Factors That Produce Mold Growth

  1. Although mold can be found almost anywhere , they need moisture and nutrients to grow. The exact specifications for optimal mold growth vary by the species of mold.  However , mold grows best in damp , warm environments. The availability of nutrients in indoor, environments rarely limits mold growth because wood , wallboard wallpaper ,upholstery, and dust can be nutrient sources.  Similarly , the temperature of indoor environments above freezing and below the temperature for denaturing proteins , can support mold growth , even if the actual temperature is not optimal.

The primary factor that limits the growth of mold indoors is lack of moisture .  Substantial indoor mold growth is virtually synonymous with the presence of moisture inside the building envelope.  This intrusion of moisture might be from rainwater leaking through faulty gutters or a roof in disrepair , from foundation leak , from condensation at an interface , or between a cold and a warm environment . Water also can come from leaks in the plumbing or sewage systems inside the structure .  Studies of mold growth on building materials , that remain wet for 48-72 hours .  Flooding particularly when floodwaters remain for days or weeks , provides an almost optimal opportunity for mold growth .


Fungi may have adequate food sources available , but without moistures the mold will not grow. Fungi digest food by excreting  special chemical enzymes.  The enzymes require moisture in order to be effective.  You can look at it like mathematical equation . If you remove moisture from the equation you remove fungi’s ability to grow as well.  Spores + Food+ Moistures = Mold


The environmental Protection Agency document in the graphic above makes it clear we must clean water damage within 24-48 hours to prevent ,old growth. This make sense when you recall the CDC stated on the last page that mold grows on materials that remain wet for 48-72 hours .


Its not just liquid water that can provide the moisture to complete the equation.  Elevated relative humidity for more than a few days at a time can also lead to enough ,moisture at the surface of materials to support mold growth . Therefore EPA ideal target range for Relative Humidity RH is 30% – 50%. Never greater than  60%.


The American Society of Heating Refrigeration and Air Condition Contractors and other groups also recommended keeping relatively humidity below 60% to avoid the potential for condensation in cold areas and subsequent mold growth .


Typically the easiest and best long term solution to mold problems is to fix moisture problems and maintain buildings so that they do not come back .   In situations where this is not possible and / or it cannot be done quickly the next best thing to do is minimize food sources .



According to EPA Mold in schools and Commercial Buildings clean water damage with in twenty fours – forty eight hours to prevent mold growth.