Ilmatiiveyteen

Ilmatiiveyteen is the Finnish illative form of the noun ilmatiiveys, commonly used in building science to refer to airtightness or the state of being airtight. In practice the term denotes measures taken to limit uncontrolled air leakage through building envelopes and components, and the resulting performance characteristic of a structure.

Airtightness is important for energy efficiency, because uncontrolled infiltration increases heating and cooling demand. It also affects indoor air quality and moisture control: excessive leakage can introduce pollutants and moisture, while overly tight construction without adequate ventilation can lead to poor air exchange and condensation problems. Therefore designs aim for a balance between controlled ventilation and high envelope integrity.

Measurement of airtightness is commonly performed with blower door tests and tracer gas methods. Results are often reported as n50 (air changes per hour at 50 Pa) or as leakage rate per unit area or volume. International and national standards, such as EN ISO 9972, describe test procedures and reporting formats used in Europe, and many building regulations set target values or requirements for new construction and retrofits.

Common techniques to achieve ilmatiiveyteen include continuous air barriers, sealing tapes and gaskets, spray foams, and careful detailing at joints, penetrations and connections. Attention to workmanship and coordination between trades is critical, as even small gaps can substantially affect overall performance.