Basic air infiltration

Some fundamental properties of building air infiltration are derived starting from propositions stressing the underlying assumptions. Possible structures of air infiltration models relating the flow to a leakage area are considered. Approximate expressions are derived for the value of the reference pressure necessary for mass conservation to hold. These results are applied to the case of enforced building pressurization. It is demonstrated that some currently used models of air infiltration violate mass conservation. Other models are shown to lead to unnecessarily large errors when applied to pressurization.