[Greenbuilding] Exterior wall construction--Again!!

[Ward Edwards]

The best method to attach the fibre cement board would be to attach 
strapping to the exterior with screws that can reach through the foam to 
the durisol or block (you would have to use tapcons or similar for the 
block) and then the fibre cement could be attached to the strapping with 
roofing nails (you need something with a large head).

You would probably be better to put the foam on the inside and seal it 
as your interior vapour barrier as you want it on the warm side of the 
wall.  On the exterior, you want a vapour permeable surface so that 
trapped moisture can escape the wall.

To attain R40 in your wall, if just using foam, you would need 8" of 
XPS, as it has a rating of R5/inch.  The durisol or block filled with 
insulation would have the problem of a lot of thermal bridging.  I 
looked at Durisol when I built, but eliminated it from consideration due 
to cost.

Ward Edwards
http://www.ownerbuilder.ca


Lynelle Hamilton wrote:
> I'm building on waterfront and am looking for the exterior wall 
> "assembly", if you will. When John spoke of the 'wetness' of the PNW.  I 
> suspect I'll be similar.
> 
> The wall core is as follows:  Durasol or Concrete block (if block, 
> cavities filled with insulating material)  cladded with foam on outer 
> wall, then...what??  A friend, who developed a type of ICF, says just to 
> put fiberglass mesh over the exterior foam and then stucco, that the 
> foam is the vapour barrier.  I don't know about stucco at the 
> waterfront, and  have toyed with the idea of cement fibre panels.  Stone 
> (other than the "artificial" stuff) is not a possibility, except 
> possibly for a partial wall.
> 
> FWIW, slab is poured concrete, insulated as much as I can.
> 
> With cement fibre panels come the need to somehow attach them (through 
> foam).  From all the discussion on this site, I now have no idea if 
> these panels are OK and if it good or not to try to attach through the 
> foam.  Also, what depth of foam do I need to attain R40 or better in the 
> wall?
> 
> Any ideas or suggestions as to where to research?  I'm building pretty 
> much on my own (as is obvious from my questions)!
> 
> Thanks
> 
> Lynelle
> 
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