10 minute read
The Daylight Layer
By JAMES R. BENYA
As we practice and teach lighting design, many lighting designers employ an approach that involves combining layers of light into a composition. In my textbook, Lighting Design Basics,1 I teach my personal layering approach that includes the ambient lighting layer, the task lighting layer, the focal lighting layer and the decorative lighting layer. But I devised this system in the 1980s and 1990s, long before LEED, WELL and especially, LED lighting and networked lighting controls. In my last article, I admitted that an update was probably due because lighting design should embrace daylighting as an integral part of lighting design, so I decided to add the daylight layer to my philosophy.
I think many lighting designers consider fenestration (i.e. windows, skylights, clerestories, etc.) and their various shading systems to be a “given” with which the lighting designer is stuck. Decisions about daylighting are often made long before the lighting design for a project was ever considered, and in all fairness, daylighting choices depend significantly on architectural reasons that tend to favor overall building aesthetics, view, energy efficiency and building economics. Some spaces will enjoy plentiful natural light throughout the day, some will be in the dark, and some will need shading to reduce direct solar glare. But, for practical and economic reasons, most fenestration consists of view windows for which manually operated shades are provided, and electric lighting works to ensure adequate illumination for indoor spaces regardless of windows and skylights, and of course, on cloudy days and at night.
I like to practice lighting design that includes daylight. I love architecture and helping an architect, or an architectural team, resolve design problems. Over a number of years, I developed skills in daylighting design and analysis and learned its language and technology. We lighting designers have a definite technical advantage because we understand the radiant energy spectrum and its energy implications, and our everyday lighting software permits us to rapidly study and assess design alternatives. And I definitely think lighting designers have the artistic advantage of seeing light when others see objects, and we are at our best when we create scenes consisting of light, dark and shadow.
That said, learning technical daylighting skills is fun but challenging. To start with, daylight can have a tremendous impact on the energy use of the structure. On a clear day at noon, the sun produces 10 watts per square foot of radiant energy, which is about 50% visible light and 50% infrared light.
Welcome in the winter, this radiant energy is 20-30 times the heat load of a modern lighting system and more than 200 times the amount of light needed in most commercial buildings. A combination of energy codes and modern shading and glazing systems work to ensure that the daylight entering occupied space is limited to a reasonable amount. But codes can’t predict the shape, size or orientation of a building, and the challenge of daylighting design remains how to ensure that the right amount of daylight is allowed inside. At the top of the list, you should learn about solar heat gain coefficient and one of the greatest inventions of the 20th century, low-emissivity (“low-e”) glazing, a coating on windows and skylights that rejects infrared light. The best low-e commercial glazing systems tend to be the most expensive, so learning when to use the best and when it is not that important is a valuable skill that will save your clients’ money.
I think the second most important skill is shading and diffusing. Shading can be simple. You should learn about the alternatives, both interior and exterior. A good example is the Arbol de la Vida dormitory community at the University of Arizona.2 Completed in 2011, this 335,000 SF, 1,088-bed LEED Platinum residence hall complex features a highly efficient building envelope, watersavings systems, daylighting, and technology to reduce energy use. In addition to using the highest performance low-e glass in insulated window assemblies with privacy curtains, simple shades on the exterior are used to reduce the sunlight striking the window on sunny days. The combination reduced the energy use for air conditioning substantially, achieving a 3-year payback over the architect’s original concept and elevating the buildings from LEED Gold to Platinum.
The third skill set is perhaps the most difficult. Zero-net energy buildings beg the design team to pursue every possible avenue of energy efficiency to conserve precious alternative energy source capacity. Generally the best opportunities involve schools in temperate climates where nighttime energy use can be almost zero (see sidebar). Depending on the climate, surrounding buildings and structures, building program and project aspirations, you and the architectural team may chase a lot of possibilities. You will soon realize that LED lighting and code compliant lighting controls have become so energy efficient that it will be very easy to make electric lighting the star of the show – other than daylighting, of course. Can you design a building that does not use electric lighting at all during the day?
To round out one’s daylighting skills, the most important lesson we have learned in the past 20 years has been that light and daylight can have a profound impact on the health and wellbeing of building occupants. Our industry rose to the challenge, and today, we have several standards including the WELL Building Standard and UL Design Guideline 24480. Both are concerned with the spectrum of light, illuminance levels, and the exposure to the combination experienced by people in each space. These guidelines can be met using electric lighting or daylight.3
But – wait. There is an issue beyond spectrum and lux. Lisa Heschong is an architect who received a 2023 EdisonReport Lifetime Achievement Award for her work in daylighting. Among her most impactful research findings was discovering and documenting the importance of view in school classrooms. It’s an honest question whether something more complex is involved with looking out the window that can’t be measured in melanopic lux. Her findings correlated student test scores with types of classroom fenestration, finding that looking out the window may in fact have significant importance in human wellbeing and learning. So, just because daylight happens to vary and change throughout the day and year doesn’t mean we need to build concrete boxes without fenestration but with technically correct melanopic lighting. While the WELL standard emphasizes spectrally correct light exposure throughout a “workday,” it should be honestly questioned whether the quality of nature’s own light provides something substantive that is hard to beat and free of charge through windows and skylights. Maybe the fourth skill set is being conscious of what we can’t measure but we know works.
