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Energy Simulation of High-Rise Residential Buildings: Lessons Learned

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This presentation covers lessons learned from an energy study of over 60 architecturally representative mid to high rise multi-unit residential buildings (MURBS) in BC.

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Energy Simulation of High-Rise Residential Buildings: Lessons Learned

  1. 1. Lessons Learned from Meter Calibrated Energy Simulations of Multi-Unit Residential Buildings ! Graham Finch, MASc & Brittany Hanam, MASc – RDH Building Engineering ! Curt Hepting, P.Eng Enersys Analytics May 12, 2011 – NBEC 13 - Winnipeg
  2. 2. Overview ! Energy Study Project background ! Collection and weather normalization of utility data ! Energy Model Calibration Process ! Energy Simulation Results and Assessment of Energy Efficiency Measures
  3. 3. Energy Study Project Background ! Energy study of over 60 architecturally representative mid- to high-rise Multi-Unit Residential Buildings (MURBs) in BC ! Constructed between 1974 and 2002 ! Half of study buildings underwent a full-scale building enclosure rehabilitation ! Allow for the assessment of actual energy use and savings from enclosure improvements ! Pre- and post-rehabilitation R-values, air-tightness characteristics determined, mechanical audits performed ! Several energy models created and calibrated using over a decade of metered data ! DOE 2.1 based FAST and eQUEST used CMHC SCHL
  4. 4. MURB Energy Study – Metered Energy Data ! 12 years of data from 1998-2009 provided for each building ! Intent to get at least 3 years pre-and post-rehabilitation ! Electrical Data ! Suites – Individually metered, but combined into one monthly amount for confidentiality ! Common areas - one meter ! Natural Gas Data ! One meter per building for all uses ! Includes domestic hot water & make-up air units ! Also includes all suite fireplaces and pools/hot-tubs, where present
  5. 5. Monthly Energy Consumption – Typical Building
  6. 6. Total Annual Energy Consumption Intensity Space Heat Energy Usage vs Year Built Total Building Energy Usage per Gross Floor Area - Sorted from Low to High 350 350 300 300 250 250 200 200 150 150 100 100 50 50 - 8 11 44 9 52 42 61 63 18 7 62 12 26 19 33 32 20 45 29 17 43 60 31 28 6 14 3 39 2 57 30 41 24 1 40 59 21 36 58 Building ID - Sorted from Least to Greatest Energy Intensity Energy Consumption - kWh/m2/yr Common Electricity Suite Electricity Gas Average = 213 kWh/m2/yr Median = 217 kWh/m2/yr Std Dev = 42 kWh/m2/yr Range = 144 to 299 kWh/m2/yr - 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Year of Construction Energy Consumption - kWh/m2/yr Total Energy Space Heat Energy
  7. 7. Understanding Energy Use & Airflow within MURBs Parking Garage Exhaust Fans Common Areas Parking Garage Building Energy Distribution Gas - To heat ventilation air for make-up air supply - To heat domestic hot water - To heat pool/hot-tubs - Suite fireplaces (if equipped) - Pilot lights for above Electricity Common Areas - Interior lighting - Elevators - Ventilation fans and motors - Parking garage exhaust fans - Water distribution pumps - Baseboard heaters - Recreation areas/pool pumps - Exterior lighting - Communication - Controls Suites - Baseboard heaters - Lighting - Appliances - Miscellaneous Electric Loads - Plug loads - Exhaust fans Gas Boiler to Pool heat pool & hot-tubs Suites Elevator Shaft Common Hallway Corridors Stairwell Shaft Electric Baseboard Heaters in all Suites Gas fireplaces in some Suites Air flow through open windows Air exhausted using bathroom/kitchen fans & windows Air leakage of heated ventilation air through elevator and stairwell shafts Ventilation air is heated using gas-fired make-up air unit (MUA) Heated ventilation air supplied to each floor common corridor (pressurized) Heated Ventilation air from corridor Domestic Hot Water is heated using Gas Some Gas & Electric Heat at Common Areas Typically Unheated Leakage of heated ventilation air into shafts Rec. Areas Enclosure air-leakage Elevator pumping Space Heating: All study buildings have electric resistance heat suites Gas fireplaces also fairly common (common gas meter) Ventilation air heated (68-72F) using gas fired make-up air units.
