The new European Norm encapsulated within the British Standard “BS EN 17037:2018 Daylight in buildings” was officially adopted in May 2019 and supersedes the previous standard “BS 8206-2:2008 Lighting for buildings – Part 2: Code of practice for Daylighting”

The Standard adopts new ways to test for daylight and sunlight in relation to proposed developments, including views out and glare.

The proposed daylight methodology encourages both higher levels of light indoors and the use of climatic data as opposed to testing under an ‘orientationless’ overcast sky.

Following a review of the Standard by a dedicated commission of UK experts, which included Dr Paul Littlefair of BRE, BSI included, as part of its publication, a UK National Annex which brings the minimum indoor lighting levels in- line with the previous BS targets. The commission reduced the minimum targets in recognition of the national need to increase urban density and deliver more accomodation.

What effect does the adoption of the above Standard have in practice?

In practice, the Local Authorities Unitary Development Plans (and their Local Plans) still refer to BRE’s “BR 209:2011- Site Layout Planning for Daylight and Sunlight – A guide to good practice” when discussing daylight as part of their policies. Given that the new Standard is only applicable to proposed developments, BR 209 remains the basis for assessing impacts upon existing neighbouring properties.

However, the BRE handbook, references the superseded BS 8206 and that’s where confusion may arise. Notwithstanding the potential confusion, it is worth noting that the new targets within the Annex were based upon the old ones when it comes to indoor illuminessence and that the technical change concerns assesssing for the median Daylight Factor value now, as opposed to the Average Daylight Factor then. Therefore, it is our opinion that the commisions intent to align new practice to the current one.

This has also been the subject of a post by Dr. Littlefair on the Planning Daylight & Sunlight Group (BRE BR209) published on LinkedIn, where BRE’S position is summarised as:

“Until BR 209 is rewritten, we are adopting a flexible approach to applying the two standards, for example in assessing
the daylight and sunlight available in new buildings. So, for example, if we were reviewing a daylight report for a local
authority, we would consider it reasonable to accept either average daylight factor tables using BS 8206 or median
daylight factors/median illuminances calculated using EN 17037, provided they were calculated and presented properly”.

BRE have discussed updating and republishing BR209 to align their guidance with the new BS sometime next year. Until that time, it is also GIA’s opinion and understanding that BR209 still applies when testing neighbouring and proposed properties, which is in- line with the references within local and national policy.

We, however, are preparing to implement all tests required within the EU norm and can provide assessments and consultancy based upon the new methodologies when appropriate or upon request of the Local Authorities and our clients.

For more information or to discuss further please contact

GIA Staff Nicola Comandini