Hi Eric,

Actually I did a horizontal run of 1.5 feet with a slight slope down
and then it curved up to a vent in the roof. The install instructions
showed that install or a wall exhaust install.

Just to give you a little more information. I actually removed the
dampener and the vent pipe and did a test of running a hot shower and
the fan venting into the attic space. After 8 minutes there was a good
size pool of condensation inside the fan. Got this idea from a few
contractors at church. This test showed that the steam from the
bathroom was not exiting the fan fast enough.

I already have the new fan and plan to install this weekend. I'll let
you know what happens.

Eric in North TX wrote:
I'm curious, does your vent go through the roof or out the wall. I ask
because I installed a nice older one in our master bath from a
demolition salvage place that removes fixtures from high-end houses,
and I was careful to slope the vent tube down to the wall exit. I've
had no problems