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
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
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
! 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
MURB Energy Study – Metered Energy Data
Monthly Energy Consumption – Typical Building
Total Building Energy Usage per Gross Floor Area - Sorted from Low to High
-
50
100
150
200
250
300
350
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
Ener
gy C
onsu
mpt
ion
- kW
h/m
2 /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
Total Annual Energy Consumption Intensity Space Heat Energy Usage vs Year Built
-
50
100
150
200
250
300
350
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
Year of Construction
Ener
gy C
onsu
mpt
ion
- kW
h/m
2 /yr
Total Energy
Space Heat Energy
Understanding Energy Use & Airflow within MURBs
Parking GarageExhaust Fans
Parking Garage
Common Areas
PoolGas Boiler toheat pool &
hot-tubs
Suites
Elev
ator
Sha
ft
Com
mon
H
allw
ay
Cor
rido
rs
Sta
irw
ell
Sha
ft
Electric BaseboardHeaters in all
Suites
Gas fireplaces insome Suites
Air exhausted usingbathroom/kitchen fans
& windows
Air leakage of heatedventilation air through
elevator and stairwell shafts Ventilation air is heatedusing gas-fired make-up
air unit (MUA)
Hea
ted
vent
ilati
on a
ir s
uppl
ied
to e
ach
floor
com
mon
cor
rido
r (pr
essu
rize
d)
HeatedVentilation airfrom corridor
Domestic HotWater is heated
using Gas
Some Gas & ElectricHeat at Common Areas
Typically Unheated
Leak
age
of h
eate
dve
ntila
tion
air
into
sha
fts
Rec. Areas
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
ElectricityCommon Areas- Interior lighting- Elevators- Ventilation fans and motors- Parking garage exhaust fans- Water distribution pumps- Baseboard heaters- Recreation areas/pool pumps- Exterior lighting- Communication- ControlsSuites- Baseboard heaters- Lighting- Appliances- Miscellaneous Electric Loads- Plug loads- Exhaust fans
Enclosure air-leakage
Air flow throughopen windows
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.
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
! 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
Energy Consumption Analysis Methods
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
Calibration of Energy Simulation using Metered Data
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
450,000
500,000
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
Ener
gy C
onsu
mpt
ion
- kw
hr/m
onth Gas
Electricity - SuitesElectricity - Common
Top Down Metered Energy Analysis
Parking GarageExhaust Fans
Parking Garage
Common Areas
PoolGas Boiler toheat pool &
hot-tubs
Suites
Elev
ator
Sha
ft
Com
mon
H
allw
ay
Cor
rido
rs
Sta
irw
ell
Sha
ft
Electric BaseboardHeaters in all
Suites
Gas fireplaces insome Suites
Air exhausted usingbathroom/kitchen fans
& windows
Air leakage of heatedventilation air through
elevator and stairwell shafts Ventilation air is heatedusing gas-fired make-up
air unit (MUA)
Hea
ted
vent
ilati
on a
ir s
uppl
ied
to e
ach
floor
com
mon
cor
rido
r (pr
essu
rize
d)
HeatedVentilation airfrom corridor
Domestic HotWater is heated
using Gas
Some Gas & ElectricHeat at Common Areas
Typically Unheated
Leak
age
of h
eate
dve
ntila
tion
air
into
sha
fts
Rec. Areas
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
ElectricityCommon Areas- Interior lighting- Elevators- Ventilation fans and motors- Parking garage exhaust fans- Water distribution pumps- Baseboard heaters- Recreation areas/pool pumps- Exterior lighting- Communication- ControlsSuites- Baseboard heaters- Lighting- Appliances- Miscellaneous Electric Loads- Plug loads- Exhaust fans
Enclosure air-leakage
Air flow throughopen windows
Elevator pumping
Bottom-Up Energy Model Simulation
200
Model Inputs
Actual Energy Use
240 220 260 180
kWh/m2/yr
