I’ve got a shower and separate water closet in the bathroom and my plan was to vent these two fans up into a conditioned attic and then combine them with another bathroom and vent them all through the side of the house. I know there are couple of companies (fantech, American aldes) that make remote fans and stuff for just this situation but why can’t I use the regular ceiling mounted fans and just combine them all in the attic? The longest pipe run would be around 12′. Each line would only have one 90 degree bend.
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Because fan A would blow back through Fan B. You could rig up some dampers to prevent that, but it's a pain. If you have the attic space, I'd use one remote fan and just duct to the locations you need.
Here's a pic of a Panasonic unit serving both a toilet area and a shower. Probably cheaper, certainly WAY quieter to boot.
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Mike Hennessy
Pittsburgh, PA
Edited 1/7/2008 2:43 pm ET by MikeHennessy
Maybe I just got lucky, but I combined two bathroom fan exhaust lines with a "Y" fitting at the penetration through the gable end of my attic. My thinking was that the air would follow the path of least resistance and exhaust rather than flow back down the 6'-7' of the other line.
It's worked fine for almost 10 years and there was never any indication of backflow thru the non running fan.
I was wondering the same thing. I have two bathrooms right next to each other. I wondered if others thought it was better to have a combined vent, or two roof penetrations. Each are about 18 in. below the roof, so it would a be a short straight shot up. Otherwise I would try and join them with a Y, although this would create an almost horizontal run for one fan because of the low roof slope.With a Y I don't think air would blow back into the other fan... there is a damper on there anyway.
Like I said, it's worked for me for 10 years. - lol
I'm not sure how well it would work with more than two exhaust lines (multiple "Y"'s), and/or with much distance between the "Y" and the exhaust point. Fluid flow is always about minimizing resistance and the longer the duct, the greater the resistance.