Common Airtightness Terms

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Some of the commonly used terms and abbreviations in Air Barrier code and practice:

0.1 L/(sāˆ™m2) 0.1 Litres per second per metre squared = Code requirement for the acceptable amount of air that can get through a material being used as a barrier. This test is done with air pressure (75 Pa) in a lab. (Reference: NBC 9.25.5 Properties and Position of Materials in the Building Envelope)
50 and 75 Pa Pascals, a measure of air pressure on a surface that imitates a strong wind.
ACH Air Changes per Hour
Assemblies Construction for specific parts of a building - e.g. wall assembly = drywall, vapour retarder, insulation, studs, exterior sheeting, etc.
ASHRAE American Society of Heating, Refrigeration and Air Conditioning Engineers (an international standards and testing organization)
Conditioned Space The inside of the building that you're ventilating, heating or cooling.
ERV Energy Recovery Ventilator - fresh air machine that also moderates humidity.
HRV Heat Recovery Ventilator - fresh air machine that exchanges heat energy from outgoing exhaust air with incoming fresh air supply.
HVAC Heating, Ventilation and Air Conditioning = the mechanical system responsible for conditioning an indoor space.
IAQ Indoor Air Quality = The quality of fresh air in a building. Expressed as ratio of how much of a pollutant, particle or gas makes up a volume of air.
Infiltration / Exfiltration Air leakage into and out of a building, respectively.
NBC National Building Code of Canada
NECB National Energy Code for Buildings
NL / NLR / NLA Normalized Leakage / Normalized Leakage Rate / Normalized Leakage Area = a measurement of the airtightness of a building, relative to its size and number of stories. Often expressed as, "Your leakage rate would be like having an X by X sized hole in the building envelope". Defined in ASHRAE Standard 119.