It's perfectly possible that it's not a problem. Depends on whether
the attic is well ventilated and what sorts of weather you experience.
If the vent drips in cold weather, maybe just put some plastic sheeting
below it to catch the drips.

Also, as to removing humidity by running furnace. Bathroom fans don't
just remove humidity; they remove stink.

On 4/6/2011 7:02 AM, N8N wrote:
Was it ever acceptable by code to vent a bathroom fan to an attic? I
was helping my cousin over the weekend with some minor renovations to
her condo - she wanted to replace the fan in one of the bathrooms, and
when I went up into the attic to unhook it I found that both it and
the one in the master bathroom were not vented to the outside, but had
a maybe 4' piece of dryer duct just tied to the trusses and venting
into the attic.

Originally I thought that this might have been a shortcut taken by the
roofers that replaced her roof just before she moved in, but either
they replaced none of the sheathing or all of it as it all looked
consistent. Also I took a look at other similar units as I was
walking down the street and I didn't see any vent caps in the likely
locations on any of the roofs.

The way she explained it to me was that anything done to the outside
of any of the condos was taken care of by the association, not her
(e.g. roofs, siding etc.) so knowing exactly who to yell at would be
important.

Worst case, I guess, would be that this was a shortcut taken by the
original builder some 15-20 years ago, and it's not going to be
fixed...

nate