Abstract: A system for insulating a building roof structure having a plurality of secondary structural members extended longitudinally between a pair of oppositely situated primary structural members includes a plurality of spaced-apart parallel support bands extended transversely across the undersides of the secondary structural members, a suspension sheet supported on said bands and extending longitudinally between a pair of primary structural members and transversely across a plurality of the secondary structural members, thermal insulation material supported on the suspension sheet and band fastener means for connecting the bands to the secondary structural members, the suspension sheet being continuous but for the passage of the band fastener means therethrough.The invention is also directed to a plurality of band hangers with coacting fastener means to facilitate connection of the bands to the secondary structural members.