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Before Nightfall: Advanced Daylighting Technologies

In between passive daylighting design strategies and active solar-powered lighting, these systems can bring unfiltered daylight into the deepest recesses of nearly any building

By Nalina Moses

AIA-Slideshow

Daylighting Systems

Diagram of a fiber optic daylighting system. Image courtesy of Parans.

Daylighting Systems

Roof-mounted fiber optic system collector.  Image courtesy of Parans.

Daylighting Systems

Tubular daylighting device fixtures. Image courtesy of Solatube.

Daylighting Systems

Diagram of a tubular daylight device systems. Image courtesy of Hutton Architecture Studio.

Daylighting Systems

Illustration of a horizontal daylighting system. Image courtesy of Glumac and Sun Central.

Daylighting Systems

A horizontal daylighting system on the facade of the Centre of Excellence at Okanagan College in British Columbia, designed by CEI Architecture. Image courtesy of Sun Central.

Daylighting Systems

Horizontal daylight fixtures at the Centre of Excellence at Okanagan College in British Columbia, designed by CEI Architecture.  Image courtesy of Sun Central.

Daylighting Systems

Diagram of a vertical daylighting system. Image courtesy of Sundolier.

Daylighting Systems

Roof-mounted vertical system collector in Abu Dhabi.  Image courtesy of Sundolier.

Mirror-lined tubes, fiber optic cables, and solar tracking devices are just a few of the cutting-edge daylighting systems that are making the fanciest double-paned, triple-glazed, argon-filled, and low-emissivity windows seem rather passé. These advanced daylighting technologies investigate the fertile middle ground between purely passive solar design strategies such as strategic building orientation and window placement, and sophisticated active solar systems (such as photovoltaic cells ) to harness natural light more directly and powerfully. Each of these systems captures more daylight and can deliver it deeper within a building than simple windows and skylights, and each can operate without the energy and maintenance costs associated with photovoltaic systems that convert light into electricity and then back to light again. They’re also all featured in the AIA Virtual Convention session “Bringing Daylight into the Core of Buildings.”

These systems are quietly subversive. They deliver daylight from the outside to interior diffusers–specially designed non-powered fittings that use lenses, shades, and baffles to purposefully distribute the sunlight. But they don't look terribly different from conventional plug-in light fixtures. However, they won't replace windows: They can't offer views and air. And they won't replace electric lights, at least at night: They’re completely dependent on the sun.

But what these advanced daylighting systems can do very powerfully is light spaces more thoroughly and consistently with daylight. Unlike electric lights, the light they deliver is alive with a vibrancy and richness that only the natural spectrum can provide, with fluctuations of color and intensity that nourish circadian rhythms. And the systems focus daylight purposefully, eliminating glare and waste in a way that windows, even those modified with the most expertly specified glass coatings and shading devices, cannot.

These daylighting systems are classified into four basic groups, based on the way they carry sunlight from the exterior to the interior of a building: fiber optics, tubular daylighting devices (TDDs), horizontal systems, and vertical systems.

Fiber optic systems

Fiber optic systems, such as those made by the Swedish company Parans, use bundles of optical cables to carry light from a small roof opening to an interior light diffuser. Electric tracking devices on the roof rotate to harvest optimal amounts of parallel sun rays throughout the day, concentrating them into a bundle of cables about 2 inches in diameter. This bundle is carried down through a small roof opening, through cavity walls and ceilings, and then to diffusers. Each bundle possesses the luminosity of a single conventional light bulb. Of the four daylighting systems discussed here, fiber optic systems are the most streamlined and require the least material and space.

Pros

    • Cables require minimal space and roof penetration, and can be concealed within conventionally framed partitions and ceilings, making them convenient for retrofits

    • Cables can turn in all directions without significant light loss

    • Useful for all building types, including very tall and very large buildings

    • Multiple floors can receive light from a single roof opening

Cons

    • Significant light loss occurs at greater distances, with a maximum distance of 65 feet

    • Harvests only parallel sun rays, so light collection is limited on overcast days

    • Relatively expensive technology


Tubular daylighting devices

Tubular daylighting devices (TDDs) are optical systems that use engineered duct-like tubes to carry light from roof openings deeper into buildings. Each device consists of a roof oculus that collects light, a tube lined with a specially engineered reflective surface, and an interior diffuser. The tubes range from 10 to 21 inches in diameter. This system relies on a simple high-school physics principle: A beam of light will bounce off a surface at the same angle of incidence at which it contacts it, so light captured at the top of a tube will move further down along the tube until it's purposefully redirected by a diffuser. TDDs are one of the most mechanically and operationally simple advanced daylighting technologies. Solatube is one company that specializes in them.

Pros

    • A simple, unpowered system

    • Can collect and concentrate diffuse, low-angle daylight

    • Roof openings filter out infrared light to prevent heat gain

    • Minimal light loss for straight tubes of 30 feet or less

    • Useful for low buildings with a large footprint

    • A decades-old tested technology that is relatively inexpensive

Cons

    • Increased light loss for each bend and turn in the tube, especially for distances of more than 30 feet

    • Requires a separate roof penetration and vertical tube for each light fixture


Horizontal systems

Horizontal systems use rows of transom-level wall-mounted panels to harvest light from the side of a building and deliver it horizontally to adjacent floors in much the same way that an exterior air-handling unit distributes fresh air through a building. The technology uses specially shaped Fresnel lenses, which are powerful but shallow, to collect and concentrate sunlight from oblique angles. Light captured by the wall panel is thus increased by a factor of 10, and then sent through a network of fanning reflective light pipes into horizontal above-ceiling ducts, and finally delivered to room diffusers. Of the four systems, this one most resembles conventional mechanical heating and ventilation systems, carrying light from one point to different parts of a building through a network of duct-like passages. It’s also one of the newest and most experimental. SunCentral in British Columbia is one company that has developed this technology.

Pros

    • Can carry light to all floors of a building

    • Can distribute light without vertical shafts

    • Ductwork can be integrated above the ceiling with HVAC and plumbing systems

    • Useful for tall buildings with small footprints

Cons

    • Panels are highly visible and need to be integrated into facade design

    • Panel locations need to be coordinated with building orientation

    • Is relatively new and has only been tested in a handful of structures

    • A moderately expensive technology


Vertical systems

Vertical systems are essentially more compact, more sophisticated TDDs. They're able to capture sunlight more powerfully and consistently than TDDs by using rotating roof-mounted solar-tracking devices (similar to those used by fiber optic systems) that follow the sun's movement throughout the day. They harvest light through a parabolic lens and deliver it to the building through a tube with a super-reflective lining specially engineered to minimize light loss. Because of their power to concentrate sunlight, vertical systems, like the ones developed by Sundolier, are the best-suited for architectural lighting effects. They deliver a concentrated amount of light to a signal point, which can be further dramatized with special fixtures and finishes.

Pros

    • Smaller tubes require minimal space and can be concealed within conventionally framed partitions, making them convenient for retrofits

    • Concentrates a large amount of light in a single point

    • Can carry light from 100 to 200 feet with three or four right-angle turns and even longer distances with no turns

    • Relatively inexpensive technology

    • Multiple floors can receive light from a single roof opening

Cons

    • Each fixture requires a 24-inch-diameter opening in the roof

    • Light loss of 3 to 5 percent with each turn of the system

    The listing of any company or product in this article should not be construed to be an endorsement by the AIA. The AIA does not approve, sponsor, or endorse any product or material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Recent Related:

Architect Magazine: Sun Child

Reference:

Check out the AIA Virtual Convention session “Bringing Daylight into the Core of Buildings.”

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