Insulation system and method for pre-engineered buildings

A method of insulating a building framework for a by-pass wall girt metal building type, wherein the building framework includes vertical structural wall columns, corner columns and roof structural members to support side walls, end walls and a roof, the wall and corner columns having exterior faces, the building framework further including parallel spaced horizontal wall girts connected to the exterior faces of the structural and corner columns, and parallel spaced roof purlins connected above and normal to the roof structural members, the method of insulating the building framework comprising:

• prior to connecting the wall girts, connecting to each exterior face of the wall and corner columns, a vapor barrier extension member formed of vapor barrier material, the vapor barrier extension member having lap extensions which extend horizontally in both directions beyond the exterior face or faces of the wall and corner columns;
• connecting the wall girts to the exterior faces of the wall and corner columns;
• installing insulation in one or more layers between the wall girts, the innermost layer of insulation being provided with an interior facing;
• fastening the lap extensions of the vapor barrier extensions to the interior facing of the insulation on either side of the wall and corner columns.