This document summarizes a study of the performance of a corridor pressurization ventilation system in a 13-story residential building in Vancouver. Measurements found significant variations in ventilation rates between suites, with most under or over-ventilated. The study found that only 8% of intended ventilation air actually reaches the suites, with significant leakage along the ventilation path. Stack effects and wind pressures were also found to influence ventilation rates and overwhelm the mechanical pressures at times. The document recommends direct ventilation of suites and improved compartmentalization of spaces to limit natural pressures and better control ventilation.

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Corridor Pressurization System Performance in Multi-UnitResidential Buildings
ASHRAE ANNUAL CONFERENCE 2014
JULY 2, 2014
PRESENTED BY LORNE RICKETTS, MASC, EIT

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Learning Objectives & ASHRAE Disclaimer
Learning Objectives:
Explain how faults in residential HVAC systems can cause excess energy consumption in homes
Describe how energy consumption data can be used to detect faults in residential HVAC systems
Define the need for occupancy education related to hybrid home operation and need for commissioning and advanced control strategies
Explain the complex interaction between active and passive HVAC systems for a net zero energy home
Describe the importance of carbon emission reduction in built environment and Singapore’s Green Mark approach in assessing energy efficiency of air-conditioning systems
Familiarise themselves with the approach surrounding successful implementation of low-cost measures as part of retro- commissioning process
Understand typical ventilation practices for high-rise multi-unit residential buildings including corridor pressurization systems
Understand performance issues with corridor pressurization based ventilation systems
ASHRAE is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to ASHRAE Records for AIA members. Certificates of Completion for non-AIA members are available on request. This program is registered with the AIA/ASHRAE for continuing professional education. As such, it does not include content thatmay be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services willbe addressed at the conclusion of this presentation.

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Outline
Introduction & Background
Testing and Measurement Program
Measured Ventilation Rates (PFT testing)
Cause of Ventilation Rates
Extension of Study Findings
Conclusions & Recommendations

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Introduction & Background
Most apartments/condos (multi-unit residential buildings) are ventilated using pressurized corridor systems
Decades of research and experience indicates that this system likely does not work very well
Still most common system
Few physical measurements
Particularly relevant now, as newer more airtight building have less tolerance for poorly performing ventilation systems
Less infiltration and exfiltration to supplement ventilation

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Pressurized Corridor Ventilation System
DESIGN INTENT
Provide ventilation air to all zones
Control flow of air contaminates between zones
HOW
Provides air to corridors directly via a vertical shaft whichpressurizes the corridor
Corridor pressurization forces air into suites via intentional gapsunder the entrance doors
Introduction & Background

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Case Study Building
13-storey multi-unit residential building in Vancouver, Canada with 37 residential suites
Constructed 1986
Enclosure renewal 2012
Below grade parking garage located under the building
Ventilated using pressurized corridor system by a single make-up air unit (MAU) on the roof
Overall, is typicalof high-rise multi-unit residential buildings
Introduction & Background

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Perfluorocarbon(PFT) Testing
Two component system:
PFT Sources (7 distinct types)
Capillary absorption tube samplers(CATS)
Sources release distinct PFT tracer gasses in different zonesand use CATS to sample the concentrations
Measured Ventilation Rates
Sources
CATS

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Order of magnitude variation in the ventilation rates
Significantly higher rates for upper suites than lower suites
Most suites under-ventilated or over-ventilated
Measured Ventilation Rates
ASHRAE 62.1-2010≈ 40 L/s per suite
Waste of Energy
Indoor Air Quality Issues

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Measured Ventilation Rates
PMCP Released in MAU

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Carbon dioxide concentration were monitored as an indicator of indoor air quality (IAQ)
Significantly higher concentration in the lower suites
Measured Ventilation Rates

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Summary:
Over ventilation and under ventilation of most suites
Higher ventilation rates in upper suites than lower suites
Better indoor air quality in upper suites than lower suites
Why is this happening?
Measured Ventilation Rates

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Maybe the MAU isn’t working correctly?
Custom powered flow hood used to measure intake flow rate of the make-up air unit
MAU airflow approximately the sameas design flow rate of 1,560 L/s (3,300 cfm)
Cause of Ventilation Rates

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Maybe the ventilation air isn’t reaching the corridors?
 Only 40% of intake flow reaches the corridors directly
Cause of Ventilation Rates
0
2
4
6
8
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0 25 50 75 100 125 150
Floor Number
Flow Rate [L/s]
MAU Supply to Corridors
Pre-Retrofit (21°C) Post-Retrofit (6°C) Post-Retrofit (16°C)
Pre-Retrofit (21°C) Total = 593 L/s
Post-Retrofit (6°C) Total = 559 L/s
Post-Retrofit (16°C) Total = 580 L/s
Fire Damper noted to be
closed on Floors 4, 8, & 12.
1 L/s ≈ 2 cfm

