ghosting

[William Warner]

Originally Posted by Energy Guy

The discoloration is due to algae and you will notice that this growth will generally appear on the north and.or easterly sides of the home, in other words, the UV radiation doesn't kill the growth as it does on the westerly and southerly sides. Short of changing the house's orientation, eradication is the only solution (excus the pun)

Recommend a higher quality shingle (of course more expensive) next replacement.