Abstract: A roofing system includes shingles having a front surface, a rear surface, an upper portion, and a lower portion. The lower portion is wider than the upper portion. A tongue extends from the upper portion and overlaps the lower portion, thereby defining a first groove between the tongue and the front surface of the lower portion. A return extends from an end of the lower portion opposite the upper portion, thereby defining a second groove between the return portion and the rear surface of the lower portion.