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Maybe the air isn’t reaching the suites from the corridors?
Airtightness tested corridors and found significant flow paths other than to the suites through the suite entrance doors. Only 20% to the suites
Cause of Ventilation Rates
1 L/s ≈ 2 cfm

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Theoretically, only 8%of intended ventilation actually goes where it is supposed to! Waste of ventilation air, and the energy needed to move and condition it.
Cause of Ventilation Rates
If only 40% of the flow rate reaches the corridorsAnd, only 20% of that air reaches the suites…
Leakage of air along ventilation flow path is a major issue.
ퟒퟎ%×ퟐퟎ%=ퟖ%

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Pressure differences were monitored with a focus on an upper floor and a lower floor (Floors 11 & 3)
Assessed relationship between exterior temperature (stack effect) and wind events using a weather station on the roof
Maybe pressure differencesare an important factor?
Cause of Ventilation Rates

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 Mechanical ventilation system creates pressure of 5 to 10 Pa
Cause of Ventilation Rates
-20
-15
-10
-5
0
5
10
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Feb 8 6:00 Feb 8 8:00 Feb 8 10:00 Feb 8 12:00 Feb 8 14:00 Feb 8 16:00 Feb 8 18:00
Pressure Difference [Pa]
Average Corridor to Suite Pressure by Floor when MAU Off
Floor 02 Floor 03 Floor 04 Floor 10 Floor 11 Floor 12
Measurement with MAU Off
Measurement with MAU Recently Turned On
Corridor-to-Suite Pressure Difference [Pa]

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 Pressures created by stack effect found to be of similar
magnitude (10 to 15 Pa) as mechanical pressures
Cause of Ventilation Rates
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0
5
10
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Exterior Temperature [°C]
Pressure Difference [Pa]
Average Suite to Corridor Pressures by Floor and Exterior
Temperature - 24 Hour Moving Average
Floor 02 Floor 03 Floor 04
Floor 10 Floor 11 Floor 12
Temp - WS' [°C]
Corridor-to-Suite Pressure Difference [Pa]

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Stack effect pressures found to distribute 69% across the corridor to suite boundary and 9% across exterior enclosure
Stack effect pressure acts primarily in the same location as mechanical pressures intended to provide ventilation and control contaminate flow
Cause of Ventilation Rates

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Vancouver is a relatively moderate climate
Should considerother climates
Case study building is13 storeys
Should consider different building heights
Extension of Study Findings

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Extension of Study Findings
Stack effect is more significant in taller buildings
Proportion of wind pressures remains relatively the same
Relative magnitude of mechanical pressures decreases as height increases
0% 10% 20% 30% 40% 50% 60% 70% Stack EffectWindMechanical(10 Pa) Percentage of Driving Force Pressure Average Proportions of Driving Force Pressure Differences -Vancouver20 m40 m60 m80 m100 mBuildingHeight

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Extension of Study Findings
Stack effect more significant in cold climates
Wind highly variable, but typically more significant in warm climates
0% 10% 20% 30% 40% 50% 60% 70% Stack EffectWindMechanical(10 Pa) Percentage of Driving Force Pressure Average Proportions of Driving Force Pressure Differnces -40m Tall BuildingMiamiHoustonLos AngelesNew YorkVancouverTorontoCalgaryFairbanks

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Comparison of Driving Forces
Since all of the pressure differences created by the driving forces (stack effect, wind, & mechanical systems) are of similar magnitude, it is possible that any one could dominate
This is exaggerated for buildings in more extreme climates than Vancouver
Ventilation system can not practically overwhelm nature.

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Conclusion
Corridor pressurization does not provide intended ventilation ratesto a large number of suites
Some significantly over ventilated while others significantly under ventilated
Significant leakage along the ventilation air flow path from the duct and the corridor (wasted ventilation)
Uncontrolled airflow wastes energy and provides poor ventilation
Stack effect and wind pressures are often similar or greater than mechanically-induced pressures
Ventilation system can not practically overwhelm nature

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Recommendations for Ventilation System Design
Ventilation air should be directly supplied to suites to limit the potential of loss along the flow path and of the system being overwhelmed by stack effect and wind
The exterior enclosure should be airtight, and suites and vertical shafts should be compartmentalized(airtight) to limit the impact of wind and stack effect on ventilation

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References
Ricketts, L. A Field Study of Airflow in a High-Rise Multi-Unit Residential Building. MAScThesis, Department of Civil Engineering, University of Waterloo, Waterloo, 2014.

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rdh.com
Discussion + Questions
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