How Sunlight Channeling Devices Function

There's nothing more frustrating than being indoors on a beautiful day. If only you could step outside, you’d bask in the sunlight rather than relying on artificial fluorescent or incandescent lights. If you're lucky enough to sit near a window, you may get a taste of natural light. But for those who are not so fortunate, it can feel pretty grim. No artificial light can replicate the warmth and vitality of the sun.

This is one of the reasons many architects are exploring ways to optimize the use of natural light inside buildings. However, the motivation extends beyond psychological benefits. Sunlight is a clean source of energy – it reduces the dependence on electric-powered lighting. Moreover, it’s free. A free and renewable source of illumination that keeps people energized and positive seems almost too perfect to be true.

There are a few challenges associated with natural lighting. For one, it is completely reliant on the sun’s schedule – once night falls, there’s no more sunlight. Sunlight is not consistent throughout the day, as windows or skylights receive varying amounts of sunlight. Additionally, the sun’s position in the sky shifts throughout the year. A window that gets a lot of sunlight in the summer might not offer as much in the winter. And adjusting the position of windows or skylights to accommodate the sun’s changing position isn’t feasible.

This is where daylighting devices come into play. A daylighting device is essentially a tool that collects, transmits, and releases natural light into a building or structure. With daylighting devices, even rooms without windows can use sunlight as a natural alternative to electric lighting.

Daylighting devices offer architects more flexibility compared to traditional skylights. The part of the device that gathers sunlight doesn’t need to be directly above the room you wish to illuminate. Even if the area of the roof above the room is typically in shadow, daylighting devices can collect sunlight from a sunnier section of the roof and channel it into almost any room.

It may seem like something out of magic, but it’s all based on simple scientific principles. In the next section, we’ll explore the basic components of a daylighting device and learn how they work together.

Parts of Daylighting Devices

A daylighting device consists of three main components: a light-collecting element, a light-transmitting component, and a light-emitting section. In simpler terms, daylighting devices rely on lenses and mirrors (or optical fibers) to channel sunlight into a building.

The lenses in the light collection part of a daylighting device funnel light into the light transmission system. This section often features a glass dome or pyramid on top. The glass directs light into the lenses. Some daylighting devices use a dual-lens system. The first lens is a convex lens, which bends light toward a central point, while the second lens is a concave lens, reflecting light rays outward toward the transmission part of the system.

The light transmission portion of a daylighting device consists of either a tube with a reflective inner surface or a series of optical fibers. Optical fibers are essentially tiny reflective tubes, so both approaches use similar principles. As light enters the tube or fiber, it reflects off the inner surface and travels further down the path until it reaches the light emitter. The longer the transmission section, the less light will reach the emitter. In other words, running a tube through a 60-story building to illuminate the basement may not be the most efficient solution.

The light emitter is the component of the device visible from inside the building. It functions similarly to a fluorescent light panel or an incandescent bulb. Many emitters feature a specialized lens that diffuses light. A diffuse lens contains small surfaces that scatter light in various directions, resulting in a broader distribution of light.

­

Daylighting devices offer several advantages over windows and skylights. One key benefit is that their performance isn’t influenced by the sun's position. Unlike windows or skylights, which allow varying amounts of light throughout the day, the daylighting device’s light-collecting section will continuously transmit light as long as it receives sunlight, though the intensity may fluctuate depending on the sun’s strength. Another advantage is the flexibility to place the light-collecting part anywhere on the roof, and you can use the transmission tube or fibers to carry the light to different areas, even around corners. Unlike windows, you don't need to sit near an exterior wall to benefit from the daylighting device.

Daylighting devices should not be relied upon as the only source of light for a building. They aren’t effective once the sun sets. Although some daylighting devices can capture ambient light on cloudy days, their efficiency diminishes when the skies are overcast. Daylighting devices work best as an additional source of light, rather than the primary one.

Advantages of Daylighting Devices

One of the primary advantages of daylighting devices is their positive effect on your mood. If you’re not getting enough sunlight, you may develop seasonal affective disorder (SAD). Symptoms of SAD include tiredness, withdrawing socially, losing interest in activities, and even weight gain. In severe cases, SAD can lead to depression. The American Psychiatric Association (APA) states that SAD is caused by a biochemical imbalance in the brain due to insufficient sunlight. Sunlight also reduces melatonin production, a hormone that regulates sleep, which increases when it’s dark or when you lack sunlight.

