feuchtigkeitsundurchlässig

Feuchtigkeit, commonly translated as humidity or moisture, refers to the presence of water in the air or in a material. In meteorology, humidity describes water vapor in the atmosphere, while in materials science it can denote moisture content within solids. Humidity is quantified by several related indicators: relative humidity (RH), absolute humidity, and specific humidity. Relative humidity expresses the amount of water vapor in the air as a percentage of what the air can hold at the current temperature. Absolute humidity is the mass of water vapor per unit volume of air, typically expressed in grams per cubic meter. Specific humidity is the ratio of water vapor mass to the total mass of moist air. The dew point is the temperature at which the air becomes saturated and condensation begins.

Measurement and control of feuchtigkeit rely on specialized instruments. Hygrometers measure humidity directly, while psychrometers use cooling or multiple temperature readings to infer RH. More precise devices include chilled mirror hygrometers and dew point meters. In industrial and laboratory contexts, moisture analyzers determine moisture content in materials by methods such as drying, Karl Fischer titration, or microwave techniques. Temperature strongly influences humidity readings, since warmer air can hold more water vapor, causing RH to change with temperature even if the amount of vapor remains constant.

Effects and applications of feuchtigkeit are diverse. High humidity can promote mold growth, corrosion, and deterioration of textiles and electronics, whereas very low humidity can cause drying, cracking, and static electricity. Controlling humidity is important in buildings for comfort and energy efficiency, in agriculture for crop health, and in storage and manufacturing for product quality. Standards often specify indoor relative humidity ranges, typically around 30–60%, though requirements vary by climate and use. In meteorology and climate studies, humidity data improve weather forecasts and analyses of atmospheric processes.