Insulated concrete forms

Q: I'm considering having a custom home built using a system of exterior walls built of concrete, but I have concerns. The approach uses foam forms that remain in place permanently as insulation. One local contractor who builds wood-framed houses told me that there's a danger of ants setting up house in the outer layer of foam. Is this true?

A: The building system you're referring to is generically called insulated concrete forms (ICF), and from everything I see, hear and read, it makes great structures. I've never seen ants express any interest in foam that's been properly sealed behind siding, but I have heard reports of them occassionally invading exposed foam. According to the numbers I've seen, and my own work with ICF forms I've used on a project of my own, the approach is somewhat more expensive than conventional wood frame walls, though insulation values and sound resistance are reported as superior.