I have a section of wall that is partially under some duct work. I want to put 1" XPS to the wall then frame in front of that. I can of course secure my pt stud to the concrete floor but can not attach my top stud to any ceiling joists above since the duct work is there.

My thought was to build the section of wall, raise it in place and secure the base plate to the concrete floor. The top plate would not secure to anything so in every other bay I would take a stud and attach it flat against the wall (tapcon thru the face of the stud, thru the XPS into the concrete)and then tie the wall stud into it's side. Does this seam reasonable, code complainat etc.?