Creating a well-lit building is vital for the well-being of people using a building as well as for reducing energy demand and carbon emissions. Whilst recognising that the amount of daylight available within a building is constrained by the amount of useful daylight outside, the aim of the AECB Daylight Standard is to provide adequate daylight between 9am and 5pm for 70% of the year and acceptable daylight 80% of the year between 10am and 2pm. To satisfy these criteria the AECB Daylight Standard requires you to assess the quality of daylight within each habitable room. The AECB Daylight Assessment is used to verify that a design meets this standard.
To determine the quality of daylight you must evaluate how evenly daylight is distributed within a room (the Daylight Uniformity), and the proportion of daylight within the room relative to outdoor conditions (the Daylight Factor).
Satisfactory Daylight Uniformity is achieved when more the 80% of a habitable room receives natural daylight. Acceptable daylighting is achieved when the specified Daylight Factor is achieved ( Appendix 1 in the Daylight Standard Guidance, describes the Daylight Factor criteria ). To reduce the risk of overheating high daylight factors (oversized windows) should be avoided. Daylight Uniformity and the Daylight Factor must be calculated in accordance with BS 8206-2 using the AECB Daylight Calculator.


Read The Daylight Standard Guidance PDF

AECB Daylight Calculator

The AECB Daylight Calculator allows you to evaluate Daylight Uniformity and the Daylight Factor within each habitable room.

Based upon BS 8206-2, and informed by BRE BR209, BRE IP 15/88 and BRE Digest 309, the AECB Daylight Calculator is a simple but powerful series of worksheets that make daylight assessment quick and easy.

The calculator is ideal for buildings that aspire to the AECB Building Standard or the Passivhaus Standard because has been optimised to make use of the normal PHPP workflow - saving time and effort. (If you are not a PHPP user don’t worry, you can still complete a conventional daylighting assessment.)

An example of the calculators simple one-page Verification report is given on the right. A copy of this report should be submitted with your AECB Building Standard documentation.

Learn about the AECB Building Standard

The AECB Daylight Calculator shares the same calculation procedure as Housing Quality Mark (HQM) and BREEAM. This means you can avoid duplicating effort and use it to assess the quality of daylight under those standards as well.

Read The Daylight Standard Guidance PDF


The AECB Daylight Assessment is a plug-in for PH Ribbon. To undertake your AECB Daylight Assessment have a look at our page on PH Ribbon

Learn about PH Ribbon

Each complimentary AECB standard adopted must be submitted as part of your AECB Building Standard submission and uploaded via the AECB Low Energy Building Database (LEBD). The report summary verifications sheets for each standard must be combined into a single pdf and uploaded as the ‘PHPP verification sheet’ entry on the LEBD.

You may still submit for the AECB Building Standard only, without any complimentary standards, however we do of course encourage you to adopt as many of these as possible in each project. You may not submit complimentary AECB Standards without submitting for the AECB Building Standard or the Passivhaus Standard as a prerequisite. If you want to retrospectively add complementary standards to an existing AECB Standard certified project please contact the AECB team via the LEBD. Evidence for the complimentary standards is to follow the standard reporting format provided by the AECB CarbonLite PHribbon software, available from the AECB.