The present disclosure relates generally to roofing products, for example, suitable for use covering and protecting the roofs of structures. The present disclosure relates more particularly to a roofing product including an upper section and an exposed section. The roofing product includes a substrate having a top surface and a bottom surface, and a plurality of zones of roofing granules disposed on the top surface of the substrate. The plurality of zones includes first, second and third zones within the exposed section. The first zone includes a first collection of algae-resistant roofing granules and has a first algae-resistance intensity. The second zone includes a second collection of algae-resistant roofing granules and has a second algae-resistance intensity. The third zone has a third algae-resistance intensity that is different from the first algae-resistance intensity.

Some embodiments of the present disclosure relate to a roofing system. In some embodiments, the roofing system comprises at least one steep slope roof substrate having a first region. In some embodiments, the first region comprises a plurality of shingles. In some embodiments, each of the plurality of shingles comprises at least one antimicrobial agent. In some embodiments, the at least one steep slope roof substrate also comprises a second region. In some embodiments, the second region comprises an antimicrobial scavenger layer that is configured to receive runoff from the first region of the steep slope roof substrate. In some embodiments, the runoff comprises an initial concentration of at least one antimicrobial agent and water. In some embodiments, the antimicrobial scavenger layer is configured to capture the at least one antimicrobial agent so as to reduce the initial concentration of the at least one antimicrobial agent in the runoff.

Biofouling of roof structures is reduced by applying to the roof a coating composition that contains an acrylic binder and a non-toxic antifouling additive that interferes with the ability of biofoulants to attach to the coating. Examples of non-toxic antifouling additives include polysiloxanes and cross-linked silicone rubbers.