Granules are the little rocks on the top of your shingle that are an integral part of your roofing system. Asphalt shingles are typically comprised of a fibreglass weave, impregnated asphalt, glueing strips and the top granule layer. The granules job is to reflect and absorb the ultraviolet sunlight. Without it, the asphalt layers will deteriorate very rapidly, and melt away in the summer heat. Some loss is normal, as many you may find some in your gutters upon clean out. Eventually though there will be none left, and you may be in need of a new roofing system. Having adequate attic ventilation can help keep attic temperatures down and prolong the life of your roof. When attic temperatures are too high and persist, the asphalt in the shingles may overheat, causing the shingle to lose hold of its granules and cause your roofing system to fail.