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Daylight Autonomy (DA)

What it is​

Daylight autonomy is the percentage of occupied hours in a year when daylight alone keeps the illuminance at a point at or above a target level — usually 300 lx:

DA300 = share of occupied hours with Edaylight ≥ 300 lx

Unlike the daylight factor, DA is climate-based: it is computed from an hourly weather file for the actual location, with a real sun and sky for every hour, so it depends on orientation, latitude, local climate and the assumed occupancy schedule. A south-facing room in Malmö and an identical north-facing room reach very different DA values.

Two related terms:

  • sDA (spatial daylight autonomy) — the fraction of the floor area that reaches a given DA. Written sDA 300/50 %: the area where daylight provides ≥ 300 lx for ≥ 50 % of the occupied hours.
  • Continuous / useful daylight variants weight partial credit differently; LUX reports DA300.

Scale and colours​

DA is a percentage from 0 to 100 %.

Loading color scale...
  • Black / dark purple — DA near 0 %; the point almost never reaches 300 lx on daylight alone.
  • Red to orange — 30–60 %; daylight covers a fair part of the working day.
  • Yellow to near-white — 70–100 %; the point is autonomously daylit for most or all occupied hours.

Download the exact stops: DA colour scale (JSON).

Where DA / sDA is used​

  • EN 17037:2018 — daylight provision, Method 2: sDA 300/50 % over ≥ 50 % of the area
  • Denmark — BR18 — Route B: 300 lx for ≥ 50 % of the daylight hours over ≥ 50 % of the area

Daylight hours vs. occupied hours​

The generic DA definition above runs over occupied hours — whatever schedule the building actually uses. EN 17037's sDA 300/50 % (and BR18's Route B, which reuses the same method) instead runs over daylight hours, a term the standard defines precisely: the 4380 hours per year (half of the 8760 hours in a year) with the highest diffuse horizontal illuminance in the reference weather file for that location. Because it's derived per-location from the weather file, the actual clock hours it covers shift with latitude and climate.

LUX support​

DA has more inputs than DF (it needs window orientation) and a separate model per location, because climate varies so much from place to place. Daylight autonomy prediction in LUX is in experimental development and is not yet available in any LUX product. Join the waiting list or follow our Substack for release news.