On Feb 10, 8:11 pm, "Victag" wrote:
On Feb 10, 6:06 pm, "Don Young" wrote:



"Victag" wrote in message

roups.com... We have just insulated our shed and put vapor barrier inside the
insulation, with a layer of tar paper between the insulation and the
siding. We are noticing that one wall is sweating and moisture is
collecting between the insulation and vapor barrier. Berfore we
drywall, we want to eliminate the moisture. The attic of the shed is
vented, so I can not understand why we are seeing this moisture
still? Does anyone have any advice as to how to fix this and why we
would still be getting moisture? We would like to use the shed as an
office and have also installed heating. Are we still lacking proper
venting or is this likely because we have not properly sealed the
vapor barrier? Thanks in advance for any help. If it makes a
difference, we are in BC Canada, moist climate with a mix of cold and
warm.

You have a vapor barrier on both sides of the insulation, which is
incorrect. Since the installation can not be absolutely air tight, some
moisture will find its way into the insulation and must have an easy escape
path. In cold climates it is recommended that the vapor barrier should be on
the warm inside and the outside be ventilated. You need to remove the tar
paper.

Don Young

Thanks for replying Don. Perhaps I used the wrong term, as the paper
is not truly tar paper...but rather the black pourous paper
recommended by the folks at Home Depot and appears to be what I see
builders using ont he new homes. Is this the wrong paper? and if so,
what should we have between the insulation and the exterior siding?

tarpaper is vapor permeable and is not considered a vapor barrier. in
fact, i believe tarpaper is more permeable than tyveck. I have yet to
see a vented wall, and if they were, the R value loss to wind wash
would be significant. is it possible that your wall got wet before
you insulated it? If it's just a small amount of condensation, it
should find its way out. otherwise, pull the vapor barrier off, and
run an electric or sealed combustion heater to dry it out.