Exhaust Fan

Old 02-03-03, 08:30 AM
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Exhaust Fan

Recently, with the extrme cold weather, my Michigan home has been experiencing what looks like condensation dripping from the bathroom exhaust fan. This condensation will occur weither the shower has been used or not.
The ranch house is 5 years old, meets what I understand as code to where the flexible 3" metal tubing runs from the bathroom 15' to a soffit vent.
I noticed that the flexible tubing, when it comes out of the fan exhaust port runs downhill towards to fan for about 2-3 feet and then runs level for at least 10 before it's abrupt downturn at the soffit vent.
My thoughts suggest that (1) the 2-3 feet downhill run back to the exhaust fan allows condensation to accumulate a work it's way back. The way to fix this is to support the tubing as soon as it comes out of the fan exhaust port reducing the 2-3 feet run.
This in turn would reduce surface area for condensation to accumulate back into the fan area and force the condinsation towards to soffit. The other suggestion is to utilize a 3" flex tube with insulation surrounding the outside.
Am I correct? Any other suggestions please?

Old 02-03-03, 09:00 AM
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Although most exhaust fans have flap doors, warm moist air still escapes from the bathroom to the unheated vent pipe, which is causing the condensation.
You can insulate the vent pipe in the attic with regular insulation batts (wrap them around and hold in place with duct tape).
Good Luck!
Old 02-03-03, 09:39 AM
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Thanks Mike...great idea.
Old 02-03-03, 10:09 AM
Phil Allen
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xhaust fan condensation

The slight downhill of the exhaust might be your problem. Though I don't think this is it. Your problem may be that the flap on the fan isn't closing all the way. Cold air falling into fan box will cause condensation Check to see if the flap is closing all the way. Most of the time I find that makeup dust collects there over a period of time or it could be a defective part. If you smoke hold a cigerette
close to the fan and see if you see the smoke blowing inwards. An incense burner works just as well. You can visit my site at XXX XXXXXXXX, Search word Home Improvement help. Hope it works for you


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Last edited by twelvepole; 02-03-03 at 09:58 PM.
Old 02-03-03, 10:15 AM
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Thanks Phil...I will take a look at the exhaust flap and clean if required.
I certainly appreciate the quick reply from you and Mike.

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