corridor pressurization system performance in murbs

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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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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


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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


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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


ASHRAE 62.1-2010≈ 40 L/s per suite

Waste of Energy

Indoor Air Quality Issues

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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


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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?


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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)


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Maybe the ventilation air isn’t reaching the corridors?

Only 40% of intake flow reaches the corridors directly


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


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.


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?


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Mechanical ventilation system creates pressure of 5 to 10 Pa


-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


-5

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


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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


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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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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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Discussion + Questions

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