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