The reason many insurance companies are threatening to cancel homeowners insurance if they don’t get their roofs cleaned. They understand that the black stains on roofs aren’t just an eye sore. It is a black algae called Gloecapsa Magma. It thrives on the Lime that is used to strengthen the shingles. If left unchecked it can diminish the life expectancy of the shingles by as much as 40%. Call David 919-207-0666