EPS deck for suspended concrete slab – good or not so good?
So I’m finishing up the foundation walls for the front basement extension of my reno. I am using 6″ core ICF to form the 3 walls which extends the basement forward and will eventually create a front porch. This is similar to how people do cold rooms under their porch, but I am doing this as part of the conditioned finished basement space.
For the concrete slab on top, I was planning on using an EPS concrete deck form. EPS deck is the product I’ve been in discussion with, but insul-deck is a more familiar brand that does the same thing.
I figured it would be efficient with the build and with achieving good insulation for the envelope. The thickness of the EPS deck would be 10″ with a 3″ concrete slab on top. This thickness would just meet my code minimum of R31. The area of the top of the deck will be roughly 5’x14′.
I’d like to ask if anyone has any experience with these deck systems and to open discussion on alternatives.
After doing some thought on it, I now have some reservations. One being that EPS isn’t the most efficient in terms of R value per inch. I would just barely be meeting code. R31 isn’t bad but I’d like to do better for higher performance. Second I noticed the flutes that create the concrete joists are quite wide. They take up a lot of volume compared to normal joists, which take up a lot of potential insulation and performance as well.
I was wondering if I would be better off with a more “conventional” wood joist and plywood deck with concrete slab assembly, or a corrugated steel pan slab assembly. Either of these would allow me to 2lb spray foam underneath to really improve the R value & performance.
Does anyone have any experience with this?
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