Understanding the Severity of Climate Loads as related to Cladding and Windows Presented by Michael A. Lacasse (NRC-IRC) and Silvio Plescia (CMHC)
Introduction
Goals – Understand some climatic phenomena – Introduce some basic elements – Reviewing response of cladding to WDR loads
The Elements
Wind and Rain WDR on the wall water penetration
υ
Wind
∆p across wall
T , WV, P + ive p
air leakage
– ive p
The Elements
∆T and ∆pw across wall
T, WV
T, WV
Heat and water vapour transfer
Climate 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)
Wind
Angle <°40
Leeward
Pressure distributions
Windward
Wind flow around obstructions
Section
v =x
Small
v =x
v =x
Medium
Large
Raindrop trajectories
Wind
Wind Velocity Pressure Wind Speed Km/h 0 5 10 20 40 50 57 60 65 70 80 90 100 103 122 150 200 300
Pa = 0.61 (wind speed, m/sec)2
m/sec 0 1 3 6 11 14 16 17 18 19 22 25 28 29 34 42 56 83
mph 0 3 6 12 25 31 35 37 41 44 50 56 62 64 76 93 124 186
1 m/sec = 3.6 Km/h
Wind Velocity Pressure Pa 0 1 5 19 75 118 150 169 200 231 300 381 471 500 700 1059 1883 4236
1 mi. = 1.609 Km
Driving Rain Wind Pressure - 1 hr avg. Code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Location Calgary AB Charlottetown PEI Edmonton AB Fredericton NB Halifax NS Montreal QC Ottawa ON Quebec QC Saskatoon SK St John's NF Toronto ON Vancouver BC Whitehorse YK Winnipeg MB Yellowknife NT Sandspit BC Victoria BC Victoria Gonz Hts BC Regina SK Iqaluit NU Sept Iles QC Shearwater NS Port Aux Basques NF
Driving Rain Wind Pressure - 5 min avg.
Code 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Location Calgary AB Charlottetown PEI Edmonton AB Fredericton NB Halifax NS Montreal QC Ottawa ON Quebec QC Saskatoon SK St John's NF Toronto ON Vancouver BC Whitehorse YK Winnipeg MB Yellowknife NT Sandspit BC Victoria BC Victoria Gonz Hts BC Regina SK Iqaluit NU Sept Iles QC Shearwater NS Port Aux Basques NF
of raindrop = Vt
Terminal Velocity
Wind and Rain
rh = rv U/Vt
Wind Speed = U
Wind and Rain
Wind-driven rain: 5 min. average
Monthly & extreme daily rainfall – Calgary Monthly Rainfall / extreme daily rainfall (mm)
140
Calgary - Climate Normals (Averages) 0ver 30 years (1971- 2000) 120 Calgary - Rainfall (mm) Extreme Daily Rainfall (mm)
100
80
60
40
20
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Month
Aug
Sep
Oct
Nov
Dec
Monthly & extreme daily rainfall – Red Deer Monthly rainfall / extreme daily rainfall (mm)
140 Red Deer - Climate Normals (Averages) 0ver 30 years (1971- 2000) 120 Red Deer - Rainfall (mm) Extreme Daily Rainfall (mm)
100
80
60
40
20
0 Jan
Feb
Mar
Apr
May
Jun
Jul
Month
Aug
Sep
Oct
Nov
Dec
Daily rainfall - June 2005 – Calgary
Rainfall (mm)
Daily Calgary Rainfall - June 2005 130 125 120 115 110 105 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
Extreme daily and Maximum July daily Maximum Septem ber daily - 1985 95.3
Maximum June daily - 1932 92.6
Maximum August daily - 1945 80.8
79.2
75.9
Calgary, AB Year / M onth
Maximum daily / June 2005 46.2 36.6
18.6
34.5
10.2 5.6
4
2
3
4
5
6
7
8
9
1927-Jul
1
1.6 2.2
0
/ / / / / /
June S ept. A ugust A ugust June July
46.2 92.6** 75.9 80.8** 79.2** , 95.3* **
Monthly Total
Monthly Norm al
247.6* 109.8 238.3 99.8 119.927.4 23.4 245.5 25.9
79.8 41.7 58.7 58.7 79.8 67.9
16 e value; ** extrem e daily value for m onth *E xtrem 17.3 13 7.6
10.4 0
1
37.1
18
14.8 8.2
2005 1985 1954 1945 25.6 1932 1927
43.2
Rainfall (m m ) M axim um Daily
0
0
7.6
0
0
0
0
0
1.2
0
7.1 0.2 0
1.2
0
0
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 2005-Jun
1932-Jun
1945-Aug
1954-Aug
1985-Sep
Daily rainfall - June 2005 – Red Deer
Rainfall (mm)
Red Deer - June 2005 - Daily rainfall (mm) 130 125 120 115 110 105 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
Extrem e daily and Maximum August daily - 1938
124.2
Maximum June daily - 1970 Maximum July daily - 1949 99.6
85.3
Max. daily @ Extreme monthy - 1999 75.2
Maxim um daily - June 2005
51.4
47.8
20.8
3
3
0.2
4
/ / / / /
June July June July August
42.7 62.4 99.6** 34 85.3** , 124.2* **
Monthly Totals 145.5 274.4* 243.8* 2nd 154.9 182.4
5
0
6
7
2005-July
6.8
5.4 0.2
0
8
9
1
0
0
0
1
0
0.2
0
0
10.4 2
0
1.4
0
0
0
0
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1999-July
1970-June
1949-July
1938 - August
Monthly Norm al 92 93.1 92 93.1 70
12.6 *Extrem e value; ** extreme daily value for m12.6 onth 8.4
7
2
2005 1999 1970 1949 1938
18.5
15.2
1
42.7
27.6
29.2
28.6
Maxim um daily
Year / M onth
52
5
Rainfall (mm )
Red Deer, AB
62.4
Calgary – total annual rainfall / 2005 to 2008
Climate Load
Calgary
MEWS: wet-wet-avg 1978-1978-1992
Climate Load (cont.)
