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Posted by ransley on May 5, 2008, 4:55 pm
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> > > I am wanting to use a thin layer of styrofoam outside of the sheathing=
> > > of my house
> > > as a thermal barrier... what i see out there (here in canada) is the
> > > standard pink (extruded) stuff
> > > and the white 'duro-foam' covered in a green vapor barrier which is
> > > quite a bit cheaper.
> > > I can tell that the durofoam is more likely to break, but assuming
> > > that i can install it in one piece,
> > > is there any difference in the lifespan/performance of these products?=
> > > (mold? rot? disintegration?)
> > > the r-values are very close.
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> > > also would i still need to use housewrap outside of the styrofoam?
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> > Polyisocuanurate usualy a foil covered boad is R7.2, the blue and pink
> > R 5, some white boards are R4 or so, You could have moisture locked in
> > and get mold, the foamboard is a vapor barrier, it should be on the
> > inside, it depends on how your house was made.
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> the house is not yet built (excavating wednesday), so i still have the
> luxury of choice...
> anyhow, isn't osb sheathing a vapor barrier as well? is there any way
> to up the r-value beyond the
> r-22 of roxul and a reflective vapor barrier inside? something to
> break the thermal bridge that the timberframe creates with the osb? i
> need to figure this out so i can know the thickness of the walls and
> order the windows...- Hide quoted text -
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> - Show quoted text -
If its not built and you want the highest R value then look a SIPS
construction R 40 walls, and R80 ceiling, vs R19 on your idea, but the
Vapor barrier should be inside. Or have the open area foamed instead
of fiberglass batt. 2x6 walls will give you what you need with foamed
walls.
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