A study was performed to understand the energy consumption in low-rise wood-frame multi-unit residential buildings (MURBs) and townhouse buildings in south-west British Columbia. Low-rise MURBs are an important building type as they make up a growing proportion of housing stock in cities across North America. Through this study, energy data was collected from electricity and gas utilities for 20 low-rise buildings (four storeys and less) and three townhouse complexes. This data was calendarized and weather normalized to determine average annual and monthly energy consumption for analysis and comparison. Two buildings were chosen from the data set for detailed analysis, one low-rise (four-storey) and one townhouse complex. The buildings were selected based on characteristics typical of low-rise MURBs in south-west BC. The purpose of the detailed analysis was to assess opportunities to improve the energy efficiency and reduce carbon emissions in existing low-rise MURBs using whole building energy modelling. This paper details the energy consumption trends observed through the data analysis, and the energy modelling results of the buildings chosen for detailed study. These results are also compared to results from a similar study which evaluated the energy use in mid- to high-rise non-combustible MURBs. The work presented here will improve our understanding of energy consumption in low-rise MURBs, and characterize opportunities for energy savings in these buildings. Presented by Elyse Henderson at the 15th Canadian Conference on Building Science and Technology

1. 1
Energy Consumption of Low-Rise
Wood-Frame Multi-Unit Residential
Buildings
CCBST CONFERENCE, VANCOUVER BC
NOVEMBER 7TH 2017
ELYSE HENDERSON, MSC; KIRA PEDERSON, EIT; BRITTANY COUGHLIN, MASC, P.ENG.
PRESENTED BY ELYSE HENDERSON

2. 2
 Introduction
 Part 1
 Energy consumption trends
 Low-Rise vs High-Rise MURBs
 Part 2
 Energy modelling
 Opportunities for savings
 Conclusion
Agenda

3. 3
Project Objectives
 Benchmark and characterize
energy consumption of low-rise
wood-frame MURBs in
southwest BC
 Compare low-rise wood-frame
MURBs to mid- to high-rise non-
combustible MURBs
(from previous RDH study)
 Identify opportunities for
energy efficiency improvements

4. 4
Project Methodology
 Literature review
 Building selection and data collection
 Analysis of building data (23 low-rise buildings)
 Energy consumption data and trends
 Compare to mid- and high-rise MURBs
 Opportunities for energy conservation
 Develop and calibrate 2 whole-building energy models
 Analysis of Energy Conservation Measures (ECMs)
 Summarize complete results in full report
Part 1
Part 2

5. 5
 Analysis of low-rise energy consumption
 End use breakdown and trends
 Compare low-rise to mid- and high-rise MURBs
 Similarities and differences
Part 1 – Analysis of Building Data

6. 6
Buildings in Study
 23 Buildings
 20 Low-rise (3-4 storeys)
 3 Townhouse
 5 Low-rise market rental
buildings
 Range of construction
years
 1974-2010
 Typical heating systems
 Electric Baseboards
 Hydronic Baseboards

7. 7
Energy Use Intensity – Low-Rise Buildings
0
50
100
150
200
250
300
11 22 13 23 9 16 7 19 14 4 12 10 5 15 2 6 8 1 18 20 3 21 17
EnergyUseIntensity-kWh/m²/year
Building ID
Natural Gas Electricity Suite Electricity Common Electricity - Combined
Average: 171 kWh/m2
/yr
Town Houses - Building ID: 21, 22 & 23
Median: 160 kWh/m2 /yr

8. 8
Energy Consumption by Suite – Low-Rise Buildings
 In some cases, electric baseboards are intended as primary
space heating, yet decorative gas fireplaces are used by
occupants (Building 23)

9. 9
Energy Consumption by Suite – High-Rise
 Average high-rise energy use per suite: ~22,000 kWh/yr
 19% increase over average low-rise suite consumption (~18,500 kWh/yr)
 Highest suite consumption, Building 57
 Luxury condominium with full amenities, i.e. air conditioning, in-suite
fireplaces, common area pool, and recreation centre
Low-rise average = 18,494 kWh/yr

