[Greenbuilding] Earth block wall section

[Rob Tom]

stephen at yourhealthyhouse.ca wrote:

> Proposed wall system from the inside out.

> 8 x 8 timber post and beam. Posts inset from slab edge by 1.5"
> Earth block wall. 4"
> 2 x 4 strap wall.
> Sprayed in place polyurethane foam wall. 4.5"=R22
> Horizontal wood siding tied to 2 x 4's.

This is likely going to sound harsh but will be straight and in keeping  
with my "40-grit"-ness...

I have to say that I think that the design is very confused.

It's seems like it's trying to be Green but doesn't quite know how to go  
about it so it's throwing everything except the kitchen sink at it in the  
hopes that one of the projectiles will hit the target.
But I haven't had a look at the sketch of the wall section.
So much for the first impressions and on to the facts.

The combination of the timber frame and the 2x4 "strap wall" means that  
one is redundant from a structural perspective and since the timber frame  
uses about three times the volume of lumber that an OVE 2x6 stud wall  
would use, the timber frame would seem to be the likely candidate for  
elimination but no doubt, the building owner wants to have the "big stick"  
aesthetic so it'll likely remain in the design.

Then there's the pee-you foam.

Since the 2x4 "strap wall" is perfectly capable of being a loadbearing  
wall if the 2x4's are oriented properly, then the earth block wall is  
really just a veneer/interior thermal mass, which is okay and makes a lot  
of sense but the reason that people usually opt for expensive,  
sprayed-in-place pee-you foam is because of limited framing cavity volume  
in which to place insulation.

That is not the case here.

There's no reason why the space between the stick-framed wall and the  
earth block wall couldn't be increased to allow R-26 or R-39 worth of  
less-expensive/more-green Roxul batt insulation, in the manner that  
double-stud walls are done, except in this case, the curtain  
wall-in-reverse would be the earth block veneer.


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Rob Tom
Kanata, Ontario, Canada
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