Ducting Systems and Air Ventilation - exhaust fan roof damper should be closed?

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Stumped1
08-26-09, 09:02 AM
I installed a ducting kit in the roof for a new exhaust fan. I propped the damper up so it is always open.

Is this correct?

Gunguy45
08-26-09, 09:29 AM
It is if you want birds and debris getting in....lol

No, it should be left closed...the pressure from the airflow will open it up. They normally are counter balanced or use a very light spring to hold them closed.
Stumped1
08-26-09, 03:44 PM
I figured it wasn't
Thanks!

GBR in WA
08-26-09, 09:07 PM
Just to be safe, and you may already know- use three sheet metal screws on each joint after you foil tape seal them. Support the pipe every 10'. Insulate and vapor barrier the duct so the hot exhaust doesn't condense on the inside pipe when going through the cooler attic. Fire-stop around the duct at the attic/house. Make sure the roof opening is bigger than the duct passing there to prevent grease from contacting any wood, paper or roofing material.
Be safe, G