• Mildew is a mold covering that grows on organic matter, and thrives especially in moist or humid climates. A British Medical Journal study found that 50 percent of the homes in America experience some type of mold. Mildew can end up aggravating asthma or allergies in a house's residents, so it's important to get it taken care of with chemicals (such as silica gel) or by a professional as soon as possible.
  
  

Moisture and Humidity

• Houses in warm and humid climates, such as in Miami, are especially susceptible to mildew. Mildew.org says mildew occurs "where humid air settles on a cooler surface and where temperatures range between 40 and 100 degrees Fahrenheit." This kind of climate is ideal for mildew. You can put a dehumidifier in a room to decrease the chances for mildew growth.
  
  

Darkness

• Darkness is a perfect environment for mildew, because light can sterilize surfaces. Well-lit rooms are less likely to get mildew; basements, closets, and crawl spaces are more likely spots. Darkness provides the climate for spores to grow on organic matter, such as wood paneling or paper (books are often a growth spot for mildew).
  
  

Poor Ventilation

• Rooms where air does not circulate well can be a target for mildew. Dry air absorbs moisture in a room, providing nowhere for mildew to grow. This is why one of the first steps in getting rid of mildew is airing out a room, either naturally or with fans. Air conditioned rooms will create air circulation and help rid the house of mildew.