May 2 2008 9:55AM | Permalink | Email this | Comments (0) |
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Hurricanes often lift the roofs off buildings and expose them to havoc and damaging conditions, even after the worst of the wind has passed. A local roofer, Virginia Tech faculty members from architecture and engineering and a graduate student have devised an inexpensive vent that can reduce roof uplift on buildings during high winds, even a hurricane.

Low-sloped roof buildings around Wytheville, Va., where Virginia Tech alumnus Chuck Johnson and his brother, Pat Johnson, operate a roofing business, have sprouted foot-high plastic structures that look vaguely like alien technology - a flying saucer connected by three narrow columns to a dome.

The Venturi Vent Technology V2T is designed for membrane roofing systems. According to a press release recently issued by the company, the Venturi Vent Technology system could revolutionize the way roofing is done."We are using physics instead of mechanical fasteners or adhesives. The harder the wind blows, the better it works," says Chuck Johnson.

The science behind the new roof system is pure physics. Called the Venturi effect, wind forced through an opening speeds up (winds blow harder through mountain passes and between city buildings).

V2T splits the airflow, speeding up the wind that is forced through the vent (between the upper saucer and the lower dome), which drops the pressure and creates a vacuum. The saucer has a hole on the bottom and the columns are tubes from the saucer to the dome and the underside of the roof membrane. The wind pressure draws the air out of the saucer and from under the membrane, pulling the membrane down tight against the substrate. "The pressure being created under the membrane is lower than the uplifting pressure of the wind over the roof. The result is a low pressure condition that prevents the uplift and detachment of the roof membrane," said Jim Jones, associate professor of architecture at Virginia Tech.

View a clip of the V2T roof vent doing its job on a very windy day here.