Abstract
In conventional low-slopped roof assemblies, where the waterproofing membrane is attached through insulation and other components to the structural deck at discrete points using fasteners, it is known as a mechanically attached assembly (MAA). In North America, approximately one fourth of low-slope buildings are roofed with a mechanically attached assembly having a single-ply membrane. In these roofing assemblies most of the attention has been focused on the performance of individual roof components to maintain the integrity of the waterproofing system. Relatively little attention has been given to the overall assembly performance with regards to air movement. A common misconception is that air movement in roofing assemblies can be characterized by air leakage similar to that which occurs in walls and windows. However, the material properties and assembly response indicate that there is no air leakage in the mechanically attached low-sloped membrane roofs. However, air intrusion does occur in these assemblies. Air intrusion is a phenomenon in mechanically attached roofing assemblies, which occurs due to the membrane response to the external wind pressures. Incorporating an air retarder at the deck level can minimize this air intrusion. National Research Council of Canada (NRC) has been conducting research on the wind uplift performance of mechanically attached roofing assemblies for the past one decade. Wind uplift data is available for different roofing configurations, which can be generalized into two categories: 1) assemblies without air retarder and 2) assemblies with air retarder. From these categories, a typical mechanically attached assembly is evaluated for wind uplift performance. By analyzing the measured membrane and insulation responses of these assemblies, this paper attempts to clarify the air movement confusion of air leakage vs. air intrusion in mechanically attached low-sloped membrane roofs.
In conventional low-slopped roof assemblies, where the waterproofing membrane is attached through insulation and other components to the structural deck at discrete points using fasteners, it is known as a mechanically attached assembly (MAA). In North America, approximately one fourth of low-slope buildings are roofed with a mechanically attached assembly having a single-ply membrane. In these roofing assemblies most of the attention has been focused on the performance of individual roof components to maintain the integrity of the waterproofing system. Relatively little attention has been given to the overall assembly performance with regards to air movement. A common misconception is that air movement in roofing assemblies can be characterized by air leakage similar to that which occurs in walls and windows. However, the material properties and assembly response indicate that there is no air leakage in the mechanically attached low-sloped membrane roofs. However, air intrusion does occur in these assemblies. Air intrusion is a phenomenon in mechanically attached roofing assemblies, which occurs due to the membrane response to the external wind pressures. Incorporating an air retarder at the deck level can minimize this air intrusion. National Research Council of Canada (NRC) has been conducting research on the wind uplift performance of mechanically attached roofing assemblies for the past one decade. Wind uplift data is available for different roofing configurations, which can be generalized into two categories: 1) assemblies without air retarder and 2) assemblies with air retarder. From these categories, a typical mechanically attached assembly is evaluated for wind uplift performance. By analyzing the measured membrane and insulation responses of these assemblies, this paper attempts to clarify the air movement confusion of air leakage vs. air intrusion in mechanically attached low-sloped membrane roofs.
Date
5/2009
5/2009
Author(s)
Molleti, S., Baskaran, B.A., Ko, K.P., Beaulieu, P.
Molleti, S., Baskaran, B.A., Ko, K.P., Beaulieu, P.
Page(s)
1-11
1-11
Keyword(s)
waterproofing; membrane; assemblies
waterproofing; membrane; assemblies