In-situ monitoring of an Omni directional roof vent on a low slope single ply roof to identify most efficient porous underlayment for maximum pressure propagation

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Virginia Tech

An experimental study was carried out on a single-ply low-slope roof using a series of different underlayment layers to test and understand distributional characteristics of negative air pressure throughout the roof assembly, when subjected to suction pressure corresponding to different wind speeds. Various underlayments were tested at the Research & Demonstration Facility at Virginia Polytechnic Institute and State University to develop design guidelines for the installation of recently developed omni-directional roof vent on low slope membrane roofing systems. The newly designed and patented low-pressure roof vent works on Bernoulli and Venturi air flow principals and helps prevent uplift and detachment of the roofing membrane during storm or high wind conditions by creating a negative pressure zone underneath the roof membrane.

The objective of this research is to further develop the Pressure Equalizing Vent System by testing the wind vent in combination with different underlayments and to determine the appropriate tributary area of each vent under dynamic wind conditions.

The determined area of influence of each wind vent therefore serves as a guideline for appropriate spacing of the vents on the roof. It will also suggest the wind speed at which the pressure is lowered and its ability to weather storm events. The pressure sensors permanently installed beneath the membrane will continuously monitor the pressures in and around the wind vent. An additional objective of the research project is to understand the distributional characteristics of negative pressure in various layers of roof assembly in combination with varying underlayment membranes under different suctionals pressure to further develop the Pressure Equalizing Vent System.

The proposal seeks to develop a cost effective roof assembly method, which can withstand the effect of extreme wind through improved understanding of air movement through different layers of roof assembly. The study explores the effect of various underlayments on spatial and distributional character of pressure field on the single ply flat roof deck in combination with omni-directional roof vent system.

negative pressure distribution, wind uplift, suction pressure, underlayment, single-ply low-slope roof