Abstract: There is disclosed a cellulose fiber thermal barrier and a method for its application. In an embodiment, the method comprises preparing a cellulose fiber thermal barrier material including joint compound, dry powder glue and dry fire retardant; mixing the cellulose fiber cellulose fiber thermal barrier material with a liquid binder mix and water; and spraying the mixture under pressure onto a surface. This cellulose fiber thermal barrier applied to a thickness of about 1¼ to 1½ inches may provide a class B, 10-minute thermal barrier in accordance with the CAN4-2124-M standard of the National Building Code.