Simulated Energy Use
The Importance of Meter Calibrations – Electricity
The Importance of Meter Calibrations – Natural Gas
! 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
Metered Energy Collection and Weather Normalization
Meter Assessment and Weather Normalization of Data
Gas Consumption Pre and Post Rehab
y = 0.2430x + 77.3001
R2 = 0.8666
y = 0.2122x + 71.974
R2 = 0.9109
0
20
40
60
80
100
120
140
160
180
200
0 100 200 300 400 500 600
Monthly HDD
Gas
Con
sum
ptio
n - G
J/m
onth
Gas - Pre RehabGas - Post RehabGas - Pre RehabGas - Post Rehab
Natural Gas – Pre-Post Rehabilitation Building 11 Make-up Air Heating Only – Fixed Thermostat
Gas Consumption Pre and Post Rehab
y = 0.0007148x2 + 0.0649066x
R2 = 0.7000204
y = 0.0004614x2 + 0.1990927x
R2 = 0.5650406
0
50
100
150
200
250
300
0 100 200 300 400 500 600
Monthly HDD
Gas
Co
nsu
mp
tio
n -
GJ/
mo
nth
Gas - Pre RehabGas - Post RehabGas - Post RehabGas - Pre Rehab
Natural Gas – Pre-Post Rehabilitation Building 17 Fireplaces Only (No MAU) – Occupant Controlled Thermostat
Suite Electricity Consumption Pre and Post Rehab
y = -0.000432x3 + 0.557175x2 - 14.989006x + 41332.105085
R2 = 0.976696
y = -0.00027x3 + 0.60575x2 + 11.18491x + 42011.83422
R2 = 0.93838
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
0 100 200 300 400 500 600
Monthly HDD
Su
ite
Elec
tric
ity
Co
nsu
mp
tio
n -
kWh
/mo
nth
Suite Elec - Pre RehabSuite Elec - Post RehabSuite Elec - Post RehabSuite Elec - Pre Rehab
Suite Electricity – Pre-Post Rehabilitation Building 33 Electric Baseboard Heat - Occupant Controlled Thermostat Suite Electricity – Pre-Post Rehabilitation Building 17 Electric Baseboard Heat - Occupant Controlled Thermostat
Suite Electricity Consumption Pre and Post 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
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
0 50 100 150 200 250 300 350 400 450 500
Monthly HDD
Sui
te E
lect
rici
ty C
onsu
mpt
ion
- kW
h/m
onth
Suite Elec - Pre RehabSuite Elec - Post RehabSuite Elec - Post RehabSuite Elec - Pre Rehab
Common Electricity Consumption Pre and Post Rehab
y = 7.1879x + 40594
R2 = 0.1849
y = 3.2597x + 38957
R2 = 0.0875
20,000
25,000
30,000
35,000
40,000
45,000
50,000
55,000
0 100 200 300 400 500 600
Monthly HDD
Com
mon
Ele
ctri
city
con
sum
ptio
n -
kWh/
mon
th
Common Elec - Pre Rehab
Common Elec - Post RehabCommon Elec - Pre Rehab
Common Elec - Post Rehab
Common Electricity – Pre-Post Rehabilitation Building 11 Common Electricity – Non-Adjusted Thermostats
Odd Occupant Behavior and Seasonal Influence Trends Buildings 34/35 - Heating Degree Days Versus Energy Consumption - Monthly
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
0 50 100 150 200 250 300 350 400 450 500
Monthly Heating Degree Days
Ener
gy C
onsu
mpt
ion
(kw
hr/m
onth
)
Total Gas
Total Electricity
September
June
! 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
Detailed Enclosure R-value Calculations
PRE R-2.92 POST R-4.26
Typical Enclosure R-values – Study MURBs
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
7 11 17 18 19 20 21 28 32 33 62 39 41 Typ Avg
Ove
rall
Encl
osur
e R
-Val
ue, h
r-ft
2 -F/
Btu
Building Number
Pre Post
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1980 1985 1990 1995 2000 2005
Ove
rall
Encl
osur
e R
-Val
ue, h
r-ft
2 -F/
Btu
Year of Construction
! 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)
Impact of Incorrect Nominal R-Value Assumptions
Accuracy of weather normalization becomes apparent here
Calibration Process – Suite Electricity
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
0
50,000
100,000
150,000
200,000
250,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DifferenceEnergy in kWh
Billed
Simulated
Difference
Avg. Monthly Error: 35.4% 9.7%
Ann. Error: 46.2%
Un-Calibrated Suite Electricity – Bldg 33