10. 10
Energy Consumption vs Year of Construction
-
50
100
150
200
250
300
1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
AnnualEnergyUseIntensity-kWh/m²/year
Year of Construction
Space Heat Total Energy
-
50
100
150
200
250
300
350
1970 1975 1980 1985 1990 1995 2000 2005
AnnualEnergyUseIntensity-kWh/m²/year
Year of Construction
Space Heat Total Energy
 Low-rise: Decrease in
total energy (blue) &
space heating (red)
 More efficient
mechanical systems,
lighting, and appliances
 Improved performance
of the building
enclosures
 High-rise: Increase in
total energy (blue)
 Amenities in newer
buildings (pools, hot
tubs, gyms)
 Higher ventilation rates
 More complex building
forms and glazing ratios
Low-Rise
High-Rise

11. 11
0
50
100
150
200
250
300
0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
AnnualEnergyUseIntensity-kWh/m²/year
Percent Glazing (window-to-wall ratio, %)
Total Energy Space Heat
-
50
100
150
200
250
300
350
0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
AnnualEnergyUseIntensity-kWh/m²/year
Percent Glazing (window-to-wall ratio, %)
Total Energy Space Heat
Energy Consumption vs Window-to-Wall Ratio
 Low-rise: Inconclusive
analysis
 Insufficient data
 Few buildings with
available data
 High-rise: Total energy
(blue) increases with
W/W%
 Building types with high
W/W% generally have
more amenities and are
newer (recall trend with
building construction
year)
Low-Rise
High-Rise

12. 12
77 79
94
134
-
50
100
150
200
250
Low-Rise High-Rise
EnegyUseIntensity,kWh/m²/year
Space Heating Energy Non-Heating Energy
Space Heating Proportion of Total Energy
 Low-rises only
consume
approximately ~2%
less space heating
energy than high-rises
 High-rises generally
have higher non-
heating energy
consumption (more
building amenities and
higher ventilation
rates)
Total: 171 kWh/m²/yr
Total: 213 kWh/m²/yr
 Low-rise space heat makes up 45% of the total building energy
 High-rise space heat makes up 37% of the total building energy

13. 13
Greenhouse Gas Emissions
Low-rise High-rise
Gas - Baseline,
58 , 43%Gas - Heat,
72 , 52%
Electricity -
Heat, 2 , 1%
Electricity - Baseline,
5 , 4%
Gas - Baseline,
111 , 44%Gas - Heat,
128 , 51%
Electricity -
Heat, 2 , 1%
Electricity - Baseline,
9 , 4%
 Average GHGI: 17 kg-CO2e/m2
tCO2e/yr and % of total tCO2e/yr and % of total
 The distribution and total amount of GHG emissions depend on
building-specific systems and fuel source
 Average GHGI: 21 kg-CO2e/m2

14. 14
 Energy modelling
 4-storey low-rise
 3-storey townhouse
 Opportunities for energy conservation
 Older, pre-retrofit buildings
Part 2 – Opportunities for Conservation

15. 15
Calibrated Energy Modelling
 Two buildings were selected for energy modelling:
 4-storey MURB
 3-storey townhouse complex
 Energy conservation measures (ECMs) were identified and
modelled on both buildings
 Bundles of ECMs were assessed as potential retrofit packages,
using the following metrics:
 Energy savings (kWh/m²/yr)
 % heating savings
 % GHG emission reduction

16. 16
Plug and appliances,
28, 16%
Lights -
Exterior,
2, 1%
Lights -
Interior,
42, 23%
Fans, 2, 1%
Pumps, 0, 0%
Electric baseboard
heating,
21, 12%
Ventilation
heating (gas),
36, 20%
DHW (gas),
49, 27%
Low-Rise – Selected for Energy Modelling
 Characteristics
 Constructed 2008
 Gross Floor Area: 5,400 m2
 60 Suites, 4 storeys
 Mechanical Systems:
 Heating – Electric baseboards
 DHW – Gas boiler, central
 Ventilation – Gas tempered MUA
EUI = 180
kWh/m²

