During the 1970's the cost of heating and cooling buildings increased and subsequently changes in construction techniques took place. Many buildings were retrofitted with insulation, vapor barriers, and new tighter windows and doors. New building construction techniques were developed to reduce the volume of air infiltration or exchange through walls, windows, and doors. As a result, the buildup of contaminants and moisture inside of buildings which provided a healthy environment in the past became an issue.
Why has indoor air quality declined?
Legionnaire's disease is an example of a Building Related Illness.