Kohta Ueno

Retrofit Ventilation Strategies in Multifamily Buildings Building America Residential Energy Efficiency Technical Update Meeting August 9-11, 2011 - Denver, Colorado

Background

Stack effect in buildings

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Stack Effect (Cold Climate)

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Background

Stack effect in buildings Use of common multistory shafts (exhaust typical)

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Stack Effect and Shafts

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Compartmentalization

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Background Stack effect in buildings Use of common multistory shafts (exhaust typical) SWA/Zuluaga/Fitzgerald work Retrofit sealing of exhaust shafts Constant airflow regulators (CARs)

24/7 runtime control strategy-modify? Reduce?

Innova Services Corporation (Philadelphia, PA) Retrofit of existing buildings Limitations on measures to be implemented

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V Buildings

Existing Building (c. 1983 Construction)

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“Before” Field Measurements (June)

Ventilation exhaust shaft leakage (CFM 50) Ventilation exhaust register flows

(kitchens and bathrooms, CFM) Ventilation exhaust at roof unit (CFM) Ventilation exhaust current draw (volt-amps) Air leakage of units (CFM 50) Not guarded/nulled tests—combined leakage to interior

& exterior Interstitial pressure measurements for localizing air

leakage locations

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Exhaust Shaft Layout

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Kitchen

Bath

Kitchen

10

V Buildings

Exhaust Shaft Leakage

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Exhaust Shaft Leakage Description Metric

Good 5 CFM 50/floor 10 CFM 50/floorTypical

Bad 15+ CFM 50/floor Zuluaga and Fitzgerald 2010

Kitchen shaft: 58 CFM 50/floor pre sealing boot Kitchen shaft: 31 CFM 50/floor post sealing boot Bathroom shaft: 44 CFM 50/floor pre sealing boot Bathroom shaft: 26 CFM 50/floor pre sealing boot Depressurization vs. pressurization

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V Buildings

Exhaust Shaft Curb Bypass Leakage

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Exhaust Shaft Curb Bypass Leakage

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V Buildings

Exhaust Airflows (Unit and Rooftop)

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Results: Unit Exhaust Airflows

Plan Callout Airflow (per unit)

ASHRAE 62.2 Rate (per unit)

Average ~80% of callout

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Results: Unit Exhaust Airflows

Plan Callout Airflow (per unit)

ASHRAE 62.2 Rate (per unit)

Average ~68% of callout

Fan Belt Issues

Loose fan belt at Exhaust Fan Shaft 2 From 250 CFM → 540 CFM after tightening

Individual unit exhausts not re-measured

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Exhaust Airflows (Unit and Rooftop)

Comparison of summed flow hood and rooftop measurements Fan efficiency Kitchen shaft ~25% “actual” leakage

1.3 CFM/W (480 CFM) 1.4 CFM/W (540 CFM) 2.1 CFM/W (720 CFM)

Bath shaft ~15% “actual” leakage

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Unit Air Leakage

Unit CFM 50 Floor Area ACH 50

CFM 50/sf enclosure ELA (sq. in.) ELA/100 sf

108 939 597 10.5 0.45 51.6 2.46 121 1104 883 8.3 0.39 60.7 2.14 202 1094 861 8.5 0.39 60.2 2.16 208 885 597 9.9 0.42 48.7 2.31 304 1216 871 9.3 0.43 66.9 2.38 307 1246 855 9.7 0.45 68.5 2.48

Only unguarded tests performed; relief to roof No correlation of corner vs. middle, etc. 7 ACH 50 LEED mid rise prerequisite 4 ACH 50 LEED mid rise ETS points

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V Buildings

Unit Air Leakage

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Proposed Retrofit Design Corridor ventilation @ 0.06

CFM/sf (ASHRAE 62.1) Replace exhaust grilles

with low-sone exhaust fans to common shafts Fans on switch + timer

control (SmartExhaust) Passive central shaft? Variable speed fan on shaft

+ constant pressure control (direct drive unit)

Ventilation Strategies in Multifamily Buildings

Further Work

Small exhaust fans vs. zone register terminals (motorized dampers on switches) + CARs? (cost effectiveness; reliability) CAR problems with very leaky exhaust shafts If exhaust fans: negative pressure “pop” level Airtightness of units: compartmentalization and

exhaust draw from adjacent Airflow modeling (CONTAM) Testing of implemented system (“after”)

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Questions? Kohta Ueno kohta@buildingscience.com

This presentation is based research covered in BSC TO2 7.6 Multifamily Ventilation

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Exhaust Component Cleaning

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Notes

~$1 - $2 per CFM of Ventilation Load Reduction for NYC climate (Zuluaga & Fitzgerald 2010)

Philadelphia design T 11°F (99.6%) Associated stack for 30 feet: 14 Pa Associated stack for 40 feet: 18 Pa

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ZRT (Zone Register Terminal)

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V

CAR (Constant Airflow Regulator)

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