Natural ventilation is the non-mechanical (without the use of fans or blowers) process of replacing indoor air with fresh, outdoor air by natural means.
Natural ventilation can be useful, but it can also create problems. For example, opening doors and windows is one way to increase natural ventilation and fresh air indoors. Natural ventilation is typically used to ventilate crawl spaces and attic spaces to remove moisture. However, air infiltration through cracks and gaps is an uncontrolled and undesirable example of natural ventilation.
In humid climates, natural ventilation is not the ideal means of ventilation because the moisture content of the air is hard to control and monitor. However, in cold and moderate climates natural ventilation can be effective as a means of summer cooling without the use of mechanical air conditioning.
If combustion equipment and appliances are present, natural ventilation may not be adequate to supply sufficient oxygen and could result in incomplete combustion. Carbon monoxide and other pollutants may be created resulting in a safety hazard.
To measure the amount of natural air exchange and pinpoint sources of air infiltration, an energy auditor will use a diagnostic piece of equipment called a "blower door."
