Posted By Lbear on 04 Nov 2013 11:28 PM

Yes, that is stainless steel. The reason why the engineers designed it that way is because stainless steel re-bar conducts 90% less thermal transfer than standard steel.

Actually it's more like 50% to 80% less than rebar. Look at mild steel, high carbon steel, 316 stainless, and stainless steel in this chart. There is a wide variance, but yes, stainless does have lower conductivity than rebar would. You could probably come up with 90% less conductivity for the entire assembly if the comparison is based on low strength steel rebar vs. high strength SS, but realistically the tensile strength of SS vs ordinary rebar is somewhat the same.

http://www.engineersedge.com/properties_of_metals.htm

Posted By dmaceld on 05 Nov 2013 10:50 PM

Posted By Lbear on 04 Nov 2013 11:28 PM

Yes, that is stainless steel. The reason why the engineers designed it that way is because stainless steel re-bar conducts 90% less thermal transfer than standard steel.

Actually it's more like 50% to 80% less than rebar. Look at mild steel, high carbon steel, 316 stainless, and stainless steel in this chart. There is a wide variance, but yes, stainless does have lower conductivity than rebar would. You could probably come up with 90% less conductivity for the entire assembly if the comparison is based on low strength steel rebar vs. high strength SS, but realistically the tensile strength of SS vs ordinary rebar is somewhat the same.

http://www.engineersedge.com/properties_of_metals.htm

The Schock engineers and testing showed the 90% reduction but like you mentioned, it is the entire rebar assembly. The thermal break of the EPS is 100% but the rebar is at 90% reduction in thermal conductivity via the rebar in the slab.

Per Schock:

To conserve the structural integrity between the exterior balconies and the interior slab, high strength stainless reinforcement bars are used to connect both sides and transfer loads (tension and shear). These traverse the insulation body of the product. This not only reduces thermal conductivity up to 70% compared to carbon steel, but also guarantees longevity through its inherent corrosion resistance. The combination of high strength concrete, small section area and low thermally conductive materials again offer advanced thermal performance in comparison to carbon steel and stainless steel. The combination of all these aspects means that the Schöck Isokorb type CM reduces the thermal conductivity at the connection by approximately 90% compared to traditional reinforced concrete connections.

Posted By Lbear on 05 Nov 2013 11:08 PM

Per Schock:

To conserve the structural integrity between the exterior balconies and the interior slab, high strength stainless reinforcement bars are used to connect both sides and transfer loads (tension and shear). These traverse the insulation body of the product. This not only reduces thermal conductivity up to 70% compared to carbon steel, but also guarantees longevity through its inherent corrosion resistance. The combination of high strength concrete, small section area and low thermally conductive materials again offer advanced thermal performance in comparison to carbon steel and stainless steel. The combination of all these aspects means that the Schöck Isokorb type CM reduces the thermal conductivity at the connection by approximately 90% compared to traditional reinforced concrete connections.

Actually, I'm sure it is a good product to use for cantilever loads like upper floor balconies. But to use it in the garage slab/driveway application is like using a Mack dump truck to haul sand to a kid's sandbox! Way overkill! It probably would take 30 years of heat savings to pay for it! Now, if you were crazy enough to put a basement under the garage, then this would be worth looking at!

Posted By dmaceld on 05 Nov 2013 11:41 PM

Actually, I'm sure it is a good product to use for cantilever loads like upper floor balconies. But to use it in the garage slab/driveway application is like using a Mack dump truck to haul sand to a kid's sandbox! Way overkill! It probably would take 30 years of heat savings to pay for it! Now, if you were crazy enough to put a basement under the garage, then this would be worth looking at!

I agree, it would be hard to justify the cost for a garage slab application. The product is better suited for concrete balconies or porches that need to be thermally broken but at the same time transfer load forces.

Thanks to every one for posting

Posted By FBBP on 04 Nov 2013 10:37 AM
Krom - you are right that it will draw heat out of the building but you need to consider a few more issues.

With a break right at the door, you significantly weaken the slab at a crucial point. The part in the door opening is on the stem wall and the part just inside is on fill and has the added vehicular weight. For sure it will shift at this point.

If you are sloping the floor to the door, any break will receive copious amount of (salt) water. This will enter the joint and cause problems over the years.

IMO you are wasting your money with mesh, especially if it is cheap rolled mesh from the box store. Use 3/8 or preferably 1/2" rebar @ 16" o/c b/w.

While you are loosing heat from a 5" slab, you are loosing more heat from the 6 to 8" core of the icf stem wall. Think of heat like water (well maybe maple syrup) It will run to the lower concentration and as concrete is very conductive, it runs quite quickly.

Possible solution. Use Smartwall's composite deck, which probably has grooves in the back, to give it a better seal and then run a couple of dovetail grooves in the from. This will help to seal out water. Drill the board 16" on center and run the rebar through to the stem wall. Yes, you will get some heat lose through the bar but that is what it is. If you want, price out some stainless for this section. Don't use epoxy coat.

Put a couple or 3 inch cap of eps (or window buck if your block supplier handles it) in the top of the core.

If you put the break right under the door, drop the finished level of the apron by 1/2 inch. This will prevent wind driven rain from backing up under the door and help inside water drain way quicker.

I was considering 5'x10' sheets of 6" mesh (its commonly used around here and makes it easy to lay radiant tubing with no tape measure needed)

My concern was drawing heat out of the 8" core of the building (as well as the floor slab), and trying to break both, yet have something that was strong enough to be driven over daily, and have lots of salt water running over it.  I was assuming there was a proven method for this that I hadn't found yet.

Since I tend to over think things...  I was trying to avoid building some sort of enormous concrete structure on its own footings to act as an apron, and have it cantilever over the stem wall to butt against the floor

I'm having a hard time picturing the bolded..  are you talking about using the composite decking as a threshold for the bottom of the door to seal against?

also when you say don't use epoxy coat, you mean epoxy coat rebar, or epoxy floor finish.

The strength of rebar in concrete is directly porpotionate to the x section of the steel. Compare the sections in total of the 10/10 mat to 1/2" bar @ 16" o/c.

See attached detail for concrete break. Don't use epoxy coated rebar as it has a higher failure rate then uncoated.

Thanks for the picture, makes sense now

Salt (from tires in cold climates) and exposed rebar (at the thermal break or at expansion joints) aren't a good mix. Galvanized rebar would help. Or perhaps short sections of stainless (expensive), basalt or no steel at all.