Außenlicht

Außenlicht is the German term for the natural or artificial light that comes from outside a building or structure. It is distinguished from Innenlicht, which denotes interior illumination. Außenlicht can be composed of direct sunlight, reflected light, or diffuse sky light, and its intensity, color temperature, and distribution vary with time of day, weather, season, and geographic location.

In architecture and building science, Außenlicht is a fundamental element in daylighting strategies. Designers aim to maximise usable daylight by orienting windows, using light shelves, skylights, and reflective surfaces. Adequate Außenlicht reduces dependence on artificial lighting, lowers energy consumption, and can improve occupant wellbeing. Regulations in many countries set minimum daylighting performance standards for new construction and renovations.

Außenlicht also plays a role in environmental health. Exposure to natural light influences human circadian rhythms, sleep quality, mood, and cognitive performance. Urban planning uses concepts such as "sun zoning" to ensure that streets and public spaces receive sufficient daylight. In agriculture, Nebenreihen of Außenlicht are essential for plant growth; artificial supplements are used in greenhouses to mimic natural light spectra and intensities.

In physics and optics, Außenlicht is analysed in terms of irradiance, spectrally resolved radiance, and luminous flux to inform lighting design and energy modelling. Computer simulations, such as radiance or Lumen, calculate Außenlicht effects on interiors under varying weather conditions. This multidisciplinary understanding supports sustainable design, public health initiatives, and energy policy development.