Wall, Ceiling, and Crawlspace Reflective Insulation OptionsCustomer Support2023-09-09T23:02:53+00:00 Need Insulation for WALLS,CEILINGS, or CRAWLSPACES ?WALLS: 2” x 4” Exterior1 2” x 6” Exterior 1 Knee Wall1 Masonry Wall1 CEILING Basement1 Cathedral (Northern)1 Cathedral (Southern)1 CRAWLSPACE R-17 Install1 R-21 Install1