Air Intrusion and Its Impact on Moisture Transport in ...

Air Intrusion and Its Impact on Moisture

Transport in Mechanically Attached Roofing

Systems

Institute For Research in Construction

Authors: Suda Molleti, Bas Baskaran, Peter Kalinger

and Pascal Beaulieu

Presenter: Peter Kalinger

International Symposium 2011

Institute for Research in Construction

Outline

Overview of Air Intrusion

Quantification of Air Intrusion – Experimental

Testing

Impact of Air Intrusion on Moisture Transport –

Experimental Testing

Conclusions


SCIENCE BEHIND AIR MOVEMENT

Pre

ssu

re D

iffe

ren

ce

Wind

HVAC

Temperature Flow Path


When air enters or leaves from one environmental

condition to the other environmental condition through the building

envelope assembly, it is termed as “Air Leakage”.

AIR LEAKAGE


When conditioned indoor air enters into a building envelope

assembly but cannot escape to the exterior environment, it is

termed as “Air Intrusion”.

AIR INTRUSION


AIR LEAKAGE VS. AIR INTRUSION

RCI INTERFACE – NOVEMBER 2010 PROFESSIONAL ROOFING– JANUARY 2010


WIND UPLIFT ACTION OF MECHANICALLY

ATTACHED ROOFING SYSTEM

WIND SPEEDS > 50 mph

MEASURED PRESSURES > 30 psf

RIALTO, CALIFORNIA


AIR INTRUSION IMPACT ON WIND UPLIFT

RESISTANCE


AIR INTRUSION IMPACT ON MOISTURE

TRANSPORT


AIR INTRUSION IMPACT ON MOISTURE

TRANSPORT

What is the relation between air intrusion and moisture transport

and what are the limits for potential condensation ?


AIR INTRUSION RESEARCH

NRC/IRC


DYNAMIC ROOFING FACILITY AIR INTRUSION TEST FACILITY (DRF-AI)


BOTTOM CHAMBER

8 ft

20 ft


DECK INSTALLATION

36” 36” 24”

Deck Overlap

Edge Seal Along Width

Deck edges on L-channel

Edge Seal Along Length

L- lock Seam


Additional

tests to fill

the data

NRCA/CRCA

SIGDERS DEVELOPED CONTROL

DATA FOR AIR INTRUSION

0.79

2.05

2.59

2.87

0.36 0.38 0.34

0

0.5

1

1.5

2

2.5

3

3.5 M

B-3

ft-N

oA

B

TP

-6ft

-No

AB

TP

-10

ft-

No

AB

TS

-10ft

-No

AB

MB

-3ft

-Wit

h S

AF

TP

-6ft

-Wit

h S

AF

TS

-10ft

-Wit

h S

AF

Rep

ort

ing

air

in

tru

sio

n v

olu

me

at

25

psf

(ft

3/l

ine

ar

ft)

WITHOUT AIR RETARDER WITH AIR RETARDER


CRCA-NRCA RESEARCH PROJECT

MEMBERS

Task 1 – System Evaluation: Quantify air

intrusion of the common roofing assembly

configurations

Task 2 –Develop a relation between air

intrusion and risk for moisture

condensation

RESEARCH TASKS

August 2009 - August 2012 Project Duration :


TASK 1:

AIR INTRUSION QUANTIFICATION


EXPERIMENTAL LAYOUT

Deck : 22 Ga -80 ksi

Membrane

EPDM

4 ft x 4 ft x 2 in. ISO

3.HD Cover Board

1.Kraft Paper

3 SYSTEMS TESTED

PVC

2.Polyethylene


AIR RETARDER INSTALLATION

S1: KRAFT PAPER

3 ft

6 in


AIR RETARDER INSTALLATION

S2: POLYETHYLENE

Tacky Tape


Mechanical

fastened

5/board = 50 fasteners

INSULATION INSTALLATION : S1 AND S2

10 boards

of

48 x 48 x 2 in

ISO

seals

along

the

width

ISO

seals

along

the

length


S3 : HD COVER BOARD(NO AIR RETARDER ON DECK)

HD: = 4 FT X 8 FT X 0.5 IN

FD: = 8 PER BOARD

INSULATION INSTALLATION

2 FT

4 FT

4 FT

4 FT

4 FT 2 FT


MEMBRANE LAYOUT

S1, S3: TS: FR = 114 IN FS = 12 IN.

S2: TP: FR = 66 IN FS = 12 IN.


DRF-AI : INSTRUMENTATION


TEST PROCEDURE : ASTM D7586 / D7586M – 11


REPORTING AIR INTRUSION VOLUME AS PER THE ASTM D7586-11

0.79

2.05

2.59

2.87 2.81

0.36 0.38

0.65

0.34

1.03

0

0.5

1

1.5

2

2.5

3

3.5

MB

-3ft-N

oA

TP

-6ft-N

oA

B

TP

-10ft- N

oA

B

TS

-10ft-N

oA

B

TS

-10ft-W

ith C

B (S

3)

MB

-3ft-W

ith S

AF

TP

-6ft-W

ith S

AF

TP

-6ft-W

ith P

oly

(S2

)

TS

-10ft-W

ith S

AF

TS

-10ft-W

ith K

P (S

1)

Rep

ort

ing

air

in

tru

sio

n v

olu

me

at

25

psf

(ft

3/l

ine

ar

ft)

WITHOUT AIR BARRIER WITH AIR BARRIER


TASK2:

