a controlled ventilation strategy for ontario...

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

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

2 14th Canadian Conference on Building Science and Technology

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


14th Canadian Conference on Building Science and Technology 3

Motivation

• Can we address ventilation energy-use while improving IAQ?

• Would a new ventilation strategy be economically feasible?



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



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)

14th Canadian Conference on Building Science and Technology


6

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)



7

A “Controlled Ventilation” Model for Ontario Homes

1.  Balanced mechanical ventilation 2.  Heat Recovery Ventilator (HRV) 3.  Airtight construction 4.  High efficiency filter



Methods

• Home Energy-Use => HOT2000 •  IAQ => Monte Carlo Simulation of steady state mass balance on PM2.5



Health Impacts of PM2.5

 Asthma  Lung cancer  Cardiovascular disease  Respiratory diseases  Premature delivery  Birth defects  Premature death



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)



Results: Annual Energy Use

-

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%



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.



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



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



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



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



Thank You



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