RESILIENT INFRASTRUCTURE June 1–4, 2016 NDM-556-1 WIND UPLIFT RESISTANCE DESIGN OF A GREEN ROOF Mike Gibbons, M.E.Sc. RWDI Inc., Guelph, Ontario, Canada Scott Gamble, P. Eng. RWDI Inc., Guelph, Ontario, Canada Shayne Love, Ph.D., P.Eng., MBA RWDI Inc., Guelph, Ontario, Canada ABSTRACT Green roofs, also referred to as vegetated roofs, have increased in popularity in recent years in North America. Traditionally their use had been more prominent in European countries, such as Germany, however the North American design community have recently adopted them, thanks in part to programs such as LEED and the City of Toronto’s Green Roof Bylaw. Toronto’s Green Roof Bylaw mandates “green roofs on new commercial, institutional and residential development with a minimum Gross Floor Area of 2,000m 2 as of January 31, 2010”. Also contained within the aforementioned Green Roof Bylaw is a requirement that the submitted green roof design explicitly state the uplift wind pressures that it has been designed for, and how the design addresses the stated pressures. This report needs to be stamped by a Professional Engineer. This requirement has led to many questions regarding the wind resistance of a green roof, which is a unique building material in many ways - it is organic, living, porous, and has a variable weight (based on the amount of water it is retaining). Conventional building materials have strict tolerances and highly standardized, whereas the properties of green roofs change on a daily basis. The intent of this paper is to discuss the design of a green roof in order to prevent lift off/fly away of a green roof assembly. The methods presented are based on applicable standards and building codes, as well as specific testing that has been undertaken on a green roof system to demonstrate its porosity and pressure equalization properties. Keywords: Wind Uplift, Green Roof, Pressure Equalization, Full Scale Testing, Boundary Layer Wind Tunnel Testing 1. INTRODUCTION Green roofs are becoming a common building typology in North America. Having been employed in Europe for decades, their adoption in North America over the past 5 – 10 years has been explosive. Much of this growth is due to the positive environmental aspects that green roofs bring to a building, such as better storm water retention and filtration, passive cooling and a reduction of the heat island effect in urban environments. The positive environmental aspects of green roofs are reflected in the allotment of LEED points for the installation of green roofs on buildings. Due to the uniqueness of green roofs as a building product – no other product is a living, breathing organic system, whose weight and porosity changes by the hour – questions have arisen in terms of how they should be treated from a design standpoint. From a wind uplift perspective, green roofs present an interesting challenge, particularly due to their porosity. The low level of rigidity in a green roof also presents an interesting challenge when it comes to wind resistance, as the applicable wind load averaging areas are substantially less than conventional building products