17. 17
Plug and appliances,
49, 18%
Lights - Exterior,
5, 2%
Lights - Interior,
41, 15%
Fans,
4, 1%
Pumps,
0, 0%
Electric baseboard
heating,
121, 44%
Fireplaces (gas),
7, 2%
DHW (gas),
50, 18%
Townhouse – Selected for Energy Modelling
-
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
100,000
EnergyConsumption,kWh
Gas Electricity Suite Electricity Common
 Characteristics
 Constructed 1983*
 Gross Floor Area: 4,000 m2
 32 Suites, 3 storeys
 Mechanical Systems:
 Heating – Electric baseboards
(and gas fireplaces**)
 DHW – Gas boiler, central
 Ventilation – Suite exhaust only
*enclosure rehabilitation in 2000
**some original wood fireplaces
EUI = 277
kWh/m²

18. 18
Opportunities for Energy Conservation (1/3)
Enclosure ECMs
 Add insulation to walls
 Exterior insulation
 Add insulation to roof
 Attic and low-sloped
 Upgrade windows
 High performance double
 Triple glazed
 Improving airtightness
 Up to US Army Corp
standard

19. 19
Ventilation ECMs
 Heat Recovery Ventilators (HRVs)
 60% and 85% efficient sensible heat recovery
 Make-up air unit (MUA)
 Efficiency improvements
 Set point temperature reduction
Opportunities for Energy Conservation (2/3)

20. 20
DHW ECMs
 DHW
 Upgrade to low-flow fixtures
 Install drain water heat recovery
 Boiler efficiency improvement
Lighting ECMs
 Lighting
 Occupancy sensors in common
spaces
 Upgrade to LEDs
Opportunities for Energy Conservation (3/3)

21. 21
0%
16%
91%
91%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
25
50
75
100
125
150
175
200
225
250
GHGEmissionReduction(%)
EnergyUseIntensity(kWh/m²/yr)
Total EUI (kWh/m²)
GHG savings (%)
Energy Analysis – Low-Rise ECM Bundles
LOW-RISE ECM BUNDLES
Bundle 01 – Better Enclosure
 Walls: add R-5 (R-21 total)
 Roof: add R-10 (R-48 total)
 Windows: H-P double-glazed (U-0.28)
 Airtightness: 0.10 cfm/ft2
(@4 Pa), a 33% improvement
Bundle 02 – Best Enclosure
 Walls: add R-10 (R-26 total)
 Roof: add R-10 (R-48 total)
 Windows: triple-glazed (U-0.17)
 Airtightness: 0.04 cfm/ft2
(@4 Pa), a 73% improvement
 HRVs: 85% efficient
Bundle 03 – plus Mechanical/Electrical
Bundle 02, plus:
 MUA: condensing (93% efficient)
 MUA: set point lowered to 17°C
 DHW: low-flow fixtures
 DHW: condensing (93% efficient)
 Lighting: LEDs, occupancy sensors
Heating energy savings is shown as %’s
Low-Rise MURB

22. 22
Energy Analysis – Low-Rise Summary
 Individual ECMs with the largest heating energy impact:
 Very high savings from HRVs are enabled by turning down
the MUA flow rate
 ECM Bundles achieve extremely low heating EUIs:
 Near 5 kWh/m²/yr
 Occupant behaviour needs to be considered
 Up to 55% GHG emission reduction
ECM Heating savings
Install 85% eff. HRVs 47%
Lower MUA set point to 17°C 17%
Airtightness (0.04 cfm/ft²) 15%
Triple glazed windows 14%

