Building walls in a full (concrete basement). There are 2" drain
pipes running from ceiling to floor, with very little gap between pipe
and concrete wall (maybe 1/4").

How does one build a stud wall around these obstacles? I was planning
on using 1" polybead (as a thermal/moisture barrier) against the
concrete and a 2x4 (insulated) stud wall.

Obviously, I can't place polybead behind the 2" pipe. Any ideas on
how I should proceed?

Cheers,
Dave