Energy
Airtightness
A building's ability to limit uncontrolled air infiltration through its envelope.
Full definition
Airtightness measures a building envelope's ability to prevent unwanted airflows. It is measured by a Blower Door test giving an n50 value. For standard construction, n50 is about 6; for low-energy housing, n50 must be below 3; for passive houses, below 0.6.
Related terms
Heat recovery ventilation
Mechanical ventilation system recovering heat from extracted air to preheat incoming fresh air.
Building energy performance
Overall indicator measuring how efficiently a building uses energy.
EPC certificate
Document certifying a building's energy performance, mandatory when selling or renting.
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FAQ
A building's ability to limit uncontrolled air infiltration through its envelope.