Roof membranes used in flat to very low-sloping roofs are particularly susceptible to the growth of fungi – such as molds and mildews, as the structural design makes them prone to poor ventilation and accumulation of moisture. Certain common membranes are particularly prone to mold growth. For instance, PVC is a popular and highly versatile membrane material due to its exceptional physical properties, fire resistance characteristics, and excellent cost-performance ratio. In fact, of the 40 million metric tons of PVC produced every year, roughly 70 percent is used within the construction industry. However, flexible PVC contains plasticizers that serve as a source of energy for microorganisms, making them highly susceptible to microbial attack.