Air pressure and buildings

Air tightness refers to the continuity of a buildings fabric and its ability to retain air (and heat), it is measured in terms of an air leakage rate through the building's envelope. Air pressure might be described as the force exerted by air on any surface in contact, in a unconfined, confined or compressed space. Air tightness is measured with reference to a certain air pressure, normally given as 50 pascals, in a building this is approximately the pressure exerted on a fabric if a 20 mile an hour wind is blowing on all of its side sides at the same time.

at a given reference pressure (usually 50 pascal) divided by the: Heated building volume V. At 50·Pa, it is called the air change rate at 50 Pa and usually noted n50(units: h−1).

, air pressure and air flow in buildings are all related but also. .. of air or any other fluid is caused by a pressure differential between two points.

Flow will originate from an area of high energy, or pressure, and proceed to area(s) of lower energy or pressure.