1 Answers
Building airtightness can be defined as the resistance to inward or outward air leakage through unintentional leakage points or areas in the building envelope. This air leakage is driven by differential pressures across the building envelope due to the combined effects of stack, external wind and mechanical ventilation systems.
Airtightness is the fundamental building property that impacts infiltration and exfiltration.
An airtight building has several positive impacts when combined with an appropriate ventilation system :
A number of studies have shown substantial energy savings by tightening building envelopes. The ASIEPI project technical report on building and ductwork airtightness estimates the energy impact of envelope airtightness in the order of 10 kWh per m of floor area per year, for the heating needs in a moderately cold region. Experimental data showing the energy savings of good airtightness were also published by the Building Research Establishment in the UK as well as REHVA journals' special issue on airtightness. They conclude 15% of the space conditioning energy use can be saved in the UK context going from 11.5 m/ @50 Pa down to 5 m/ @50 Pa.