Dagsljusandel

Dagsljusandel is a Swedish term used in building design and daylighting analysis to describe the proportion of time or area that receives sufficient natural light. It is typically expressed as a percentage and indicates how often a point or a fraction of a room meets a specified daylight illuminance threshold during occupied hours. In practice the metric is commonly employed with thresholds in the range 200–500 lux, with 300 lux often used for general workspaces.

The concept is closely related to international metrics such as daylight autonomy, and is used to assess daylight availability, inform window and façade design, and support compliance with daylighting requirements in planning and certification. Calculation is usually performed by simulation tools that combine climate-based sky models with interior geometry and material properties to estimate hourly illuminance over a year; the dagsljusandel is then the share of hours meeting the target.

Advantages of using dagsljusandel include its intuitive percentage format and its relevance to occupant needs and electric lighting savings. Limitations include sensitivity to the chosen threshold, limited information about temporal or seasonal distribution beyond the aggregate share, and no direct measure of glare, visual comfort, or light quality. It is commonly used alongside other measures—such as daylight factor, spatial daylight autonomy, and glare indices—to provide a more complete evaluation of daylight performance.