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Current Trends and the Impacts of Enclosure Upgrades
Energy Consumption in Mid- to High-Rise Multi-Unit Residential Buildings
Graham Finch, MAScWarren Knowles, P.EngEric Burnett, PhD
BEST 2 - PortlandNovember 12, 2010
Overview
Energy Consumption within Mid to High-Rise Multi-Unit Residential Buildings –Current Trends, & Issues
Effective R-values and the Impacts of Enclosure Upgrades on Energy Savings
Recommendations for Energy Efficient MURBs
MURB Energy Study
Industry sponsored research project, governments, utilities, engineering consultantsLooks at energy consumption a large population of similar mid-to high-rise MURBsSelected representative MURBs of past and current architectural designDecade of natural gas & electricity data provided by gas & electric utilitiesAllows the assessment of actual, not modeled energy consumption trends
MURB Energy Study
Several MURBs selected for the study were rehabilitated for water-ingress issues, “leaky condos”
More efficiently re-clad, Better windowsReduced air-leakageHigher overall R-values
Allows the assessment of actual energy savings from enclosure retrofits
A Few of the Energy Study Goals
Provide data for the current state of MURB housing stock Set achievable targets for MURB energy efficiencyDevelop recommendations for building code changes affecting MURBsDevelop recommendations for effective & efficient MURB energy upgradesIncentive ProgramsCalibrate energy models
Context
Energy consumed in Buildings accounts for 30-40% of all the energy used in Canada/USA
~55% used in residential buildings~45% used in commercial/institutional
Of the residential use: ~20% (Canada) is used in multi-family residential Energy use, or incentives forMURBs have not been looked at in as much detail as for single familyhomes
Resident ial
17%
Commer cial &
Inst it ut ional
14%
Indust r ial
37%
Tr anspor t at ion
30%
Agr icul t ur e
2%
Canada
Context: Local Utility Providers
Suite Energy Consumption by Year of Building Construction
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
< 1970 1970s 1980s 1990s 2000s AllYear of Construction
kW
h/s
uite
Rentals
Condos
Common Area Energy Consumption by Year of Building Construction
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
< 1970 1970s 1980s 1990s 2000s AllYear of Construction
kW
h/s
uite
Rentals
Condos
BC Hydro Data for all MURBs in Vancouver, BC
BUT: BC Hydro & Terasen Gas werre missing each others data
Building Enclosure Rehabilitations
Focus is to cost effectively repair moisture damageOwners burdened with large repair costs and are typically unwilling to spend extra for energy consumption improvements, however
Windows typically replaced,Air-leakage reduced,Exterior insulated assemblies, Improved cladding attachment strategies.
Energy improvements, if any, are aside benefitOwners typically report improvements:
ComfortEnergy ConsumptionAcoustics, quieter
and Current Building Practices…
High glazing percentages, 50-70% are normalSteel stud framing/window-wallExposed concreteExposed slab edges, balconies, and “eyebrows”Very low effective R-values
“Not so Hot” MURB Architecture
1970’s Vintage Cooling Fins, Waterloo, ON
2010 “New and Improved” Cooling Fins, Vancouver, BC
One of John & Joes Waterloo Favourites Window-Wall “Cooling Tower”
Study Buildings
68 MURBs in study55 high-rise – 10 to 33 storeys13 mid-rise – 5 to 9 storeysConstructed from 1974-2002
