Daylighting is an efficient method for providing better learning conditions and health in schools. Research studies have proven that students exposed to natural light not only concentrate better and for longer periods of time, but they also tend to learn faster and more efficiently. Therefore, it is essential to provide good quality daylight within the learning environments.
EFA Daylight Design Guide contains guidance on lighting design and daylight modeling for schools. Lighting Guide 5: Lighting for Education (LG5) identifies two criteria:
Useful Daylight Index (UDI) defined as the annual occurrence of illuminances across the work-plane that is within a range considered ‘useful’ by occupants. The output specification sets a minimum target of an average of 80% UDI-a (100 to 3,000 lux)
Daylight Autonomy (DA) is the amount of time a space can expect to reach a target illuminance level on the working plane. This criterion is aimed at delivering an energy-efficient space. It sets a minimum target DA of 50% of the time for 50% of the working plane, with a target illuminance of 300 lux.
covetool can be used to show the daylight level compliance using Spatial Daylight Autonomy (sDA) metric. sDA describes the percentage of occupied floor area that receives at least 300 lux for at least 50% of the annual occupied hours.
DA metric is slightly different from sDA in definition as DA represents the percentage of time while sDA represents the percentage of space. However, covetool's sDA analysis still can indicate the DA compliance.
sDA and DA metrics are very similar as they both have three common factors of time, space, and lux requirements. If a project in covetool indicates a sDA result of 50% or more, it will also pass the DA compliance requirements because a 50% sDA means for at least 50% of occupied hours, 50% of the occupied floor area receives the target illuminance of 300 lux. We just described the DA minimum criteria! In other words, 50% DA and 50% sDA represents the same condition.