Bathroom Venting

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  #1  
Old 04-12-19, 02:17 PM
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Bathroom Venting

I have seen quite a few bathroom venting forums but mine seemed a bit unique when I went in the attic. The flex lines fell down and I only noticed it when I was cleaning my ac drain. When I got closer I realized that it wasn't a single flex line, it was 3. The builder apparently shoved all 3 flex lines (2 fans from one master bathroom and 1 fan from another) into the one roof vent. I've often wondered why condensation was a problem in these bathrooms; I'm beginning to see why. I'm not even sure if this is even the proper way to do it, period. How do I go about fixing this?



 

Last edited by stryker2000; 04-12-19 at 02:23 PM. Reason: upload pics
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  #2  
Old 04-12-19, 02:23 PM
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When 2 or more vent lines are combined you usually want a remote (inline) fan that is mounted in the attic to speed up the air flow. Otherwise you would likely have restricted air flow.
 
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Old 04-12-19, 02:29 PM
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Would this come on when either fan is powered? This I've never read about; if this is the case, I can make another trip to the attic. Is there a better method of attaching these lines instead of just jamming them in there though?
 
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Old 04-12-19, 02:42 PM
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Two wye connectors inline (or one of these) would be the neatest way to connect 3 lines into one. An electrician would know how to wire the switches so that any combination of fans would power the one inline fan.

You would need to consult your bath fan specifications to calculate the total CFM and get an inline fan that is compatible with your needs. Also, it might be that a larger duct is needed as more fans are combined.

Simply pointing ducts at a roof vent is not the proper way to ventilate your bath fans. Generally they should have a dedicated roof louver of their own with a damper.
 

Last edited by XSleeper; 04-12-19 at 02:58 PM.
  #5  
Old 04-12-19, 03:41 PM
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I went back up there. No inline fan in sight. Each fan has a dedicated duct but all share the same roof vent.
 
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Old 04-12-19, 03:52 PM
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I see. Well typically you don't want your bath fan ducts stretching all the way up to the roof peak, as that just encourages condensation to run back down them. I have frequently seen it done that way, but it's not the right way to do it.

IMO it's best to keep the ducts buried in insulation and to keep the roof vents for the bath fans low on the roof. If there is a gable end nearby, it's best if they go straight out the siding. If not, I typically use a Broan/Nutone 636. They also make larger ones like the 634 for larger ducts.
 
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