While most people experience SAD during the fall and winter months, it's possible to be affected by it at any time of the year. If you spend a lot of time indoors away from sunlight, you may suffer from SAD even in summer. The APA recommends a walk in the sunshine as a remedy for alleviating symptoms of SAD.

A daylighting system can provide a consistent level of sunlight exposure year-round. Business owners may notice improved employee productivity and overall happiness with increased access to natural light.

Certain tasks can be easier to complete under natural light compared to artificial lighting. A study at Cornell University explored how different lighting conditions affected fatigue levels in students. Over four days, two groups of students were asked to study or do coursework for four hours each day. One room had standard 'cool white' fluorescent bulbs, while the other used a type of fluorescent bulb designed to mimic sunlight. The students were unaware of the different bulbs used in the experiment. Results showed that although the students didn’t notice any subjective differences, they performed visual tasks better on days with sunlight-simulating bulbs.

Daylighting systems are also a great way to reduce energy usage. As the push for sustainability grows globally, many individuals and businesses are seeking ways to lower their environmental impact. Using natural sunlight not only lessens your electricity needs but also reduces waste, as you won’t need to replace light bulbs as often. If the sun goes out, worrying about your living room's lighting will be the least of your concerns.

Lower energy consumption translates to lower electricity bills. So, using natural lighting is not only an eco-friendly choice, but it can also save money in the long run. Keep in mind, however, that the initial investment for daylighting systems can be significant.

Now, let’s take a closer look at the costs associated with purchasing and installing a daylighting system.

The Price of Daylighting

How much do daylighting systems cost? The truth is, it varies based on your needs and the supplier you choose. Solatube, for example, offers a variety of daylighting models for both home and commercial use. In addition to basic systems, they offer specialized accessories like diffusers, roof mounts, effect lenses, dimmer switches, and light kits. The light kits allow you to install an incandescent bulb into the daylighting fixture, providing light after sunset from the same device.

The price of your daylighting system will rise as you add additional features or extend the length of the transmission tube. For instance, if you only need a short tube, your costs will be relatively low. However, if you need 20 feet (6.1 meters) or more, the price will increase significantly. Additionally, custom tube sections designed to navigate around obstacles like support beams will also drive up the price.

In addition to the cost of the parts themselves, there are installation fees to consider. Solatube suggests that most professionals can complete the installation of a daylighting system in just a few hours, while DIYers might require a full day. Regardless, you'll incur costs either for professional labor or for purchasing the necessary tools to install the system yourself.

To give you an example of how much a daylighting system might cost, let's look at Solabrite, a Solatube dealer, which offers two models for homeowners. The 10-inch (25.4 cm) Solatube 160 DS is priced at $649, while the larger 14-inch (35.6 cm) 290 DS costs $749. Both prices include up to four feet of transmission tube; however, longer tubes will raise the price. If you'd like a dimmer for the daylighting system, that feature will cost an additional $325 to $335 depending on the model. The prices include installation, but if you choose to install the system yourself, the cost will be significantly lower.

Solatube assures customers that one cost you won’t have to worry about is replacing faded furniture. The ultraviolet rays in sunlight can cause fabrics to lose their color over time. However, the lenses and diffusers in Solatube devices filter out most UV radiation. This means you can enjoy natural sunlight without the risk of damaging your furniture or skin from UV exposure.

While the initial installation may seem like a significant expense, it can be a smart investment if you're facing high electricity costs. Over time, you won't need to replace light bulbs as frequently, which helps reduce your overall spending. It might take several months to recoup the costs, but in the long run, daylighting systems will pay for themselves—and you'll be cutting your carbon footprint as well!

With the continued rise of the green movement, it’s likely that we'll see more lighting innovations harnessing natural resources. Who knows? In just a few years, we might all be enjoying the advantages of sunlight, even if we're spending most of our time indoors.

For more information about daylighting devices and other related topics, be sure to check out the links provided on the next page.