jeffc wrote:
One year old house. I was in the crawlspace (no basement) and noticed the
subflooring was wet around one of the air vents. The line is pretty well
insulated all the way to the vent. I'm not sure why that vent in particular
would be a problem, but it seems to be the only one. I'm concerned the
subfloor will start to rot over time. I checked it about a month ago and it
was the same. There is no moisture I can detect from inside the house on
the floor (pine flooring.) Any ideas why this is happening or what to do?
I will call the builder, but it's a couple months beyond warranty and he
might not do anything. Need to be armed with information....

Somebody else got the one-word answer to what it is and basics of
why...

If the subflooring is what is wet, then the moisture is either
condensing above it and soaking through or the vent/ducting is running
in contact w/ it or there is a collection point at which the moisture
is dripping onto the subflooring.

I'm guessing the problem is that somewhere they missed an area that
isn't insulated and that's where the condensation is forming. As the
above suggests, that point _could_ be a considerable distance from
where you're noticing the symptoms so don't confine your search only in
the immediate neighborhood but think of how water could have gotten
there from elsewhere considering the ducting arrangement, gravity,
support straps as conduits, etc., etc., ...