Thank you both for the input.
Jay, forgive me, but what is OPC?? I'm figuring you are talking about concrete based on what you say after, I just haven't heard the term. But then I'm confused because I had no idea concrete accounts for that much of greenhouse gasses. Either way, I appreciate your input, and I have a lot of time to adjust my plans.
Roger,
You make a great point about adapting to new needs should I ever need to cut part of the wall. Also, I do see the difficulties of siding outside if the wall is concrete.

SO, what are your ideas for walls between TF? The cobb idea is cool that Jay mentioned above, but I don't think it's something I want my whole house being.