RDH has looked at, or worked on, each in the past –access to drawings, sites~50% have had a major building enclosure rehab in past 3-10 yearsMajority heated with electric baseboard & gas-heated ventilation air to pressurized corridors. Two have hydronic gas-heat baseboardsAll market housing condominiums, not rental apartments or social housing.Non air-conditioned
Study Buildings
Will present data from 39 MURBs today
Data from several of the initial buildings was not usable for the study
• Missing or erroneous data• Metering issues
12 years of data from 1998-2009 for each building
Electricity for suites (combined) and for common areas separately1 gas meter per building is typical
• Includes domestic hot water, make-up air units, all fireplaces (some buildings), pools (sometimes)
Total Building Energy Usage per Gross Floor Area - Sorted from Low to High
-
50
100
150
200
250
300
350
81
14
4 95
24
26
16
31
8 76
21
22
61
93
33
22
04
52
91
74
36
03
12
8 61
4 33
9 25
73
04
12
4 14
05
92
13
65
8
Building ID - Sorted from Least to Greatest Energy Intensity
Energ
y C
onsum
pti
on - k
Wh
/m2/y
r
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
Average = 67.5 kBtu/sf/yr
Range = 45.6 to 94.8 kBtu/sf/yr
Median = 68.8 kBtu/sf/yr
Std Dev = 13.3 kBtu/sf/yr
63 k
Btu
/sf/
yr
Total Energy Consumption per Suite
Total Building Energy Usage per Gross Floor Area - Sorted from Low to High
-
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,0008
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 by total building energy intesity - low to high
Energ
y C
onsum
pti
on - k
Wh/s
uit
e
Common Electricity
Suite Electricity
Gas
Average = 21,926 kWh/ suite
Median = 21,358 kWh/ suite
Std Dev = 7,130 kWh/ suite
Range = 11,566 to 50,611 kWh/ suite
Building 57 Has Air-conditioning & several common amenities
Space Heat Energy Usage vs Year Built
-
50
100
150
200
250
300
350
19
72
19
74
19
76
19
78
19
80
19
82
19
84
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
20
02
20
04
Year of Construction
Energ
y C
onsum
pti
on - k
Wh
/m2/y
r
Total Energy
Space Heat Energy
Total Energy Consumption vs Age of Building
63 k
Btu
/sf/
yr
Space Heating
With exception of hydronic heated buildings, all buildings in the study have electric resistance baseboard heaters in suitesAll buildings have ventilation air, heated by indirect gas-fired rooftop MAUs – supplied to suites using pressurized corridor approach
MAU designed air flow rate observed from 30 cfm/suite in the 1980s to greater than 120-150 cfm/suite in recent yearsDesigned for 60-65F, however set at 68-74F by strata’s to reduce complaints of cold drafts
Some buildings have gas fireplaces (in some or all suites) in addition to electric baseboards & MAU
Distribution of Purchased Space Heat Energy
% of Total Building Energy Used for Space Heat
0%
10%
20%
30%
40%
50%
60%
26 18 11 6 1
57 2 7
43 21
32
61
52 14 24
59
44 17 29
42
40
30 31
41
20
28
62
45
60
33
19 36
58 12 39 3 8
63 9
Building ID
% T
ota
l Energ
y W
hic
h is H
eat
Electrical Heat
Gas Heat
Average 37% of total building energy is
used for heat
Of this portion an average of 69% of
this energy is from gas
% Total Building Heat which is Gas
0%
20%
40%
60%
80%
100%
11
42
62
61
44 6
18
17
43 7
28
40
29
32 1 2
57
26 8
33
14
31 3
59
30
52
63
60 9
20
39
12
24
41
21
58
45
36
19
% S
pace
Heat fr
om
Gas
Average of 69%, Majority of Space-Heat
Energy from Gas Sources
Hydronic Gas Heat
MURBs with fireplaces in
majority of suites
Percentage of Purchased Space-Heat from Gas Sources
