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Understanding the Severity of Climate Loads as related to
Cladding and Windows
Presented by
Michael A. Lacasse (NRC-IRC)
and
Silvio Plescia (CMHC)
IntroductionIntroduction
�Goals
– Understand some climatic phenomena
– Introduce some basic elements
– Reviewing response of cladding to WDR loads
The ElementsThe Elements
, WV, P, WV, PTTυυυυ
+ ive p – ive p
Wind and Rain ���� WDR
on the wall ���� water
penetration
Wind ����
∆∆∆∆p across wall ����
air leakage
The ElementsThe Elements
, WV, WVTT, WV, WVTT
∆∆∆∆T and ∆∆∆∆pw
across wall
Heat andwater vapour transfer
Climate Parameters – Cladding / windowsClimate Parameters – Cladding / windows
• Two climate parameters considered
• Wind velocity
• Rain intensity
• Combined to derive façade related parameters
• Driving Rain Wind Pressure (DWRP)
• Wind Driven Rain (WDR)
WindWind
v =x v =x v =x
Small Medium Large
Wind flow around obstructions
Section
Win
dw
ard
Le
ew
ard
Angle <°40
Pressure distributions
Raindrop trajectories
WindWind
Wind Velocity PressureWind Velocity Pressure
Pa = 0.61 ���� (wind speed, m/sec)2 1 m/sec = 3.6 Km/h 1 mi. = 1.609 Km
Km/h m/sec mph
Wind Velocity
Pressure Pa
0 0 0 0
5 1 3 1
10 3 6 5
20 6 12 19
40 11 25 75
50 14 31 118
57 16 35 150
60 17 37 169
65 18 41 200
70 19 44 231
80 22 50 300
90 25 56 381
100 28 62 471
103 29 64 500
122 34 76 700
150 42 93 1059
200 56 124 1883
300 83 186 4236
Wind Speed
Driving Rain Wind Pressure - 1 hr avg.Driving Rain Wind Pressure - 1 hr avg.
Code Location
1 Calgary AB
2 Charlottetown PEI
3 Edmonton AB
4 Fredericton NB
5 Halifax NS
6 Montreal QC
7 Ottawa ON
8 Quebec QC
9 Saskatoon SK
10 St John's NF
11 Toronto ON
12 Vancouver BC
13 Whitehorse YK
14 Winnipeg MB
15 Yellowknife NT
16 Sandspit BC
17 Victoria BC
18 Victoria Gonz Hts BC
19 Regina SK
20 Iqaluit NU
21 Sept Iles QC
22 Shearwater NS
23 Port Aux Basques NF
Driving Rain Wind Pressure - 5 min avg.Driving Rain Wind Pressure - 5 min avg.
Code Location
1 Calgary AB
2 Charlottetown PEI
3 Edmonton AB
4 Fredericton NB
5 Halifax NS
6 Montreal QC
7 Ottawa ON
8 Quebec QC
9 Saskatoon SK
10 St John's NF
11 Toronto ON
12 Vancouver BC
13 Whitehorse YK
14 Winnipeg MB
15 Yellowknife NT
16 Sandspit BC
17 Victoria BC
18 Victoria Gonz Hts BC
19 Regina SK
20 Iqaluit NU
21 Sept Iles QC
22 Shearwater NS
23 Port Aux Basques NF
Wind and RainWind and Rain
Wind Speed = UTe
rmin
al V
elo
cit
y
of
rain
dro
p =
Vt
rh = rv U/Vt
Wind and RainWind and Rain
Wind-driven rain: 5 min. averageWind-driven rain: 5 min. average
Calgary - Climate Normals (Averages) 0ver 30 years
(1971- 2000)
0
20
40
60
80
100
120
140
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Mo
nth
ly R
ain
fall
/ e
xtr
em
e d
ail
y r
ain
fall
(m
m)
Calgary - Rainfall (mm)
Extreme Daily Rainfall (mm)
Monthly & extreme daily rainfall – CalgaryMonthly & extreme daily rainfall – Calgary
Red Deer - Climate Normals (Averages) 0ver 30 years
(1971- 2000)
0
20
40
60
80
100
120
140
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Mo
nth
ly r
ain
fall
/ e
xtr
em
e d
ail
y r
ain
fall
(m
m)
Red Deer - Rainfall (mm)
Extreme Daily Rainfall (mm)
Monthly & extreme daily rainfall – Red DeerMonthly & extreme daily rainfall – Red Deer
Daily rainfall - June 2005 – CalgaryDaily rainfall - June 2005 – CalgaryDaily Calgary Rainfall - June 2005
34.5
10.4
43.2
7.6
16
23.4
8.2
18.614.8
5.6
36.6
18
10.2
04
1 1.6 2.20 0 0 0
