← All Metrics

Average Daylight Factor

Compute the area-weighted average Daylight Factor across a room — the primary BREEAM daylighting criterion for residential and commercial spaces.

BREEAM UK planning
⬇ Free Evaluation Download
Average Daylight Factor result for a room
Indoor Daylight

Area-weighted mean DF for compliance

The Average Daylight Factor is the area-weighted mean DF across a room. It is the primary BREEAM daylighting criterion, directly compared against BREEAM thresholds for Excellent, Good, and Pass ratings in both residential and commercial spaces.

DL-Light automatically calculates Average DF and generates the BREEAM-compliant report, with pass/fail status per space. The result is also used in UK planning policy to assess daylight adequacy of new dwellings.

  • Area-weighted mean DF per room
  • Automatic BREEAM Excellent / Good / Pass rating
  • Used in UK planning daylight assessments
  • Per-room and per-building results
  • Part of the core DF module
DF report with average values

DF report with average values

Frequently asked questions

What is Average Daylight Factor?

Average Daylight Factor (Avg DF) is the mean daylight factor calculated across a surface or space. It represents the average percentage of exterior illuminance received indoors, providing a single metric to assess overall daylighting performance.

How does DL-Light compute it?

DL-Light calculates average daylight factor using ray-tracing simulations with the Radiance engine under standard overcast sky conditions. It computes the DF at multiple points and calculates the arithmetic mean across the analyzed surface.

What thresholds or standards apply?

BREEAM assesses average daylight factor for compliance with specific targets depending on building type and room function. Typical targets range from 2% for offices to 1% for other building types. Average DF is part of the Daylight Factor assessment.

Going further

Read the full DL-Light user-guide reference for Average Daylight Factor: Windows guide · macOS guide.

Start using Average Daylight Factor today

Download the free evaluation — no time limit, no credit card required.

⬇ Free Evaluation Download Buy a License