23. 23
Energy Analysis – Townhouse ECM Bundles
TOWNHOUSE ECM BUNDLES
Bundle 01 – Better Enclosure
 Walls: add R-5 (R-16 total)
 Roof: add R-10 (R-28 total)
 Windows: H-P double-glazed (U-0.28)
 Airtightness: 0.10 cfm/ft2
(@4 Pa), a 50% improvement
Bundle 02 – Best Enclosure
 Walls: add R-10 (R-21 total)
 Roof: add R-20 (R-38 total)
 Windows: triple-glazed (U-0.17)
 Airtightness: 0.04 cfm/ft²
(@4 Pa), an 80% improvement
 HRVs: 85% efficient
Bundle 03 – plus Mechanical/Electrical
Bundle 02, plus:
 DHW: low-flow fixtures
 DHW: condensing (93% efficient)
 Lighting: LEDs, occupancy sensors
Townhouse
0%
26%
75%
74%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
50
100
150
200
250
300
350
GHGEmissionReduction(%)
EnergyUseIntensity(kWh/m²/yr)
Total EUI (kWh/m²)
GHG savings (%)
Heating energy savings is shown as %’s

24. 24
Energy Analysis – Townhouse Summary
 ECMs with the largest heating energy impact:
 Airtightness plays a bigger role in leakier baseline building
 Up to 32% GHG emission reduction
 Lower than Low-Rise due to gas fireplaces
 No Make-Up Air, so MUA ECMs do not apply to this archetype
ECM Heating savings
Airtightness (0.04 cfm/ft²) 24%
Install 85% eff. HRVs 19%
Triple glazed windows 10%
Adding R-10 to walls 8%

25. 25
Potential Impact on Older, Pre-Retrofit MURBs
 Archetypical pre-retrofit building models
 Low-Rise and Townhouse models were adjusted to reflect
typical materials/practices from the 1970’s era:
Walls
› 2x4 framing with R-11 batt and
uninsulated balconies (R-7.5
effective)
Windows
› U-1.0/R-1.0, single glazed with
aluminum frames
Air leakage
› 0.20 cfm/ft² at operating
pressure (leaky)

26. 26
Potential Impact on Older, Pre-Retrofit MURBs
 ECM Bundles for existing, pre-retrofit
low-rise buildings can result in:
 Near 50% total energy savings
 Near 90% heating energy savings
 Up to 60% GHG emission reductions
 Big opportunity in the existing, low-rise
housing stock
 Especially at time of enclosure renewals

27. 27
Conclusions
 Energy trends for low-rise multi-unit residential buildings:
 EUIs are lower for buildings constructed more recently
 Average low-rise EUI is 171 kWh/m2/yr
 High-rise energy consumption per suite is 19% higher than
low-rise energy consumption per suite
 Very high energy savings are possible for low-rise MURBs
 Three biggest opportunities:
 HRVs
 Airtightness
 Triple-glazed windows
 Higher net energy savings are possible with older MURBs
 GHG savings depend on the fuel breakdown

28. 28
Full Report is Available with More Information

29. 29
Questions
FOR FURTHER INFORMATION PLEASE VISIT
 www.rdh.com
 www.bchousing.org
OR CONTACT THE PRESENTER
 ehenderson@rdh.com

30. 30
Extra Slides

31. 31
Baseline Model Assumptions
KEY BASELINE MODEL INPUTS*
Building 15 (Low-Rise) Building 21 (Townhouse)
Walls
R-16 – 2x6 framing with R-20 batt
and insulated balconies
R-11 – 2x4 framing with R-12 batt
and insulated balconies
Roof
R-38 – Vented attic with R-40 batt
insulation
R-18 – Low-slope with batt insulation
Windows
U-0.35 – Double glazed with vinyl
frame and low-e coating, w/w 36%
U-0.40 – Double glazed with vinyl
frame, w/w 23%
Air-leakage 0.15 cfm/sf at operating pressure 0.20 cfm/sf at operating pressure
Mech. vent. 2,400 cfm MUA (gas-tempered, 21°C) None (natural only)
1° Heating Electric baseboards, 22 °C Electric baseboards, 23 °C
2° Heating None Gas fireplaces, 7.5 W/m²
DHW flow 2.5 L/m²/day 2.2 L/m²/day
Lighting
5 W/m² in suites, 8 – 17 W/m² in
common areas, 2200 W exterior
8 W/m² interior, 4400 W exterior
*Obtained from architectural/mechanical drawings, site visits,
and calibration to real utility data