Bath ventilation

Old 07-19-01, 06:16 AM
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I purchased an older home where the only recent "improvement" had been a bathroom update. I'm sure this was only done to dress it up for the sale, A very poor quality "improvement". I recently just learned how poor it really was. The bath is being vented into some "dead" attic space. The space is only accessible from an outdoor window. It has soffit vents, but as of yet, has no other venting. I am conserned about dumping all that humidity into this space. I would like to continue the vent duct to exit outside. I would rather not have to put a roof vent in b/c I hate messing with old shingles, It's usually a loosing battle for me. I would like to put a vent in the wall. MY QUESTION IS... Is there a limit to how long the duct can be? Number of turns it makes? Is it dependent on the fan's CFMs? If the quality of the other "improvements" is any judge, I'm sure the fan was the cheapest they could find, therefor probably has very low CFMs. The run will be about 20 feet with a couple sharp bends. I was going to use some flexible (vinyl or plastic ?) duct. If it matters, I live in the Northeast.
Old 07-19-01, 12:17 PM
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As you guessed, it depends on the cfm of the exhaust fan on how well it will work at 20' with a couple of sharp bends. It should be o.k. though.
You can run it out of a wall or the roof, but definitely get all of that moist air out of your attic.
Also, running warm, moist air through a vent pipe in an unheated attic in the winter will cause condensation to form on the inside of the vent pipe up there, and it will run back down into the fan fixture.
You can overcome this problem by wrapping insulation around it in the unheated attic space (just duct tape it in place), however.
Good Luck!

Old 07-19-01, 02:32 PM
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insulation question...

Thank you for such a prompt reply. Good point about the need for insulation, never even thought about it. Is there insulation specifically designed for this purpose, or do I just use standard insl. batting taped on? I asume this will add some weight, the duct is currently held up with very light guage wire.

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