Spacial Daylight Autonomy (sDA)

Lighting designers can use sDA values to compare different spaces on equivalent daylighting terms. sDA is shown in Percentage (%) and it refers to percentage of regularly occupied space area where over 50% of time [1] achieves a certain minimum annual average lux illuminance. sDA analysis requires running an hour by hour illuminance analysis for a whole year.

[1]: Definition of time: working hours that requires daylight is defined by project team members and is usually 5 days a week from 8am to 6PM.

Green Star Requirement

sDA definitions in GSB v1A: % of regularly occupied space where over 80% of the nominated hours, achieves minimum 160 lux.

In Green star, the following requirements apply:

GSB requires for non residential areas sDA>40% with each tenancy sDA>20%.
GSB requires for residential bedroom+Living room (excluding kitchen) to achieve sDA>60% with each unit or room to have sDA>20%.


NCC requirement for daylight

NCC 2019 (FP4.1 Natural lighting) requires that sufficient daylight to be provided to regularly occupied areas (more than 2 to 3 hours a day). In technical language, it requires to deliver average daylight factor of not less than 2%.  This applies to a 1 hour hypothetical hour where sky is overcast at 10,000 lux illuminance.

Examples of sDA results and interpretation

In fowling example the office achieves 300 lux for more than 50% of working daytime hours. Hence it achieves sDA= 68.5% which is more than 50% threshold of most of the schemes.

In following, the outputs of Diva software are detailed which helps to better understand daylighting results terminology: