BUILDING AIRTIGHTNESS OR ‘ENVELOPE AIRTIGHTNESS’ CAN BE DEFINED AS THE RESISTANCE TO INWARD OR OUTWARD AIR LEAKAGE THROUGH UNINTENTIONAL LEAKAGE POINTS OR AREAS IN A BUILDING. 

These ‘leakages’ can be caused by internal ventilation systems, wind or general air movement creating changes in pressure which may ultimately create increased levels of energy consumption, drafting effects and potential moisture extremes such as condensation.