% of Total Building Energy Used for Space Heat
-
20
40
60
80
100
120
140
160
19
74
19
75
19
81
19
84
19
85
19
85
19
85
19
86
19
87
19
89
19
90
19
90
19
90
19
90
19
92
19
92
19
92
19
93
19
93
19
93
19
94
19
94
19
94
19
94
19
94
19
95
19
95
19
95
19
95
19
95
19
96
19
96
19
96
19
97
19
97
20
01
20
01
20
02
20
02
Year of Construction
Space
Heat Energ
y C
onsum
ed
- k
Wh/m
2/y
r Gas MAU or Fireplace Space Heat
Electric Resistance Space Heat
Type of Space heat versus Age of Building
% of Total Building Energy Used for Space Heat
-
20
40
60
80
100
120
140
160
19
74
19
75
19
81
19
84
19
85
19
85
19
85
19
86
19
87
19
89
19
90
19
90
19
90
19
90
19
92
19
92
19
92
19
93
19
93
19
93
19
94
19
94
19
94
19
94
19
94
19
95
19
95
19
95
19
95
19
95
19
96
19
96
19
96
19
97
19
97
20
01
20
01
20
02
20
02
Year of Construction
Space
Heat Energ
y C
onsum
ed
- k
Wh/m
2/y
r Gas MAU or Fireplace Space Heat
Electric Resistance Space Heat
Electric Space Heat Trend
Gas Space Heat Trend
Impact of Make-up Air Unit Flow Rate on Space Heat
Influence of Gas Fireplaces and MAU on Electric HeatGas and Electric Space Heat Use
0
20
40
60
80
100
120
140
160
30% 40% 50% 60% 70% 80% 90% 100%
Percent of Total Space Heat Energy which is Gas
Gas a
nd
Ele
ctri
c S
pace H
eat En
erg
y k
Wh
/m2/y
r
Electric Space Heat
Gas Space Heat
Total Space Heat
Gas Space Heat Trend
Electric Space Heat Trend
hydronic
buildings
Buildings without Gas Fireplaces Buildings with Gas Fireplaces
Space Heat Efficiency & Total Energy ConsumptionWhole Building Energy Consumption vs Space Heat Energy Consumption
0
20
40
60
80
100
120
140
160
100 120 140 160 180 200 220 240 260 280 300
Total Whole Building Energy Consumption - kWh/ m2/ yr
Tota
l S
pace
Heat Energ
y C
onsum
pti
on - k
Wh/m
2/y
r
2 to 3.5 x more heat used
Range of more efficient buildings
Average high-rise MURB (67.5 kBtu/sf/yr)49% of Energy is Electricity (32.4 kBtu/sf/yr)
• 57% of Electricity is used in Suites – 38% is used for electric baseboard heating– 62% is used for appliances, lighting, electronics etc
• 43% of Electricity is used in Common Areas– Elevator, Lighting, HVAC distribution,
ventilation, plumbing, fans, pumps etc.
51% of Energy is Gas (35.2 kBtu/sf/yr)• 51% is used for Ventilation Air (MAU) heating
and fireplaces (where provided)• 49% is used for domestic hot-water
37% of Total Energy is for Space Heat
Where does the energy go?
22% Heat
Other
Electricity
51% Heat
OtherGas
Average 280 Tons CO2/yr in BC
Operating Energy Costs
Whole Building (Average):
$128,000 per Year (Range$27,000 to $260,000)
$1.07/sqft floor area/year
$49,000 Gas
$79,000 Electricity
Per Suite (Average):
$1,200 (Range of $700 to $3000 per year)
Occupants Pay for Suite Electricity Individually – see bills monthlyCommon Electricity and Gas is paid by Strata (HOA)
Paid by occupants through monthly strata fees of $100-400+/month Occupants do not typically see complete energy bills, or understand what for
Average MURB Energy Cost Distribution28% Suite Electricity Energy = $408/yr (Occupant Paid)21% Common Area Electricity = $323/yr (Strata Paid)51% Gas Heat and Hot water = $455/yr (Strata Paid)
Only 36% of Total Energy Cost is Directly Paid by Occupant
69% of Building Space Heat is from Gas (Paid by Strata):Occupants are only directly paying for 31% of space heating costNeed to address this disconnect to become more energy efficient
Disconnect Between Consumption and Billing
Common Gas & Elec.
Suite Elec.
