Dirty Roofs Sweeping the Midwest
Roof Cleaning is a must to get maximum roof life and maintain curb appeal.
You may have noticed a growing number of homes with dark black streaks running down the roof. Maybe you have seen this on a friend’s roof or a relative’s roof, but beware, if those streaks are on your neighbor’s roof, your roof may be next. It may already be discolored. Those streaks sure are ugly .
Those streaks are actually algae (gloeocapsa magma) eating the limestone filler in the shingles. This filler was added to shingles about 30 years ago when asphalt shingles were largely replaced with the heavier, more wind-resistant fiberglass shingles we have today. Algae lives on limestone.
You may notice that the discoloration is primarily on north-facing roofs. This is similar to moss growing on the north side of a tree. Since north-facing roofs generally get the least amount of sun, they stay wet longer from rain and morning dew. This, combined with the limestone smorgasbord, creates a perfect home for any algae spores that may land on the roof.
The algae spores are not actually black when they land on a roof. If there are black streaks on only a north-facing roof, the other roof faces are probably infested also. The algae spores just have not turned black yet. They create that dark sheath to protect themselves from ultraviolet rays. Unfortunately, this dark pigment can also affect energy bills since dark colors absorb more heat than light colors.
The spread of the algae (and the corresponding black streaks) from roof to roof is likened to that of dandelions spreading from yard to yard. If your neighbor has them, you probably will too. Another similarity is the best method to get rid of them. Mowing your yard can make a lot of dandelions disappear…for a little while, but the only way to keep them gone is to aliminate them. The same is true for the algae on a roof.
Policy#: CBP4289130 