It is not uncommon in new buildings to see the formation of mold and mildew. How can this happen?
Over the years I have observed the mold formation phenomenon resulting from a variety of causes, but generally all come down to poor construction technique. In one case, the staged drywall was allowed to get wet. In another, lined ductwork was left out in the rain before installation.
In each case, the construction materials were allowed to get damp or wet. After installation, the air conditioning was turned on, and the materials were exposed to low dewpoint temperature air. The result: dampness became liquid water, and spores grew into mold.