Infiltration/exfiltration is the uncontrolled inward/outward leakage of outdoor/indoor air through air permeable materials, joints, cracks, interstices and other unintentional openings of a building envelope, caused by the pressure effects of wind, the stack effect or operation of HVAC-systems . Infiltration/exfiltration causes convective heat and moisture transfer, resulting in excessive heat loss and potential moisture problems in the building envelope. The building airtightness measurement aims at finding, quantifying and reducing those unintentional cracks and openings in order to get the intended airtightness of the building.
 M. Limb, “Technical note AIVC 36- Air Infiltration and Ventilation Glossary” International Energy Agency energy conservation in buildings and community systems programme, 1992.
Posted in: Building Airtightness