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Corridor Pressurization System
Performance in Multi-Unit
Residential 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 that may 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 will be 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 which pressurizes the
corridor
Corridor pressurization forces air into
suites via intentional gaps under 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 typical of 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 zones and 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 same as 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
10
12
14
0 25 50 75 100 125 150
Flo
or
Nu
mb
er
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 corridors
And, only 20% of that air reaches the suites…
Leakage of air along ventilation flow path is a major issue.
𝟒𝟎%× 𝟐𝟎% = 𝟖%
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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 differences
are 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
15
20
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
Pre
ssu
re D
iffe
ren
ce [
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 OffMeasurement with MAU Recently Turned On
Co
rrid
or-
to-S
uit
e P
ress
ure
Dif
fere
nce
[P
a]
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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
15
20
25
-10
-5
0
5
10
15
20
Exte
rio
r Te
mp
era
ture
[°C
]
Pre
ssu
re D
iffe
ren
ce [
Pa]
Average Suite to Corridor Pressures by Floor and ExteriorTemperature - 24 Hour Moving Average
Floor 02 Floor 03 Floor 04
Floor 10 Floor 11 Floor 12
Temp - WS' [°C]
Co
rrid
or-
to-S
uit
e P
ress
ure
Dif
fere
nce
[P
a]
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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 consider
other climates
Case study building is
13 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 Effect Wind Mechanical(10 Pa)
Pe
rce
nta
ge o
f D
rivi
ng
Forc
e P
ress
ure
Average Proportions of Driving Force Pressure Differences - Vancouver
20 m
40 m
60 m
80 m
100 m
BuildingHeight
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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 Effect Wind Mechanical(10 Pa)
Pe
rce
nta
ge o
f D
rivi
ng
Forc
e P
ress
ure
Average Proportions of Driving Force Pressure Differnces - 40m Tall Building
Miami
Houston
Los Angeles
New York
Vancouver
Toronto
Calgary
Fairbanks
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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
rates to 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. MASc Thesis, Department of Civil Engineering, University of
Waterloo, Waterloo, 2014.
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rdh.com
Discussion + Questions
FOR FURTHER INFORMATION PLEASE VISIT