GJ 2.2% 76 GJ 0.4% 16 GJ 1.1% 35 GJ
Climate zone average 0.9% 29 GJ 0.5% 19 GJ 1.0% 36 GJ 2.4% 94 GJ 2.8% 114 GJ 0.6% 27 GJ  

 

Table 4 Monetary fuel savings associated with reduced building energy usage

Archetype Climate Zone Archetype Average
4 5 6 7A 7B 8
Secondary School -$150 $80 $3,060 -$210 -$60 $2,170 $820
Primary School -$30 $80 $1,420 $230 $180 $980 $480
Small Office -$20 $0 $90 -$20 -$10 $80 $20
Medium Office -$10 $30 $1,010 -$180 $20 $630 $250
Large Office -$860 -$280 $2,590 -$3,780 -$3,320 $3,170 -$410
Small Hotel -$70 $40 $650 $30 $60 $520 $210
Large Hotel $70 $210 $1,600 $450 $470 $1,200 $670
Warehouse -$20 $70 $1,180 $110 $180 $750 $380
Retail Standalone $20 $40 $510 $70 $100 $400 $190
Retail Strip mall -$20 $30 $570 $240 $90 $420 $220
Quick Service Restaurant -$10 $0 $80 -$20 -$10 $90 $20
Full Service Restaurant -$10 $10 $120 $0 $0 $100 $40
Midrise Apartment -$10 $70 $420 $210 $180 $290 $190
Highrise Apartment -$370 -$70 $760 -$840 -$370 $520 -$60
Hospital -$260 $0 $1,650 -$550 -$90 $2,060 $470
Outpatient -$100 $40 $810 -$140 -$10 $620 $200
Climate zone average -$110 $20 $1,030 -$280 -$160 $880  

 

Table 5 Envelope cost increments associated with the proposed thermal transmittances

Archetype Climate Zone
4 5 6 7A 7B 8
Secondary School 0.5% $13,000 0.2% $5,400 0.5% $12,500 1.1% $27,400 1.2% $30,200 0.4% $9,200
Primary School 0.6% $7,900 0.2% $3,300 0.5% $7,500 1.2% $16,500 1.3% $18,100 0.4% $5,500
Small Office 0.7% $900 0.3% $300 0.7% $800 1.4% $1,800 1.6% $1,900 0.5% $600
Medium Office 0.9% $3,600 0.4% $1,500 0.8% $3,400 1.8% $7,500 1.9% $8,000 0.6% $2,500
Large Office 1.7% $21,200 0.7% $8,600 1.5% $20,000 3.4% $44,100 3.6% $47,100 1.1% $14,400
Small Hotel 1.3% $3,200 0.6% $1,500 1.2% $3,300 2.5% $6,800 2.7% $7,600 0.8% $2,100
Large Hotel 1.3% $8,100 0.6% $3,300 1.2% $7,700 2.6% $16,800 2.7% $18,200 0.8% $5,500
Warehouse 0.8% $8,000 0.3% $3,300 0.8% $7,600 1.7% $16,700 1.8% $18,300 0.6% $5,600
Retail Standalone 0.7% $3,200 0.3% $1,300 0.6% $3,000 1.3% $6,700 1.5% $7,300 0.5% $2,200
Retail Strip mall 0.7% $2,900 0.3% $1,200 0.6% $2,800 1.3% $6,100 1.4% $6,700 0.5% $2,000
Quick Service Restaurant 1.1% $600 0.4% $200 0.9% $500 2.1% $1,200 2.2% $1,300 0.7% $400
Full Service Restaurant 0.8% $800 0.3% $300 0.7% $800 1.5% $1,700 1.6% $1,900 0.5% $600
Midrise Apartment 1.1% $2,200 0.6% $1,200 1.1% $2,500 2.2% $4,700 2.5% $5,400 0.7% $1,400
Highrise Apartment 1.9% $7,100 0.8% $2,900 1.7% $6,700 3.5% $14,700 3.7% $15,800 1.1% $4,800
Hospital 1.2% $11,600 0.5% $5,100 1.1% $11,500 2.4% $24,300 2.6% $26,700 0.8% $7,800
Outpatient 1.3% $4,300 0.5% $1,800 1.2% $4,100 2.6% $8,900 2.8% $9,600 0.9% $2,900
Climate zone average 1.0% $6,200 0.4% $2,600 1.0% $5,900 2.0% $12,900 2.2% $14,000 0.7% $4,200

 

Additional documentation for this proposed change is available on request at Codes.Publicreview@nrc-cnrc.gc.ca.

Enforcement implications

There would be no change in enforcement as there is no change in design. No extra steps will be required to verify insulation.

Who is affected

Designers, engineers, architects, owners, manufacturers, and installers.

OBJECTIVE-BASED ANALYSIS OF NEW OR CHANGED PROVISIONS

[3.2.2.3.] 3.2.2.3. ([1] 1) no attributions
[3.2.2.3.] 3.2.2.3. ([2] 2) [F92-OE1.1]
[3.2.2.3.] 3.2.2.3. ([2] 2) no attributions
[3.2.2.3.] 3.2.2.3. ([3] 3) [F92-OE1.1]
[3.2.2.3.] 3.2.2.3. ([3] 3) no attributions
[3.2.2.4.] 3.2.2.4. ([1] 1) [F92-OE1.1]
[3.2.2.4.] 3.2.2.4. ([1] 1) no attributions
[3.2.2.4.] 3.2.2.4. ([2] 2) [F92-OE1.1]
[3.2.2.4.] 3.2.2.4. ([2] 2) no attributions
[3.2.2.4.] 3.2.2.4. ([3] 3) [F92-OE1.1]
[3.2.2.4.] 3.2.2.4. ([3] 3) no attributions
[3.2.2.4.] 3.2.2.4. ([3] 3) no attributions
[3.2.2.4.] 3.2.2.4. ([4] 4) [F92-OE1.1]
[3.2.2.4.] 3.2.2.4. ([5] 5) no attributions
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