Transcript Approach for the Simulation of Wetting due to Rain

Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Investigating the role of the vapour
retarder in the drying response of
wood-frame walls wetted by
simulated rain infiltration
Anik Teasdale-St-Hilaire, B. Eng., Ph.D., Morrison Hershfield
Dominique Derome, arch., Ph. D., Concordia University
Paul Fazio, Ph. D., Concordia University
May 25, 2006
British Columbia Building Envelope Council
British Columbia Building Envelope Council
May 25, 2006
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Outline
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•
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Introduction
Overview of experimental study
Experimental facility
Experimental protocol
Experimental results
WUFI simulations – Montreal & Vancouver
Conclusion
Discussion
British Columbia Building Envelope Council
May 25, 2006
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Introduction
• Vapour barriers were introduced to reduce flux of
vapour diffusion, thus reducing interstitial
condensation
• Required by building codes, e.g. NBCC
• However, there are other sources of moisture:
– construction moisture
– air migration leading to condensation
– wind-driven rain infiltration
• Vapour barriers reduce ability of envelopes to dry
by inward diffusion
British Columbia Building Envelope Council
May 25, 2006
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Overview of experimental study
• Study to investigate role of vapour retarder in
drying response of wood-frame walls
• Experiment performed at Building Envelope
Performance Laboratory, Concordia U.
• 6 large-scale wood-frame walls
• Pre-wetted ‘bottom plate insert’ – initial M source
• Spring weather in Montreal
• Duration: 35 days
• Experimental variables: type of sheathing woodbased sheathing, and type of vapor retarder
British Columbia Building Envelope Council
May 25, 2006
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental Facility
Environmental
Chamber,
Building Envelope
Performance
Laboratory,
Concordia U.
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental protocol
Panels no. 1 to 6
Monitoring in each wall:
Instrumentation in the Framing
CL
7 thermocouples
1 RH sensor
6 MC gravimetric samples
access panel in gypsum
bottom plate insert
existing bottom plate
13
1,000
1 DP
Elevation - Interior View
sample Bp_CV
(introduced
British Columbia Building Envelope
Council
Elevation - Interior View
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental protocol - (cont’d)
inside
25
Sample CH2
Sample CH1
25
13
Sample CV
Sample CHU
70
outside
Bottom plate insert
British Columbia Building Envelope Council
May 25, 2006
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental protocol (con’td)
Outside
Inside
Polyethylene membrane, permeance: 3.4 ng/m2sPa
From outside to
inside:
• Sbpo membrane
 exterior sheathing
 38 mm x 140 mm
wood studs
 glass fiber
insulation
 13 mm gypsum
board
 primer (one coat)
and latex paint (2
coats)
Low permeance primer paint, permeance: 35 ng/m2sPa
Typical wall assembly – plan view
British Columbia Building Envelope Council
May 25, 2006
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental protocol (cont’d)
Wall no.
Sheathing
Vapor retarder
1
OSB
PE
2
Plywood
PE
3
Asphalt-coated fiberboard
PE
4
OSB
Low perm. primer
5
Plywood
Low perm. primer
6
Asphalt-coated fiberboard
Low perm. primer
British Columbia Building Envelope Council
May 25, 2006
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental protocol –
Wetting methodology
• based on results of 2 previous experiments
• simulated rainwater infiltration into back wall
leads to MC accumulation in bottom plate and
sheathing at bottom of wall
• partial immersion of six 38 x 140 x 360 mm3
bottom plate inserts in 13 mm deep pool of water
• lead to MC in inserts of 53.0 – 56.8% MC
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental protocol –
Climate loading
Period
simulated
Duration Exterior Exterior
[days]
T [oC]
RH [%]
Interior
T [oC]
Interior
RH [%]
Average
DPv [Pa]
April
28
1.6 to
10.9
64
21
40
30 to
400
May
7
8.6 to
18.7
63
21
43
-90 to
200
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
