CosyWall Insulation CosyWall Insulation (CWI) is a full extemal wall cavity insulation system (EWCIS) for providing thermal and acoustical insulation to wall cavities lined on both sides. After installing AIRFOAM for 6 years, in 2013 we changed to Cosy Wall Insulation for existing walls. CosyWall insulation is manufactured in selected North American plants by melting