Building chases around waste stacks
I'm getting ready to insulate the part of my basement where all 5 waste stacks run. Unfortunately, all five are on the perimeter wall, each approx 3-4 inches from the block wall. The stacks are all copper, installed in 1951. Some have clean-out plugs at the bottom, some do not.
My plan for the walls there is to place 1 inch foam panels against the block walls, then stud walls with fiberglass, then sheetrock. But the five waste stacks will either need to be skipped, or chased, correct? I'm not aware of any other way to deal with them.
Does anyone have advice on how much clearance to give each stack? Or whether to leave an opening in the chase for the clean-outs? I'm assuming if any work ever needed to be done on a stack, its chase would have to be demo'd anyway.
Any advice appreciated.