I'm trying to figure out how to do transition from the concrete floor slab when it comes to a door with ICFs. I've attached a picture based on my understanding of how a door is commonly installed on a concrete floor slab. So in this example, the ICF forms are put on top of the footing, and a door buck is framed for the door rough opening (blue in my drawing). This door buck sits directly on top of the footings. Then the ICF concrete is poured. Now, when it is time to pour the floor slab, 2" of insulation is put down and the floor slab is poured 4" thick. But here is the part I don't like -- the floor slab continues out the door buck to create a level platform for the door to sit on so the bottom is aligned with the top of the floor slab. The problem to me is that this is a giant thermal bridge from the outside concrete to the inside floor slab. It seems like this kind of thing must be very common and I'm sure you all have good solutions for fixing this problem. I'd appreciate the advice. Thanks.

Leave the outside foam in place and pour the floor against it. If the footings are as shallow as shown, wrap them with foam as well. The floor will loss heat to the footings at an alarming rate.

I haven't seen this done yet, but a material that can be used for solving problems like this is Compacfoam, a super-high-density foam that is thermally insulating but almost wood-like in strength.

https://foursevenfive.com/product-category/thermal-insulation/compacfoam/

Hello, Thanks much for the response. I'm not sure if I'm understanding what you are saying for sure, so I drew up a diagram based on what I think you might be saying -- can you tell me if that is what you are talking about or if I did it incorrectly? And yes, I realize I wouldn't want the footings to be exposed like that and they wouldn't be -- in my original diagram I had left off the stem wall which goes down 4' and I'm putting 1.5" XPS on the outside of it.

So on this new diagram I have, after ICF pour is done, putting 2" XPS insulation down through the door rough opening and then building a 4" riser of 1.5" XPS on the outside edge of where the door would go, and then pouring the 4" slab all the way to that. Is that kind of what you were talking about doing? Thanks for the help.

Dark - You say that you are going to put a four foot stem wall in place. This indicates to me that you are in a cold climate. Even if you are only putting an 18" stem wall in place why would you use CIP for the stem wall and then switch to ICF?
Concrete is a great building material but it is highly thermally conductive. Thinks of heat as water. Well okay, maybe maple syrup except that it does not obey gravity. The foam is the container. Any where that you do not have foam on the concrete is a hole for the heat to leak out. If you place ICF on top of the bare concrete stem wall the heat is just going to drain out. If you put foam in front of the stem wall you will slow the drainage but it will still leak out the back. Ideally you want your concrete totally encapsulated in foam.

When you bring your ICF stem wall up to the grade level and come to your door opening, cut your outside layer of ICF foam to the height of the top of the floor. Cut your inside ICF foam layer to the height of the bottom of the floor. When you pour your concrete, keep the concrete down the depth of the thickness of your ICF foam and fill that space with scrap pieces of ICF, tapping them a bit to embed them in the concrete.

When you pour the floor, there should be foam under the floor, butting up against the inside layer of ICF foam. The concrete pour over this foam, over the inside layer of the ICF, over the scrap pieces you have installed at the bottom of the door opening and against the outside layer of the ICF foam. Now there is no concrete exposed to air or soil except the footings. The footing should be placed on high density foam and the sides and top that is not covered by the ICF also wrapped with foam. Don't let concrete touch air or soil and you will have the most energy efficient, long lasting home that can be built.

http://www.schoeck.com/en/news/construction-site-video-clip--1875