AIR INTRUSION - MOISTURE TRANSPORT

EXPERIMENTAL STUDY WITH DYNAMIC PRESSURES

AND DIFFERENT RELATIVE HUMIDITY


TEST SPECIMENS AND CONDITIONS

THERMOSET SYSTEM WITHOUT AIR RETARDER

S1: No Suction Pressure

(Vapor Drive) S2: With Suction Pressure

S3: No Suction Pressure

(Vapor Drive) S4: With Suction Pressure

Relative Humidity

25%

35%

50%

65%

THERMOSET SYSTEM WITH AIR RETARDER

Outdoor Target

Temperature:

-50C (230F)

Indoor Target

Temperature:

220C (720F)


SUCTION PRESSURE

CSA A123.21 –DYNAMIC LOADING CYCLE

LEVEL 2200

CYCLES

Target Pressure: 60 psf

15 psf: 800 cycles

30 psf: 1100 cycles

45 psf: 225 cycles

60 psf: 75 cycles


TYPICAL TEST SPECIMEN CONSTRUCTION

Temperature

And RH

sensors


EXPERIMENTAL APPARATUS

Temp: 22°C

Humidity:

25 – 65 %

Temperature:-5°C

4ft x 4 ft


TEST PROCEDURE Insulation boards pre weighed and the specimen constructed

Test chamber set to a target temperature of -50 C (230F)

Temperature and relative humidity set to 220C (720F) and 25% in the humidity

chamber.

After temperature and relative humidity stabilization, specimen subjected to

CSA A123.21-10 dynamic pressures for a duration of 5 hrs

Test stopped for visual inspections of condensation and insulation boards

weighed to measure the moisture content

Insulation boards put back and specimen reconstructed for testing at next

humidity level

With above outdoor and indoor temperatures, each specimen is subjected to

four different humidity levels of 25%, 35%, 50% and 65% and with dynamic

pressure application at each humidity level

Each specimen subjected to four days of testing (One humidity condition /day)


25% 35 %

S1:NO AIR RETARDER - NO SUCTION PRESSURE VAPOR DRIVE


50% 65 %

S1:NO AIR RETARDER- NO SUCTION PRESSURE VAPOR DRIVE


35%

RH

S2:NO AIR RETARDER-WITH SUCTION PRESSURE


50%

RH



65%

RH



50% 65 %

S3:WITH AIR BARRIER-NO SUCTION PRESSURE

VAPOR DRIVE


65%

RH

50%

RH

S4:WITH AIR RETARDER-WITH SUCTION PRESSURE


BREACH IN

THE AIR

RETARDER

DURING

INSTALLTION




RETESTED

65%

RH

50%

RH


MOISTURE GAIN : COMPARISON

0

10

20

30

40

50

60

70

80

90

100

S1 S3 S2 S4

Mo

sit

ure

ga

in,

gm

Test Specimens

Board 1 Board 2 Board 3 Board 4

NO AB-NO SP AB- NO SP NO AB- SP AB- SP

0

1

2

3

4

5

6

7

8

9

10

S1 S3 S2 S4 Mo

sit

ure

Co

nte

nt

( %

of

DW

)

Test Specimens

Board 1 Board 2 Board 3 Board 4

Vapor Drive

Vapor Drive


AIR INTRUSION LIMIT FOR POTENTIAL

CONDENSATION

0.79

2.05

2.59

2.87 2.81

0.36 0.38

0.65

0.34

1.03

0

0.5

1

1.5

2

2.5

3

3.5

MB

-3ft-N

oA

TP

-6ft-N

oA

B

TP

-10ft- N

oA

B

TS

-10ft-N

oA

B

TS

-10ft-W

ith C

B (S

3)

MB

-3ft-W

ith S

AF

TP

-6ft-W

ith S

AF

TP

-6ft-W

ith P

oly

(S2

)

TS

-10ft-W

ith S

AF

TS

-10ft-W

ith K

P (S

1)

Re

po

rtin

g a

ir in

tru

sio

n v

olu

me

at

25

ps

f (

ft3/l

ine

ar

ft)

Outdoor T : -50 C

Indoor T: 220 C

Indoor Humidity: 65%

WITHOUT AIR RETARDER WITH AIR RETARDER


In collaboration with CRCA, NRCA and four major roofing manufacturers,

a research project focussing on air intrusion quantification and its impact

on the moisture transport was started.

The kraft paper and polyethylene sheet did minimize the air intrusion into

however both underperformed compared to the self adhered film as air

retarders.

Installing HD cover boards on top of the insulation provided no resistance

to air intrusion as the cover boards do not seal the primary flow paths of

the steel deck.

The risk for potential condensation and increased moisture gain within the

system from air intrusion is considerably higher than the potential moisture

gain due to vapour transmission.

CONCLUSIONS


CONCLUSIONS

Air retarder at the deck level can minimize the moisture gain in the roof systems

both due to vapor transmission and air intrusion. However, trapped air due to air

intrusion between the air retarder and air barrier (membrane) within the roof

system can cause condensation.

At an outside temperature of -50 C (230F) and indoor conditions of 230C (720F)

with 65% relative humidity, an air intrusion volume of 0.63 ft3/ linear ft (17 L /

linear m) could be said to be the critical volume for potential condensation in

mechanically attached roofing systems.

Further study is needed to investigate and develop the limits for potential

condensation at different outdoor and indoor conditions, and at different humidity

levels.

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