We are designing our next home, hopefully we will be starting within the next year.  If I had my druthers, it would be next week!  If anyone feels like taking a stab at one of these I'd love the input!

We are looking at zone 3 NC warm/humid, and we've looked at SIPS, AAC, CMUs, steel-frame, log cabins, metal building barndominiums, and even shipping-container homes over the last year.  We've settled on concrete - it's really just lovely...as a mom with a child with autism, I have to say that his physical curiosity tends to be more than traditional construction materials can handle.  Holes in drywall, water in plywood/composites from "helping to clean", mold and asthma, noise and huge electric bills from a hot-natured child that needs heavy blankets...so that's where we are. 

Buildblock icfs look to be the most friendly for a build where we are the GCs and do quite a bit ourselves - but I'm definitely contracting an experienced concrete contractor for the foundation, wall, and ceiling pour.

So here are some of the goals (with my horrible humor mixed in):

• large open spaces, plain old-school plaster walls - no more mystery wall cavities, or drywall patches after I pull out the legos and toilet paper
  
• no wood beyond doors - with no plywoods or composites - no more soggy floor
  
• stained/coated concrete with rugs rather than attached flooring -
  
• isolated plumbing - short runs to kitchen/baths located around a mechanical closet - no more crawling with the bugs and snakes when something needs a look-see
• stucco or architectural stucco coating and a solid concrete shell to the roof - no more defending delicate vinyl or hosting the area's wasp population in crumbling soffits
  
• Mini-splits that manage two or three separate climate zones - no more mystery mold to try to clean from ductwork, and hopefully no more electric bills that make me want to live in a tent in the woods
• Thinking we will use the forms that use plywood on the interior that's removed after the pour for bare concrete walls - they leave attachment points for plaster mesh
  

Here are the burning questions I'm pondering at this stage:

1. Am I thinking correctly that having the icf blocks with removable interior sandwich sides gives me some mass wall benefits to hold interior temperatures? 
   
2. I don't want to plumb through the slab - not really.  Is it possible/prudent to think that I could have a second concrete floor over a barrier through the mechanical room that borders the kitchen and baths, and plumb through that?  How about permanent built-in low cabinets to house plumbing waste drains from wall-mounted toilets?
3. Are PVC weep screeds a good choice?  I've read a lot of arguing about stucco and weep screeds, but in a humid climate, it seems like they would be necessary whether we do real or architectural stucco.  Any suggestions on easy, durable exterior cladding would be awesome.  I'm thinking at this point that we will have roofing overhangs 360 around the house, so hopefully that should mitigate some issues.  thoughts?
4. Planning freestanding dehumidifiers rather than an integrated system with the HVAC.  We have one now, and it's been AMAZING - only cost $200, and if it's affected the electric bill, it's been miniscule.  But the ventilation issue raises questions here with the tight house problem - what's the simple, cost-effective, easy to maintenance venting/fresh circulation method?  I tend towards a whole-house fan with coordinated vents, but I don't know if I'm thinking about this the right way.
5. I'm thinking that either a post-tensioned monolithic slab or icf footer walls with a floating slab are going to be the way to go.  The soils around here are notoriously not awesome - so how do I manage the cold joint between the slab and walls?  I've seen a lot of bug highways through those joints with CMU walls. 
   

Please don't think that you'll insult me if something I've said is not terribly bright - I didn't know what ANY of this was two years ago, but it's amazing how well you can learn just enough to be dangerous when you have the Google.  What I'm hoping is that my unbelievable inexperience will translate into weird innovation simply because I've never learned not to say "well couldn't we just..."  

Have you looked into Durisol blocks? They are supposedly good for humid climates and breath so makes the interior air better. Mike Holmes from DIY network endorses them for a builder in Canada. The main drawback is shipping from Ontario, Canada. I live in NC and hoping to use them for the good features they have. Hope all goes well for your build and we all learn so much from each other so keep on asking anything you need.

