For a cozy application, the same thickness of XPE will provide 21.8% more warmth retention than Reflectix. XPE is a sandwich of PET, foil, PE, and XP (cross linked polyethylene foam). Reflectix is a 5/16" sandwich of foil/bubble/bubble/foil. Both of these insulations are designed to be used with air gaps facing the foil on the hot side. A conventional cozy application doesn't provide the required air gap. This is the reason that this application, for 5/16" Reflectix, is only R 1.1 and for 5/16" XPE is only R 1.41.