Naive question about ICF
Before browsing this site for the past year or so I had never heard of ICF. Now, I hear about it and see lots of build update pictures with ICF walls.
Can somebody give me the low-down on ICF walls as opposed to generic wooden walls? Are they more energy efficient? Are they more expensive to build? How they are they compared to 2x4 or 2x8 wooden walls? Are most ICF walls exterior only or exterior and interior?