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netsrik 03-30-2008 12:59 PM

Bathroom moisture a real problem
We are getting ready to put our house on the market and really want to solve this problem before we do w/out too much expense. I just can't pass this problem onto the next person. Our house is almost 10 years old. It's 6 x 13 with a tub/shower unit. The exhaust fan is 100 CFM but really doesn't seem to pull much. You can put a piece of toilet paper to it and it'll hold but it doesn't really "suck" onto the fan like it's getting pulled up. The tub/shower unit is on an outside wall and there's a cold air exchange that runs behind the wall behind the head of the tub. I haven't had any problems wiping the mildew off the walls and ceiling, but the walls will literally look like moisture is running down them. It does seem worse in the wintertime, but will notice it during warmer weather also, just not quite as bad. If you take a shower and leave the door shut, the exhaust fan won't really clear the mirror. I think the cold air exchange could possibly have something to do with it, (but I hope not a lot because there's not much we can do with that) and our bathroom is usually pretty cold because we don't really heat it, but the water temperature is pretty high. Do you think just lowering our water temperature and possibly getting a low flow shower head would help. Also, our walls are painted with a flat paint, and I thought maybe a different paint would help.

Any suggestions??

glennjanie 03-30-2008 01:27 PM

Yes, use lower water temperature, the low-flow head and paint with mildew resistant latex enamel. Increase the fan to 300cfm and I think you'll have it knocked.

netsrik 03-31-2008 08:20 PM

thanks so much, Glenn. I haven't seen a fan with 300 CFM but I'll be checking that out!!

sunroom wizard 03-31-2008 08:27 PM

The 300cfm fan should be the answer to this. Do a search for them online they'll show up.

Hube 04-02-2008 10:18 AM

netsrik; The 100 cfm fan you have should be able to do the job, IF installed properly.
a 6 x13 bathroom with (i assume) a normal 8 ft ceiling= 624 cu ft.
A 100 cfm fan should be able to move approx 600 cfm every 6 minutes, and over an hour should move approx 6000 cfm. which would be equivilent to approx 10 air changes in an hour.
8 to 10 air changes in an hour is what is normally recommended for a bathroom, so your present fan should be more than adequate.
Either you are not running the fan long enough or there is restrictions in the exiting air flow. Are you sure the fan's "backdraft" is opening upon start-up? Also, is the exhaust piping free and clear of any debris,etc. and does it expel the exhausted air to the outside?
What size is this exhaust piping? 4" or larger? Hopefully it is not 3"

Quattro 04-02-2008 01:21 PM

If you want to upgrade the exhaust fan, I highly recommend the Panasonic brand. They are relatively expensive (~$130) for a fan/light combo. However, they are extremely quiet, and very efficient at moving air. Upgrade the vent pipe while you're at it.

Another thing to consider is a louvered door on the bathroom. Drawing air from the adjacent room (or hall) will help move the moist air out the vent.

At the very least, get up in the attic and check to be sure your current vent is clear, as Hube suggested.

Hube 04-02-2008 04:38 PM

Quote by Quattro;
" get up in the attic and check to be sure your current vent is clear, as Hube suggested"....

A better plan would be to get up on the ROOF and check the vent out.
Hopefully the vent terminates to the outside air.
Terminating a vent in an ATTIC space is an absolute "NO-NO"

Quattro 04-03-2008 08:05 AM

Not much you can do on the roof. However, from the attic you can remove the vent pipe from the roof jack and the fan itself, and check it out.

Hube 04-05-2008 07:07 AM


Originally Posted by Quattro (Post 17606)
Not much you can do on the roof. However, from the attic you can remove the vent pipe from the roof jack and the fan itself, and check it out.

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Wrong!! from the ROOF you can remove the cap,etc and look into the pipe to see if it is obstructed.
From the attic you will never be able to remove the outside part of the pipe from the roof jack, as the caulked weather skirt will prevent this from happening. And even if you could you would never be able to recaulk around the weather skirt without going onto the roof.

Square Eye 04-05-2008 09:04 AM

Most of the exhaust fans in this area are vented with flexible lines. They're not hard to detach from the roof jack and a man can easily reach up into the roof jack and clear any blockages. If this fan is vented with flexible line, the line could be crushed, there could be a blockage at the fan housing, he may discover that it was never vented to the outside at all... There are several reasons to check the attic. Personally, I've seen a vent fan buried under 10 - 12" of blown-in insulation. I don't know if it was forgotten or just installed without but it happens.

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