Hi all, I'm about to start the siding on my ICF house that has been exposed for a year. The blocks have a chalky film on their surface. Should I brush it off with a stiff brush or does it not pose any problems. Thanks Joey

What brand are of ICF are you using? I think it's generally reccomended that you use a wire brush or rasp and lightly rough up the outside. It's not supposed to be exposed to the sun for that long of a time frame, but my opinion is that it doesn't hurt much, more so just looks. I think whats more important is what you are going to put on the outside. You may need to rasp it to give it "tooth" for whatever to stick too. Unless it's something like vinyl siding then I wouldn't worry.

A scrub brush on a handle will get rid of the oxidized eps. But you only need to do that if you are using a EIFS coating, then follow the manufacturer's recommendations.

I had some leftover ICF pieces laying behind my storage building, in direct sun, for about 2.5 years (until my wife made me clean up the mess). The exposed interlocking teeth had deteriorated somewhat, but the body of the foam was still strong and stable.
The only problem with the chalky residue is that it makes one heck of a mess when you touch it. If possible, I would powerwash the walls before working on them. It will save a lot of grieve come laundry time.