Air leakage occurs through openings in the building envelope, this air leakage affects the building’s energy performance, The need to reduce CO2 emissions has led to changes in building regulations, therefore buildings now need to meet a level of air tightness. The air-tightness of a building is the air permeability or leakage rate through a structure. Air leakage is the uncontrolled flow of air through the building envelope; this does not include the structure ventilation system.
To determine if building regulations for air tightness are met, a test is carried out, which usually involves placing a blower-fan in the doorway of the structure and pressurising the building envelope. These measurements are used to calculate the air tightness of the structure. A certificate is produced which will be passed on to the SAP assessor who is responsible for assigning a buildings energy rating. In the case of buildings that have an existing energy rating, this process can be used to easily improve it’s grading. This test must be carried out after all building works are complete.