BSI consults on new European daylighting standard

The British Standards Institution (BSI) has issued for comment a consultation draft of a new European Standard BS EN 17037 ‘Daylight of buildings’. This will specify minimum recommendations for daylight and sunlight provision in buildings, as follows:

Daylight to spaces lit by windows:

  • an illuminance level of at least 300 lux over at least 50 % of the space for at least half of the daylight hours in the year; and
  • an illuminance level of at least 100 lux over 100 % of the space for at least half of the daylight hours in the year.

Sunlight to habitable rooms in a dwelling, patient rooms in a hospital and playrooms in a nursery, etc., or any room where sunlight is considered to be of value should be available for a minimum of 1.5 hours on 21 March.

The new standard will also give recommendations for view out and how to limit glare.  It will apply to all spaces that may regularly be occupied by people for extended periods.

The calculation methods in the new standard are relatively complex, compared with those in BS8206-2:2008 ‘Code of practice for daylight’ and BRE Report 209, ‘Site layout planning for daylight and sunlight – A guide to good practice’. They will require calculations of internal illuminances or point daylight factors (rather than the simpler average daylight factor), percentage of a room achieving certain minimum view out criteria and the annual occurrence of glare using the Daylight Glare Probability metric.

In obstructed urban areas, the minimum recommendations could present a difficulty for designers and developers and the relatively complex calculation methods will increase the work involved in evaluating a design. It remains to be seen whether the Building Research Establishment will update their guidelines to reflect the new European Standard once it is published and whether the new standard will filter through into supplementary planning guidance published by local planning authorities.

The deadline for comments on the consultation draft is 20 September 2016.

For more information, please contact:

Lance Harris, Director,
Matthew Craske, Director,
Heather Schöpp, Director,
Stephen Mealings, Director,

Sign up to our newsletter