Understanding the Functioning of Daylighting Devices

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Home Improvement

A diagram showing the cross-section of a daylighting device installation
(c) Solatube International, Inc.

Being stuck inside a building on a beautiful day can be frustrating. If only you could step outside and soak up the sunlight instead of basking in the glow of fluorescent or incandescent light bulbs. Though if you are lucky enough to sit near a window, you can still enjoy some of the benefits of natural light. However, if you are situated farther away from a window, it might seem impossible to soak up the sun’s rays.

The need to maximize the use of natural light in buildings has led many architects to explore ways to achieve this. Besides the psychological benefits, natural light is clean energy. It reduces the need for electric-powered lighting solutions, and it is free. A free, clean lighting source that also enhances people’s productivity and happiness sounds too good to be true.

However, natural lighting comes with a few challenges. For instance, it depends entirely on the sun’s schedule, and once night falls, there is no natural light source. Also, sunlight is not constant, and the amount of sunlight that windows or skylights receive varies throughout the day and year. With windows or skylights, it is not possible to continually adjust their positions to compensate for the sun’s angle.

Daylighting devices come in handy in such situations. These devices collect, transmit, and emit daylight into a building or other structure. They provide a natural alternative to electric lighting even in rooms that have no windows.

Compared to skylights, daylighting devices offer architects more flexibility since the section of the roof above the room to light does not have to be directly overhead. With a daylighting device, light can be collected from a sunny part of the roof and transmitted to almost any room in the building.

The working of these devices is based on simple scientific principles. The next section explains the basic components of a daylighting device and how they work together.

Components of Daylighting Devices

A diagram showing how the SolaTube daylighting device captures and transmits sunlight into a light panel inside a house.
© Solatube International, Inc.

Daylighting devices consist of three main components: a light-collecting device, a light-transmitting device, and a light-emitting device. These devices use lenses and mirrors (or optic fibers) to transmit sunlight into a building.

The lenses in the light collection part of the device direct sunlight into the light transmission component. This component often has a glass dome or pyramid that directs the light into the device’s lenses. Some daylighting devices use a pair of lenses. The first lens, a convex lens, refracts light towards a central point. Below the convex lens is a concave lens that reflects light rays outward towards the light transmission part of the device.

Daylighting devices use either a reflective tube or a series of optical fibers to transmit light. The light enters the tube or fiber and bounces off the reflective surface until it reaches the light emitter section. A longer transmission section means less light will reach the emitter. The emitter is the visible part of the device inside the building and may have a diffuse lens to spread the light. Daylighting devices have advantages over windows and skylights as they are not affected by the sun’s position and can be placed anywhere on a roof. However, they should not be the sole source of lighting and work best as a supplemental light source. Solatube offers butterfly-valve shutters to control the amount of light. Daylighting devices have a significant benefit for mood, as a lack of sunlight exposure can lead to seasonal affective disorder (SAD) and even depression.

SAD, or seasonal affective disorder, can occur at any time of the year, not just in the late fall and winter months. If you spend most of your time indoors away from sunlight, you may experience symptoms of SAD, even in the middle of summer. One way to alleviate symptoms is to take a walk outside on a sunny day. Daylighting devices can help maintain exposure to sunlight throughout the year, which can lead to increased productivity and happiness for employees. Studies have shown that tasks performed under natural sunlight can be easier than those done under artificial lighting. Additionally, using natural lighting can reduce energy consumption and electricity bills. However, the upfront cost of purchasing and installing a daylighting device varies depending on the length of transmission tube needed and any additional options required. Companies such as SolaTube offer a variety of options for residential homes, commercial businesses, and schools.

The cost for a daylighting device includes more than just the parts. Solatube claims that professionals can install the device in a couple of hours, while do-it-yourselfers may need an entire day. Regardless, there will be installation costs that include labor or tool expenses. Solabrite, a Solatube dealer, offers two models for homeowners: the 10-inch Solatube 160 DS for $649 and the 14-inch 290 DS for $749, which both come with up to four feet of transmission tube. Longer tubes will cost more, and a daylight dimmer can be added for an additional $325 to $335 depending on the model. The UV filters in Solatube’s devices prevent fabric colors from fading and protect against sunburn. While initial expenses may be high, the devices can reduce electricity costs and pay for themselves over time, as well as reduce carbon footprint. As the green movement grows, more natural lighting solutions may become available, allowing everyone to benefit from sunlight even while indoors.