25.6
0 0 0 0 1.2 0 0.2 0 1.2
27.4
0 0
95.3
46.2
79.2
17.3
7.1
80.8
37.1
7.6
13
75.9
25.9
92.6
05
10152025
30354045
505560
65707580
859095
100
105110115120
125130
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Rain
fall
(m
m)
1927-Jul 2005-Jun 1932-Jun 1945-Aug 1954-Aug 1985-Sep
Extreme daily and Maximum July daily -
Maximum September daily - 1985
Maximum June daily - 1932
Maximum August daily - 1945
Maximum daily / June 2005
Calgary, AB Rainfall (mm )
Year / Month Maximum
Daily Monthly
Total Monthly Normal
2005 / June 46.2 247.6* 79.8 1985 / Sept. 92.6** 109.8 41.7 1954 / August 75.9 238.3 58.7 1945 / August 80.8** 99.8 58.7 1932 / June 79.2** 119.9 79.8 1927 / July 95.3*
, ** 245.5 67.9
*Extreme value; ** extreme daily value for month
Red Deer - June 2005 - Daily rainfall (mm)
57
3
15.2
0.2 0
8.4
0.2 0 1 0 0
5.4
0 1 0
20.8
0.2 0 0
6.8
20
12.6
1.4 0 0 0
12.6
0
42.7
28.6
62.4
47.8
75.2
99.6
85.3
34
10.4
124.2
29.227.6
51.4
52
18.5
05
101520253035404550556065707580859095
100105110115120125130
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Ra
infa
ll (
mm
)
2005-July 1999-July 1970-June 1949-July 1938 - August
Extreme daily and Maximum August daily - 1938
Maximum June daily - 1970
Maximum July daily - 1949
Max. daily @ Extreme monthy - 1999
Maximum daily - June 2005
Daily rainfall - June 2005 – Red DeerDaily rainfall - June 2005 – Red Deer
Red Deer, AB Rainfall (mm)
Year / Month Maximum
daily Monthly Totals
Monthly Normal
2005 / June 42.7 145.5 92 1999 / July 62.4 274.4* 93.1 1970 / June 99.6** 243.8*
2nd 92
1949 / July 85.3** 154.9 93.1 1938 / August 124.2*
, ** 182.4 70
*Extreme value; ** extreme daily value for month
Calgary – total annual rainfall / 2005 to 2008Calgary – total annual rainfall / 2005 to 2008
Climate LoadClimate Load
MEWS: wet-wet-avg
1978-1978-1992
Calgary
Climate Load (cont.)Climate Load (cont.)
MEWS: wet-wet-avg
1965-1965-1968
Edmonton
Cladding responseCladding responseStucco Stucco
1st 4 months (frame every 4 hours)
Cladding responseCladding response
3 years (frame every 24 hours)
Stucco Stucco
• Moisture management system• Concealed stucco with local
drainage• Stucco finish:
• 19 mm lime-cement plaster• Self-furring metal lath:
• woven wire• Sheathing membrane:
• 60 min building paper• Sheathing board:
• 11 mm OSB
MEWS* MEWS* –– water penetration tests on stucco wallswater penetration tests on stucco walls
*MEWS – Consortium for Moisture Management for Exterior Wall Systems – http://www.nrc-cnrc.gc.ca/eng/projects/irc/exterior-walls.html
Water penetration - Stucco ⇒⇒⇒⇒ “Static”Water penetration - Stucco ⇒⇒⇒⇒ “Static”
0
200
400
600
800
1000
1200
0 20 40 60 80 100 120 140
Time (min.)
Sta
tic
pre
ss
ure
dif
fere
nti
al (P
a)
75 Pa
300 Pa
150 Pa
500 Pa
0 Pa
1000 Pa
5
6
3
10
2.16 L /20 min.
2.52 L /20 min.
2.66 L /20 min.
3.1 L /20 min.
1.25 L /20 min.
9
7
12
16
14
13
4Water entry beneath
electrical box (4 min.) and ventilation duct (9 min.)
Penetration of sheathing board at (a) - 35 min. and in cavity at (b) beneath window - 90 min.
Window leakage at 65 min.
11
1010
22
33 44
55
66
77
88
99
1212
1111
1414
13131515
1616
Position of moisture sensors
Stucco - Continuous water sprayStucco - Continuous water spray
Estimate of water seepage
Seepage path
along boundary of
discontinuity
Entry point
Micro droplet ~ 35µL*
OSBPresence of water
on OSB surface
∆P ~ 250 Pa
Run-off
Q = 35µL/min x 60 min. x 15 = 31.5 mL/hour.
