An insulation system for coupling to a building substrate comprising a plurality of insulation panels, bracket members and splice members. Each insulation panel includes a longitudinal slot. Each bracket member is formed from a polymer and includes an elongated body having a body wall, a first end wall and a second end wall. Upper and lower ribs extend from the body wall and are structurally configured to extend into the longitudinal slot of each of the plurality of insulation panels, and to elastically deform the longitudinal slot so as to effectively seal along a length thereof, defining a vapor barrier. A similar structure is on each splice member. The bracket members are positioned in a spaced apart relationship with insulation panels therebetween. The upper and lower ribs extend into corresponding ones of the longitudinal slots of the insulation panels, with splice members extending between adjacent adjacently abutting insulation panels.
