Introducing daylight design

Chris Lowe, BDP

Throughout human evolution, we’ve been conditioned by the way sunlight changes. Delivering light into the heart of buildings is an essential task of architecture – however modern or ancient. But it seems to have lost ground to other factors, to the detriment of human needs.

Chris Lowe, Lighting Associate at BDP, guides us through the importance of daylight design in evoking human response and creating energy efficient spaces.

Image: Pantheon, Rome
Pictured is the oculus of the Pantheon in Rome. Completed by the Roman emperor Hadrian in 126 AD, the Pantheon still has the world’s largest reinforced concrete dome. Its main source of light is the 8.8 metre diameter oculus, which lights the interior like the sun lights the sky. It also cools and ventilates the building, and lightens the load of the dome. A feat of daylight design that remains effective today.
What is lighting design? Chris Lowe, BDP

Human benefits of daylight

Natural light makes us more creative and productive (source: Human Spaces) and it supercharges our learning abilities (source: Clever Classrooms). It also has a direct impact on our biology, by regulating our hormonal systems (e.g. production of cortisol and melatonin).

What is chronobiology?
Chronobiology is the branch of biology that examines the effects of cyclical phenomena – like solar activity – on living organisms. Circadian rhythm describes the daily synchronisation of our biological day with the astronomical day, and this relies on the right frequency and intensity of light.
Natural light variation (next slide)
The image on the next slide captures natural light variation over the course of a day. Notice the change in CCT (correlated colour temperature), intensity and position of the sun, in relation to the time.
Biological cave Cost-effective construction processes gave 20th Century architects new opportunities, but also new challenges. Whilst outside, we might get 50,000–100,000 lux – but in a typical office or classroom, we might get less than 500 lux. These deep-plan environments are biological caves that don’t meet our basic needs.
Daylight, artificial light and darkness But in the same way we need natural light, our bodies also need darkness to work effectively. Light that’s good for us at midday can become carcinogenic at midnight. This means we have to design natural light, artificial light and darkness together, as one, to maximise form and function without sacrificing health and wellbeing.
Climate-based daylight modelling Climate-based daylight modelling has replaced daylight factors as the preferred method of predicting daylight penetration in buildings. Its metric is Useful Daylight Illuminance (UDI), and this is subdivided into UDI-autonomous and UDI-supplementary. Theorised by Professor John Mardaljevic of Loughborough University in 2006, CBDM uses real local climate data on computer models to calculate usable daylight, and provide a more accurate and intuitive assessment of daylight availability, according to a project’s location. The image shows daylight penetration at summer solstice and winter solstice.
Case study: UEA Enterprise Centre Better understanding of chronobiology and aesthetics can help create energy efficient spaces. BDP were briefed to deliver “the most sustainable building ever” in the University of East Anglia’s Enterprise Centre. Combining natural light, artificial light and darkness seamlessly into the design, BDP delivered massive energy savings – achieving BREEAM Outstanding and Passivhaus certification.

What’s Next?

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Many thanks to Chris Lowe and the team at BDP’s Manchester offices, where we filmed and collected this material in summer 2017.