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Re: GSBN:RE: 5 perms / no ventilation; and top-of-wall



Mark,

The general practice in Scandinavian countries is to have less
permeable interior finishes then outer. Meaning for instance that
wooden window frames tend to have less coats of paint or thinner on the
outer surfaces then inner. Another practice is that air barriers
including caulking when made are on the inner side of the structure.

The Scandinavian practice is boiling over to the Netherlands and I
suppose many other Northern European countries. I have also seen a very
applaudable practice at a some German strawbale buildings of taping all
seems that intersect with interior plaster surfaces.

Rene
On Mar 7, 2007, at 23:10, Nehemiah Stone wrote:

         Illustration 10C in the Details and Design chapter says that
vapor in the wall assembly tends to rise, and can condense on the
bottom of a roof bearing assembly. We know that air movement within
the wall assembly can be a bad actor, as implied by Mister Stone in
7.3; we know (through modeling) what happens to the thermal
resistance of a bale wall when there are gaps between the cladding

Besides the above measures regarding air tightness avoiding cold
bridges is also of great importance. The top wall plate has serious
potential for creating a cold bridge. It would be good practice to
apply an insulating facia to the outer surface of the wall plate before
plastering. A good material would be something like pavatherm which is
a woodfibre insulating board, Lambda .045 (metric value). An added
bonus of this type of board is that plasters adhere readily  to its
surface.