Excess moisture and dampness is one of the most important factors in mold growth. Some molds only like slight dampness, and others prefer saturation. Stachybotrys, the toxic black mold, prefers extremely wet areas. There are many causes of moisture and dampness, including:
Moisture can be caused by normal everyday activities of occupants in a home or building. Simple everyday personal tasks such as showering, cooking food, and doing laundry can add moisture to the indoor air. Humidity will naturally fluctuate during the day and over time depending on the conditions and activities of the occupants.
Emergencies and Unpreventable Water Leaks
Moisture can also by caused by unpreventable or emergency situations such as water pipe leaks, floods, and inclement weather. Rainwater and groundwater leaks in ceilings, walls, or foundations can cause moisture to seep deep into the building materials and cause extensive damage. Some of the damage may not be seen until it’s widespread.
Furnishing Materials and Arrangement
A homeowner’s selection and arrangement of furnishings can also contribute to moisture problems. Having cloth upholstered furniture can invite mold growth in the fabric. Placing furniture close against walls can reduce air flow and trap moisture allowing a warm moist spot for spores to multiply. Carpets also absorb moisture from the room and have a lot of humidity. In fact, wall-to-wall carpeting can have a higher humidity level than the air in the same room.
Condensation and Wicking
Condensation from moisture running off and along surfaces can contribute to mold growth. You can often see condensation on windows and windowsills in the winter months. Wicking, where a porous surface absorbs water from touching another surface such as a pipe, can also contribute to mold growth. This can be a problem that causes hidden mold inside walls and ceilings.
Air Conditioning Units
Moisture can accumulate in air conditioning and refrigeration drip pans due to poor condensate draining. It can also grow in air conditioning cooling coils.
Improper or Inadequate Venting
Humidity producing fixtures and appliances should be vented to the outside properly. When poorly designed or inadequate, dishwashers, washing machine, dryers, kitchen and bathroom fixtures, and spas can all contribute to high levels of humidity in indoor air.
Storing Wet Materials in Home
Wet materials kept enclosed inside a home, such as after a flood, can increase the moisture level. Following a flood or other saturating event, removing wet materials as soon as possible is critical to avoid mold growth.
The types of mold you find may be impacted by the amount of moisture occurring in your home. Some can grow with only minimal to moderate amounts of occasional moisture (such as Penicillium and Aspergillus), such as steam from a bathroom shower. Other types (such as Stachybotrys) must have a substantial amount of moisture, as in flooding or severe leaks, to grow and multiply.