The OP is talking about the expansion felt or foam that you would put along a building, retaining wall, or other
slab that you would want the new concrete to move independently of.
Two totally different things.


If it were against my house I'd want foam with lots of caulking. No
felt next to the house! I'm no expert, but I dn't think I've ever
seen felt next to a structure. You would want something waterproof
like caulking.