Poor indoor air quality can result from inadequate or inappropriate ventilation. In commercial office spaces, Sick Building Syndrome is a real concern, and can be a result of HVAC systems that don’t adequately distribute air to occupants. In homes with a lot of air infiltration, the normal filtration mechanism in the HVAC system is bypassed by much of the outdoor air that leaks in through gaps in the building envelope. If the outdoor air quality is poor (such as in major cities), this situation is less than desirable from both an indoor air quality perspective as well as an energy-efficiency one. For tighter buildings, efficiency mechanical ventilation systems can ensure clean indoor air.
Efficient HVAC systems should ensure that occupants get adequate, filtered, fresh air. They should deliver the correct amount of air to the desired locations. Typically, inefficient systems are not only energy-inefficient, but also ineffective at doing their intended function.