Mold in a home can be a serious problem, and one that deserves your immediate attention. Any problem with mold means there is a moisture problem. In addition to cleaning up the mold, you need to determine source of excess moisture solve the problem.
Building an energy efficient home or making energy saving home improvements should always be done with a good understanding of moisture and methods to control rain entry, humidity and hidden condensation. For more insight into moisture management in homes, see articles in www.buildingscience.com. The U.S. Environmental Protection Agency offers excellent advice on mold cleanup and on protecting yourself.