The Impacts of Building Enclosure Rehabilitations
Results from 4 buildings presented here todayEnclosure rehabilitations to address water leakage Various window types & claddingsEnergy improvements were unfortunately not a primary consideration when designing rehabilitations
Detailed R-value Calculations
Pre- & Post-Rehabilitation R-values to assess space-heat savingsCalculated U-values for every detail of each wall, roof, window assemblyCalculated area-weighted U-values using detailed areas from sketch-up
PRE R-2.92 POST R-4.26
Building 19 – Pre Rehabilitation
Building 19 – Post Rehabilitation
Building 19 – Pre & Post Rehabilitation R-values
Pre Rehabilitation Post Rehabilitation Building #19 Pre and Post R-value
Improvement Assembly Description R-value Assembly Description R-value
Walls (52% of enclosure):
Steel Stud w/ R-14 fiberglass.
Slab edges un-insulated,
balconies 3.9
Walls:
Exterior insulated, R-9.5 mineral
wool between steel z-girts. No
stud cavity insulation. Slab
edge insulated, balconies
uninsulated.
5.3
Windows ( 27% of enclosure,
34% of wall area):
Non-thermally broken
aluminum frames. Clear glass,
air filled IGUs with aluminum
spacers
1.37
Windows:
High performance thermally
broken aluminum frames. Soft-
coat low-e, air filled IGUs with
aluminum spacers
2.16
Roof (21% of enclosure):
Inverted assemblies with 3”
extruded polystyrene
14.3
Roof:
Inverted assemblies with 4”
extruded polystyrene.
18.3
Overall Building 2.92 Overall Building 4.26
Rehabilitation improved R-value by 46% (31% reduction in U-value)
Rehabilitation Resulted in a Space-Heat Savings of Approximately 10%
Building 62 – Pre and Post-Rehabiliation R-values
Pre Rehabilitation Post Rehabilitation Building #62 Pre and Post R-value
Improvement Assembly Description R-value Assembly Description R-value
Walls (47% of enclosure):
Steel Stud w/ R-12 fiberglass.
Exposed concrete. Slab edges
un-insulated, balconies 3.5
Walls:
Exterior insulated, R-9.5 mineral
wool between steel z-girts. No
stud cavity insulation. Slab
edge insulated, balconies
uninsulated.
4.6
Windows ( 46% of enclosure,
50% of wall area):
Non-thermally broken
aluminum frames. Clear glass,
air filled, IGUs with aluminum
spacers
1.35
Windows:
High performance thermally
broken aluminum frames. Clear
glass, air filled IGUs with
aluminum spacers
1.67
Roof (7% of enclosure):
Inverted assemblies with 1.5”
to 2” XPS
8.2
Roof:
Inverted assemblies with 3 to
3.5” XPS. Improved detailing
12.5
Overall Building 2.07 Overall Building 2.60
Rehabilitation improved R-value by 26% (20% reduction in U-value)
Rehabilitation Resulted in a Space-Heat Savings of Approximately 22%
Building 32 – Pre- and Post-Rehabilitation R-values
Pre Rehabilitation Post Rehabilitation Building #32 & 33 Pre and Post R-
value Improvement Assembly Description R-value Assembly Description R-value
Walls (47% of enclosure):
Steel Stud w/ R-12 fiberglass.
Portions of exposed concrete.
Slab edges un-insulated,
balconies
3.8
Walls:
Exterior insulated, R-13 mineral
wool between steel z-girts. No
stud cavity insulation. 3” EIFS
over exposed concrete, slab
edges insulated, balconies
uninsulated.
7.1
Windows ( 42% of enclosure,
47% of wall area):
Non-thermally broken
aluminum frames. Clear glass,
air filled, IGUs with aluminum
spacers
1.34
Windows:
High performance thermally
broken aluminum frames. Soft-
coat low-e, air filled IGUs with
aluminum spacers
2.02
Roof (12% of enclosure):
Uninsulated sloped
assemblies, flat Inverted
assemblies with 2” XPS
10.9
Roof:
Insulated sloped assembles,
flat Inverted assemblies with 2”
XPS. Improved detailing
12.8
Overall Building 2.26 Overall Building 3.56
Rehabilitation improved R-value by 58% (37% reduction in U-value)
Rehabilitation Resulted in a Space-Heat Savings of approximately 17% to 22%
Energy Savings from Enclosure Upgrades
Space-Heat energy savings have typically been observed in billing data
Suite electricity typically reduced by a few % up to 30%In a few case, gas for MAU seemingly reduced as well
Models using DOE 2.1 code do have difficulty in predicting MURB energy consumption
Monthly Bill Calibration is required to fine-tune MAU gas and electric baseboard heatUn-calibrated models seem to be over-estimating the real energy savings… several ramifications for MURB modelingOn-going research into this
• Occupant behaviour? In-situ air-leakage rates?