Edmonton
MEWS: wet-wet-avg 1965-1965-1968
Stucco
Cladding response
1st 4 months (frame every 4 hours)
Stucco
Cladding response
3 years (frame every 24 hours)
MEWS* – water penetration tests on stucco walls • 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 – Consortium for Moisture Management for Exterior Wall Systems – http://www.nrc-cnrc.gc.ca/eng/projects/irc/exterior-walls.html
Water penetration - Stucco ⇒ “Static” 1200
3.1 L /20 min.
3
Static pressure differential (Pa)
1000
4
Water entry beneath electrical box (4 min.) and ventilation duct (9 min.)
1000 Pa 5
Window leakage at 65 min.
800
6
12
600
7
13
Position of moisture sensors
10
500 Pa
14
400
9
2.66 L /20 min.
16
300 Pa
200
2.52 L /20 min.
0
0 Pa20
40
55
11
88
22
60
80
Time (min.)
100
120
99
66
2.16 L /20 min.
75 Pa
15 15
14 14
150 Pa 0
13 13
11 11
140
1.25 L /20 min.
Penetration of sheathing board at (a) - 35 min. and in cavity at (b) beneath window - 90 min.
33
44
77
10 10
12 12
16 16
Stucco - Continuous water spray Estimate of water seepage Presence of water on OSB surface
OSB
Seepage path along boundary of discontinuity Entry point Micro droplet ~ 35µL*
Run-off
∆P ~ 250 Pa
Q = 35µL/min x 60 min. x 15 = 31.5 mL/hour.
Effect 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
– – – –
Deflect Drain Dry Durable
• Soffits (Eaves-”overhang”) • Drip cap flashing • Sill flashing • Deflectors at jambs
Moisture load – affected by overhangs
Tool to assess rain fall load • 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)
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
– – – –
Deflect Drain Dry Durable
Performance Monitoring of Rainscreen Wall Assemblies Vancouver British Columbia
RDH Building Engineering
Performance Monitoring of Rainscreen Wall Assemblies Vancouver British Columbia
RDH Building Engineering
Performance Monitoring of Rainscreen Wall Assemblies 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
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 defects CATEGORIZATION OF PROBLEMS BY AFFECTED BUILDING ELEMENT Number of Problems Category ID 1 2 3 4 5 6
7 8 9 10 11 12 13 14 15 16 17
Description
Stucco Windows: No sealants at frame/cladding joint 9 Windows: No sealants at corner mitre joints 10 Windows: Poor flashing at head or sill 13 Windows: Poor building paper installation 6 Subtotal Windows 38 Poor Deck/Walkway/Balcony Waterproofing: Field 12 Poor Deck/Walkway/Balcony Waterproofing: 16 Junction with walls Subtotal Deck/Walkway/Balcony 28 Poor Guardrail Saddle Joints 13 Poor Guardrail Cap Flashings 8 Poor Parapet Cap Flashings 7 Subtotal Horizontal Surface Flashings 28 Poor Base/Transition/Control Joint Flashings 14 Poor Roof/Wall Joint Flashings 3 Poor Eavestroughs / Downspouts 3 3 Poor Concrete Slab / Wall Joints Poor Dryer Vents: Lint plugged, leaking in wall 6 Poor Vents: No sealing or flashing at hood 5 Poor Other Details 8 Material / Installation Defects: 10 Cladding, Weather Barrier, Sheathing TOTALS 146
Vinyl 1 1 1 3 3
Wood
Other
1 3 4 1 1
0
3 3 1 1 5
2 5 4
0 1
9 1
1
1
1 2 2
1 1 2 2 1 4
17
27
1
1 3
Total # of Problems 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
