Light matters

CBDM underpins the first major change to international daylighting standards since the 1950s

According to WHO, we spend about 90% of our time indoors. Without natural light, our long-term health and well-being can be compromised, and our productivity diminished.

Our climate-based daylight modelling (CBDM) research – spanning more than 20 years – is transforming building design and influencing the settlement of Rights to Light legal cases.

Crucially, it led to the formulation of the daylight performance basis of the European CEN Standard for Daylight in Buildings (EN17037) – the first significant upgrade to daylighting standards in over half a century – influencing policy and practice worldwide.

Image courtesy of John Mardaljevic
The New York Times Building (Architect: Renzo Piano)
John Mardaljevic's daylighting evaluation at the design stage was the first application of CBDM on a major iconic building.

Our impact

European CEN Standard for Daylight in Buildings (EN17037)

  • The Standard has been adopted by all 34 CEN member states, including the UK (2019), and incorporated into the Danish Building Code.
  • It has influenced several daylighting rating schemes, including in the US, Sweden and Ireland.

Adopted by the International WELL Building Standard

  • The first Standard to focus “solely on the health and wellness of building occupants”, it is used worldwide.
  • It recently adopted the methodology and recommended daylight levels specified in EN17037.

Market transformation

  • Many daylight modelling software tools have been upgraded to compute the metrics required for EN17037.
  • Eight international dissemination events about EN17037 (September 2018-May 2019) were attended by more than 1,000 delegates, accelerating CBDM skills-uptake.

Settling rights to light (RTL) disputes

  • CBDM has been used in several high-profile RTL and daylight injury cases, including New York’s Central Park Tower.

Open Country – Windows (BBC Radio 4)
Professor Mardaljevic discusses the significance of his work with Helen Mark.

Listen to the discussion

The research

For 50 years, daylight provision was determined at the building design stage, using a relative measure called the daylight factor (DF). This method does not always deliver indoor spaces that are comfortable year-round.

Professor Mardaljevic first published his pioneering work on CBDM in 2000. It has subsequently transformed the way daylight in buildings is determined and has underpins fundamental changes in international daylighting standards.

Uniquely, CBDM creates annual profiles of absolute levels of indoor daylight illumination, supporting building design and internal space layout that ensures “good daylighting” throughout the year.

Now, an internationally recognised and adopted method, CBDM is a mandatory design requirement for the UK’s Priority Schools Building Programme, and has informed several major commercial building projects worldwide. It has also supported the National Trust’s work to protect and preserve historic artefacts.

Professor Mardaljevic's development of alternative methods of measuring and assessing light loss – such as CBDM – is ground breaking, and enormously important to support the establishment of an alternative to the Waldram Method.

Matthew Baker Partner – Pinsent Masons LLP

Development partners

  • British Standards Institution
  • European Committee for Standardization

Meet the experts

Photograph of John Mardaljevic

Professor John Mardaljevic

Professor Emeritus of Building Daylight Modelling