A whole house ventilation system is a system designed to remove stale air from a home and bring in fresh air from outside by ventilating the home. Many builders and homeowners choose to build tightly sealed homes without "leaks" that would allow air in and out. Sealing a house tightly to prevent air from entering or leaving is often preferred because of the need to heat and cool homes: No homeowner wants air conditioning or heat escaping through gaps near windows or walls.
A tightly sealed home can create problems with indoor air quality (IAQ), however. Toxins, pollutants, bacteria, and odors are unable to escape the home, and fresh outdoor air is unable to enter. As a result, the air inside the sealed home becomes stale and, in some cases, unhealthy. A whole house ventilation system is used to allow a house to be tightly sealed and free of drafts, while still ensuring proper circulation so fresh air can enter the home and stale air can leave.
According to the American Society of Heating, Refrigeration and Air Conditioning Engineering (ASHRAE), the air within a home should change .35 times per hour, or at least 15 cubic feet (.4 cubic meters) of new air should enter the home each minute for each person present. Kitchens and bathrooms are recommended to have even higher air turnover, up to the rate of 100 changes per minute, often achieved by the use of an exhaust fan. These "changes" require outdoor air to be able to enter a room, either through an window, a door, a fan, a window air conditioner, or a whole house ventilation system.
Homeowners who wish to ensure proper whole house ventilation have the option of using a mechanical ventilation system. Mechanical ventilation systems are designed to push air out of rooms and bring new air in. Such a system can be as simple as an exhaust fan in a bathroom or as complex as a multi-room system that precisely calculates the ventilation needs of each room in the house based on settings customized by the installer. Some mechanical ventilation systems even have heat-recovery devices built in that pre-heat the outdoor air as it enters the house in winter.
A whole house ventilation system thus provides a balance between energy efficiency and indoor air quality. Homeowners can maintain a draft-free home and not tax their heating and cooling system with unwelcome outdoor air. A ventilation system can allow them to still achieve sufficient air turnover to keep their home free of bacteria and odor.