  8. 8. Ventilation Distribution and Air Flow within MURBs Pressurized Corridor: Design flow rate varies <30 cfm/suite in older buildings to >130 cfm/suite post 2000s. Actual flow rate making it into the suites less, often as low as 1/3 of design. Ventilation/IAQ problems are common in MURBs
  9. 9. Energy Consumption Analysis Methods ! Top Down Analysis (Metered Energy Analysis) ! Total electricity & gas consumption known based on bills ! Can approximate space-heating using baselines ! Can approximate some end use energy but not refined ! Bottom Up Analysis (Energy Model Simulation) ! Total electricity & gas consumption estimated based on building type, occupancy, use and design • Input mechanical equipment, schedules, building enclosure characteristics ! Can approximate end use energy distribution for all components ! Needs metered data calibration for accuracy and to evaluate energy efficiency measures
  10. 10. Top Down Assessment vs Energy Simulation – End Use Estimates Bldg #33 Top Down Meter Analysis – No Energy Simulation Bottom Up Analysis using Calibrated Energy Model Simulation
  11. 11. Calibration of Energy Simulation using Metered Data Top Down Metered Energy Analysis 500,000 450,000 400,000 350,000 300,000 250,000 200,000 150,000 100,000 50,000 0 Aug-98 Dec-98 Apr-99 Aug-99 Dec-99 Apr-00 Aug-00 Dec-00 Apr-01 Aug-01 Dec-01 Apr-02 Aug-02 Dec-02 Apr-03 Aug-03 Dec-03 Apr-04 Aug-04 Dec-04 Apr-05 Aug-05 Dec-05 Apr-06 Aug-06 Dec-06 Apr-07 Energy Consumption - kwhr/month Gas Electricity - Suites Electricity - Common Parking Garage Exhaust Fans Common Areas Parking Garage Building Energy Distribution Gas - To heat ventilation air for make-up air supply - To heat domestic hot water - To heat pool/hot-tubs - Suite fireplaces (if equipped) - Pilot lights for above Electricity Common Areas - Interior lighting - Elevators - Ventilation fans and motors - Parking garage exhaust fans - Water distribution pumps - Baseboard heaters - Recreation areas/pool pumps - Exterior lighting - Communication - Controls Suites - Baseboard heaters - Lighting - Appliances - Miscellaneous Electric Loads - Plug loads - Exhaust fans Gas Boiler to Pool heat pool & hot-tubs Suites Elevator Shaft Common Hallway Corridors Stairwell Shaft Electric Baseboard Heaters in all Suites Gas fireplaces in some Suites Air flow through open windows Air exhausted using bathroom/kitchen fans & windows Air leakage of heated ventilation air through elevator and stairwell shafts Ventilation air is heated using gas-fired make-up air unit (MUA) Heated ventilation air supplied to each floor common corridor (pressurized) Heated Ventilation air from corridor Domestic Hot Water is heated using Gas Some Gas & Electric Heat at Common Areas Typically Unheated Leakage of heated ventilation air into shafts Rec. Areas Enclosure air-leakage Elevator pumping 180 220 240 260 Bottom-Up Energy Model Simulation 200 Actual Energy Use Model Inputs kWh/m2/yr Simulated Energy Use
  12. 12. The Importance of Meter Calibrations – Electricity
  13. 13. The Importance of Meter Calibrations – Natural Gas
