All roofing contractors agree that cleaning and maintaining your roof can extend its life. Keeping your roof free of debris, routine gutter cleaning at least once a year, and repairing any loose or missing shingles will go a long way to extend the life of your roof.
Never, ever under any circumstances pressure wash your roof shingles on your own or pay a company to do so. Sure, it's tempting to want to get any moss, algae, dirt, etc. off of your roofing shingles. But pressure washing your asphalt roof will do more harm than good.
A soft wash incorporates special low-pressure nozzles on the end of a pressure washing gun or wand. That's combined with a biodegradable chemical that removes the biological elements (mold, algae, pollen, dirt, moss) and other stains without damaging surfaces on your home or harming your plants and leaving all the granules in tact. The soft wash solution turns the growth white in color and over time it dies off and decenegrates and blows off with help from wind and rain.