[Greenbuilding] outsulating gut/rehab CMU house (was Re: embodied energy was Polyiso strength on roof )

[RT]

On Fri, 12 Dec 2014 10:36:41 -0500, AA-man wrote:

> A current project is the gut rehab of a modest '40's house, with walls  
> made of stuccoed concrete block.
>
> Current thinking is to fasten treated 2x's directly to the masonry, with  
> 1 1/2" thick Roxul Comfort Board installed between members.

> cover that with a continuous layer of more RCB, a good breathable WRB,  
> furring, and back vented siding.

As my Newfie fisherman friend might say :

    "Oither ye tinks beeg or ye goes home, By."

Seems like a lot of trouble just to get 3 inches of insulation.

I'd be inclined to take those same 2x's, rotate/flip them 90 degrees and  
suspend them 12 inches or so away from the CMU wall, fill the cavity with  
multiple layers of Roxul batts, joints staggered/overlapping between  
layers  -- R-40-plus with no foamed plast-ecchhh! (and attendant long  
fasteners so pricey that you feel that a pimp would be appropriate in the  
transaction).

Air-seal/WRB at the exterior surface of the block first of course,  
rainscreen cladding hung from the 2x's and lard tunderin jayzuz,  oi tinks  
yer dun.


-- 
=== * ===
Rob Tom ADT1
Kanata, Ontario, Canada
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