Resolving bathvent problem


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Old 01-01-09, 05:35 PM
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Resolving bathvent problem

Hi,
So I finally figured out why it appeared my bathfan hasn't been venting properly. I climbed up in the attic, there is a poor connection to the roof vent. I can only assume this is from when the previous owner had the place re-roofed.

So I have some moisture up there now. But as far as resolving it what here is my question. Are there different types of roof vents for bath fans, classified by the amount of air cfm? Because even with the connection not air tight, I don't think the fan is pushing hard enough to open that flapper door.

Or if I just make the connection more sound should that take care of it? I hope this all makes sense. Thanks.
 
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Old 01-01-09, 07:09 PM
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I am assuming that you are venting into roof cap intended by the manufacturer for use with the bathroom fan, and not trying to vent through a low profile ("mushroom style") roof vent intended for attic ventilation or some other type of cap or vent.

Best practice if you are in a cold climate is to vent through through solid metal wall metal pipe. insulated to help control condensation:



- Venting Exhaust Fans Through The Roof

Some installers recommend the use of spray foam insulation instead.

If you're using flexible pipe up make certain that there no compressed bends, or dips were water condensing out of the bath exhaust can accumulate, and with either type of vent pipe that no other bathroom or other exhaust fans are venting through the same cap:



Typical consumer grade bathroom fans can have difficulty achieving their rated exhaust through longer,convoluted ductwork, one option is to install a in-line fan, some of of these are intended to serve several bathrooms, they can share bathroom exhaust lines because they are pulling, rather than pushing,exhaust air toward the vent cap, and are installed after the last junction of vent pipes from the bathroom.
 
 

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