MC results of bottom plate insert
for OSB walls 1 & 4
60.0
Polyethylene wall 1
56.0
D = 3.0
53.0
55.0
Low perm. primer paint wall 4
50.0
Moisture content [%]
April
May
45.0
40.0
35.0
30.0
26.7
D = - 4.0
22.7
25.0
20.0
15.0
0
7
14
21
28
35
Time [d]
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Mass loss results of bottom plate insert
for OSB walls 1 & 4
Normalized cumulative mass loss in the bottom plate inserts of walls 1 and 4
400.00
April
May
350.00
Normalized mass loss [g]
300.00
250.00
200.00
150.00
100.00
Polyethylene wall 1
Low perm. Primer paint wall 4
50.00
0.00
0
7
14
21
28
35
Time [d]
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
MC results of bottom plate insert
for plywood walls 2 & 5
60.0
Polyethylene wall 2
54.9
53.1
55.0
D = 1.8
50.0
Low perm. primer paint wall 5
Moisture content [%]
April
May
45.0
40.0
35.0
30.0
25.0
21.9
21.4
D = 0.5
20.0
15.0
0
7
14
21
28
35
Time [d]
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
MC results of bottom plate insert
for fiberboard walls 3 & 6
60.0
D=3.2 56.8
53.6
Polyethylene wall 3
55.0
Low perm. primer paint wall 6
50.0
Moisture content [%]
April
May
45.0
40.0
35.0
30.0
25.0
20.7
D=3.2
17.5
20.0
15.0
0
7
14
21
Time [d]
British Columbia Building Envelope Council
28
35
May 25, 2006 15
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Mass loss results of bottom plate insert
for fiberboard walls 4 & 6
Normalized cumulative mass loss in the bottom plate inserts of walls 3 and 6
400.00
April
May
350.00
Normalized mass loss [g]
300.00
250.00
200.00
150.00
Polyethylene wall 3
Low perm. primer paint wall 6
100.00
50.00
0.00
0
7
14
21
28
35
Time [d]
British Columbia Building Envelope Council
May 25, 2006 16
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
MC results – explanation
• the results show that the role of the vapor
retarder depends on the type of sheathing
Water vapour permeance vs. relative humidity
1800
Water vapour permeance [ng/sm2Pa]
1600
1400
1200
OSB 12.7 mm
OSB 9.5 mm
OSB 11.1 mm
Plywood 19.1 mm
Plywood 12.7 mm
Plywood 15.9 mm
Asphalt-coated fiberboard 11.1 mm
1000
800
600
400
200
0
0
10
20
30
40
50
60
Relative humidity [%]
British Columbia Building Envelope Council
70
80
90
100
Derived from
Kumaran et al.
2002
May 25, 2006 17
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental results of sheathing samples
25.0
April
May
20.0
D 2.5%
Moisture content [%]
D=2.2
15.0
10.0
OSB-polyethylene wall 1
Plywood-polyethylene wall 2
Fiberboard-polyethylene wall 3
OSB-low perm. primer paint wall 4
5.0
Plywood-low perm. primer paint wall 5
Fiberboard-low perm. primer paint wall 6
0.0
0
7
14
21
28
35
Time [d]
British Columbia Building Envelope Council
May 25, 2006 18
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental results – Pv in stud cavity
above bottom plate – OSB walls
1800
April
May
1600
in
out
Vapour pressure [Pa]
1400
1200
1000
800
600
400
Pv,interior
Pv,exterior
200
Pv,OSB-polyethylene wall 1
Pv,OSB-low perm. primer paint wall 4
0
0
7
14
21
28
35
Time [d]
British Columbia Building Envelope Council
May 25, 2006 19
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental results – RH on surface of
OSB-sheathed walls
Relative humidity on inside surface of sheathing
100
Relative humidity [%]
90
80
70
Polyethylene wall 1
Low perm. primer paint wall 4
60
50
0
7
14
21
28
35
Time [d]
British Columbia Building Envelope Council
May 25, 2006 20
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental results – Pv in stud cavity
above bottom plate – fiberboard walls
1800
1600
1400
Vapor pressure [Pa]
1200
1000
800
600
Pv,interior
400
Pv,exterior
200
Pv,fiberboard-polyethylene wall 3
Pv,fiberboard-low perm. primer paint wall 6
0
0
5
10
15
20
25
30
35
40
Time [d]
British Columbia Building Envelope Council
May 25, 2006 21
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Experimental results – RH on surface of
fiberboard-sheathed walls
Relative humidity on inside surface of sheathing
100
Relative humidity [%]
90
80
70
Polyethylene wall 3
Low perm. primer paint wall 6
60
50
0
5
10
15
20
25
30
35
40
Time [d]
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
WUFI simulations – Montreal vs.