Short answers:

1, leave the foam, run interior 6 inch walls, and be happy with the mass. The ability to do different wall finishes would be a little better then concrete walls with a straight plaster application.

2, sleeve all plumbing lines and if the waste lines are correctly done, with accessible cleanouts, there isn't a valid reason to go to an expensive alternative.

3, use a product like BuildCrete, or a RhinoShield, and seal the home, soffits also.

4 You need an experienced HVAC tech to do load calculations and answer the other technicals.

5 ICF footer, with a shield built in, and float the slab. Do not skip on solid compaction.

Good luck.

I looked at them really closely - and was really excited.  I think the shipping would eat us alive, unfortunately - part of the reason for the move and complete change in how we're living is trying to scale down costs for anything we don't need - even eliminating kitchen cabinetry and going to open shelving.  Our budget is tight, unfortunately.  We looked at EZ blocks and aerated autoclaved concrete, and those look like amazing products as well (though appear from some sources to be not so great in very high humidity).

The buildblocks from most accounts really appear to be simple enough to manage.  The cost of the blocks and accessories is reasonable, and even the shipping estimate was manageable (fortunately they have a facility in NC for the majority of the forms).  Take a peek at their hardwall faced forms - they give the option of the interior wall face as bare concrete after they are set, and leave fastening points for other wall cladding choices. 

The EPS breathes to a degree as well, which seems like a win if I can keep it on the outside, although if I can't it's still a huge improvement on air quality from what we're dealing with currently.  Keep posting as you move forward with yours too!

Thank you!  I like what I've seen of the BuildCrete as well, that's probably what we'll go with.  It's reasonably priced from what I can tell, which is a big plus. 

It looks like the buildblock system either incorporates solutions to most of these issues, or lends itself well to enough good options that I shouldn't have huge problems if I keep doing due diligence. 

I appreciate the reassurance on the slab plumbing.  Having a child who likes to see "what happens if I do this..." has conditioned me to trying to stay a step ahead of disaster, so that advice really clears a couple of obstacles that were giving me grief in layout!

I would probably stay away from the BuildCrete if your a 1 timer. It seems simple but is technically harder than the standard blocks. Are you going to use your own plywood for the forms. I think the reason for your choice is the solid backer for the sheet rock. With the full backing of the standard block I don't think drywall penetration by your little Tasmanian Devil should be a problem. While I haven't used the product, I'm wondering how you find the little attachment spots when your installing drywall. You would be hard pressed to find a sheet rocker to install on your job. I believe your in NC with Buttner as your Mold site. Try Uship for freight rates. I never use the shipping supplied by the manufacturers. I find my own.

I imagine they are harder, which is my concern. The webs have end pieces that screw into the plywood. After the concrete sets,the plywood is removed,but the buttons leave attachment points that can either be patched or used to attach cladding. Honestly I like concrete walls, stained Crete is beautiful, and hand plastered walls have so much potential for texture and color. Having the attachment points remaining will be a good option in bedrooms though. I would be using our own plywood. There will be plenty of shelving, storage and such in the garage shop and storage sheds to use a good bit of it. Maybe I'll get lucky and find someone who's used them, it would be really nice to hear what it's really like

This is the hardwall block http://buildblock.com/products/buildlock-knockdown-icfs/buildblock-hardwall/

Thank you for the shipping tip!!!

The only problem with the stained concrete idea that I can see is the thousands of little holes that have to be filled. Your also going to lose insulation value.

Leave the inside foam on. I'm a little curious why you wouldn't want to plumb thru the slab ? I tell people with bad soils to import good soil, if possible. From a drainage and compaction stand point it is well worth the money spent. I'm all in with the stucco. Our next home will be a single story Fox Blocks house with stucco on all exterior surfaces.

