I have a terraced south facing lot in MN and planning a modern passive solar home.   Prelim drawings have my walkout basement ceiling height about 14 feet.  It'll basically be 3 sides inground and the walkout south facing side the only exposed side.   It'll be recreational area (bar, home theater, workout, some storage etc..)   w/ concrete floors.

Question is considering ICF or a Poured foundation.  What kind of extra costs or challenges am I facing with 14 foot basement walls on a terraced lot?

Engineer design for that height, beyond the scope of the IRC and it doesn't matter if it's ICF or PIP, they are both concrete just one we leave the forms after we pour.

If you have not already check with Kevin Hofmeister. He can probably answer your question.612-328-1741.
If not Ulteig engineering would be a good bet.