The answer to 'how to clean architectural shingles' is to use a soft-bristle brush and a mild, non-abrasive detergent mixed with water. Gently scrub the shingles to remove dirt, mildew, and other buildup, then rinse thoroughly with a garden hose. Avoid pressure washers as they can damage the shingles.
It's recommended to clean architectural shingles every 1-2 years, or as needed to maintain their appearance. Be sure to take safety precautions when working on the roof, such as wearing non-slip shoes and using fall protection equipment if necessary. If you're uncomfortable working on the roof or the cleaning requires specialized equipment, it's best to hire a professional roofing contractor.