[GSBN] Under slab and edge insulation at doorways

[Chris Magwood]

Hi Kelly,

Edge of slab insulation has been a thorn in my side ever since I started 
to build. In the end, I've solved the problem for myself by not building 
thickened edge slabs anymore. Instead, I'm doing a perimeter of 
double-wythe CMUs (usually 6 inch), which leaves a space of 4-9 inches 
(depending on the bales and orientation) for insulation between the CMU 
walls. This all sits on a concrete footing. Then, inside this wall 
(which can be down to frost depth or can be shallow (with a skirt of 
recycled carpet in our case) we can either pour the concrete slab (yech) 
or do floors of various earthen or recycled varieties.

One of the advantages of this system for us is that the CMU wall is code 
compliant, whereas slabs require engineering each time. The whole thing 
either uses less or the same amount of concrete as the thickened edge 
slab, and a lot less rebar, and no forming. And, the insulation is in 
the middle of the wall, where it lines up nicely with the walls 
themselves and doesn't leave any cold bridging as often happens with 
slabs insulated on the exterior. The insulation between the CMUs can be 
your perlite, mineral wool or a variety of other insulations that don't 
need to be rigid because they're contained.

There's my 2-cents!

Chris


-- 
www.chrismagwood.ca