On 1/30/2020 6:36 AM, Gary wrote:
Cindy Hamilton wrote:
I'm a little curious. Do steamy showers or baths affect the humidity
in the attic space that much? My bathroom vent fan exhausts to the
outdoors, so I've never thought about the humidity that might leak
around the fan housing. (The attic access--right outside the bathroom--
has a gasket.)
I had a customer once with bathroom exhaust fan that went to the
roof but had bad water stains on the ceiling around the vent in
the bathroom. Problem was the exhaust duct between the vent and
the roof was exposed in the cold attic (in winter). It didn't
leak but it got bad condensaton when the duct got warm from a
shower and condensation ran down the outside back towards the
bath ceiling vent.

Solution was to insulate the exposed duct in the attic.

Â* Gary , the scenario you presented is physically impossible ! Water
condenses on COLD surfaces , not warm . I suggest the cold attic chilled
the duct causing the warm moist air inside to condense on the INSIDE .
It's still gonna cause the damage you describedÂ* as the condensation
wicks out into the surrounding drywall/plaster/whatever . Solution is
the same ...

--
Snag
Yes , I'm old
and crochety - and armed .
Get outta my woods !