  14. 14. Metered Energy Collection and Weather Normalization ! Calendarization ! Conversion of metered data (any recording period) into individual calendar months (ie Jan 1st to 31st) ! Weather Normalization ! Process to combine and average > 1 year of monthly energy data and develop typical year of data for analysis purposes ! Process is performed pre- and post- building enclosure rehabilitation and mechanical upgrades (if performed) ! Energy data is correlated with monthly heating degree days (at different baselines) to develop a HDD relationship • Benefit of this study to correlate assumptions with daily data • Normalization easy to do in a spreadsheet – need to see & understand trends with the data • Pre-packaged software can do this – but may not accurately represent some energy use behavior
  15. 15. Meter Assessment and Weather Normalization of Data 33 Suite Electricity – Pre-Post Rehabilitation Building 17 Electric Baseboard Heat - Occupant Controlled Thermostat Natural Gas – Pre-Post Rehabilitation Building 17 Fireplaces Only (No MAU) – Occupant Controlled Thermostat Common Electricity – Pre-Post Rehabilitation Building 11 Common Electricity – Non-Adjusted Thermostats Natural Gas – Pre-Post Rehabilitation Building 11 Make-up Air Heating Only – Fixed Thermostat Suite Electricity Consumption Pre and Post Rehab Common Electricity Consumption Pre and Post Rehab Gas Consumption Pre and Post Rehab y = -0.00027x3 y + = 0.60575x2 0.2430x + 77.3001 + 11.18491x + 42011.83422 R2 = 0.8666 y = 0.2122x + 71.974 R2 = 0.9109 55,000 90,000 300 160,000 200 80,000 50,000 180 250 140,000 70,000 160 120,000 45,000 60,000 140 200 100,000 120 50,000 40,000 150 100 40,000 35,000 80 100 30,000 60 30,000 20,000 50 40 10,000 25,000 20 0 80,000 60,000 40,000 20,000 0 100 200 300 400 500 600 Monthly HDD Gas Consumption - GJ/month Gas - Pre Rehab Gas - Post Rehab Gas - Pre Rehab Gas - Post Rehab Gas Consumption Pre and Post Rehab y = 0.0007148x2 + 0.0649066x R2 = 0.7000204 y = 0.0004614x2 + 0.1990927x R2 = 0.5650406 0 0 100 200 300 400 500 600 Monthly HDD Gas Consumption - GJ/month Gas - Pre Rehab Gas - Post Rehab Gas - Post Rehab Gas - Pre Rehab Suite Electricity Consumption Pre and Post Rehab y = -0.000432x3 + 0.557175x2 - 14.989006x + 41332.105085 R2 = 0.976696 R2 = 0.93838 0 0 100 200 300 400 500 600 Monthly HDD Suite Electricity Consumption - kWh/month Suite Elec - Pre Rehab Suite Elec - Post Rehab Suite Elec - Post Rehab Suite Elec - Pre Rehab y = -0.000333x3 + 0.297434x2 + 10.057163x + 37032.022306 R2 = 0.918362 y = -0.000513x3 + 0.464302x2 - 23.867279x + 44178.404540 R2 = 0.875213 0 0 50 100 150 200 250 300 350 400 450 500 Monthly Suite Electricity Consumption - kWh/month Suite Elec - Pre Rehab Suite Elec - Post Rehab Suite Elec - Post Rehab Suite Elec - Pre Rehab y = 7.1879x + 40594 R2 = 0.1849 y = 3.2597x + 38957 R2 = 0.0875 20,000 0 100 200 300 400 500 600 Monthly HDD Common Electricity consumption - kWh/month Common Elec - Pre Rehab Common Elec - Post Rehab Common Elec - Pre Rehab Common Elec - Post Rehab
  16. 16. Odd Occupant Behavior and Seasonal Influence Trends Buildings 34/35 - Heating Degree Days Versus Energy Consumption - Monthly 900,000 800,000 700,000 Total Gas Total Electricity month) September 600,000 kwhr/(500,000 Consumption 400,000 Energy 300,000 200,000 June 100,000 0 Monthly Heating Degree Days 0 50 100 150 200 250 300 350 400 450 500
  17. 17. Detailed Enclosure R-value Calculations ! Very detailed Pre- & Post-Rehabilitation U/R-values calculated for input into energy model ! Calculated U-values for every detail of each wall, roof, window assembly ! Calculated area-weighted U-values using detailed area calculations PRE R-2.92 POST R-4.26
