bathroom exhaust fan

Old 12-21-06, 06:44 AM
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bathroom exhaust fan

I have to install a bathroom exhaust fan since there is none and I keep getting mold because of the build up. The problem I am having is the bathroom is in the middleof the house and at the back of the house. I do not have and eve so I have no place to stick the vent. I am wondering how to go about this. I was told that I have to vent this and not to just vent it into the attic. There is about 15ft from the bathroom to the left side of the house where I could put the vent.
Old 12-21-06, 03:31 PM
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Three palces to vent a bath fan that is mounted toward an attic, thru the roof, at the eve(if there is enough space), thru a gable end(depends on the size of the fan and the length of the run). Vent caps are available at home and roofing supply stores. All caps need a damper flapper to prevent wind from blowing in. Roof and siding(gable) vents need some sort of flashing. Eve vents need something to prevent bugs and critters from getting into the vent tubing. The longer the tubing, the more fan power is needed, and the pipe needs very little restriction, no corrugated tubing. A good fan should have 1.5 times the capacity of the room in CFM. A 60 sq ft bathroom should have a 90CFM fan. There are those that will argue this, so be it.
Old 12-22-06, 10:14 PM
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Calulating CFMs for Bathroom Vent

To calculate the required CFMs for a bath vent:

Calculate cubic feet of bathroom (length x width x height)

Divide by 60 (# minutes in an hour) (8 air exchanges/hour is recommended)

Multiply by 8 (for the 8 required exchanges)

This number will give you the number of CFMs required for the vent/fan.

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