Do you want your roof looking beautiful and lasting longer, butyou're also concerned about using high pressure on your shingles? You're already on the right track! According to ARMA (Asphalt Roofing Manufacturers Association) the algae eating away at your shingles and causing those unsightly black streaks should be washed off using a gentle sprayer (ours uses roughly 100 psi compared to many 3000-4000 psi machines people sometimes use) with the right solution! Don't take the risk with someone who will most assuredly remove excessive amounts of Asphalt from your very expensive investment, your roof! Here's our crew in action (the after photo shows the moss dying off over the course of a few weeks since we DON'T use high pressure).