Research, metrics, and technology are key to biophilic lighting
Even in an urban winter, this softly layered lighting approach evokes the biophilic design of a sunlit green garden terrace adjacent to a blue sea.
By Shanna Olson and Tammy Dyce
Biophilic design – one of the newer buzz phrases in the building industry – is an umbrella term that describes concepts in the built environment that contribute to our sense of and connection to nature. It correlates to all aspects of building design, including natural and artificial lighting.
Intuition, a growing body of research, and advancements in technology have led to an increased surge in design teams applying the principles of biophilic design in their practice. IMEG is no exception, with the influences of biophilic design beginning to be seen in many of our designs, including those involving architectural lighting services.
As with any innovation, however, information and misinformation about biophilic design abounds. What should you believe? To set the record straight on one aspect, here’s a look at biophilic lighting.
Feel the (circadian) rhythm
The sun and, to a lesser extent, firelight, have shaped our circadian rhythms throughout the history of humankind. Intuitively we have long understood the importance for daylight in our designs and while daylighting design is not new, we have learned a great deal about best practices for bringing effective and balanced natural light into interior environments. This is a critical component of biophilic design, since lighting that changes in accordance with the time of day supports our circadian rhythms and links us to the outdoors.
In recent years the design community has created metrics to measure not just the quantity but also the quality of daylight in our spaces. This includes spacial daylight autonomy (sDA), which measures the percentage of area that exceeds a specified illuminance target for a certain amount of time. In general, SDA asks, “Is there enough daylight in the space?” Annual sunlight exposure (ASE), another metric, describes how much of the space receives too much sunlight, which is commonly thought of as glare. Software applications continue to make this evaluation within reach and should be considered for many projects.
Since well-designed window and skylight layouts may not be enough to achieve a balanced daylit space that provides both high levels of sDA and low levels of ASE, several key ingredients can be added for a harmonious recipe for daylighting and a robust biophilic design. These elements include architectural components such as building orientation and shading, interiors factors such as appropriate reflectance values and furniture layout, and lighting elements such as luminaire orientation and daylight harvesting.
Technological evolution of electric light sources and luminaires also has provided new and viable options to support our circadian rhythms and strengthen biophilic design in our interior environments. Since the relatively recent discovery of humans’ non-visual photoreceptors – intrinsically photosensitive retinal ganglion cells, or IPRGC – researchers have been working extensively to understand how these cells work and how they react to natural and electric light sources. Studies show that quantity of light, its spectrum, time-of-day exposure, duration, and distribution all play a part in determining the effect of any light source on our circadian system.
New metrics offer guidance
Recent research has contributed to the creation of new metrics to measure the effectiveness and relationship of light sources to the circadian system. Circadian stimulus (CS), a metric developed at the Lighting Resource Center at Renssalaer Polytechnic Institute, is an example. Another, somewhat similar metric, equivalent melanopic lux (EML), is employed in certain green building rating systems to measure circadian lighting design. Analogous to sDA and ASE, these metrics are useful guides when implementing circadian design concepts.
All of this is to show that there is a great deal of information to sort through when making biophilic lighting choices for a building project. Understanding the range and effect of the quality of light – including electric light versus daylight, the parallels and differences between spectrum and color temperature, and what circadian stimulus is appropriate for each age group and application – can be challenging. With the proper professional guidance, however, goals can be defined to effectively determine the unique biophilic design targets for each project and how to best achieve them.