  18. 18. Typical Enclosure R-values – Study MURBs 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 7 11 17 18 19 20 21 28 32 33 62 39 41 Typ Avg Overall Enclosure R-Value, hr-ft2-F/Btu Building Number Pre Post 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 Overall Enclosure R-Value, hr-ft2-F/Btu Year of Construction
  19. 19. Impact of Incorrect Nominal R-Value Assumptions ! Assuming nominal R-values (i.e. neglecting thermal bridging) has significant impact on modeled consumption ! Use of nominal values results in underestimations of space-heat by 7% to 29% for study buildings (if only we built this well)
  20. 20. Calibration Process – Suite Electricity 20% 15% 10% 5% 0% -5% -10% -15% -20% Energy in kWh Difference Accuracy of weather normalization becomes apparent here 250,000 140,000 120,000 200,000 100,000 150,000 80,000 60,000 100,000 40,000 50,000 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg. Monthly Error: 35.4% 9.7% Ann. Error: 46.2% Billed Simulated Difference Un-Calibrated Suite Electricity – Bldg 33 20,000 .0% 2.7% Ann. Error: .1% Calibrated Suite Electricity – Bldg 33 Adjustments to Electric Space Heat Output & Lighting Baseboard heat constrained within DOE model – to represent occupant behaviour, zoning – Uniform across ALL buildings studied
  21. 21. Calibration Process – Common Electricity Un-Calibrated Common Electricity – Bldg 33 Avg. Monthly Error: Avg. Monthly Error: -42.7% .2% 1.7% .6% Ann. Error: -42.7% 20% 15% 10% 5% 0% -5% -10% -15% -20% 60,000 50,000 40,000 30,000 20,000 10,000 0 Energy in kWh Difference Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann. Error: 1.6% Billed Simulated Difference Calibrated Common Electricity – Bldg 33 Adjustments to Elevators & Lighting Adjustments to account for equipment & heating
  22. 22. Calibration Process – Natural Gas 20% 15% 10% 5% 0% -5% -10% -15% -20% 800 700 700 600 600 500 500 400 400 300 300 200 200 100 0 Natural Gas in GJ Difference Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Avg. Monthly Error: 31.5% 3.5% Ann. Error: 27.1% Billed Simulated Difference UCna-lCibarliabtreadt eNda Ntuartaul rGaal Gs a–s B –ld Bgl d3g3 3 3 100 Avg. Monthly Error: .6% .6% Ann. Error: .7% Adjustments to Make-up Air Flow-rate (ie from nameplate to actual installed), MAU Temperature & DHW systems
  23. 23. Distribution of Energy Consumption – Typical MURB Average of 13 Buildings = Total 206.3 kWh/m2/yr Equipment and Ammenity (Common), 28.3, 14% Plug and Appliances (Suites), 18.7, 9% Units of kWh/m2/yr, % total Electric Baseboard Heating, 25.1, 12% Fireplaces, 37.7, 18% Ventilation Heating, 39.7, 19% DHW, 32.9, 16% Lights - Common, 3.7, 2% Lights - Suite, 15.9, 8% Elevators, 4.2, 2%
  24. 24. Impact of Fireplace Energy Consumption 120 ! Fireplace use simulated in model and calibrated with data from buildings with only gas fireplaces on meter 100 ! Average 17.6 GJ/year/suite average fireplace use (13.3 to 24.1 GJ depending on manual pilot light shut-offs 80 2.8 Natural Gas, GJ/suite 1.9 2.0 37.5 25.1 29.1 1.3 0.8 Billed Simulated 39.9 39.9 0.3 0.1 0.1 0.5 1.2 2.1 2.6 3.0 2.5 2.0 1.5 1.0 0.5 0.0 60 40 20 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 Suites with Fireplaces Suites without Fireplaces Annual Space Heat Consumption, kWh/m2 Fireplace Gas Suite Electric Space Heat MAU Gas -37.5 for fireplace +4 for electric heat 10:1 ratio?
