Homeowner from Oklahoma here, late in the design process with an architect for a new home. We started out with a plan to use a particular kind of shell construction usually known as a SCIP (structural concrete insulated panel). Basically it is an EPS sandwiched between two wire grids which are then covered in shotcrete. For a wide variety of reasons, it’s looking like we may no longer use that material. However, we are way, way down the design path with the architect and we love her design. However, in taking full advantage of the properties of the SCIP, the design is extremely curvaceous. So, if we abandon the SCIP, we are left with either a total re-design OR finding another material that would work. We’d like to start with the latter.
Our first priority is high R-value and our walls are currently planned at 12″ thick. I can imagine a way to frame with 2x wood to achieve the curve + wall thickness (Larsen truss, for example), but I’m not sure how we’d insulate–what we would use and how (if necessary) we would contain it. A naturally-curvy insulation doesn’t exist that doesn’t also need some sort of containment. (Or, rather, none that I’ve been able to find.) Cellulose or spray-foam (various types) would both conform to the curve–any ideas on how to form up around the 2x’s that could also handle the curve of the wall?
I’ve also thought an insulated earthen wall (double-wall cob) would handle the curves….but I think the wall would have to be thicker than is practical for us–even if we took the load-bearing function out of the mix. (Parts of the house are 2 stories tall.)
SCIPs aren’t too different from ferrocement and I think we could use some of the best from both, but I haven’t really found anyone experienced in ferrocement that would come build for us….it’s labor-intensive, so I would think it would only be cost-effective as an owner-builder project. And I don’t yet “get” how to insulate them, either, though I know people do.
Are there any ICFs that could work with a REALLY curvy design? (We truly don’t have a straight wall in the entire building, though most of the house has larger curves, with only part of the house having tighter curves.)
Any ideas would be appreciated and assist us in salvaging our beautiful design!
Replies
I'm addressing this to a man who has succesfully made some curves with ICFs, just to make sure that he reads your post. As I recall Frenchy said it was relatively simple.
moyerles 1
Hello! I successfully used ICF's in my sharply curved portico and had a wonderful experiance with them and wouldn't hesitate to use them again should the oppertunity ever arrise. It does require several additional steps (but that's the cost of building curves in an industry where straight lines are the norm)..
I was told about a company that specialized in curved ICF forms and I would certainly look into them if the curves are gentle and not as sharp as my portico. (10 foot radius) One thing you must accept is that building curved walls has tradionally been rarely done so the chances of finding someone experianced doing that is slim to non-existant. Instead of looking for experiance you will be far better off looking for someone willing, indeed anxious to do that..
There is nothing that cannot be achieved with some careful thought and creativeness. But forget about getting a low price to do so. There are risks and unknown involved and if you ask your contractor to asume all of those risks his bid will have to be extremely high to cover all of the unknowns. You might consider a differant arrangement. Instead of a fixed price bid a arrangement whereby you asked for a best guess. Then reward him for coming close to his best guess. For a rough idea I would figure out the normal cost of building a straight house and add at a minimum 15 to 20% to do a curved one.
Frenchy, What brand ICF did you use? Our house will be bermed into the side of a hill and ICFs for the bermed side was something I was considering already. However, one thing I liked about the SCIPs is that it made the thermal mass available to the interior of the building and had more-or-less "outsulation". I have been told that once the ICF was sufficiently cured, one could remove the EPS on the inside of the wall, making the thermal mass available. I know there is one brand of ICFs where the outside EPS is (or can be) thicker than the inside.
moyerles1
I used Reward forms. I don't know what brand those curved ones are. My forms were straight I figured and easy and secure way to curve them.. (ask and I'll share details)
I think you need to understand something about ICF walls.. the insulational value of them is a combination of the outside R value as well as ithe inside R value. If located where I am you need that full insulational value. In certain southern location that's not needed..
To retain thermal mass on the inside you could expose spots where the stucco or whatever is in contact with the core Thus combining the gain of both the wall covering and the concrete. Doing so I believe would be of marginal net gain. There is no real advantage in a cold climate.
