><< Among homebuilders there is a decided
> retreat from housewraps and back toward #15 felt under claddings. >>
>
>Most interesting.  Is this a regional phenomenon, widespread, or what? Since
>when, and why?  Under any particular forms of siding? Under good or bad
>builders?
>
>Ralph
>

The housewrap companies (Dupont and Simplex anyway) have had two effects
pointed out to them. 1) Extractives in some woods and waxes in hardboard
siding will act as surfactants that make water penetration through the
wraps very easy. 2) If the cladding or brick veneer are wet then heated
with sun, the vapor pressure in the cavity will go high, so the vapor drive
is strong toward the inside of the building. Both companies are doing
product modifications.

#15 felt has neither of these problems, so in the homebuilder's chat rooms
http://www.taunton.com:8090/WebX?14@@.ee6b303
http://www.jlconline.com/forums/techniques/index.html
there's a lot of talk in this direction. I doubt that Dupont or Simplex see
felt as hurting their bottom lines.

I don't think it's regional. For the last few years, homes have been going
up with no weather barrier at all, though BOCA has recently frowned on that
practice. The extractives problem is about three years old, first pointed
out I think by Joseph Lstiburek www.buildingscience.com. The sun-driven
vapor issue goes back many years in theory, but seems to have led to
visible degradation only with more widespread use of OSB.

The industry views everything as a workmanship issue (shallow pockets)
until you see companies reformulating their products.