Air Leakage in MURBs
MURB Airflows & Air-Leakage Difficult to predictCan measure shell air-tightness, but $$ and timelyBuilding Pressures over the course of a year difficult to determine for a suiteWhat about occupant behaviour?
Air intermittently
exhausted OUT using
bathroom/kitchen fans
Air leakage IN/OUT through
elevator and stairwell shafts
Ventilation Air IN
(Mechanical + Pressure)
Natural Air-Leakage
IN/OUT through
Enclosure
Air flow IN/OUT
through open
windowsWind Pressure
Stack Effect
Buoyancy
Pressure
Interior Air-
Leakage between
suites/common
areas/floors
Air flow IN/OUT
through entry
Impact of Whole Building Air-tightness
Air-tightness Rates from current literature provide an expected range of air-tightness rates for MURBSAdditionally, select MURBs in study were air-leakage tested post-rehabilitationCan significantly influence Space-Heat Loss
Impact of Open Windows on Effective Air-Tightness
Open windows drastically change effective air-tightness, pressure, and air-flow regimesWindows are opened to improve ventilation, reduce condensation, for fresh airBuilding 33, Enclosure Air-tightness = 0.066 cfm/ft2 (2.73 in2/100 ft2)
Enclosure Area 73,000 ft2
Equivalent hole size of 2,000 in2
One open window = 1,000 in2
One window open per floor (low estimate), 20,000 in2 (10x higher than enclosure tightness)
How does this affect energy modeling?
Key Findings
Energy Consumption of High-rise residential buildings has apparently not improved in the past 30 years Space heat energy is the most largest driver in energy consumption and hence efficiencyPrimarily gas space-heat is being used in MURBs
Somewhat surprising considering buildings are designed primarily for electric heatHeat from ventilation air is poorly distributed
• Significant energy consumed for ventilation• MAU efficiency, flow rate and distribution is important
Gas fireplaces are very inefficient and are a considerable driver in the less efficient buildings
An enclosure R-value of R-2 to R-5 is not energy efficient
Towards Energy Efficiency in MURBs
Improve Building Enclosure & address mechanical issuesThermally Efficient & “R-value Balanced” Enclosure
First Consideration = Windows• Reasonable glazing percentages • Larger the glazing area, the better the windows must be• High Performance window R-values of R-4 to R-6. Non-conductive
frames and low-e/argon double to triple IGUs
Second Consideration = Walls• Consider effective R-values of assembly choices• Minimize thermal bridging, slab edges, girts, shelf angles etc
Compliance with ASHRAE 90.1 or other energy codes
Air-tight EnclosureSuite Compartmentalization
Towards Energy Efficiency in MURBs
Effective & energy efficient ventilation strategyVentilate for health, not for heatConsider alternate ventilation methods, directly to suites (where needed instead of through corridors)Reconsider rooftop gas-fired MAU units Have already seen this successfully done in Portland MURBs…\Heat Recovery makes a lot of sense
Efficient in-suite heating, hydronic or electricAvoid gas fireplaces (unless user pays)Individual Metering and Smart controls Necessary
Bill occupants for more of what they useTurn off heat when windows open
A Few Final Thoughts
Why do we continue to design and build poor performing buildings?
Lack of consideration of end users & how they operate buildings?Lack of integration between disciplines?Inadequate minimum building code requirements?Inadequate maintenance and renewals?Value engineering?
