I built my last house out of ICF's. Like any building material it has its pro's and cons, some of which have already been discussed. I was not a professional builder and I've done exactly one ICF house, so my perspective is limited.
Note, my whole structure was built out of ICF's, not just the foundation.
First, the pros:
The first thing you notice about ICF houses is that they are quiet. Because the walls are solid concrete, you just don't get the street noise you get in a regular wood framed house. Remember the first time you ever rode in a Mercedes? It's like that.
You do not get the drafts either. Wood framed houses, even those with Tyvek, still let in air.
They are energy efficient, no doubt, but don't believe everything the manufacturer says. I've seen claims of up to R50 in the walls! Take that with a grain of salt. That being said, you will spend less to heat and cool them, but you still need proper insulation in the floors and attic.
In building with ICF's you frame,sheath and insulate all at the same time.
You're basically living in a bomb shelter...hopefully you don't need to worry about drive by shootings, but it's nice knowing your walls are literally bullet proof. If a fire sweeps through your neighborhood, your structure (at least the parts that are not wood) will survive. Same with a hurricanes. ICF houses are about 10x stronger than wood frame ones, so they are often built in areas prone to natural disasters.
Impervious to rot, termites, carpenter ants, etc
There are more pros but those really are the biggies...
Now for the cons.
Although they are marketed as being "green" you do need to understand the initial carbon footprint of an ICF house is pretty big. Manufacturing Styrofoam for the blocks is a pretty nasty. Some block companies are claiming to use less environmentally disastrous manufacturing processes, but I don't have any direct experience with them. Concrete itself is also a very carbon unfriendly product and you'll use a lot in the construction. Now, you will use less energy to heat and cool the house over its lifetime, so thats where the "green" building line can get fuzzy.
Stacking the blocks is simple...like stacking Legos.
Pouring the concrete however can be a royal bitch kitty. The blocks need to be braced or they will not stay plumb or square and will blow out when you pour. You will need a very good concrete crew who can manage the "lifts" correctly, vibrate the concrete within the blocks to make sure you don't end up with voids and folks standing by with plywood patches to handle blow outs when they happen (and they will.....nothing like watching your expensive concrete squirt out onto the ground like cake frosting). Pouring is not something you and a few friends can manage...unless those friends are professional concrete guys with lots of experience :)
Running electric can be interesting. With plumbing, you want most of your pipes to be run through interior wall, but electric goes everywhere. Many electricians will not have experience with ICF walls. They do make tools for "melting" channels into the styrofoam, but you may then be required to run your wires in conduit as you can't protect romex with nail plates.
Many ICF blocks come with strips embedded in them that you can screw into.....you'll use them for hanging the drywall, cabinets, etc. However, once the house is done and you want to hang a picture or a mirror...you won't be able to find a single one close to where you want to hang something (or so it will feel like). You'll be getting out the hammer drill to hang your picture of Aunt Edna.
And yes....there are more cons for sure.
The fact is I loved my ICF house. Would I build with ICF's again? Absolutely.
Are they the most perfect building solution in the world? Of course not.
One final thing...and this isn't a con, just an FYI...
You will spend more money to build out of ICF and it will be worth it...to you.
However, it doesn't add any value to the house. It won't change the appraisal, nor will you get a bigger offer from a potential buyer. Most buyers don't care it's a better way to build, only that it has walls.
