On Sat, 20 Mar 2010 08:58:17 -0400, LSMFT wrote:

On 03/20/2010 08:22 AM, Phisherman wrote:
On Fri, 19 Mar 2010 20:14:02 -0500, "Jerry V"
wrote:

Would it work to connect an exhaust fan in bathroom to the main stack (cast
pipe)?



No. The main stack contains sewer gas, possibly explosive. Exhaust
the bath fan directly to the outside (not in a crawl space, not in an
attic space, not under a deck, etc)

Why not the attic if it's vented?

The exhaust fans in my house vent an inch or two below the ridge vent
at the peak of the roof. I suppose it could have even been even with
the bottom of the vent if they had tried.

The propulsion of the air by the fan would cause it to continue up
into the ridge vent and out the holes. And the heat of the air vented
from the bathroom would cause it to rise into the ridge vent and out
the holes.

And I guess when there is any breeze, or a hot air differential, the
exhaust air would get carried along by the general air current from
the soffits to the ridge rail.

It doesn't matter for me, because I only use the exhaust fan after I
clean the bathtub, and there is no extra humidity, but the other
hundred houses are probably built the same. But I spend very little
time talking with neighbors about their houses so if this has caused a
problem, I woudn't know.

(Every ten years I need to remove a layer of milkweed from tthe bottom
of the soffett vents.)