I like the idea of no interior foam. Why not access and use all that thermal mass instead of isolating it? It's the biggest fault with ICF's. Add that insulation to the outside where it belongs. You can put any wall coverings you want with no major problems. You'll have to plan for electrical conduits in the walls for flush outlets or exposed conduit or knee walls are other possibilities to hide electric, plumbing, and HVAC that isn't dealt with in the pour. There are a lot of very durable concrete coatings available that seal and finish - some are epoxy or the like. Google it. Most of the pros here seem reluctant to do more than promote themselves and their chosen products so take things with a grain of salt.

Stick with the foam on both sides. With foam on the outside only, the wall most likely won't meet code minimum insulation so you would have to add more foam on the outside to get the R value to code minimum...

Without the foam, you have no place along any of those walls to route electrical wiring or plumbing if needed...

If you are worried about drywall penetration, you could add a barrier between the drywall and foam such as 1/4" ply? 100% foam backed drywall will be pretty tough IMO. It might dent or crack from a solid impact, but I think you will be hard pressed to punch holes in it unless you go after it with a claw hammer. You can also plaster/stucco right over the foam, in either case the only cavity would be the one that is dug into the wall at the break/penetration and relatively easy to fill and repair

From a construction standpoint as a possible DIY project, what will you do with all that form plywood(several thousand sq/ft) after the pour? That is a LOT of now concrete exposed ply that doesn't appear to have any further purpose in the build?

If you are worried about below slab plumbing, run it in a sleeve. That way, if it ever needs replaced the actual line can be replaced without having to tear out any concrete. Below slab plumbing is done every day and done right as mentioned above can be very troublefree. Can you do some of the other things you mentioned? Of course you can, but some may require some added engineering cost to implement properly/safely. Since Sub slab plumbing is done everyday, you probably have a lot of experience in your area readily available to consult with.

If you pay attention to the air sealing, you will probably want a HRV or maybe even an ERV which will help preserve an inside humidity level the mini-splits have provided while still giving you a healthy air exchange. This would be a central ventilator box(not very large) with a heat exchanger. It uses small ducts to several rooms in the home and to the outside to exchange and distribute the air at a slow steady rate, while exchanging heat between the incoming and outgoing airstreams. IE: with a HRV(heat recovery ventilator)if you are heating the inside, it transfers heat from the outgoing air to the incoming fresh air so you have less heat to make up with the fresh incoming air. If you are cooling, the warm incoming air transfers most of it's heat into the stale outgoing air so you don't have to add too much additional cooling for that fresh air. In humid climates, an ERV will also exchange moisture between the two airstreams to help maintain the interior humidity level.

Consider metal siding - for example corrugated galvalume with a steel / sliver color.

It will probably not work if you want to achieve a traditional architectural style so you may need to end up with a more modern look.

On the benefits side I see: durability (50+ years), better rain protection (virtually rain proof if flashed properly), better thermal insulation on areas exposed to direct sun (the air gaps between the metal and the EPS allow venting and the shiny metal surface is fairly reflective), reasonably cheap $1-2/sqft. Also, since you don't have to worry too much about rain you can have less or no overhangs which may save some dollars as well (no fascias, no soffits, simpler framing).

Mojoe, I missing an agenda here. How many icf projects have you been involved with. The product she is considering using is a commercial product. The expose thermal has been dealt with on this site probably since its inception in the early 2000's when it started as icfweb. One consideration to any house build should be what will the market be for a New York loft style interior in eastern NC, Some day the house will be sold and the decisions that you make now will effect its price. I would use Quad Lock unbalanced wall system. Whatever thickness of foam you choose outside with their 2.125 " insulation inside. I don't sell the product but I think it is something that a DIYer could use. It's a knock down so shipping from Georgia shouldn't be too much.

