tiiveystasot
Tiiveystasot is a Finnish term used in building science to describe the airtightness levels of structures, assemblies, and components, i.e., how resistant they are to unintended air leakage. The concept is used to classify and compare how well buildings prevent air from passing through the envelope, with implications for energy use, indoor air quality, and moisture control. In practice, tiiveystasot is most commonly expressed as an air permeability value or as air changes per hour at a reference pressure, most often ACH50, which denotes how many times the indoor air volume would be replaced per hour at a 50 pascal pressure difference.
Measurement and standards: Airtightness is typically assessed with a blower door test, where a calibrated fan
Applications and interpretation: Tiiveystasot data are used in energy performance certification, design optimization, and retrofit planning.
See also: airtightness, energy efficiency, blower door test, passive house.