Tips for integrating natural light with artificial light.
By Omar Rivera, LEDVANCE
Contemporary lighting design is being shaped by four major trends: energy codes, daylighting, using the LED as a primary electric-light source, and connecting LED lamps and luminaires to responsive controls.
These concepts should not be considered independently, but rather combined, to provide a holistic illumination solution. Natural light and artificial light, in concert with lighting control, form an integrated illumination system. Following are tips for achieving a system in lighting design that produces good vision and good visual comfort and rendering.
Natural light is a highly desirable free and abundant illumination source. Leveraging this resource is called daylighting in sustainable design. It can provide a connection to nature, excellent color rendering, sensory variability, good modeling, and indirect light on walls and ceilings, resulting in a pleasant and comfortable space. Numerous studies over the past 50 years attest to its value for human beings in the built environment.
1. Avoid direct sunlight. Good daylighting design harnesses sunlight and delivers it to an interior space as a general light source. That’s not the hard part. The hard part is controlling the light to avoid visual glare and thermal gain. Direct sunlight should therefore be avoided except in circulation spaces.
2. Control the daylight. For illumination, the design goal should be to maximize the uniform distribution of diffuse daylight. Light coming into a building can be controlled using glazing, shades, blinds, louvers, or other media. Generally, all sides of a building should be shaded except for the north side. Light-control media can be automated or tied together for remote user control.
3. Maximize daylighting distribution. Natural light can enter a building through sidelighting or toplighting, the design of which allows architects to control the quantity and quality of natural light entering. Generally, natural light should enter a space from as high a vantage point as possible and cover areas where users need it. To maximize usable daylighting area, perimeter zones can be increased. Features such as light shelves can push the light deeper into the space while diffusing it. Automatic devices such as heliostats can maximize usable daylight.
Artificial electrical lighting may be considered as three functional layers: task, ambient, and accent lighting. Natural light generally provides ambient lighting and is integrated with that layer. The design goal is to provide quality illumination that has a seamless look and feel—in other words, ensuring a space that looks great with natural light and without. The way to accomplish this is to establish clear illumination goals for each space is to merge natural light with artificial electric light into a cohesive design, resulting in a high-performance and integrated system.
4. Design electric lighting to match natural light patterns. Natural light may not cover an entire space uniformly but instead as gradients of intensity reaching into it. General lighting should be placed parallel to the natural light, allowing luminaires to turn off or dim when sufficient natural light is available. Otherwise, the electric lighting should place light on the same surfaces as the natural light. If the natural light is distributed on walls and ceilings (as is often desirable), the electric lighting should do the same. Note that some variation in light levels over the course of the day may be acceptable and even preferred, but surface brightness should remain relatively consistent. Use light-colored surfaces, with brighter surfaces kept out of the line of direct sunlight.
5. Match the color quality. Specify the light source with a neutral- or cool-white correlated color temperature (CCT, typically 3500 K to 4100+ K). Otherwise, if a warm-white CCT (<3500 K) is specified, the light emission, when mixed with very cool daylight (>5000 K), may make the light sources appear yellow.
6. Consider supplemental lighting. Be aware of contrast between areas and surfaces receiving natural light and those that will not. In deep spaces, consider wall washing or accent lighting on rear walls. In spaces where natural light provides insufficient light on ceilings, such as spaces with skylights, consider luminaires with some uplight distribution.
Automatic lighting controls are a staple in new construction and renovations because of commercial-building energy codes, and they typically require daylighting-responsive control. This control strategy reduces lighting through switching or dimming to maintain a target light level, saving energy. Switching is typically ideal for circulation spaces, while dimming is ideal for spaces that are regularly occupied by users performing intensive visual tasks. The introduction of automatic lighting controls creates an opportunity to realize value far beyond basic energy savings.
7. Dimming is standard. With fluorescent luminaires, dimming could be costly, while with LEDs, it is fairly standard. Dimming is ideal for automatically reducing lighting while a space is occupied. Good performance requires selection of a quality driver in the LED luminaire. It should be confirmed that the driver and all control devices are interoperable.
8. Consider luminaire-level lighting controls. Energy codes stipulate daylighting areas, control zoning (lights assigned to controls for daylight response), and minimum load-reduction capability. A simple way to address this and other code requirements is through luminaire-level controls, which integrate occupancy and light sensors into luminaires for highly responsive control and maximum energy cost savings.
9. Connected lighting offers big value. Advances in wireless communication and microprocessing have produced a second revolution in lighting: intelligent control. Connected lighting offers connectivity, intelligence, sensors, and two-way data communication, and as such could be considered Internet of Things (IoT) ready, though the devil is in the details as to how accurate that is for a given product. In any case, the result is maximum energy cost savings, ready energy-code compliance, and the ability to produce data viewable in control system software or shared with third-party software. This information, in turn, can be used for purposes such as space optimization, producing greater value.
10. Control color. Another big opportunity with LED lighting is its ability to change the spectral content in the light emission. In other words, with certain products, we can change the color or shade of white light. This allows the light in a space to gradually change to match the quality of the natural light and simulate the daylighting cycle in spaces not receiving natural light. Spectrum, along with dimming, can be used in circadian lighting strategies, a nascent trend in the industry.
Getting it right
Good daylighting and natural light/electric light integration can benefit from commitment throughout the project, good planning, modeling and mockups, and commissioning, to make sure the final installed project satisfies an owner’s project requirements. For daylighting and daylight response, energy codes provide a suitable baseline from which additional opportunity can be derived by understanding how occupants will use the space. Architects should continually educate themselves on new technology and opportunities with LED lighting and lighting controls. Specifiers should seek out manufacturers and channel partners with the appropriate experience, expertise, and reputation.
By understanding the application and properly integrating natural light and artificial electric light, architects can deliver illumination that satisfies clients with its functionality, comfort, flexibility, energy efficiency, and added value.
Omar Rivera is head of luminaires in the United States and Canada for LEDVANCE, Wilmington, MA, maker of Sylvania general lighting in the U.S. and Canada.