In my last house I used 1 1/2" foam insulation board covered with flannel. Just moved to a new house and my current vehicle wouldn't handle the large foam sheets. At my local Lowes store I found packages if 3/4" foam 13 5/8" x 48", 6 sheets per pack. I bought 3 packs. Used Silicon to attach 16 sheets to wall. I now have an 8x8' design wall, again covered by flannel.