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Energy Consumption in Low-Rise Wood Frame Multi-Unit Residential Buildings

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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

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Energy Consumption in Low-Rise Wood Frame Multi-Unit Residential Buildings

  1. 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. 2  Introduction  Part 1  Energy consumption trends  Low-Rise vs High-Rise MURBs  Part 2  Energy modelling  Opportunities for savings  Conclusion Agenda
  3. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 28 Full Report is Available with More Information
  29. 29. 29 Questions FOR FURTHER INFORMATION PLEASE VISIT  www.rdh.com  www.bchousing.org OR CONTACT THE PRESENTER  ehenderson@rdh.com
  30. 30. 30 Extra Slides
  31. 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

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

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