By Jon in Ellicott City, MD on 12/10/2007
I've left my ICF semi-exposed for nearly two years, and it seems to be holding up fine. I used an airless sprayer to apply a coat of exterior latex paint. The paint seems to be enough to stop the UV damage. I also have some scraps of ICF laying around that are unpainted. They have behaved just as Ken described - outside layer degrades but the majority of the material is sound.
I'm not suggesting leaving your ICF exposed is the greatest of ideas, but my walls seem to be fine. I wouldn't let this issue sway your decision. The ICF is probably fine for a few months. A coat of paint seems to protect it if you want to leave it for several months to a year.
As far as CMU... I've bought standard 8x8x16 blocks for $1 each. The old rule of thumb was $1/block for a mason to lay them up. I think the younger guys are charging about twice that. You'd also have expense for rebar and filling some of the CMU cores.
My WAG would be about $4 per sq ft just for the CMU wall. When you add the cost of insulation and furring strips, I'd guess that you're getting pretty close to the $6-$7 range. ICF tends to run in the $8-$10 range, if you do the install yourself.
Labor, concrete and pumping service prices can vary quite a bit from region to region. The only numbers that will really be of use to you are the quotes from your local masons and concrete guys.
One additional thing you might consider is that a poured concrete wall will be significantly stronger than CMU. If your foundation wall will have a lot of unbalanced fill (say, more than half the total height of the wall), then that extra strength may be a major plus.