Vancouver
Typical wall assembly: residential construction
• non-hygroscopic cladding
• air space
• spun-bonded polyolefin
• plywood sheathing
• 150 mm (6”) fibreglass batt insulation
• polyethylene membrane, 6 mil
• gypsum board, primed and painted
British Columbia Building Envelope Council
May 25, 2006 23
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
WUFI simulations – Montreal vs.
Vancouver
30.00
25.00
Montreal, North, PE
Moisture content [%]
Vancouver, North, PE
20.00
15.00
10.00
5.00
0.00
Mar-00
Jun-00
Oct-00
Jan-01
Apr-01
Jul-01
Nov-01
Feb-02
May-02
Sep-02
Date
British Columbia Building Envelope Council
May 25, 2006 24
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
WUFI simulations – Montreal vs.
Vancouver
3500
Montreal
Vancouver
Vapour pressure, exterior [Pa]
3000
2500
2000
1500
1000
500
0
Mar-00
Jun-00
Oct-00
Jan-01
Apr-01
Jul-01
Nov-01
Feb-02
May-02
Sep-02
Time
British Columbia Building Envelope Council
May 25, 2006 25
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
WUFI simulations – Montreal vs.
Vancouver
Exterior plywood
surface
Interior plywood
surface
100
90
80
70
RH [%]
60
50
40
30
20
10
0
Mar-00
Jun-00
Montreal - RH ext plywood
Montreal - RH int plywood
Vancouver- RH ext plywood
Vancouver - RH int plywood
Oct-00
Jan-01
Apr-01
Jul-01
Nov-01
Feb-02
May-02
Sep-02
Time
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Vancouver – vapour retarder vs. no
vapour retarder
30
25
Vancouver, North, PE
Moisture content [%]
Vancouver, North, no VR
20
15
10
5
0
Mar-00
Jun-00
Oct-00
Jan-01
Apr-01
Jul-01
Nov-01
Feb-02
May-02
Sep-02
Date
British Columbia Building Envelope Council
May 25, 2006 27
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Vancouver – vapour retarder vs. no
vapour retarder
30
25
Vancouver, North, PE
Moisture content [%]
Vancouver, North, no VR
20
15
10
5
0
Mar-00
Jun-00
Oct-00
Jan-01
Apr-01
Jul-01
Nov-01
Feb-02
May-02
Sep-02
Date
British Columbia Building Envelope Council
May 25, 2006 28
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Conclusion
•
•
Experiment performed to test role of vapour
retarder in hygrothermal response of wood-frame
wall
Source of moisture was a pre-wetted bottom
plate insert that was used to simulate the effects
of wind-driven rain infiltration
British Columbia Building Envelope Council
May 25, 2006 29
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Conclusion
•
Influence of vapour retarder permeance on
moisture behaviour:
–
–
–
for OSB-sheathed walls: significant influence =>
compare avg. drying rate of
0.96 %MC/day (wall with PE)
vs.
0.75%MC/day (wall with low perm. primer)
for in plywood-sheathed walls: insignificant
influence, as shown by MC results in insert and
sheathing, and in pv cavity measurements
for fiberboard-sheathed walls: influence very
slightly significant
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May 25, 2006 30
Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Conclusion
•
•
•
Surface water absorption of sheathing had an
impact on the performance: lower absorption
increased stud cavity RH
All walls showed steady drying patterns where if
the test had been prolonged, the bottom plate
inserts would have reached acceptable MC, i.e.
< 20% MC, reducing risks of damage
WUFI simulations for Vancouver show use of
vapour retarder does decrease winter “wetting”
by diffusion (as expected)
British Columbia Building Envelope Council
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Investigating the role of the vapour retarder in the drying response of
wood-frame walls wetted by simulated rain infiltration
Discussion …
British Columbia Building Envelope Council
May 25, 2006