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DifferenceEnergy in kWh
Billed
Simulated
Difference
Avg. Monthly Error: .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
Calibration Process – Common Electricity
Un-Calibrated Common Electricity – Bldg 33
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
0
10,000
20,000
30,000
40,000
50,000
60,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DifferenceEnergy in kWh
Billed
Simulated
Difference
Avg. Monthly Error: -42.7% .2%
Ann. Error: -42.7%
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
0
10,000
20,000
30,000
40,000
50,000
60,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DifferenceEnergy in kWh
Billed
Simulated
Difference
Avg. Monthly Error: 1.7% .6%
Ann. Error: 1.6%
Calibrated Common Electricity – Bldg 33
Adjustments to Elevators & Lighting Adjustments to account for equipment & heating
Calibration Process – Natural Gas
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
0
100
200
300
400
500
600
700
800
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DifferenceNatural Gas in GJ
Billed
Simulated
Difference
Avg. Monthly Error: 31.5% 3.5%
Ann. Error: 27.1%
Un-Calibrated Natural Gas – Bldg 33 Calibrated Natural Gas – Bldg 33
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
0
100
200
300
400
500
600
700
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
DifferenceNatural Gas in GJ
Billed
Simulated
Difference
Avg. Monthly Error: .6% .6%
Ann. Error: .7%
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
Distribution of Energy Consumption – Typical MURB
Average of 13 Buildings = Total 206.3 kWh/m2/yr
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%
Plug and Appliances
(Suites), 18.7, 9%
Equipment and Ammenity (Common), 28.3, 14%
Elevators, 4.2, 2%
! Fireplace use simulated in model and calibrated with data from buildings with only gas fireplaces on meter
! Average 17.6 GJ/year/suite average fireplace use (13.3 to 24.1 GJ depending on manual pilot light shut-offs
Impact of Fireplace Energy Consumption
2.8
1.9 2.0
1.3
0.8
0.30.1 0.1
0.5
1.2
2.1
2.6
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Natural Gas, GJ/suite
Billed Simulated
39.9 39.9
25.1 29.1
37.5
0
20
40
60
80
100
120
Suites with Fireplaces Suites without Fireplaces
Ann
ual S
pac
e H
eat C
onsu
mpt
ion,
kW
h/m
2 Fireplace Gas
Suite Electric Space Heat
MAU Gas
-37.5 for fireplace +4 for electric heat 10:1 ratio?
Calibration Results – Total Energy Consumption
0
50
100
150
200
250
300
Bldg07 Bldg11 Bldg17 Bldg18 Bldg19 Bldg20 Bldg21 Bldg28 Bldg32 Bldg33 Bldg62
Tota
l Ene
rgy
Con
sum
ptio
n, k
Wh/
m2
Meter Pre-Rehab
Model Pre-Rehab
Meter Post-Rehab
Model Post-Rehab
-15%
-10%
-5%
0%
5%
10%
15%
20%
25%
Bldg07 Bldg11 Bldg17 Bldg18 Bldg19 Bldg20 Bldg21 Bldg28 Bldg32 Bldg33 Bldg62
Tota
l Ene
rgy
Cons
umpt
ion,
kW
h/m
2
Metered Savings
Modeled Savings
Average Metered (Actual Savings) = 7.5% (-11% up to 19%) Average Modeled Savings = 3% (0% to 7%) In all cases* actual savings exceeded modeled
! Improve glazing
Applying Calibrated Model to Assess Energy Efficiency Measures
! Improve ventilation & heat recovery
! Reduced thermal bridging
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
Combination of Energy Efficiency Measures Simulated
102.4
38.2
9.7
0.0
20.0
40.0
60.0
80.0
100.0
120.0
Baseline Good Best
An
nual
Spa
ce H
eat C
onsu
mpt
ion,
kW
h/m
2
Potential for MURB Space Heat Consumption in Vancouver
91% Space Heat Savings
63% Space Heat Savings
110.3
60.839.4
96.0
81.3
74.2
0
50
100
150
200
250
Baseline Good Best
An
nu
al E
nerg
y Co
nsu
mp
tion,
kW
h/m
2
Electricity
Gas
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.
Current Levels ~ 200 kWh/m2/yr We can get to ~100 kWh/m2/yr
! 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
Conclusions – MURB Energy Simulations
Questions? [email protected]