Per the Mandatory Requirement of ASHRAE 90.1-2007 section 6.4.3.4.2 a gravity vent is required to be equipped with dampers that shut automatically. Though the 90.1 does not have an exception if the system operates continuously. Of course this may be the interpretation since is states the damper shall close when the system is not in use. Since the system is always in use, does it require the installation of gravity/motorized dampers? The local energy code does spell out this exception.

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Scott Bowman

LEED Fellow

Integrated Design + Energy Advisors, LLC

LEEDuser Expert

377 thumbs up

Sat, 08/05/2017 - 16:42

LEED references standards, not codes. So in a way, the local code does not matter. In my opinion, the application would be important. If you are talking about gravity relief vents that will relieve pressure from inside the building during economizer, then there should definitely be some sort of damper. If it is an exhaust fan that is intended to operate 24/7/365 and is alarmed if not running, then perhaps the damper is not really needed. This is such a small issue that following the local energy code as required by law should be sufficient.

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