Ilmatiheys

Ilmatiheys is a Finnish term that translates to "airtightness" or "air leakage" in English. It refers to the degree to which a building or building component resists the uncontrolled passage of air. This is a critical aspect of building performance and energy efficiency.

In construction, ilmatiheys is achieved through careful design and execution of air barriers, which are continuous layers within the building envelope. These barriers prevent drafts, reduce heat loss in winter and heat gain in summer, and help control moisture movement. Poor ilmatiheys can lead to a range of problems, including increased energy bills, discomfort due to drafts, and potential damage from moisture buildup, such as mold growth.

Measuring ilmatiheys is typically done through a blower door test. This test depressurizes or pressurizes the building and measures the amount of air that leaks in or out. The results are often expressed as air changes per hour at a specific pressure difference (e.g., ACH50). Building codes in many countries specify minimum ilmatiheys standards for new construction to ensure energy efficiency and occupant comfort. Achieving good ilmatiheys requires attention to detail in sealing all joints, penetrations, and interfaces within the building envelope, such as around windows, doors, pipes, and electrical outlets.