Building pressure is the result of a difference between the outside air and exhaust air mechanically forced into and out of a building. The objective is to maintain a building NET positive during periods of dehumidification (cooling) and NET neutral during periods of humidification (heating).
In some areas of the country, a 1,000 cfm negative pressurization flow can transport up to 1,000 gallons of water across the building envelope each year.
When the outdoor dew point is high, a positive pressurization flow will dry the building envelope and prevent air carried water transport, thus reducing mold.
The pressurization flow is most effectively controlled by maintaining airflow differentials within a pressure zone.
Unlike static pressure control, airflow control is stable; unaffected by changes in adjacent pressure zones or wind.