Cause of basement bathroom condensation

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Posted by: from Waterdown

My basement bathroom has a lot of moisture/condensation after each shower. Mirrors are completely fogged and water is dripping from the walls and celiing. I have what appears to be a working exhaust fan and have checked the ventilation from the outside and it seems to be venting properly. So why the condensation? Would a dehumidifier in the basement help? Any idea(s) would be helpful.

I look forward to your responses - thanks!

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After all it is a basement bathroom and we all know in the basements the air has a lot more moisture. I would suggest installing a bigger fan (more CFM rating) and upsize the exhaust pipe to 5 or 6 inch. Also

Make sure someone installs a moisture detecting sensor which will keep the fan running until all moisture is removed. I hope this helps.


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1st how did you confirm that the Venting is working properly? Did you do the toilet paper test?

2nd I am thinking you likely don't have a fan that have enough cfm? You needed something that is 1/7.5 of your cubic feet volume inside the bathroom

(w*d*h/7.5). Check your model of fan to see if it is enough.

3rd if the fan have enough cfm. Maybe you don't have enough air intake.. Is there a gap under the door of around 1/2 inch.. If not there may not be enough air for the fan to pull and it may become a Vaccum that stalls air instead and moisture will linger.

Those are the things I will look at first.. If not you need to look for for hvac company or etc.

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