"Bob" wrote in message
oups.com...
Well the weekend has past and here are the results of my
troubleshooting. For the sake of being brief I will use bullet points:
- With the Window open for more air flow I still get condensation
insided the vent fan.
- With insulation around the air duct and bathroom fan I still get
condensation inside the vent fan.
- I switched to the smooth metal air duct instead of the flexible type;
condensation.
- I ran the fan for 5 minutes before running the shower and for 5
minutes after and still condenstaion.
- When I turn the fan on I can hold a piece of paper by the fan and the
paper will stick to the grille.

Also just to be clear the condensation will build up over 2 days to
form standing water and ends up dripping out of the fan.

The vent flap on the roof vent opens when the fan turns on, the flap on
the fan is opens as well. The condesation is not coming back from the
vents because I have a slight angle going down, away from the fan.

A couple of other items for thought. My bathroom fan is in the attic
about 3-4 feet away from a soffit vent. It's not directly by it but
it's in the area. Also I am using aircondition/heater vent insulation;
about 3/4" thick. Could these things be an issue?

The next thing I am going to try is remove the flap from the fan, to
see if this allows faster airflow. Also someone mentioned to me that
it's possible that the climate in my house and attic is just going to
produce this affect of condenstaion so I might need to figure out a way
to get the condensation out. Possibly there is a fan made with some
sort of drip that I can attach pipe to to channel the water out;
similar to how A/C. Any thoughts on this.


Insulating the fan box then preheating it before running the fan might help
but if you read my earlier post, I suggest it's a lost cause since very
humid air will still condensce on even warmish surfaces because the dew
point is raised so high when steam is present.

I suggest instead of preventing the water, deal with it instead, give it a
place to collect and drain or better yet, evaporate. A sponge or cloth
inside the housing will absorb the water and with its large surface area,
evaporate that water more efficiently than standing in a puddle.

Checking the Broan website they suggest the same advice you already have,
namely the condensation is from cold duct work. My observation and
seemingly yours is that most of the water is forming on the fan metal
housing moreso than the duct. In this case insulate more directly on top of
the fan and make sure the flapper is closing so cold outside air does not
chill the housing more than necessary