The north wall of the sun porch needs to be EPS-crete. It’s the barrier wall between the new bedroom (not built yet) and the sun porch, so it needs to be okay with being splashed, non-wicking, insulating and have thermal mass properties. It doesn’t have to be structural. Don’t get me wrong, EPS-crete is great structural stuff, but the little guest house we’re building is a pole building. Structural infill just isn’t necessary.
My brother, the whiz, is making me an EPS shredder. We have masses of EPS foam waiting to be shredded for mixing with concrete. I could stick all the EPS bits together and build a wall, but it would have zero thermal mass and would need covered on both sides to finish it off and make it durable. Yuck. I vote for EPS-crete and lime plaster.
I want to mix the EPS-crete and pack it into a form on top the foundation. I’m going to bury a couple layers of 6x6x10x10 in the middle of the bottom half as there will be dirt against the bottom foot and a half on the sun porch side. The extra support may not be necessary but I’d rather be sure.