bathroom ventilation questions


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Old 10-11-08, 07:44 AM
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bathroom ventilation questions

my addition includes a master bath that is 145ft2. that includes the 10ft2 closet within bath. there is also a 24ft2 toilet area that is NOT included in that number. The toilet area is getting a fan of 60CFM. The HVAC guys were also putting in a 60CFM unit for the bath. this seems way inadequate. when I calculated it out (using formula on panasonic web site (ft2 x 8ftceiling/60 x 8 turnovers) I got that bath needs 155CFM and toilet would need 26CFM. I am not worried about toilet area. but I think I need to upgrade unit in bath. they ran 4" pipe. I think I need 6" as the fans that provide 150CFM+ seem to require 6". I am on the right track here? Do I need to include the 10ft2 closet in the calcs? If not then I need 144CFM. I am looking at a Nutone QTXEN150--150CFM 1.4sones -so quiet also. I have a shower and a separate jetted tub. I was thinking of putting it right between the door of shower and the tub.
 
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Old 10-11-08, 09:44 AM
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I think your plan is good. Locating the fan between the shower and spa will pull out most of the warm humid air before it condenses on the mirror, walls, etc. Since the toilet closet is isolated, you may want a small fan in there. Those who say theirs don't stink have weak sniffers. Go with the 150 cu ft for the main area and a separately switched small fan for the toilet area.
 
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Old 10-11-08, 11:23 AM
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they did put a 60CFM unit in the toilet room. They already ran vent for a unit in bathroom, but it was going to be 60also. I will have to change it to 6" for the 150CFM unit.

separate issue-do you need a vent in laundry room, other than the dryer vent? If I have to switch to 6" vent and run everything again I might just take it through the roof or on other wall(since the route they took was all the way across addition-total length of around 30ft!-it was more cosmetic this way but maybe not very efficient). thought maybe I could use the hole they had to add vent in laundry if that is something that makes sense
 
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Old 10-11-08, 01:36 PM
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No need in the laundry room. Just a tub of warm water sloshing around which doesn't raise the humidity enough to worry.

The dryer, along with removing the moisture from the clothes, also pulls in room air and warms it to dry the clothes. All go out the dryer vent.
 
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Old 10-11-08, 06:08 PM
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dont forget these fans work better under preasure ..for instance if your duct is to big moisture will build up inside the duct it needs a higher velocity to evac the moisture out of the pipe.. also .. I would think that that little 150 cfm fan with a 4 in pipe would give you your 150cfm at about 15 - 1800 feet per min 5 in pipe would be around 1000-1300 fpm..6 in would be 6-800 fpm. at some point moisture will build up in the pipe ..depending on the length of the run (if its short) I would use a 5 in...
 
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Old 10-11-08, 08:19 PM
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Ok just measured. It looks like total length is 20ft. there are also 4 90 degree elbows, and one of them is attached to the fan unit. What I read said you want a straight piece from fan before any turns for the air to get some velocity. I could eliminate two of these elbows and have a longer straight section before the first elbow if I redo the duct using same path. or I could go up to roof or out other side, both of which would be a run of about 5ft. Of note, the roofer is going to have to come to put multiple vents through roof for the plumbing, so it would not be a big deal to have him do the fan also. The outlet of the fan is 6" should I use the 6" if I go up through roof? wasn't sure what you were getting at when you said if run is short use 5"--does that mean if long use 6" or 4"(which would have more velocity)--and would 20ft be considered long?

thanks for input.
 
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Old 10-12-08, 07:52 PM
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keep it short ,if you can ...if not, use 6 in to after elbows then reduce to 5 in . if you go up vertical use 5 in .myself I would use 5 in . if its in an attic, insulate it , and try not to use flex
 
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Old 10-12-08, 08:52 PM
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it will be in an attic. Is the insulation to try to keep the moisture from condensing in the the cold attic? do they make circular insulation for 5 in and 6in ducts? I will tell the HVAC guys that I want them all insulated. Actually, I guess the one in the toilet doesn't need to be since it isn't carrying moisture rich air-just stink!
thanks
 
 

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