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Posted by marson on December 28, 2006, 7:47 pm
buffalobill wrote:
> problem may be vapor barrier. the website where you will find all your
> answers on page 18:
>
http://www.buildingscience.com/resources/mold/Read_This_Before_You_Design_Build_or_Renovate.pdf
> then browse thru the search feature and don't forget climate when you
> select a construction style. this free construction website is better
> than excellent.
> http://www.buildingscience.com/resources/
>
>
> jmsajan@sbcglobal.net wrote:
> > I have read most of the posts pertaining to my issue, but still have a
> > few questions unique to my situation. I live in Michigan and have
> > recently added an addition off the back of my two story tutor home.
> >
> > Background
> > The existing second story roof pitch was continued rearward to create
> > the addition roof. It is a 12:3 pitch--not very steep. The existing
> > attic appears and always has appeared very dry to me. It has about
> > 3"-4" of blown-in insulation. It has two side vents and two roof
> > vents. There is a bathroom fan on the second floor but I have it
> > vented into one of the side vents.
> >
> > Because I extended the existing roof pitch onto the new addition it
> > created very little space for insulation and air venting. I put soffit
> > vents along the entire eave/over hang. I then put those plastic air
> > vents from the soffit all the way into the existing attic space. I
> > then put 5-1/2" R-21 insulation with vapr barrier facing the interior.
> > Because I am working only with the depth of the joist I literally have
> > roof board/air vent/insulation/drywall all stacked on top of eachother.
> > The only air gap is the one created by the plastic air vents.
> >
> > I was getting ready to drywall when I noticed serious condensation on
> > the flanges of the air vents--the area where you staple. The area of
> > the air vent that is off of the roof is dry but where the flange goes
> > up to contact the roof board it is really wet. Not just like a little
> > condensation where you could write your name, but like many big drops
> > of water. My insulation was wet. I have ten "runs" and they all have
> > this same condition.
> >
> > Any suggestions on how to resolve this issue? Somebody told me that I
> > need to have equal amount of inlets as I have outlets. I probably have
> > more inlets then I do outlets. Should I install an attic fan? I was
> > reading about a solar powered one, which means it only operates during
> > the day, would that be sufficient?
first of all, what kind of vapor barrier do you have? you should have
6 mil poly, seams taped and all penetrations sealed. that alone should
go a long way in preventing trouble.
second, it sounds like you have a lot of moisture in your addition.
did it rain during construction or something? if so, you might want to
try to dry it out for a bit.
finally, a better way to vent a roof is to use a cardboard chute which
are available here in the midwest. this staples onto the joists and
leaves a continuous air space unlike the foam chutes which just leave
an air space in between two joists.
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