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interested 12-10-2009 06:33 AM

range hood venting
curious as to correct way to insulate and terimnate range hood vent through roof?

Bob Mariani 12-10-2009 07:00 AM

Wrap insulation blanket around the duct work in the attic space after taping all seams with metal duct tape. Use a covered roof vent cap on the 6" duct exiting the roof. Use a roof boot on the roof.

interested 12-10-2009 07:02 AM

do they make ones that don't allow backdraft?

Bob Mariani 12-10-2009 07:10 AM

use an inline damper for this, not the roof cap. The cap should have an insect screen also.

Michael Thomas 12-10-2009 09:09 AM

Damper required in range exhaust hood

Originally Posted by Bob Mariani (Post 364424)
use an inline damper for this, not the roof cap. The cap should have an insect screen also.

Yup, a damper required by M1502.1: "Range hoods shall discharge to the outdoors through a single-wall duct. The duct serving the hood shall have a smooth interior surface, shall be air tight and shall be equipped with a backdraft damper...."

Gary in WA 12-10-2009 10:37 AM

I would insulate with more than the R-7 required by some codes. The idea is to stop condensation and grease from depositing on the pipe insides. You want the pipe as warm as possible. I would use a roof cap damper w. screen rather than an in-line damper that lets cold air in the rest of the pipe when the unit is not being used. The attic temperature will help temper the pipe a little more, to stop condensation if the pipe was warmer than the outside air. And..... Welcome to the forum!
Be safe, Gary

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