luftdurchlässig

Luftdurchlässig is a German term used in engineering and everyday language to describe materials or layers that allow air to pass through their pores or interstices. It denotes the property of air permeability and is the opposite of luftundurchlässig or luftdicht. The concept is applied across domains such as textiles, membranes, building components, and porous geologic or horticultural materials. While related, luftdurchlässig is not synonymous with breathability (atmungsaktiv); breathability usually also encompasses water vapor permeability.

In textiles, air permeability affects comfort, wind penetration and draft protection. It is quantified by measuring the rate at which air passes through a fabric under a specified pressure difference, commonly reported as cm3/(s·cm2) in textile standards such as ISO 9237 or ASTM D737. In construction and architecture, luftdurchlässigkeit describes how easily air can move through building assemblies or joints. Airtightness testing, often performed with blower-door methods, yields an air leakage rate expressed in volume per area per time at a defined pressure (for example m3/(h·m2) at 50 Pa) and informs energy performance and moisture risk.

Applications aim to balance air exchange with moisture control. High luftdurchlässigkeit can improve ventilation but may increase energy losses if not complemented by proper insulation; low permeability reduces drafts and helps with energy efficiency but may require deliberate ventilation strategies. The term is used across industries, including textiles, building technology, and agriculture where soil aeration and potting media rely on air passage.