By Torrin Greathouse | March 06, 2015
In the not so distant past, energy consumption was not a widely discussed topic. Now, with natural resources dwindling and energy costs rising, a movement has developed pushing for the utilization of more green and sustainable devices in our everyday lives. With this growing movement, many companies have developed new, sustainable products to help customers reduce their energy costs and their impact on the environment.
Even within the category of lighting, there are a plethora of solutions to choose, from LEDs to fiber optics to commercial skylights. Within the category of skylights there are several distinct styles of device: traditional skylights, tubular skylights, prismatic skylights, and solar-tracking skylights. With so many options manufactured for the evolving market, it can be difficult to decide which is the right device for your facility.
Although there are a number of factors which determine the quality of commercial skylights, the National Fenestration Rating Council (NFRC) is responsible for administering objective ratings, and many devices can be compared based on their ratings. Here is a breakdown of the manufacturers and the ratings of some of the most widely-known commercial skylights on the market today.
These are what most people think of when they hear the word skylight. They follow a traditional window-in-the roof style design. While they are less expensive to buy and install than other commercial skylights, these stationary units also provide less indoor light. This is because the units are completely passive to the sun, and they do not adjust to bring more light in during the early morning and late afternoon hours.
Traditional skylights are the oldest form of commercial daylighting and also the most common. They come with a small variety of special features such as rounded acrylic or polycarbonate lenses, hurricane insulation and impact resistant domes, UV filters, ventilation hatches, etc.
They do, however, suffer from a few key flaws. For example, they are susceptible to both heat gain and loss. According to the NFRC ratings, traditional skylights typically let 55% of the heat generated by sunlight into the building, and if the interior of a building is warmer than outside, the skylight will allow up to 76% of that heat to escape from the building. Not only that, but the direct light from a traditional skylight often creates glare, light pooling, and hot spots on the floor.
Traditional skylights are the least expensive, so they are a good option when the budget is tight, but they are also the least efficient of all the skylight designs available today. While they offer the best price point, their inconsistent light makes them ill-suited for large commercial installations and their heat gain makes them impractical for small developments.
Another option for stationary skylight units are prismatic skylights. The lenses of these devices are imprinted with a series of special glazes to reflect and diffract the incoming sunlight, creating diffuse, glare-free light within buildings. While slightly more expensive than traditional skylights, these units address some of their significant flaws: glare and light-pooling.
Prismatic skylights have been given better ratings calculated by the NFRC than traditional skylights. The Sunoptics prismatic skylight allow only 49% of the sun’s heat to enter a building, 6% lower than traditional skylights, but 82% of the heat inside of the building is able to escape, releasing 6% more of the building’s heat into the environment than traditional skylights.
Prismatic skylights work best when lighting a large facility. They resolve certain flaws of traditional skylights, and they offer a better long term investment.
Tubular skylights also have a stationary design, however, they are different from traditional and prismatic skylights in two major ways. First, the lens of a tubular devices is typically quite small, ranging between 10 and 21 inches in diameter. Second, they have a tubular lightwell--the design feature from which they draw their name. Solatube is perhaps the best known manufacturer of tubular skylights. The design was invented by Solatube’s founder, Steve Sutton, who created a tubular lightwell that could pass from the roof level through an open or dropped ceiling in to a room below, allowing sunlight to be directed downward over a long distance into a building interior. Solatube’s tubular lightwells can also be connected with angled joints to maneuver around HVAC units and electrical wires in the ceiling.
Because of their small lens and insulating lightwell, tubular skylights only allow about 34% of outdoor heat to penetrate into a building and only 43% of indoor heat is able to escape. Tubular skylights insulate against nearly half as much heat gain and loss as traditional and prismatic skylights. The small size of the tubular skylights is one of the advantages of this design, but it is also a great disadvantage. The small entry for light and tubular lightwell prevents heat gain and loss, but more devices are needed to illuminate a space.
Tubular skylights work best in a building with a high roof or obstructed ceiling space. These devices are best suited for smaller areas, where they can provide even, consistent, light throughout a room, otherwise they will require supplemental electrical lighting.
Active daylighting devices, unlike passive skylights, are designed with moving parts that follow the sun throughout the day. They provide more hours of light per day than other skylight devices, and they also usually do this with zero electrical cost, because solar power generates the energy to move the mechanical parts.
The active daylighting market is growing, and it is already filled with many unique devices. The Sundolier Daylight Harvester, which resembles a large satellite dish, tracks the sun, reflecting light down into the building through a series of mirrors. The Harvester delivers a far greater level of illumination than passive devices, however, they are bulky, and their unwieldy size makes them difficult to install, especially in close proximity to one another.
The Parans system is another active device, which is distributed in America by Wasco Skylights. The Parans system has a movable receiver which tracks the sun and captures light with specially designed optical lenses and transports sunlight across fiber optic cables into the building. The fiber optic cables are more maneuverable and far-reaching than other skylight technology. The fiber optic cables are even able to transport light into lower storeys. The downside to this technology is the high price--a single roof or wall collector unit costs approximately $7000, with each foot of fiber optic cable only adding to the price.
The Ciralight SunTracker is more compact than the Daylight Harvester, and it is available at a far lower investment price than the Parans system. SunTrackers use a combination of solar power and GPS technology to precisely track the sun with a set of mirrors which directs the light downward into a building. This unit provides free, abundant, natural light for up to 10+ hours a day. The NFRC ratings show that the SunTracker only allows 32% of outdoor heat into a building and only 40% of indoor heat is able to escape. These percentages are comparable to the Solatube ratings, but SunTracker units have an edge over the competition, because they provide more than twice the amount of sunlight as a Solatube unit. Ciralight SunTrackers are so efficient that they pay themselves off with energy savings in 2 ½ - 4 years.
Active daylighting devices are great investments if you have a slightly larger budget and want a long-term sustainable solution. Active daylighting devices use little to no electricity, plus they provide a surplus of light, so they offer an impressive return on investment.
To learn more about Ciralight SunTrackers, contact our sales team today.
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