[Greenbuilding] wall envelope - rainscreen

[RT]

BCJohn wrote:

[sneeped]
> The exterior sheathing ply is being taped and sealed as an air barrier  
> and
> outside of that is a wrb and then a 1/2" rainscreen cavity then 3.5" of  
> more
> eps foam mechanically screwed through to the wall. Foam will then have  
> some
> render on it.

> Now my problem is the cavity location in the overall wall and its affect  
> on
> the outboard insulation (possible convective losses)and wall drying

Without any comments about the foamed plast-ecch! insulation/outsulation  
and the pseudo-stucco render...

Would increasing the rainscreen cavity to 1" so that it could be filled  
with semi-rigid Roxul
DrainbBoard be an option (perhaps decreasing the 3.5" of EPS to 3" if  
overall wall thickness is an issue ?

The Roxul would still allow drainage to occur but would minimise air  
movement in the venting cavity.

(But of course, then the obvious question would be "Why not replace all of  
the foamed plast-ecchhh! outsulation with Roxul and replace the  
pseudo-stucco with a real cladding ?" ... but I won't ask that question.)

-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  c a >
manually winnow the chaff from my edress if you hit "reply"
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