Bathroom venting

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Old 11-12-16, 05:33 AM
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Bathroom venting

I have a customer who bought a house and is doing retro "fixing". I have installed windows and some other work. He took me up to the attic stating he was not getting good ventilation from his bath (toilet area) nor from his shower. What I observed (and should have taken a picture) was a 4" booster fan mounted on a rafter with the two locations tied together ahead of the fan and the exhaust run back down to the eave. Whoever installed it used 8" insulated flex to make the connections.

My proposal is to reduce the size of the pipe from 8" to 4" hard pipe and move the exhaust from the eave to the gable which is 3' away. Just looking for either blessings or alternative ways of doing it.

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  #2  
Old 11-12-16, 08:05 AM
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I like the inline fans as they are so quiet if mounted properly. Your approach sounds good, especially use of hard pipe. I would check that the CFM of the fan is sufficient for the two spaces. For a bath you want at least 8 air changes per hour. I like to go higher for shower areas.
 
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Old 11-12-16, 10:48 AM
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I'm guessing the "spuds" on the fan inlet and outlet are sized for 3 inch and 4 inch duct. How in heck did he seal the 8 inch duct to the fan?

I agree that 4 inch hard pipe is a better duct and going straight out the gable is better than going down to the eave. I would suggest a slight downward (toward the outside) slope to the discharge duct to encourage any condensation to exit through the outside grille/flapper. Insulating the duct is generally a good idea.
 
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Old 11-12-16, 11:21 AM
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I did not get a chance to take any of the joints apart, so I am like you, how the heck did he join them? Good point on the downward slope, too. I'll take some before and afters when we do it. Thanks.
 
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Old 11-12-16, 01:17 PM
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A short section of properly sized flex to isolate vibration isn't a bad idea. I usually put it right at the inlet and outlet of the blower.
 
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Old 11-12-16, 03:10 PM
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I had planned on using either a piece of flex if I had some, or maybe a Fernco. Good idea.
 
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Old 11-13-16, 07:21 AM
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You might want to add (if not already there) one of the delayed off switches to keep the fan running for some preset time after being turned off. That will help clear the bathroom of moisture and odors.

Bud
 
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Old 11-13-16, 07:44 AM
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They have it on 3 way switching ( bath and shower), but will suggest that to them. Thanks.
 
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Old 11-18-16, 04:11 AM
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What a difference a little modification made. We eliminated the pipe to the bathroom since it was only 5' from the shower, changed it to 4" hard pipe, insulated it with the wrap from the original flex. Now it will suck a piece of toilet paper from 2' away. Customer is happy.
 
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