a controlled ventilation strategy for ontario...
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A Controlled Ventilation Strategy for Ontario Homes:
A Comparative Analysis of Energy-Use, Air Quality, and Economics
Adam Di Placido, MASc, University of Toronto Professor Kim Pressnail, University of Toronto
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Motivation
• Energy efficiency requirements of the Ontario Building Code (OBC) were updated in 2012
• Improved home energy efficiency by 40%
Buildings for Tomorrow Conference – Toronto Canada - October 28-30, 2014
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Motivation
Ceiling 3%
Walls 17%
Windows 21%
Doors 2%
Basement 16%
Ventilation 41%
Components of Annual Heat Loss: Ontario home built to the minimum energy efficiency
requirements of the 2012 OBC
Di Placido et al., 2014, Building & Environment
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Motivation
• Can we address ventilation energy-use while improving IAQ?
• Would a new ventilation strategy be economically feasible?
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The Ontario Building Code
• Minimum mechanical exhaust based on CAN/CSA-F326. • Typically 0.3 ACH
• Ventilation can be provided by exhaust-only or balanced systems
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Exhaust-Only Ventilation Advantages: • Low first costs • Passive filtration • Depressurization to avoid
condensation Disadvantages: • Little control over where
makeup air is drawn from • Cannot take advantage of
active heat recovery • Depressurization issues can
occur with airtight construction
Image credit: (Oikos Green Building Source, 1995)
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Balanced Ventilation
Advantages:
• Greater control over makeup air
• Ability to add active heat recovery
• Flexibility in pressure regime
Disadvantages:
• Greater first costs • More ductwork
Image credit: (Oikos Green Building Source, 1995)
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A “Controlled Ventilation” Model for Ontario Homes
1. Balanced mechanical ventilation 2. Heat Recovery Ventilator (HRV) 3. Airtight construction 4. High efficiency filter
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Methods
• Home Energy-Use => HOT2000 • IAQ => Monte Carlo Simulation of steady state mass balance on PM2.5
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Health Impacts of PM2.5
Asthma Lung cancer Cardiovascular disease Respiratory diseases Premature delivery Birth defects Premature death
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Methods: The Model Home
Base Case Model Controlled Ventilation Models
Size: 200 m2, two storey, detached home
Hea)ng/Cooling: Forced-air natural gas furnace/ AC unit
Ventilation System Type:
Exhaust-only Balanced
Heat Recovery: No HRV HRV (64% efficiency)
Air Leakage: 2.5 ACH @50Pa 1. 1.5 ACH (R-2000) 2. 0.6 ACH (Passivhaus)
Air Filter: Building envelope MERV 13 filter
Photo credit: The Toronto Star (2004)
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Results: Annual Energy Use
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10
20
30
40
50
60
70
2.5 ACH Baseline 1.5 ACH + HRV 0.6 ACH + HRV
Hea
tin
g a
nd
Co
olin
g E
ner
gy
Co
nsu
mp
tio
n (
kWh
/m2 )
Cooling Heating
46% 39%
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Methods: Mass Balance
( )( )( )
VQ
+F-1+F++
SC -1+PC
recircoffonventinf
indooroutventmakeupinfin
ηββλλ
ληλ +=
Outdoor PM2.5 Concentrations: Toronto, 2012
HVAC Runtime Fraction: Stephens et al. ,2011, Bldg & Env.
Recirculation Flow Rate: Stephens et al. ,2011, Bldg & Env.
Deposition Rate While HVAC off: Long et al. ,2001, Env.Sci. & Tech. Riley et al., 2002, Env.Sci. & Tech.
Deposition Rate While HVAC on: Emmerich & Nabinger, 2001, HVAC&R Research
Penetration Factor: Long et al. ,2001, Env.Sci. & Tech. Williams et al., 2003, Atm. Env. Marsik & Johnson, 2008, En. & Bldgs
Filter Efficiency for Makeup Air: Riley et al., 2002, Env.Sci. & Tech.
Filter Efficiency for Recirculated Air: Riley et al., 2002, Env.Sci. & Tech.
Indoor Sources: Hanninan et al. , 204, Atm.Env.
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Results: Annual Average PM2.5 Concentrations
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
2.5 ACH 1.5 ACH 0.6 ACH
Ind
oo
r P
M2.
5 C
on
cen
trat
ion
(μ
g/m
3 )
- 1.7 μg/m3
- 1.6 μg/m3
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Results: Peak PM2.5 Concentrations
0
5
10
15
20
25
30
2.5 ACH 1.5 ACH 0.6 ACH
Ind
oo
r P
M2.
5 C
on
cen
trat
ion
(μ
g/m
3 )
- 13.7 μg/m3
- 15.4 μg/m3
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Results: Economics
1.5 ACH 0.6 ACH Upgrade from exhaust-only to balanced system with HRV $1,250 $1,250
Incremental cost to improve air tightness $400 $1,500
Annualized Cost of Upgrades $117 $195
Cost savings from electricity -$80 -$87
Cost savings from natural gas $146 $173
Net Annual Cost $51 $109
Four Residential MERV 13 filters (3 month service life) -$140 -$140
Reduced Health Care costs, 4 occupants $258 $248
Net Annual Savings (including health care) $67 -$1
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Conclusions
• Results are not conclusive but suggestive • HRV impacted energy, filter impacted IAQ • Air tightness was less influential • A controlled ventilation model can significantly reduce
energy use at a small expense to the homeowner
• Factoring in external costs, a controlled ventilation model will likely cover its own first costs
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Thank You
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