Effect of climate loadsEffect of climate loads
� Climate loads differ across country
– Intensity, duration and frequency of precipitation determines moisture load at given location
� Interaction of wind on building affects degree of precipitation –
– Building height, shape affect pattern of wetting and redistribution of rainfall
� Moisture load – affected by other building features such as
– balconies, overhangs, mullions, and flashing
– Features collect and redistribute rainwater
Mitigating effects of WDR Mitigating effects of WDR
– Deflect
– Drain
– Dry
– Durable
• Soffits (Eaves-”overhang”)
• Drip cap flashing
• Sill flashing
• Deflectors at jambs
Moisture load Moisture load –– affected by overhangsaffected by overhangs
• Cladding / window exposure nomograph• Provides qualitative sense of rainfall load on cladding /
window – “protection from Overhang”
• Considers:• Exposure/surroundings – i.e. terrain / topography
• Exposed; rural; suburban; “built-up”
• Exposure category (NBCC, Moisture index = MI)• MI (Calg. = 0.37; Edm. = 0.48; Vanc. (region)=1.14 to 2.07)
• Overhang ratio = Overhang width / wall height • Varies from 0 to 0.5• An ���� in ratio provides increased protection to rainfall
• Determines exposure category• High (redundant design); moderate; low (minimum acceptable)
Tool to assess rain fall load Tool to assess rain fall load
Example 1
Single Storey House (suburbia)
Toronto (MI = 0.80 to 0.86)
Eaves: 16”
Bottom of Window: 4.5 feet below
eaves; OHR = 1.3/4.5 = 0.288
Example 2
Same as above except:
Single Storey House (centretown)
• Water penetration through face of wall assemblies • Low to moderate risk depending on degree of
exposure and protection• Yes – there will be water absorption in porous
materials• Stucco – including surface cracks• Brick – through mortar joints
• What can be done to further reduce the risk to water penetration to sheathing board?
Mitigating effects of WDR Mitigating effects of WDR
– Deflect
– Drain
– Dry
– Durable
RDH Building Engineering
Performance Monitoring of Rainscreen Wall Performance Monitoring of Rainscreen Wall Assemblies Vancouver British ColumbiaAssemblies Vancouver British Columbia
RDH Building Engineering
Performance Monitoring of Rainscreen Wall Performance Monitoring of Rainscreen Wall Assemblies Vancouver British ColumbiaAssemblies Vancouver British Columbia
General conclusions –
•Rainscreen wall assemblies used in wood frame buildings performed adequately
•Overhangs reduce wetting of walls in proportion to their size and ratio to wall height
•WDR increases MC of strapping but takes longer to affect sheathing
•Rainscreen cladding alone
• Will not prevent wood MC from reaching levels which can support fungal growth
• if interface (or other) details allow bulk water or other moisture source (dryer vents) to infiltrate behind the exterior cladding for prolonged periods of time
Performance Monitoring of Rainscreen Wall Performance Monitoring of Rainscreen Wall Assemblies Vancouver British ColumbiaAssemblies Vancouver British Columbia
Mitigating effects of WDR Mitigating effects of WDR
– Deflect
– Drain
– Dry
– Durable
– Selection and compatibility of materials
– Sequence of installation
– Attention to installation details at wall penetrations; e.g.
– Windows
– Ducts
– Electrical outlets
Categorization of wall defectsCategorization of wall defects
CATEGORIZATION OF PROBLEMS BY AFFECTED BUILDING ELEMENT
Number of Problems
Category ID Description Stucco Vinyl Wood Other
Total # ofProblems
1 Windows: No sealants at frame/cladding joint 9 1
2 Windows: No sealants at corner mitre joints 10 1 1
3 Windows: Poor flashing at head or sill 13 3
4 Windows: Poor building paper installation 6 1Subtotal Windows 38 3 4 0
5 Poor Deck/Walkway/Balcony Waterproofing: Field 12 3 16 Poor Deck/Walkway/Balcony Waterproofing:
Junction with walls16 1
Subtotal Deck/Walkway/Balcony 28 3 2 0
7 Poor Guardrail Saddle Joints 13 3 5 1
8 Poor Guardrail Cap Flashings 8 1 4
9 Poor Parapet Cap Flashings 7 1Subtotal Horizontal Surface Flashings 28 5 9 1
10 Poor Base/Transition/Control Joint Flashings 1
11 Poor Roof/Wall Joint Flashings
12 Poor Eavestroughs / Downspouts 1 1
13 Poor Concrete Slab / Wall Joints 1 1
14 Poor Dryer Vents: Lint plugged, leaking in wall 2
15 Poor Vents: No sealing or flashing at hood 1 2
16 Poor Other Details 2 1 1
17 Material / Installation Defects:Cladding, Weather Barrier, Sheathing
2 4
TOTALS 17 27 3
14
3
3
3
6
5
8
10
146
10
12
16
7
45
16
17
33
22
13
8
43
15
3
5
5
8
8
12
16
193
J. E. H. MacDonald - Autumn in Algoma 1918