A process of simultaneously molding either a plurality of shingles or double walled shingles or other substantially planar exterior building products is provided, such that a blow moldable thermoplastic material is provided, of a composite parison that is then blow molded in a hollow mold, to produce novel shingles according to the process. Ventilation and/or insulation can be provided to a hollow interior between spaced apart walls of a double walled shingle.