Daylighting design is taking an increasingly important role in both architecture and planning; meanwhile undergoing its own revolution in terms of both sustainability and computer-aided design. And where daylighting designers incorporate the expertise of lighting designers, synergies inform and enhance the process at nearly every stage of building architecture. Light-friendly interiors will leverage both daylighting and electric lighting – never use the term artificial lighting. After all, photons are photons.
Lisa Petterson, who recently joined SRG Partnership as a senior associate, is daily using new technologies along with her expertise in both daylighting and electric lighting design. Just as in architecture, urban planning, master planning and the new concept of spatial design are all now grounded in iterative computer design and analysis. Massings of individual buildings, and master plans, are now arranged to optimize both daylighting in interiors and the daytime experience outdoors. Complex facades, including faceted designs and curvilinear forms, can extend daylighting in neighborhoods while controlling reflections and glare.
“At the most basic level, daylighting design should start at the urban design and planning scale, but we often don’t have that opportunity. So really, most architects start with what I would call the site planning and building massing scale,” said Petterson. With advances in computing power and 3D modeling, daylighting analysis of different building massings is relatively quick.
“At the next scale, which is the architectural scale, that’s where the decisions are made around shaping and sizing of apertures, and how the building’s exterior and interior elements are used to reflect and redirect light.” Radiance, developed decades ago at Lawrence Berkeley Laboratory, is still the most widely used calculation engine for daylighting analysis. Today, Radiance interfaces with 3D modeling software, making it easier to calculate annual energy savings and determine, simplistically, whether the daylighting contribution meets code or LEED requirements.
Petterson expressed frustration that interior modeling of daylighted spaces remains too difficult to model accurately. Even when interior finishes and furnishing schemes are modeled with fidelity, there remains a quantity of equipment, decor and “stuff” to be accounted for. Post-construction, she finds reductions as much as 15 percent, compared to the computer model.
Kera Lagios is a daylighting specialist at the “deep green” engineering firm Integral Group. She has a background in lighting design and is on the team that develops DIVA, the popular Radiance-based daylighting analysis and energy simulation tool. She sees architectural renderings, energy modeling, daylighting analysis and lighting calculation software as multiple paths to achieving net zero in many different types of new construction and renovation projects.
When looking for potentials to reduce energy use, design teams tend to look first at HVAC. “But lighting and daylighting are intricately linked,” Lagios explained. “Your shading strategy, for instance, will not just impact your daylighting, but it’s also going to have a huge impact on the thermal performance of your building and [therefore] its energy performance.” The cost of a careful façade design and limiting heat loads from LED lighting during the day can be justified by smaller HVAC sizing.
Here’s where lighting designers become critical, particularly under increasingly restrictive energy codes. According to Lagios, skilled lighting designers work with the daylighting designer to leverage minimal watts and lumens for maximum visual comfort. “We know what the code requirements are, but as lighting designers, we want to look at the whole space and look at what the people need and what the space needs.”
This focus on aesthetics and ergonomics positions lighting designers well in integrated design teams implementing new controls technologies. (As opposed to the twentieth century model of adding lighting toward the end of the design process.) “By understanding what energy modelers are looking at, by understanding what a building’s EUI [energy use intensity] is, by understanding dimming protocols, and by engaging with new technologies – I think it’s actually a really good time for lighting designers to have more agency in the process,” Lagios said.
Designing for light
When it comes to shaping interiors, the physics of daylighting and electric lighting are very similar. Ceiling heights, clerestories, partitions and other obstructions, as well as interior finishes can work synergistically to create an airy, light-conducting environment – or not. “The geometry of the building and how it deals with light – how it receives light and how it emits light – are very related. Those two things have a lot to do with early massing decisions,” she added. “That’s not something people usually think about: how the form of the building affects its ability to be lit with electric lighting.”
Petterson also cites the potential for interior materials to reflect light and control contrasts. For instance, light shelves that are used to redirect daylight can easily integrate LED lighting. “The same strategy could be used for electric lighting as is for daylighting. But you need to have it in mind as you’re conceptualizing it, so that you can actualize it cleanly in the design going forward,” she said. Be careful of electric light fixtures that obstruct or contain reflective/refractive components that can redirect daylight in unexpected ways.
Kjell Anderson, an associate at LMN, works with lighting designers on his own projects and, as sustainability coordinator, collaborates with lighting designers on other projects, as well. According to Anderson, reflected ceiling plans need to maximize daylight harvesting using layout and granularity of controls. “Controls have become very complicated since the lights are tied into the building systems in ways they haven’t been before.” Scheduling, sensor thresholds, timeouts and dimming rates must strike a difficult balance between energy savings and annoying distraction.
Despite limited LPDs, Anderson relies on LED lighting to even out brightnesses in daylit spaces. Daylighting can deliver thousands of footcandles, and high contrasts can be counter-productive. “In many cases we can get daylight into half of the areas that we’d really like to, so that means we need to balance them with electric lighting,” he said. “When we’ve settled on an approximate geometry, we can figure out where the lighting problems are from a daylight perspective. We have the lighting designer advise us on how to mitigate those problems during the day, and then at night, of course, how to light the entire space.”
Architects also rely on experienced lighting designers to look carefully at daylighting analysis along with electric lighting calculations from programs such as AGI. “It’s a little-known fact that most energy modeling software doesn’t do lighting and daylighting particularly well,” said Anderson. “And if the energy model doesn’t accurately take into account the cost savings of daylighting, then the owner can’t evaluate properly in terms of cost savings vs first-cost increases. That’s a problem that the industry needs to work on.”
Author’s note: Thanks to Azadeh Omidfar at the University of Michigan for kickstarting this article.
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