Think of it this way.. Coffee in a thermos will remain warm only so long, eventually all the heat will be lost. Keep that thermos in a warm spot and the coffee will remain warm longer. Same with using thermal mass as a heating media.. As to a cooling media slightly differant principles apply.
Yes, of course I do understand that removing EPS from the interior wall reduces the R-value. I would want to add additional insulation to the exterior to bring it up to the R-value I desire (which is way above the recommended value--see link below). I know I can add thermal mass in other ways & I plan to. I'm meeting with an engineer next week to discuss other options that he can see. I think our project will be right up his alley. If anyone else has suggestions, please pass them along.Here's the beta version of an R-value calculator written by someone I highly respect regarding these things: http://www.greenfret.com/how_much_insulation.html
What radii are you desiring?
I don't use ICFs in my concrete houses because insulating from the mass defeats the tempering effect of the mass. A Monolithic-style dome designer here dug out the gov't test info (Oak Ridge Labs) several years ago. You apparently already understand the function of mass.
Nothing particularly wrong with ICFs, I recommend them to anybody unwilling to do traditional concrete forming. But with traditional forming, the insulation goes where it's best, on the outside. Then stucco or whatever your choice.
For your bermed wall, you could use a type of frost-protected shallow foundation cape. That would make a portion of your backfill a part of the house mass. This is what passive annual heat storage (PAHS) does, but on a much larger scale. Provides my heating and cooling, passively.
Curves, eh? Here're a couple: PAHS works. Bury it.
VaTom,One part of our home has a gradual sort of curve similar to the design you attached....It looks like our curve is tighter than that one, but not by too much. The other part, though, has a much tighter curve....there are two curves that represent the "Golden Mean", tapering down to about a 2' diameter (or less) at it's end.Meeting w/ the engineer is tomorrow. Thanks for everyone's input!--L.
Hey Frenchy:
I am curious how you built and braced the ICF's curved.
I have never installed them but the idea that they can be worked for varying different situ's is alluring.
JeffinPa
All I did is slice the forms into 3 parts with I think it was a 7 1/2 degree cut on my table saw. Then I stacked them up and joined them back together with a simple wooden brace at the split that I screwed together after taking a similar wedge slice on each boards edge. I then screwed that brace into the forms where the sheet rock is normally attached. Very fast and straightforward.
I'll try to get my daughter to bring me back my digital camera so I can take some pictures to show you..
I could do any radius with the same process. All you need to change is the angle it's cut at.
I'm too dumb to figure things out mathmatically so I simply laid a string across the forms at the radius I wanted.. that angle is what I cut each piece at..
If you wanted to free form things you could do it pretty much the same way, slice forms apart and put them back together at whatever bevel you want using that center brace I came up with..
If you did a lot of them you might want to bend a stiff piece of sheetmetal instead of wood. You could make the wall weave back and forth like a snake if you wanted to..
A sharp curve is pretty much self bracing so normal wall braces weren't needed and since I back filled the outside of the wall with dirt I didn't need the scaffolding usually required. Simplified the project as well.
Sounds pretty nifty..
Did you cut the one web, flip the block and cut the other side? I guess you had to have several different adjustments on your fence set so you could be effecient???
I am trying to pict how to cut it on the table saw easily.
JeffinPA.
nah!
I'd make one cut on a side thru all of the forms , flip the forms over and make the second cut, adjust the fence make that cut thru all of the forms, flip it over etc.. didn't take very long..
I found an ICF with a radius wall form (pre-cut): Nudura http://www.nudura.com/EN/ConstructionProfessional/nuduraicfproducts.aspxI also see that Rastra: http://www.rastra.com might be a good option.Here's a photo I found of Rastra used in a curved wall: http://www.icfhomes.com/images/rastra03.jpg . The fact that these forms work standing up on end makes curving them a lot easier--not so much piece-by-piece cutting (lowering labor costs). And then there is Performwall Panel System: http://www.performwall.com/index.sstgThis is similar to Rastra. Here are a couple of curved wall photos: http://www.performwall.com/view_gallery.sstg?g=36&f=307 and http://www.performwall.com/view_gallery.sstg?g=36&f=316 Several others in their "architectural" gallery.
Cempo ICFs are another option. They can be shaped easily.