>I am planning to build and I want to be as "green" as possible on my
budget.
I think I am going ICF for insulation, >durability and resale value
ICF is good for insulation and durability, resale value may be problematical because the extra value is hidden in the walls where people can't see it. The realtors won't talk it up because they have no idea what it is or how it works.
>but
it uses a fair amount of concrete which has a CO2 impact.
In the short run you are releasing a little more Carbon to build it, but I expect that the energy saved on heating/cooling will quickly make up for it, and permanently reduced Carbon use. In the long term you always come out ahead.
>I'm not too concerned because I am trying to minimize the usage and also
if that concrete is in a building that is occupied >for 200+ years
To get the full life expectancy out of the structure I believe you need to think about how to protect the rebar in the walls from rusting. Just being buried in concrete may not be good enough.