Is a rain screen needed with ICF?
We’re building a pretty good home in Indiana, climate zone 5. The exterior walls will be ICF, all the way up to the roof. We are looking at LP Smart Side for cladding. There builder says we can put this directly onto the exterior foam of the ICF. I however wonder if we shouldn’t include a rain screen, and if so furring strips or something else.
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Rain screens help walls dry, but they also help dry cladding. I think rain screens were originally developed to improve cladding and paint durability. A small gap can make a big difference, but 10mm is a good minimum. An air gap at the top of the rain screen is ideal. There have been articles here (GBA) and at the BSC website.
I wouldn't think that the foam component of ICFs would have sufficient structural integrity to mount and hold cladding. Some of the ICF manufacturers include plastic components inside the foam for mounting, but this may be for interior items - drywall, cabinets, etc.
I would give serious thought to creating a rain screen to help dry the siding by fastening vertical strapping securely to something other than the foam.
If in doubt, contact the ICF manufacturer for specs.