It is possible for homes to have too much humidity, which will create its own set of problems, particularly the issue of condensation. This does not typically occur in older homes, but new, tightly constructed buildings will retain more heat and moisture, which is when mechanical ventilation is important. During the winter you will first notice this at windows: when warm, moist air comes in contact with a cold window, air temperature drops and it can no longer hold the water vapor and condensation results. If a home does not have the proper mechanical and natural ventilation, excess water vapor can travel through walls and ceilings, causing wet insulation, peeling paint, and mold on walls and rot in woodwork.
How to Gauge Indoor Humidity Levels: