Replies

1. 
   TLRice | Feb 20, 2003 04:34pm | #1

   Brian,

   You didn't say what type of vent pipe or what it vents. Condensation, in all instances, occurs when the dew point of the air in contact with the object in question is above the temperature of the surface. Two ways to prevent condensation are to lower the dew point (humidity) of the air or raise the temperature of the surface. Controloling the temperature of a vent (flue?) is not practical, so you would have to concentrate on the air. Is there a source of moisture in the area of the condesation?

   If the vent is from a condensing, fuel burning appliance, I would bet the vent is leaking. Not knowing the details, this is just a guess. See if there is a joint near the problem area. More details needed.

1. 
   Tag | Feb 20, 2003 05:08pm | #2

   I didn't have any takers, so I ran a post under General Discussion called "Condensation is rotting my walls".  It's on a bath plumbing vent, actually.  Water is/was condensing on the PVC at ceiling level, inside the wall, at the hole in the top wall plate.  Then it dripped down inside the wall to the floor, and out under my bathroom flooring. 

   I only discovered this during recent bathroom remodeling, when I took the floor up.  I previously had the bath exhaust fans venting to the attic - That was laziness on my part that I didn't connect the vent fans to the outside after I re-sided the house last summer.  I have since corrected this condition, and I'm waiting to see if the condensation stops.  I initially didn't think this was the cause, since I perceived the condensation to be happening just inside the wall, separate from attic air/humidity.  If the dripping continues, I'm not sure what to do next.  I'll have to do some inspection and get back to you.  It's been getting up to around 40 here lately, though, and I'm not sure if it would condense anyway.

   Thanks for any input you feel like sharing.