by Jerry Peck - Codeman on Fri Aug 04, 2017 5:35 pm
First, don't use "drywall" (gypsum) type backer board in wet areas (such as around tubs with shower, shower, behind sinks, etc), use cementitious board there.
What most people use over furring strips on block walls is that foil insulation, and it basically goes everywhere on furring over block walls.
Typically, that foil insulation also serves as a vapor retarder.
Jerry Peck - CodeMan
AskCodeMan.com
Construction Litigation Consultant - Retired
Construction and Code Consultant - Semi Retired