So here's what I've kinda planned on for my new construction. I don't have much price data yet to base this on, so this is purely my ideal situation. (If anyone knows where I can get price data please feel free to point me in that direction)

So a quick overview: I'm in zone 3, Oklahoma City wanting to build with ICF walls and SIP roof. I'm going to ballpark the livable floor space between 3000-3500 square feet including a basement.

I'm planning on my sub-grade wall and basment construction to be very similar to:



Now disregard the wood structure because I would continue the ICF walls all the way up to the point where it will meet the roof. Now for the above grade exterior walls, I would really like to add an extra inch of insulation to have a little bit better thermal performance. So, this is where my order gets confusing to me. We will most likely want a brick exterior facing. So I'm thinking it would be a great opportunity to put and inch of polyiso on the ICF, then allow a 1/2"-3/4" air gap between that and the brick.

As far as the roof, I would want to use steel SIPs for a cathedral ceiling interior. Then I would put the asphalt shingles on top of that. 

I may be missing some things but that's why I'm asking you pros. What considerations am I missing to acheive a great building envelope?  Thanks

Why not raise the whole thing up about 8' and save most of the digging, avoid leakage problems, allow windows (if desired) and make it countable square footage?

That's also a consideration, but I was mainly posting for feedback on my above grade wall design. To better answer your question though, we are in a very tornado prone area so a basement "vault" is very appealing. Plus I figure you save heating and cooling loads and purchasing less windows and doors and various other things if a nice portion of your floor area is underground. Just my opinion, but anyhow my main point was for feedback on my wall design.

Other than some probably not very significant thermal bridging from the footing to the center of the wall and perhaps EPS vs XPS under the slab, the drawing looks OK to me. I assume you have looked at your desired tradeoffs between insulation levels and costs for your climate.

Unfortunately I'm having quite a bit of trouble finding pricing info other than Home Depot and Lowes. Any other sources that you know of for pricing would be greatly appreciated. Since you give the preliminary OK, can you educate me a little on a water and air barrier? Obviously it would go between the polyiso and the EPS, but I suppose I'm asking what you would recommend? An EPS rated peel and stick? Or perhaps a roll-on? I'm not too familiar with products.

Also, would you be familiar with how to properly attach the polyiso to the sides?

EPS of just about any density & thickness is available about everywhere through building supply distributors.

http://www.atlaseps.com/pages/dist_com/ok.asp

Building Specialties (L & W Supply) would almost certainly be willing quote you on Dow polyiso products, if you told them the exactly what you're looking for, maybe even ballpark it for you over the phone as opposed to a hard quote.

There is nothing gained by adding a layer of iso. It's probably cheaper and more reliable (and a LOT less complex to go with a thicker (or assymetric) ICF.

With stone or masonry cladding you have the the issues of how to support the siding without introducing a thermal bridge.  If you rest the stone on stepped-in concrete (even cantilevered) there is a thermal bridge between the concrete of the lower section and the exterior siding, breaking the continuity of the exterior insulation, robbing it of a bit of performance:

http://www.quadlock.com/images/engi...sembly.png

This not a tragedy, since you have continuous EPS on the interior, but it's a performance hit nonetheless. This is one of the as-yet-unsolved issues when brick veneer is demanded- there are no obvious ways to get around it. (Some have tried AAC block forming the bottom course between the concrete & masonry cladding, with mixed results.)

I'm not sure what the point of asphalt shingles on a steel SIP would be (on an OSB SIP, sure), or how you'd go about doing it.  Pre-finished with a 50 year bake-on enamel or powder-coat or whatever would be far more durable and reliable than the crummy-shingle standard on a steel SIP.

What are your thoughts on the brick ledge forms that some icf manufacturers make? Would that be sufficient enough for brick veneer, or would it result in the same issue?

Would you please go into more detail as to why the polyiso would yield no gain?

Would you happen to know some icf manufacturers that make asymmetric blocks? I'm having a devil of time finding one.

The shingles would be purely aesthetic but I wasn't aware of other finishing options. Would you happen to know where I can find pics of the bake on or powder coat options you mentioned?

Sorry for all the questions but you brought up things I hadn't considered. That's exactly why I posted!

Tacking polyiso to EPS adds unnecessary complication to the assembly, since you can just go with thicker EPS on that side (several manufacturers make assymetric ICFs now), to hit the same R.

QuadLock does it with slotted panels that slip inside their standard ICF:

http://www.quadlock.com/images/icf_components/R-Values/ICF_Walls_R-Values.png

Slipping 1.5" more EPS into the form before the pour is the thermal-equivalent of adding 1" of iso on the exterior, but the labor content is a tiny fraction of the iso paste-on, and the reliability MUCH higher.

IIRC others have options of using say a 4" block on one side of the form 2.5" on the other, etc.

I've never fully investigated the finishing options for steel SIPs, but there are options that look pretty much like finished-metal roofing. Shoot a PM to Chris Kavala (cmkavala: http://www.greenbuildingtalk.com/Forums/tabid/53/afv/profile/uid/3685/Default.aspx ), who should be able to point you to a gazillion pretty pictures of steel SIP buildings & roofs.

Wow that's pretty great info. Quad-Lock has some great stuff. It seems the R-30 configuration with 2" inside and 4" outside would be excellent. I understand your position now with adding polyiso. The extra EPS from the start would cut construction times drastically.

Get read of creating a rim joist. It's the worst thing to try and air tight and insulate. Place treated mud still on wall, use joist hangers and drop the joist in to the hangers. The top of mod still and joist hangers are the same elevation. Run your sub deck all the way out over your wall. www.buysipsonline.com

I honestly have no idea what you are talking about TS. I didn't even understand half of what you said. Do you have maybe a detail or something?

I think he is refering to the picture and saying to drop the joists to be inside and below the top of the ICF wall. Which I think is what you are planning anyway with your above grade ICF wall.

Ah, okay. Thanks jonr. A little bit of a communication barrier there. But yes that 's exactly what I would do if I decide to go with wood joists. I'm actually considering concrete decking.

I would think that for the best tornado protection, you would want at least one small room to have concrete or steel overhead.