Finally, there comes the question of how we move forward as an industry. Several years ago, I worked with Professor Robert Koester at Ball State University’s School of Architecture to develop and teach a semester studio called “Daylectric Lighting.” A visionary architect and fabulous teacher, Bob created a senior level architecture studio in which student teams were challenged to design a two-story civic building in Muncie, Indiana. After helping set up the design challenge and teaching what I presented here, the students were turned loose, and I returned to work with each team in a studio and crit format. I was overwhelmed by the quality of their work! This makes me think that access to daylight and one’s circadian rhythm is natural, and, with the right design direction, many architects intuitively grasp good lighting and daylighting ideas. But, they do better when the boundaries are opened, and some guidance points them in the right direction.
For sure, there remains a level of daylighting expertise well above mine. For instance, a decade ago I took a week-long seminar at Harvard’s Graduate School of Design with Christoph Reinhart (now head of MIT’s Sustainable Design Lab) and developed some valuable knowledge and skills, an investment well worth the time and cost. For quality education in daylighting, you might also check out Velux, the international skylight manufacturer, who offers live and online daylighting classes throughout the world. Kalwall, a company that makes insulated light diffusing panels for walls and skylights, offers online education and design assistance in their products and technology. And of course, advances in building computer modeling have provided a useful level of daylighting design and analysis support. With the rewards from WELL and UL for achieving daylight-quality light at appropriate times, adding daylighting to your lighting
design skills will be natural for many. You will be surprised what a difference you can make, even if your contribution is as modest as helping select the right type of fenestration and the right amount of daylight and spectrally tuned electric light to achieve melanopic goals.
Who or What Is Using Our Power?
A Zero-Net Energy (ZNE) building typically employs photovoltaic (PV) panels to support energy use by day while sending excess capacity to the grid, and then to draw power from the electric utility at night. The strategy is to minimize energy use overall to reduce the cost of the PV array, and then turn off darn near everything at night. At the Redding School for the Arts, we did everything in the book, including using motion sensors for outdoor lighting.
But, upon system startup and testing, there was a mysterious 10 kW of power being consumed all night! A long evening of sleuthing turned up four unexpected power users: an oversized sub-transformer, reptile environments with all-night heaters, an extremely inefficient commercial milk refrigerator required for schools by the state, and two high-capacity chargers for golf-carts used by maintenance personnel. Not to be deterred, more PV panels were added to the point where the School generated more net positive energy during the day to achieve Net Zero and LEED Platinum.
If you have a spectrometer or a keen eye for color, you will notice that the most efficient low-e windows increase the color temperature of the transmitted light. Because the objective of low-e windows is to eliminate infrared light, the more energy efficient they are, the more they reduce the red end of the visible spectrum. Since the short wavelengths produce the most melanopic response, I don’t think that this is a problem. Anyone for 5500K?
The Mount Angel Abby Academic Center SRG Partnership
Each classroom employs a large central skylight with operable louvers to “dim” the light on sunny days and still provide adequate daylight on Oregon’s gray winter days. The artful shading system creates direct/indirect light. A joint effort of Kent Duffy, FAIA (then Principal of SRG), Professor Brown and me.
One of architecture’s greatest professors of daylighting, G. Z. “Charley” Brown (1943-2020), was both a mentor and a nemesis to me. As a member of the faculty of the University of Oregon, he worked with me on a number of projects and issues during my 17 years in Oregon. We did not always see eye to eye, but I was always better for the experience.
Karlen, Benya and Spangler, Lighting Design Basics, Third Edition 2017. The layering system described above was originally written for the First Edition and is essentially the same in all three Editions.
AR7 Architects, ME Engineers, Monrad Engineering, Inc. and Benya Lighting Design, Edison Award for Environmental Design, 2011
When we designed the world’s first LEED Platinum/WELL Platinum project, we employed north-facing windows to provide plenty of melanopic light almost all the time during the day. We had to fight with WELL to allow daylight to meet their first-generation standards, because when measuring melanopic light levels, WELL demanded that the window shades be closed!