  25. 25. Calibration Results – Total Energy Consumption 25% 300 20% 250 15% 200 10% 5% 150 0% 100 -5% 50 0 Average Metered (Actual Savings) = 7.5% (-11% up to 19%) Average Modeled Savings = 3% (0% to 7%) In all cases* actual savings exceeded modeled Bldg07 Bldg11 Bldg17 Bldg18 Bldg19 Bldg20 Bldg21 Bldg28 Bldg32 Bldg33 Bldg62 Total Energy Consumption, kWh/m2 Meter Pre-Rehab Model Pre-Rehab Meter Post-Rehab Model Post-Rehab -10% -15% Bldg07 Bldg11 Bldg17 Bldg18 Bldg19 Bldg20 Bldg21 Bldg28 Bldg32 Bldg33 Bldg62 Total Energy Consumption, kWh/m2 Metered Savings Modeled Savings
  26. 26. Applying Calibrated Model to Assess Energy Efficiency Measures ! Improve glazing ! Improve ventilation & heat recovery ! Reduced thermal bridging
  27. 27. Combination of Energy Efficiency Measures Simulated Scenario Simulation Inputs Baseline Pre • Walls effective R-3.6 • Windows single glazed U = 0.7, SC = 0.67 • Air tightness “Tight – High Average”, 0.15 cfm/ft2 • Make-up air temperature set-point 68°F • No heat recovery Good • Walls effective R-10 • Windows double glazed, argon fill, low-e, low conductive frame; U = 0.27, SC = 0.35 • Air tightness “Tight – Low Average”, 0.05 cfm/ft2 • Make-up air temperature set-point 64°F • No heat recovery • No Fireplaces Best • Walls effective R-18.2 • Windows triple glazed, argon fill, low-e, low conductive frame; U = 0.17, SC = 0.23 • Air tightness “Very Tight”, 0.02 cfm/ft2 • Make-up air temperature set-point 60°F • 80% Heat Recovery • No Fireplaces
  28. 28. Potential for MURB Space Heat Consumption in Vancouver 102.4 63% Space Heat Savings 38.2 9.7 120.0 100.0 80.0 60.0 40.0 20.0 0.0 Baseline Good Best Annual Space Heat Consumption, kWh/m2 91% Space Heat Savings
  29. 29. Impact of Space Heat Energy on Total Energy Consumption ! Can reduce energy by almost half with ventilation and enclosure upgrades only ! Further improvements from DHW, Lighting, Appliances, Controls etc. m2 kWh/Consumption, Energy Annual 110.3 60.8 Baseline Good Best 39.4 96.0 81.3 74.2 250 200 150 100 50 0 Electricity Gas Current Levels ~ 200 kWh/m2/yr We can get to ~100 kWh/m2/yr
  30. 30. Conclusions – MURB Energy Simulations ! 2-3 years of monthly utility data usually sufficient for energy assessments of existing MURBs ! Careful with HVAC/enclosure changes, may need more data ! Careful with weather normalization – usually non-linear relationship when occupants have control of thermostat ! Need accurate R-values and mechanical inventories (detailed audits necessary), basic understanding of air-tightness/airflows ! Energy models need to be calibrated with actual data – apply findings, tweaks & knowledge to new building models ! Calibrated models can predict approximate space-heat energy savings for enclosure rehabilitations ! Some difficulty with gas fireplaces and make-up air consumption & influence ! Mechanical system changes (ie balancing of make-up air, set-point temperature increases, dead controls) can throw of estimates (and real savings) ! Occupant behaviour and airflow within tall buildings have significant influence on actual energy consumption and savings potentials
  31. 31. Questions? gfinch@rdhbe.com

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