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Introducing Siphonic Roof Drainage Common in Europe, now gaining traction stateside by William Verdecchia All images courtesy Zurn Industries ALL ROOFS ARE SUBJECT TO THE DESTRUCTIVE EFFECTS OF SEASONAL WEATHER CHANGES, ENVIRONMENTAL CONDITIONS, LOADING, AND AIR POLLUTANTS. ALTERNATE CYCLES OF WETTING, DRYING, FREEZING, AND THAWING CAUSED BY WATER LYING ON THE ROOF LEADS TO EXPANSION, CONTRACTION, AND ROTTING—THIS RISKS DAMAGE TO THE ROOF AND EVEN THE BUILDING SUBSTRUCTURE. Drainage is a significant component of roof design itself. Roof collapses typically occur because water accumulation exceeds the roof’s structural capacity. With proper water drainage in place, many major causes of failure are eliminated. For this reason, siphonic roof drainage is coming into its own in the United States. First developed in Finland by engineer Ovali Ebeling in 1968, these systems are used around the world—in Europe, they account for one-fifth of commercial projects. This sustainable technology crossed the Atlantic in 1999 with the Boston Convention Center’s installation as the first major example, and acceptance has steadily grown. Siphonic roof drainage differs from conventional gravity drainage in what is called ‘full-bore flow.’ Unlike conventional drainage, a fully engineered siphonic roof drain system prevents air from entering, allowing the pipes to be completely full of water. The unique component of a siphonic drain that sets it apart from conventional gravity drains is the air baffle, which prevents air from entering the piping system at full flow and protects against debris. 48 the construction specifier | march 2014 CS_March_2014.indd 48 2/13/14 10:04 AM