R-30 insulation between 12" thick concrete floors

[Remington]

Hi,
We have a hillside home that requires 12 inch thick concrete floor. For structural integrity, the concrete floors should be continuously extend out without any jogs or breaks. Als, Here in California, we require R30 insulation between floor and exteriors. The question is, where is the insulation applied? If you see the concrete floor structure between the living room and master bedroom, a portion of the 12 inch thick concrete floor is partial on grade, and partially overhanging.

Also, trying to achieve R30 insulation without adding too much additional thickness may also be a factor. Apparently, a 5.5-inch-thick ISO board (rigid insulating) offers R-31.9. Would spay foam offer a higher value without creating too much additional thickness?

building section <-- link

 

[Yankee Chronicler]

Respectfully, these are questions you should be discussing with your architect.

 

[steveray]

I believe you need to look at the slab floor section

 

[Joe.B]

Did someone do an energy report? I've seen multiple energy reports that don't match the plans. In your case they may have done the report assuming a perimeter foundation, R-30 is totally appropriate for that, but not for a slab. If they redo the energy report for a slab on grade, they'll probably come back with 2-inch foam with about an R-10 (8-12 depending on quality). It would look something like this:

 

[bill1952]

But for the portion of the slab not on grade? I think it's floating, cantilevered or supported. Not simple. Maybe code doesn't require it explicitly but I'd want it protected - from rodents if nothing else.

 

[Paul Sweet]

The ceiling of the master bedroom needs to be insulated below the deck. I'd be surprised if the energy code allows a slab to cantilever without thermal breaks or encasing the top & bottom of it in insulation.

 

[bill1952]

The ceiling of the master bedroom needs to be insulated below the deck. I'd be surprised if the energy code allows a slab to cantilever without thermal breaks or encasing the top & bottom of it in insulation.

It's a complicated building, at least from insulation point, and Yankee was right.

That said,out of curiosity, why couldn't master bedroom ceiling slab be insulated on top, like a roof?

Just following now.