Photo by Adam Mørk
Is EN17037 part of building regulations?
As a brand new standard, EN 17037 ‘Daylighting in buildings’ is not referred to anywhere in national building regulations in the UK. There is currently no prescribed minimum level of daylight for buildings in the UK, although guidance written for specific sectors may set minimum performance criteria (for example, the Priority Schools Building Programme).
National building regulations set minimum standards, mostly concerned with making buildings safe to use rather than optimising occupant comfort and wellbeing. The provision of glazing in a building is often governed by the need to contribute to energy efficiency, provide ventilation, and ensure the availability of a means of escape - and not to ensure a particular level of daylight.
Are existing daylighting standards referenced in building regulations?
Part L of the Building Regulations in England requires that summertime solar heat gain be limited by window size and orientation. It also says that providing adequate levels of daylight should be ‘considered’ while doing so, and references BS 8206-2 ‘Code of practice for daylighting’ as a source of guidance.
An accompanying note says that minimum daylight requirements are not specified within the Building Regulations. It offers a general guide that a total area of glazing less than 20% of the total floor area is likely to result in poor levels of daylight and increased use of electric lighting.
EN 17037 supersedes BS 8206-2, and the reference will therefore be updated in due course. However, given the current focus on overhauling building regulations to improve safety, it seems unlikely that specifying minimum daylighting standards will be a priority.
Balancing daylighting with other aspects of building performance
The same note acknowledges how reducing window sizes has to be judged in terms of the trade-off between reduced carbon dioxide emissions and increased use of artificial lighting.
Glazing plays a significant role in total heat loss from the building fabric, as well as providing solar heat gains (that are desirable in winter but can easily be excessive in summer), and impacting on the extent to which electric lighting is relied upon. All of those factors are accounted for in the SAP and SBEM assessment methodologies that demonstrate compliance with energy efficiency regulations.
Achieving energy efficiency targets does not guarantee good daylighting, however. With greater awareness of building designs that respond to the current climate and achieve genuine occupant comfort, glazing design and performance is going to become more important. A better appreciation of daylighting may therefore follow.
As the first Europe-wide standard for daylighting, the standardisation that EN 17037 provides for daylighting design - and covering a broader range of principles than just daylight factor - could lay the foundations for it featuring more widely in UK building regulations. For now, however, it will be a feature of voluntary environmental assessment standards.