I've read this one before, but I have a similar problem yet it might be different.. here goes nothing.
We have a constant leak in our family room, which is directly below the bathroom and our children's bedroom. Upon further inspection, removing part of the ceiling where the leak has discolored the drywall, we see the elbow joint of a PVC vent which leads upstairs inside the wall behind the tub but between the rooms. I focus my flashlight up inside the exposed cavity showing the elbow joint more clearly, and can see that the water (which is very very lightly streaming down) begins from further up the pipe. I investigate further by heading upstairs. I enter the kids room, open the closet, and remove the drywall which is fit somewhat loose (so to get at the pipes behind the tub of course) and notice the PVC vent is showing signs of this same very very light stream of wetness. Now I decide to head to the attic, which the entry point is directly above me in the same said closet... poke my head inside with my flashlight to find where the water begins. There are no signs of wetness eminating from inside of the attic... not from the PVC vent, no sign of water on the insulation, not under the insulation between the vapor barrier and wood... no stains from past water.... nothing!
I've recently had someone in to look at this problem. It was suggested that it may be condensation from cold air in the attic, warm air in the PVC vent, and that the condensation starts from within the wall where the heat and cold meet. The drip is slow and at night time is somewhat steady. It doesn't matter if it is winter, or summer, if it is raining, snowing, or hail... it comes back eventually again and again.
The solution suggested to me was to add an extra 20R rated insulation crossways to the already 20R insulation in my attic. It's an older house from the early '70s so..? It was also pointed out that the trusses were jammed with insulation, and that because this has been done, no air can rise inside and draw out through the vents above... which essentially is the culprit for the moisture retention, and build-up of condensation on the pipe within the wall - "cold meets hot". One more bit to add on top of putting more insulation in the attic was to wrap the PVC vent in the attic with insulation as well.
Could someone please let me know if this all sounds correct? I would really... really appreciate the assistance. We're re-doing our family room, and until we can this straightened out we're at a stand-still.
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