Algae and mold growth on siding
Mold, algae and mildew accumulate on all kinds of surface including vinyl aluminum wood and brick. Although these small plants enjoy moisture and shade, even in sunny areas siding can turn green and brown.
Mold releases particles and spores into the air as they being to colonize. Many people have allergic reactions and sensitivities to these spores and may cause asthma attacks and headaches.
As they grow, they begin breaking down surfaces they are growing on causing oxidation and discoloration . They are normally present in the air outside and after finding surface to adhere too, they begin multiplying. As they multiply, so do the spores in the air and thus siding begins turning greener and greener. The more humid and wet an area the quicker mildew and mold will spread.
There are a few types of algae including red brown and green but the end result is normally a discoloration of the surface they are living on. These small organisms can be carefully cleaned off vinyl or other types of siding by pressure washing. Here is a link for those of you interested in trying your hand at cleaning your vinyl or aluminum siding.