City of Vancouver Mandate to reduce energy consumption of all buildings by 50% by 2020. Net Zero is on horizon
This should mean <100 kWh/m2/yr MURBS in 10 yearsSignificant changes in design will be required
Energy Unit Conversions
1 kWh/m2 = 3.155 kBtu/ft2
1 GJ = 9.48 Therms
1 GJ = 277.78 kWh
1 GJ = 0.947 mmBtu
1 kWh = 3.12 kBtu
1 kWh = 0.034 Therms
1 kBtu/ft2 = 0.317 kWh/m2
1 Therm = 0.105 GJ
1 kWh = 0.0036 kWh
1 mmBtu = 1.055 GJ
1 kBtu = 0.321 kWh
1 Therm = 29.3 kWh
Metric units from Imperial Imperial Units from Metric
Understanding Energy Use in MURBs
Parking Garage
Exhaust Fans
Parking Garage
Common Areas
PoolGas Boiler to
heat pool &
hot-tubs
Suites
Ele
vato
r S
haft
Com
mon
Hallw
ay
C
orr
idors
Sta
irw
ell
Sh
aft
Electric Baseboard
Heaters in all
Suites
Gas fireplaces in
some Suites
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)
Heate
d v
enti
lati
on a
ir s
up
plied
to e
ach
flo
or co
mm
on c
orr
idor (p
ressuri
zed
)
Heated
Ventilation air
from corridor
Domestic Hot
Water is heated
using Gas
Some Gas & Electric
Heat at Common Areas
Typically Unheated
Leakage o
f h
eate
d
venti
lati
on a
ir into
sh
aft
s
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
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
Enclosure air-
leakage
Air flow through
open windows
Elevator pumping
Effect of Window Area on Overall Building R-value
Monthly Energy Consumption Comparison
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
180,000
200,000
Aug-9
8
Dec-
98
Apr-
99
Aug-9
9
Dec-
99
Apr-
00
Aug-0
0
Dec-
00
Apr-
01
Aug-0
1
Dec-
01
Apr-
02
Aug-0
2
Dec-
02
Apr-
03
Aug-0
3
Dec-
03
Apr-
04
Aug-0
4
Dec-
04
Apr-
05
Aug-0
5
Dec-
05
Apr-
06
En
erg
y C
on
su
mp
tio
n -
kw
hr/
mo
nth
Gas
Electricity - Suites
Electricity - Common
Total
Rehabilitation –Ignore Data
Gas-Data missing, ignore years data
We typically see reduced gas/increased electricity
Pre-Upgrade Post-Upgrade
Data Analysis
Typical Monthly Consumption – Typical Building
Mont hl y Ener gy Consumpt ion Compar ison
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
180,000
Au
g-0
2
Sep-0
2
Oct-0
2
No
v-0
2
Dec-0
2
Jan
-03
Feb
-03
Mar-0
3
Apr-0
3
May-0
3
Jun
-03
Jul-
03
Au
g-0
3
Sep-0
3
Oct-0
3
No
v-0
3
Dec-0
3
Jan
-04
Feb
-04
Mar-0
4
Apr-0
4
May-0
4
Jun
-04
Jul-
04
En
erg
y C
on
su
mptio
n -
kw
hr/m
on
th
Gas
El ect r icit y - Suit es
El ect r icit y - Common
Baseline Gas – No Space Heat
Baseline Suite Electricity – No Space Heat
Estimate Space heat from monthly minus baseline
value
Thermal Anatomy 101 – Multi-Family High-rise
R-12 Insulation in steel-stud wallsR-5 accounting for steel studs
R-20 Roof InsulationR-1.8 Windows, 60% Wall Area
Aluminum window wall, hard-coat low-e, air fill
U-overall = 1/5 * 0.38 + 1/20 * 0.06 + 1/1.8 * 0.56
= 0.39 --> R-overall =2.6 80% Heat Loss through windows
240 suites, 180,000 sq.ft.Envelope area = 38% walls, 6% roof, 56% windows
