question on venting bathroom fans and the use of backdraft dampers


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Old 10-18-12, 12:46 PM
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question on venting bathroom fans and the use of backdraft dampers

I'm fortunate enough to be building a new home. I'm trying to prep for my bathroom ventilation setup. So far all I have purchased is the actual ventilation fans (Panasonic 110cfm) , which come with a built in backdraft damper in them. I will be running rigid 4" pipe, not the flex pipe (a run of a few feet for each bath to the exit point) and venting out the side of the house. I was looking around at the various wall vents available as I didn't want to go with the typical cheap plastic louvered vents. They make some that have built in backdraft dampers. To me it seems the best place to install them is at the exit point, that way no cold air is brought into the home, as would be the case if I just went with the dampers built into the fans, the cold air would still be traveling into the house up to that point. So my question is am I better off going with the damper at the wall vent? And if so, should I remove the damper from the ventilation fan as I fear 2 dampers would restrict the ability for adequate ventilation. Thoughts?
 
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Old 10-18-12, 02:15 PM
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Congratulations on the new home!! I would opt for the damper at the wall just for the reasons you mentioned. I would not worry about removing the one at the fan. There will be enough cfm's to move the air past both, and one will be a failsafe should something lodge in one, such as a weird blown leaf or twig.
 
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Old 10-18-12, 02:44 PM
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Hi wags,
Actually forward draft, for lack of a better phrase, is just as bad at bringing in cold air, it just doesn't dump into your bathroom. What leaks out must equal what leaks in, somewhere. Plus, if your fan is up high on a second floor ceiling the natural pressures will want to exhaust air continuously. First floor ceiling in a single story would be less but still a problem. First floor ceiling in a two story would be the best as the natural pressures (stack effect) are generally the least at that elevation. I have seen discussions where one particular builder would run his ceiling fan vents down and then out to take advantage of the lower pressures.

I mention this only because you are in the building phase and probably building an energy efficient home where every leak counts.

Enjoy,
Bud
 
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Old 10-19-12, 05:35 AM
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Thanks for the feedback. I neglected to tell you that the home is a single story ranch home. Sounds like a don't need to remove the damper from the fans and can pick up some spring loaded dampers built into the exhaust vents as well.
 
 

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