Thank you thank you thank you for all these perspectives!!!!  This project is so much more than a house for us - this move is one we have to make for an environment that's safe to keep my son at home (and that we can afford during that time as well).  We're having to walk a tight line between form, function, and cost, and there are very few resources in this area interested in a conversation about materials and practices like these. I can't blame them, I don't think it would be worth it for most professionals to take this on given the learning curve and how tight we need to keep the budget.

Some of the things I'm thinking and worrying about are based on having a very different set of daily living challenges, and some of them are based on us having been recently very sick from problems in our current and most recent homes.  Some are just a product of not having enough background to understand.  That being said, that makes every bit of questions, suggestions, and criticism so important to us!!!

-I worry about the commercial aspect of the hardwall product as well.  It's going to take more research before I lock down on that, for sure. Are the holes in the concrete that you're referring to aesthetic in nature, or functional? 
-We talked about the tradeoffs in running conduit, etc - fortunately, we are modern/minimalist/generally odd, so exposed conduit is a potential design aspect that doesn't bother us.  We like the flexibility of being able to rearrange space without going through drywall, and we are also toying with kneewalls that double as toy/bookshelves on top, etc.  We've had to move several outlets to adjust to my son's changing behaviors and needs, so going through the walls isn't appealing for much (nor is having them within reach in most instances, which will likely require an exception from the code official, or a removal after-the-fact).
-You make a good point Smartwall, the resale on our particular design taste is likely to be tough.  If we were in Chapel Hill, that would be one thing, but we know that resale will likely involve a moveout and an interior cladding redo.  Fortunately, leaving the hardwall "buttons" (as I call them in my head) should keep this from being too awful.  Unfortunately, a resale isn't possible with my son and I living there anyway, so this wouldn't be too far beyond what we'd likely face either way.  On the other hand, being able to offer choices of financial incentives to a buyer - perhaps a choice of financial allowances or having us redo things in materials they choose - perhaps that will make a difference?  Ultimately, we are accepting that in the end there may only be so much we can do to avoid taking a hit here.  Hopefully the face that many of our preferences are less expensive will balance some of this out.  The wall cladding is likely to be the least unappealing aspect of the house to others unfortunately - our design and space layout that we want has made most of my friends look at me like we're aliens.  It's essentially almost two completely separate residences that converge in a large kitchen/utility.  Perhaps the market for people with parents living at home after retirement, or extended families, will like it? 
-Fortunately, the code in 3/hot humid for mass walls with the insulation on the outside is R5, R10 if more than half is on the inside.  2.5" of EPS on the exterior of the Buildblock sandwich at R4 per inch almost doubles the code requirement, which is fortunate.  We're also relying heavily on passive solar with overhangs, blackout shades, no west windows, and landscaping shade. 
-I'll look back at Quadlock - it's been a while since I looked at that product.  What do you think of EZ blocks?  To me, they don't look very DIY friendly, but I could be missing something.  It looks like it would be very easy to make big mistakes.
-the plumbing through the slab is likely paranoia on my part.  I'm sure the sleeving with accessible cleanouts will be sufficient and then some - thank you! 

The plywood - yeah, that's almost 2800sf of plywood.  We are roofing the garage workshop separately, to which this could go.  That's only about 1200sf, though, even with pitch.  We have two accessory buildings that we would like to have functional within a year of the move (a garden shed, and a storage for items that don't require climate control), and a good bit of it would end up there.  Garage/workshop shelving is another stop for a good bit of it. 

From a selfish standpoint, we both enjoy building/creation projects around the house and property.  If we have $1000 of plywood left over after the repurposing for roofing, sheds, and shelving, and trying to resell to our concrete supplier or another doesn't work, then that's a lot of material for date nights! 

We haven't ruled out metal siding completely - we actually really like vertical metal siding. The industrial look would likely work well within the solar panels and such!

What about MgO applied directly to the interior, or even used as the interior sandwich of the hardwall blocks?

Look at Nudura as well. They have a very good system and they also offer the option of a block with EPS one one side only. I can't find it on their website but I know I've seen it.