Additional Information

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Other Useful Links

  • Solatube International, Inc.

Sources Cited

  • American Psychiatric Association. “Facts About Seasonal Affective Disorder (SAD).” 2006.
  • Eljadi, David A. et al. “Daylight Collection and Distribution System.” U.S. Patent 5,408,795. Apr. 25, 1995. http://www.google.com/patents?id=ZpooAAAAEBAJ&dq=5408795
  • Grubb, Dennis Allen. “Tubular skylight.” U.S. Patent D382347. June 4, 1996. http://www.google.com/patents?id=7ikHAAAAEBAJ&dq=Solatube
  • Grubb, Dennis. “Method and apparatus for a tubular skylight system.” U.S. Patent 6,256,947. Oct. 14, 1999. http://www.google.com/patents?id=7ikHAAAAEBAJ&dq=Solatube
  • Harder, Nick. “Little skylight can have a big effect.” OC Register. March 26, 2005. (Dec. 15, 2008). http://www.ocregister.com/ocr/sections/home_garden/hg_home_improvement/article_456191.php
  • Henderson, Tom. “Reflection and Its Importance.” The Physics Classroom Tutorial. (Dec. 16, 2008) http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/refln/u13l1d.html
  • Maas, James B. et al. “Effects of Spectral Differences in Illumination on Fatigue.” Journal of Applied Psychology. 1974. Vol. 59, No. 4, pp. 524-526.
  • Prenn, Joseph W. et al. “Butterfly valve for skylight.” U.S. Patent 7,082,726. Jul. 7, 2003. http://www.google.com/patents?id=wSJ6AAAAEBAJ&dq=7082726
  • Psychology Matters. “Bright Lights, Big Relief.” American Psychological Association. June 26, 2006. (Dec. 16, 2008) http://www.psychologymatters.org/brightlights.html
  • Solatube. http://www.solatube.com
  • Steneby, Bengt. “Day lighting device.” U.S. Patent 7,295,372. Nov. 13, 2007. http://www.patentstorm.us/patents/7295372.html



What are daylighting devices?

Daylighting devices are systems that allow natural light to enter a building through strategically placed openings, such as skylights, windows, or light shelves. They are designed to maximize the amount of natural light inside a building while minimizing the need for artificial lighting. Daylighting devices can be used in residential, commercial, and industrial buildings, and offer numerous benefits such as reduced energy consumption, increased productivity, and improved health and well-being.


How do skylights work as daylighting devices?

Skylights are one of the most popular types of daylighting devices. They are installed on the roof of a building and allow natural light to enter through a clear or translucent dome or window. The light is then diffused or reflected throughout the room, providing a comfortable and even illumination. Skylights can be fixed or operable, and are available in a variety of sizes and shapes to fit any design or architectural style.


What are light shelves and how do they work?

Light shelves are horizontal surfaces that are installed above windows to reflect natural light deeper into a building. They are usually made of high-reflectance materials such as aluminum or polished stone, and are angled to bounce light up onto the ceiling. This creates a brighter and more evenly lit space, while reducing glare and heat gain. Light shelves are particularly effective in buildings with deep floor plates or narrow windows, where natural light penetration is limited.


How do automated shading systems enhance daylighting?

Automated shading systems are designed to control the amount of natural light entering a building by automatically adjusting the position of shades or blinds based on the time of day, the angle of the sun, and the desired light levels. This allows for optimal daylighting while minimizing glare and heat gain. Automated shading systems can be integrated with other building systems such as lighting and HVAC, and can be controlled remotely through a building automation system.


What are the benefits of using daylighting devices in buildings?

Daylighting devices offer numerous benefits for building owners, occupants, and the environment. They can help reduce energy consumption by reducing the need for artificial lighting and HVAC systems, which can result in significant cost savings. They can also improve occupant health and well-being by providing natural light and views, which have been shown to boost productivity, reduce stress, and improve mood. In addition, daylighting devices can enhance the aesthetic appeal of a building and contribute to its overall sustainability.

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