View Full Version : Bathroom exhaust fan -- ok to vent to space above ceiling?
02-14-2007, 10:30 AM
We're having a bathroom remodeled, gutting it and starting from scratch. When the contractor removed the old sheetrock from the ceiling, I noticed that the existing exhaust fan doesn't vent to the outside, just to the space above the finished ceiling.
I assume this is not preferable, but is it acceptable? I purchased a new exhaust fan, and I'm not sure if I should ask the contractor to add an exterior vent.
You really want moisture laden air vented outside the structure.
The new fan may move more air ,so even if you see no damge now from venting it there ,you might in the future.
02-14-2007, 11:07 AM
Most building codes require that the bathroom exhaust be vented outside the structure. Even if this is not the case venting all of this moisture laden air into the attic will greatly inctrease the probability of mold and mildew problems. Outside venting is in your best interest.
02-14-2007, 11:26 AM
Thanks for the replies. I just told the contractor to add an outside vent.
02-14-2007, 10:47 PM
The fan needs to be vented to the outside in some way. I believe it is code in most areas.
02-14-2007, 10:59 PM
I just vent them into the mother-in-laws guest room.;)
dan sw fl
02-14-2007, 11:30 PM
I just vent them into the mother-in-laws guest room.
Is that with or without a by-pass damper?
Our older houses would vent directly to the attic. Agreed it is code to vent outdoors, but I have to wonder about the thousands already installed in older homes. Why are they not causing problems right and left?
In my own S.Texas climate I have tried to think about the psychrometrics and what real world conditions would cause condensation. Many typical conditions would not. Dilution of bathroom air is a factor hard for me to quantify, but that dilution will inhibit condensation.
People sometimes suggest things like 80% relative humidity and 85 degrees, which I think will never happen. In my master bathroom conditions are about 70 degrees and 33% RH about now, even taking a bath or shower will not raise that much. If there is going to be a problem it surely must be in cold weather to permit condensation. So far none of my attic visits have allowed me to see that.
Just trying to figure these things out better than I understood before.
Best wishes -- Pstu
I just replaced mine this week, what a PIA. It was the builders unit from 1969. They nailed it to the underside of the ceiling joists(16d nails:mad: ) then put the sheetrock over it. 1 hour job turned into over 6 hrs with sheetrock work, oh well it's done now. Mine was the same way. Vented to the attic insulation area where plywood covers the joists, no ventilation at all. Now it's vented to the old furnace flue through the roof. 2 teenagers taking 20 minute showers each, I needed more cfm's:D
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