In the "top 10" thread, I was asking for comments on the Hercuwall vertical ICF system.  I know they are busy but I have been trying to get some technical info on the product, as well as any comparative pricing, install or experiences from installers or engineers. 

Heat lose from conduction ?

Good point.  It gets to 40 below here and frost lines on the interior drywall could just be an issue.

Could be significant, especially considering the steel webs that go all the way through. Coupled with the concrete with an R value near zero those steel fastening strips are going to conduct a lot of heat. If I remember correctly, a while back when I was comparing the heat transfer capacity of steel vs wood I calculated that a 1/16" thick steel web will conduct the same amount of heat as a wood 2 x 4. Wood has the advantage of providing resistance based on distance from hot side to cold side. Steel is zilch.

No question the additional foam will help, but the greater benefit would be the thermal break over the steel webs. That is why it helps on 2 x 4 walls also. I'll see if I can find time to do some calculations in the next few days to get a better handle on it. It might even be that 1/2" would help so much the incremental benefit of 1" wouldn't be worth it. On the other hand, some advocates of high R value walls would say add 5" more!!

As far as thermal mass of the concrete, you'll find strongly differing viewpoints regarding its benefit in cold climates. I think all the arguments make valid points. A search here should bring up several threads from the past year or so. You'll find interesting reading in them.

Yes, if we could just pack all houses in a tightly packed flax bale system, an R80 wall would make all these R20 - 30ish values pale by comparison. .  Designing the heating system would be easy too. Buy one large candle per year!

I find it surprising that even a thin foam would serve as enough of a thermal break, but I do look forward to your technical evaluation (if you find the time).

Your background (and photo) sounds like you might be a structural or mechanical systems engineer.  Regardless, I have enjoyed monitoring your intellectual responses.

Sask, thanks for the compliment. Yeah, my background is mechanical engineering although I haven't been deeply involved enough in any particular aspect of it to lay claim to being a PE.

Have you looked closely at the photo gallery on the Hercuwall web site? As you know, there's no technical info published there. I just spent time looking at all the photos and have decided I can't garner enough info to justify doing a heat transfer estimate through their wall. Besides, after looking at it closely they do not have steel going all the way from one side to the other, which lessens the heat conductance somewhat. But that also raises concerns about their design.

If you look really close you'll see their walls are a post and beam concrete structure. This means you've got all the potential issues of concrete flow and voids to deal with with that kind of pour. Concrete has to flow into all the beam sections from the columns. Get into to much of a rush and I can see air being trapped in the beam sections causing voids in the concrete in them. You'd have to be extremely careful to have the right slump to assure complete flow. Of course, you do use less concrete so that is a plus.

But what concerns me most is the absence of any solid material connecting the inner and outer panels together, other than foam. It looks like the panels are glued to the inner web foam. I wonder just how structurally sound that system is when you've got 8 or 10, or even 12 ft of concrete pressure against the panels. The way the rebar hooks in the steel are designed the horizontal rebars don't provide any interconnection between the inner and outer panels.

The wall sections appear to be hand assembled in the factory. When you look at all the steel they use, and all the manual labor they use, to fabricate the wall sections and compare that to the typical ICF block which has plastic webs and is molded by machine, you have got to really wonder about the cost compared to typical ICF blocks. And then there's that channel they use on the footer. It has to be punched to go over the dowels which means time is expended in either getting all the dowels in exactly the right spot, or in making sure the holes get punched in the right spot to fit the dowels.

I don't know. I've built only one house, and have experience with only Buildblock, so I'm no ICF expert, but I sure would be hesitant to use the Hercuwall system.

Oh, and the photo is just one of my favorites I took. It's a historic and scenic concrete bridge over the Payette River on state Hwy 55 just north of Smith's Ferry in Idaho.