This month, our lighting design team received the jumbo copy of The Lighting Handbook, 10th Edition by the Illuminating Engineering Society. It is almost four inches thick and weighs about 10 pounds. It is the accumulated knowledge of the organization dubs itself "The Lighting Authority." It is impressively massive and cumbersome, ironically not a "handbook" at all.

Unfortunately, it is also a metaphor for how lighting design is typically practiced. Conventionally, the emphasis has been on making buildings attractive. This has driven lighting designers to an approach that endeavors to maximize the lighting budget and energy allowance to create beautiful architectural compositions while meeting standardized illuminance targets. As energy codes have become more stringent, designers who start with a "maximum energy" approach will always be resentful of energy codes as a creative constraint.

Instead, I have been steadily working toward a different design philosophy that comes from the opposite direction. Using a "Base Zero" lighting design approach means that I start from scratch.  I build up a lighting system from baseline darkness. By beginning from zero light (and zero energy consumption) it is possible to develop a lighting design that serves the visual experience for the building occupants while using the least amount of equipment and energy consumption. By understanding the purpose of the building and the visual needs of its occupants, a designer can start by optimizing daylighting and task lighting, before adding accent lighting and ambient lighting, then finally a judicious application of decorative lighting. By lighting for people first, then for architectural effect, I can clearly prioritize my design strategies. By treating light as a precious environmental resource, I can advise my clients on the most effective and valuable light sources, luminaires, and controls for their projects.

The human visual system is very accommodating. We can adapt to 100,000 lux of sunlight and 0.1 lux of full moonlight and everything in between. We naturally prefer a variation of luminance patterns over uniformity. We tend to like lighting of vertical planes to delineate interior space. Daylight is free, but must be treated with respect. Windows and skylights are not just simple openings in walls and ceilings. Daylight dynamically combines direct sunlight, indirect skylight, and diffuse cloudy light. It continually shifts - predictably by location, date, and time and unpredictably by climate and weather. Reflective interior finishes and smart space planning improve the effectiveness of daylighting and architectural lighting systems.

By clustering similar visual tasks and taking advantage of perimeter fenestration, lighting can be most efficiently organized and controlled. The smart selection of light sources and luminaires can provide suitable intensity, direction, diffusion, and color to supplement daylight during daytime and to create desirable visual environments after dark.

The 15th century Gallarus Castle on the Dingle Peninsula in County Kerry, Ireland, is simply illuminated during daytime by tall, narrow-slot window openings. The thick stone walls are straight vertical surfaces on the outside, but splayed and whitewashed on the inside to amplify and spread the light well into the castle interior.  Benches built into the walls adjoining the window would have enabled occupants to see well during the day within the otherwise dark confines. The light is sufficient for modern visitors to climb the interior 4-story stairs without the need for flashlights or electric lighting. These relatively tiny windows provided view, strategic ports for archers to defend the castle, and surprisingly generous illuminance so that valuable candles or torches could be saved for nighttime. While I wouldn't want to spend an Irish winter in Gallarus Castle, it has some valuable lessons about light as an essential building material and a precious environmental resource.

The next few lighting articles will explore "Base Zero" design approaches for integrating daylighting and electric lighting to correlate with new understandings of the human visual system. By addressing essential visual needs in creatively pragmatic ways, lighting systems can perform well within energy code constraints. Stay tuned.

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