Buildings are dynamic – ever changing, much like people. In the same way that monitoring blood pressure can give indications to problems or potential problems in people, measuring building pressures can give indication of a “building’s health” condition. These pressure differentials are relatively small. Over time, though, these small pressures can have either beneficial or detrimental affects on the building, it’s contents and even it’s occupants.
Pressures are created by one or more forces that interact with the building. Two are of natural causes – wind and stack and two related to human interaction – combustion and fans. There are four pressure fields that can be measured and monitored in buildings.
Exterior – the pressure difference across the building’s envelope as a result of natural effects such as wind and stack.
Interior – Room-to-room and room-to-outside pressure differentials can be associated with air handler fan operation, makeup air, exhaust fans, interior door closure, duct leakage, etc..
Air distribution systems – the duct work that moves air from room-to-room and room to outside. These “tubes” will either be at a higher or lower pressure than that of its surroundings. Air is moved from place to place.
Interstitial – there are cavities within the building that act as “ducts”. Generally, these cavities are not considered to have air movement or pressure differentials. They may, in fact, have large pressure differentials and move a great deal of air.