EPA has a number of resources available, you can start with the Indoor Air Quality Building Evaluation and Assessment Model (I-BEAM).  I-BEAM updates and expands EPA's existing Building Air Quality guidance and is designed to be comprehensive state-of-the-art guidance for managing IAQ in commercial buildings.  This guidance was designed to be used by building professionals and others interested in indoor air quality in commercial buildings. I-BEAM contains text, animation/visual, and interactive/calculation components that can be used to perform a number of diverse tasks.

How to Identify the Cause of a Mold and Mildew Problem. 

       Mold and mildew are commonly found on the exterior wall surfaces of corner rooms in heating climate locations.  An exposed corner room is likely to be significantly colder than adjoining rooms, so that it has a higher relative humidity (RH) than other rooms at the same water vapor pressure.  If mold and mildew growth are found in a corner room, then relative humidity next to the room surfaces is above 70%.  However, is the RH above 70% at the surfaces because the room is too cold or because there is too much moisture present (high water vapor pressure)?

The amount of moisture in the room can be estimated by measuring both temperature and RH at the same location and at the same time.  Suppose there are two cases.  In the first case, assume that the RH is 30% and the temperature is 70^oF in the middle of the room.  The low RH at that temperature indicates that the water vapor pressure (or absolute humidity) is low.  The high surface RH is probably due to room surfaces that are "too cold."  Temperature is the dominating factor, and control strategies should involve increasing the temperature at cold room surfaces.