preliminary results from field experimental study of rain...

Preliminary Results From Field Experimental Study Of Rain Load And Penetration Into Wood-frame Wall Systems At Window Sill Defects

E. Ngudjiharto1, F. Tariku2, and P. Fazio1 1Building, Civil and Environmental Engineering, Concordia University, Montréal, Canada. 2Building Science Centre of Excellence, British Columbia Institute of Technology, Burnaby, Canada

Current State of WDR Research

 Research in predicting the quantity of WDR impacting walls.

 Guides on estimating the hygrothermal performance of wall assemblies are abundant.

× Still missing: the correlation between the rain penetration and the WDR.

Buildings for Tomorrow Conference – Toronto Canada - October 28-30, 2014

14th Canadian Conference on Building Science and Technology 2

Current State of WDR Research

•  “In the absence of specific full-scale test methods and data for the as-built exterior wall system being considered, the default value for water penetration through the exterior surface shall be 1% of the water reaching the exterior surface.” (ANSI/ASHRAE Standard 160, 2009)



Today’s Presentation: Field Experimental Study •  Introduction

• Methodology

• Preliminary Results

•  Findings So Far

• What’s Next?



Introduction

• OBJECTIVE: To find the correlations between measured amount of rainwater collected through various specified defects to the corresponding rain and wind data recorded during fall and winter rain events in BC.

•  This paper presents the preliminary findings from one defect type at one of the stucco wall panels during the month of September 2013.



Research Variables

• WDR parameters (horizontal rain, the wind speed & direction) and rain duration.

• Wall cladding types (stucco and vinyl siding).

• Wall defect types at window sill.



Test Facility

Google Street View



Monitoring Types

•  Leakage rate monitoring.

•  Long-term hygrothermal monitoring (temperature & moisture content at wood studs, plates & sheathing, and relative humidity in wall cavity).

• WDR, outdoor & indoor conditions.



South East façade



Wall construction



Wall installation



Stucco cladding

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Finished walls



Instrumentation

•  WDR parameters (horizontal rain, the wind speed & direction) and rain duration.

•  Wall cladding types (stucco and vinyl siding).

•  Wall defect types at window sill.



Instrumentation



Stucco Wall 6



Stucco wall 6



Leakage tipping bucket gauge



Preliminary Results



Preliminary Results

• Wind-driven rain (WDR) onto south east façade of test facility:



WDR Calculation

• Rwdr = DRF(rh) • cos (θ) • V(h) • rh

(Blocken and Carmeliet 2010; Straube and Burnett 2000)

• DRF(rh) = driving rain factor which depends on the terminal velocity of raindrops: •  DRF (rh) = 1/ Vt (d)

•  Vt (d) = -0.166033 + 4.91844d – 0.888016d2 + 0.054888d3

•  D-50 = 1.30 rh0.232

* 0.69 1/n

(Best 1950)

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Preliminary Results

• Calculated hourly WDR intensity plotted against measured hourly rain intensity on SE façade near W6 by Top North gauge:



Preliminary Results

• Calculated hourly WDR intensity plotted against measured hourly rain intensity on SE façade near W6 by Bottom North gauge:



Comparison of the occurrence and intensity of the calculated wind-‐driven rain on SE façade to the measured leakage amount through corner defect of W6 by leakage gauge:



Findings So Far

•  There are good correlations between the measured and calculated wind-driven rain on the walls.

•  There are some correlations between the wind-driven rain parameters (horizontal rain, the wind speed & direction, and rain duration) and rain penetration for the specific wall defect type.

• Results indicate correlations to be explored further for better predictions of rain penetration through wall defects.



What’s Next?

• Analyze WDR and leakage data collected for the vinyl siding walls.

• Compare the effects of the different cladding materials (vinyl siding and stucco) on rain penetration.

• Compare the effects of the different wall defect types on rain penetration.

• Compare the hygrothermal performance of the walls of different cladding and defect types.



Bibliography •  ANSI/ASHRAE Standard 160. 2009. Criteria for moisture-control design analysis in buildings. American

Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA. •  Best, A.C. 1950. The size distribution of raindrops. Quarterly Journal of the Royal Meteorogical Society, 76:

16-36. •  Blocken, B., and Carmeliet, J. 2010. Overview of three state-of-the-art wind-driven rain assessment models

and comparison based on model theory. Building and Environment, 45 (3): 691-703. •  Morrison Hershfield Ltd. 1996. Survey of building envelope failures in the coastal climate of British

Columbia. Report for Canada Mortgage and Housing Corporation, Ottawa, Ontario. •  Straube, J.F. and Burnett, E.F.P. 2000. Simplified prediction of driving rain deposition. Proceedings of

International Building Physics Conference, Eindhoven, September 18-21, pp. 375-382. •  Tariku, F., Cornick, S.M., and Lacasse, M.A. 2007. Simulation of wind-driven rain effects on the

performance of a stucco-clad wall. Proceedings of Thermal Performance of Exterior Envelopes of Whole Buildings X International Conference, Clearwater Beach, Florida, December 02, pp. 1-15.

•  TenWolde, A. 2008. ASHRAE Standard 160 P-Criteria for Moisture Control Design Analysis in Buildings.

ASHRAE Transactions, 167-171.



What’s Next?



Acknowledgement

• BCIT

• Concordia University

• NSERC Canada

• Staffs at BCIT: Doug Horn, Wendy Simpson, Tim Lee and Jordan Ho



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