“First, a mold fact: Mold needs three things to grow–a food source (usually wood or paper-backed drywall), proper temperature (warm), and moisture. Take one of these three things away, the mold can no longer grow.
So, with that in mind, the reason newer homes are more subject to mold problems is because they have something old homes don’t, namely insulation. Insulation’s job is to slow or stop air movement through the wall. The better insulated a house is, the less air moves through it–which is good because if you’ve paid to heat that air you want to keep it inside in February.”
Click the image below to read more from Mark on ‘old house web.’