Too Airtight?

An airtight house, as opposed to a drafty house, is often thought desireable to conserve heat and energy.  Home weatherization programs often work to "seal" or block as much outside air from infiltrating around doors, windows, and other areas as much as possible.  Many do not realize that a house can be "too" airtight.  An "average" house may have an air exchange rate of about five (5) times per day.  This means that each day, the air in the house would be completely exchanged with fresh outside air five times.  A lot of heat may be lost, but fresh air is added.  A house that is too airtight can create problems of its' own such as concentrations of stale or polluted air (indoor air quality is usually poorer than outdoor air), oxygen depletion, and moisture rention which may lead to mold and mildew growth.  Newer homes that are built to minimize air infiltration rely on mechanical ventilation, air filtration, and dehumidification systems to make up for what the "drafty" old house did naturally.  New commercial building requires that 20% of the air circulating through the system must be fresh outside air.  The cost of operating and maintaining these additional mechanical systems must be accounted for in determining the houses overall energy consumption picture.  Energy conservation is important, but realize that air exchange is very important as well.