Benchmarking Lab Wind Performance with In Situ Monitored Data of Modular Vegetated Roof Assemblies
Publication: Journal of Architectural Engineering
Volume 26, Issue 1
Abstract
The National Research Council of Canada (NRC), as part of a consortium with members from vegetated roof industries and roofing associations, established a national wind resistance standard for modular vegetated roof assemblies (MVRAs), named CAN/CSA A123.24, “Standard Test Method for Wind Resistance of Modular Vegetated Roof Assembly.” Currently, this standard is widely used on a voluntary basis by the Canadian roofing industry for wind performance compliance of MVRAs. CAN/CSA A123.24 was developed based on extensive data collected on various MVRAs by simulating wind in laboratory conditions. Toward codification of CAN/CSA A123.24, the consortia members decided to validate such collected data with in situ performance data. This paper presents and discusses the validation process. Different MVRAs were installed on the rooftop of a Humber College building, located in Toronto. The validation was conducted by comparing the three wind performances of MVRAs as follows: (1) pressure equalization (between the top and bottom of the vegetated system); (2) coefficient of lift, ; and (3) estimated overturning wind speed, , at different wind conditions. Data comparisons (laboratory versus field) showed consistent agreement in the global trend. Some discrepancies in the absolute values were observed; however, these discrepancies are due to the inherent variability of the field wind conditions and the limited amount of field data. The forecasting of the overturning wind speed provides a valuable tool to adequately evaluate MVRA design alternatives for acceptable wind resistance compliance in accordance with the National Building Code of Canada.
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Acknowledgments
The present research was carried out by a consortium composed by members of the roofing industry and modular vegetated system manufactures. The consortium was formulated by the National Research Council Canada under the umbrella of the Canadian Roofing Contractor Association (CRCA) with partners Armtec, Bioroof Systems, City of Toronto, City of Ottawa, CLEB, LiveRoof, Soprema Canada, Vitaroofs, and Xeroflor. Special thanks go to Humber College for offering the field site and associated collaborators. NRC technical team efforts (P. Beaulieu, A. Duric, S. K. P. Ko, D. Van Reenen, and H. Yew) are greatly appreciated.
References
ANSI/GRHC/SPRI (American National Standards Institute/Green Roofs for Healthy Cities/Single Ply Roofing Industry). 2011. Procedure for investigating resistance to root penetration on vegetative roof systems. Waltham, MA: ANSI/GRHC/SPRI.
ANSI/SPRI (American National Standards Institute/Single Ply Roofing Industry). 2010. Wind design standard from vegetative roofing systems. Waltham, MA: ANSI/SPRI.
ASCE. 2016. Minimum design loads and associated criteria for buildings and others structures. ASCE 7. Reston, VA: ASCE.
Bartko, M., S. Molleti, and A. Baskaran. 2016. “In situ measurements of wind pressures on low slope membrane roofs.” J. Wind Eng. Ind. Aerodyn. 153 (Jun): 78–91. https://doi.org/10.1016/j.jweia.2016.03.010.
Baskaran, A., S. Molleti, K. P. Ko, and D. Van Reenen. 2011. “Field monitoring the wind performance of commercial roofs—Part 1: Data from Ottawa site.” In Proc., 13th Int. Conf. on Wind Engineering (ICWE13), 1–4. Ottawa: National Research Council of Canada.
Baskaran, A., S. Molleti, and H. Yew. 2016. “Top 10 questions and answers on wind performance of modular vegetated roof assemblies for better understanding of CAN/CSA A 123. 24.” Interface J. RCI 9: 14–17.
Baskaran, A., D. Van Reenen, J. Overton, and K. K. Y. Liu. 2009. “Engineering performance of garden roofs in north (Canadian) climate—5 years of field data.” In Proc., 24th Int. Convention and Trade Show, 1–6. Raleigh, NC: International Institute of Building Enclosure Consultants.
Cao, J., Y. Tamura, and Y. Yoshida. 2013. “Wind tunnel investigation of wind loads on rooftop model modules for green roofing systems.” J. Wind Eng. Ind. 118 (Jul): 20–34. https://doi.org/10.1016/j.jweia.2013.04.006.
Castro, I. P., and A. G. Robins. 1977. “The flow around a surface-mounted cube in uniform and turbulent streams.” J. Fluid Mech. 79 (2): 307–335. https://doi.org/10.1017/S0022112077000172.
CSA (Canadian Standards Association). 2015. Standard test method for wind resistance of modular vegetated roof assembly. CAN/CSA A123.24. Rexdale, ON, Canada: CSA.
Green Roofs for Healthy Cities. 2017. “2016 annual green roof survey—Executive summary.” Accessed September 15, 2017. http://www.greenroofs.org.
Irwin, P., C. Dragoiescu, M. Cicci, and G. Thompson. 2012. “Wind tunnel model studies of aerodynamic lifting of roof pavers.” In Advances in hurricane engineering: Learning from our past. Reston, VA: ASCE.
Kind, R. J., and R. L. Wardlaw. 1982. “Failure mechanisms of loose laid roof insulation systems.” J. Wind Eng. Ind. 9 (3): 325–341. https://doi.org/10.1016/0167-6105(82)90022-8.
Ko, K. P., P. Beaulieu, H. Yew, S. Molleti, and A. Baskaran. 2014. Development of wind resistance standard for vegetated roof assembly—Year 1 archive report. Ottawa: National Research Council of Canada.
Levitan, M. L., K. C. Mehta, W. P. Vann, and J. D. Holmes. 1991. “Field measurements of pressures on the Texas tech building.” J. Wind Eng. Ind. Aerodyn. 38 (2–3): 227–234. https://doi.org/10.1016/0167-6105(91)90043-V.
Molleti, S., A. Baskaran, and F. De Souza. 2015. “Development of standard test method to determine the wind resistance of vegetated roof assemblies.” In Proc., 30th RCI Int. Convention and Trade Show. Raleigh, NC: International Institute of Building Enclosure Consultants.
Mooneghi, M. A., P. Irwin, and A. G. Chowdhury. 2014. “Large-scale testing on wind uplift of roof pavers.” J. Wind Eng. Ind. 128 (May): 22–36. https://doi.org/10.1016/j.jweia.2014.03.001.
NRCA (National Roofing Contractors Association). 2009. The NRCA vegetative roof systems manual. 2nd ed. Rosemont, IL: NRCA.
Richards, P. J., R. P. Hoxey, and L. J. Short. 2001. “Wind pressures on a 6m cube.” J. Wind Eng. Ind. Aerodyn. 89 (14): 1553–1564. https://doi.org/10.1016/S0167-6105(01)00139-8.
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©2019 American Society of Civil Engineers.
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Received: Jan 26, 2018
Accepted: Mar 6, 2019
Published online: Nov 27, 2019
Published in print: Mar 1, 2020
Discussion open until: Apr 27, 2020
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