Venting a range hood or bathroom fan


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Old 07-22-10, 06:33 AM
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Venting a range hood or bathroom fan

When we bought our 1970 built house 24 years ago, the bathroom exhaust and range hood vented into the attic. Not wanting to put additional holes in the roof, I ran flexible hose from the outlets and routed them so that they exhaust directly under a roof vent.

How effective do you think this approach is vs a dedicated vent thru the roof to the outside?

FWIW, I don't see any evidence of mold or excessive moisture in the attic.
 
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Old 07-22-10, 06:47 AM
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Hi lmacmil,
FWIW, would you really want to wait until you saw mold to decide venting into the attic wasn't good?

A couple of issues. Long runs reduce the volume of air vented. Flex, because it is never straight forces the air to change directions which reduces air flow. If condensation forms inside the flex duct, which does happen, it can pool water and grow stuff, nasty. These type of installations are out of sight out of mind and once installed will rarely be revisited. Yet other activities that affect the amount of moisture being vented may change.

Review your options, insulate the pipe to avoid condensation inside, use rigid pipe with few bends, oversize if possible to accomodate larger fans, and direct those vents to the outside.

Avoid soffit venting as the moisture can be pulled back in.

And yes, there are more reasons, I'm just trying to keep the post short.

Bud
 
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Old 07-22-10, 07:59 AM
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Originally Posted by Bud9051
A couple of issues. Long runs reduce the volume of air vented. Flex, because it is never straight forces the air to change directions which reduces air flow. If condensation forms inside the flex duct, which does happen, it can pool water and grow stuff, nasty.

Review your options, insulate the pipe to avoid condensation inside, use rigid pipe with few bends, oversize if possible to accomodate larger fans, and direct those vents to the outside.

Bud
Thanks Bud. This will be a project for the fall when the attic cools. I do remember now that my range hood vent is rigid but the bathroom vents are definitely flex. Always something to do when you're a homeowner.
 
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Old 07-22-10, 08:23 AM
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"when the attic cools" absolutely!

Some of the other reasons to get that fixed correctly deal with appraisals, inspections and such. With the current emphasis on energy efficiency and tight homes, those vents are on everyones check list and heaven forbid they see the wood in that area showing a darker color and out come the maybe questions.

When everything you own requires some level of repair or maintenance, you can only own so much before you run out of time. You either need to own less or get rich enough to pay someone else to do the work. So here I am stuck in the middle AGAIN .

Bud
 
 

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