You can not glue the insulation to plywood. However, you can glue it to a fully prepared deck. A fully prepared deck requires a vapour barrier such as ALUTRIX or ELOTENE to be installed onto a clean deck with their compatible primer. When glueing you must only use tissue-faced boards such as Kingspan TR27 or TT47 or RECTICEL Powerdeck F. You cannot use foil-backed insulation when glueing.