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Residential lighting accounts for 15% of the energy consumed in a home (World Watch Institute). Reduction of that lighting can have a significant impact on energy use and household budget. There are several ways to reduce the amount of energy used for lighting. These can include:
· Turning off lights that are not in use · Substituting low wattage compact fluorescent bulbs (CFL's) for standard incandescent bulbs · Altering home design to allow for more natural lighting · Increasing available natural light through the use of Skylights and Solar Tubes
Not to minimize the effects of the first two items on our list, I want to quickly address them. Being diligent to turn off lights that are not in use is hard to measure, but is certainly beneficial to the reduction of power usage. The second item, incandescent bulb substitution for (CFL's) is more measureable. The use of CFL's will reduce lighting energy consumed by 75% (Connecticut Light & Power). These CFL's also last 10 times as long as incandescent bulbs. So a first step for homeowners that are interested in saving electricity is to monitor the use of lights and to take a simple step of replacing standard incandescent bulbs as the burn out with CFL's.
Beyond these first two simple measures are some additional steps that can be taken to reduce lighting energy consumption. For the purposes of our discussion, we are trying to address items that can be added to new or existing residential homes. The idea of altering design to allow for more lighting is only possible for new houses or additions. However, there is a product that can be used on existing homes to add interior natural light and to decrease the need for powered lighting. These are solar lighting tubes.
Solar lighting tubes are a modern way to increase interior natural light. The basic concept of the solar tube is to collect and funnel the natural sunlight into the house. Since the tubes come in various diameters, they can be installed in tight spaces that are too restrictive for standard skylights or in large areas with generous room. They can also be angled through intricate roof framing for light in usually unreachable spaces. The solar tube has a collector on the roof and then magnifies the light as it comes through the mirrored tube. At the bottom of the tube is a diffuser that spreads the light throughout the room (The Common Green American).
There are two companies that are in the forefront of Solar Tube technology. Velux® is a company that began in 1941 and is best known for skylights. In 1975, Velux America was established and later the inception of Sun Tunnel® tubes. The other company heavily involved in Solar Tube technology is Solatube®. Solatube® was established in the 1980's. Their first product was brought to market in 1991 as the "light catcher". In 1992, they established Solatube North America. Since that time, both companies have been improving their products and making them more versatile in the residential market.
Solar tubes are composed of 3 basic parts:
· An exterior rooftop collector · A magnifying tube · A diffusing lens at the interior
Solar tubes come in a variety of sizes. The most common are 10", 14" and 21". These sizes allow for penetration between roof framing of 16" and 24". The 10" size allows for installation into tight spaces. The spacing of the solar tubes is based in the Mounting Height (MH) above the work plane. In office spaces, kitchens or dining rooms, the work plane is the distance to the table top to the ceiling. In hallways, the work plane height is the distance from the floor to the ceiling. Spacing of the solar tube needs to be 1.5 times the MH (Solatube Spacing).
The basic cost for a 10" solar tube is $500 installed. The pricing can go up from there as tube size increases and as complexity of installation changes. There are also creative options that are available to add on to your standard solar tube. These options include (Solatube Options):
· Designer diffusers · Ventilation fan kits · Night time lighting kits · Natural Daylight dimmers
Energy savings due to integrated day lighting can be as high as 80% (Builder News). At Solatube International's headquarters in Vista, California, a retrofit to include 21-inch Solatube units has resulted in an 86.1% reduction in lighting costs for the daylit portion of the office and a 68.2% reduction for the warehouse area (Solatube Facts & Figures). A 10" skylight will light up an area the size of a 10'x10' room. That same room would require approximately 2-75 watt light bulbs. Those 2 light bulbs over a one year period will cost:
75 watts *2 = 150 watts * 12 hours = 1800 watt hours= 1.8KW hours
21.60 cents/ day * 365 days = $78.84 per year
It is obvious that there are monetary savings with solar tubes. However, with the scenario that we have listed, it will take approximately 6.5 years to pay for the investment of a solar tube. As we dug further into these devices, we discovered an additional benefit that we didn't expect. This second benefit was the natural light itself.
The quality of natural light versus artificial light and the quantity of natural light both play a large role in improving indoor activity. A study by the Florida Energy Conservation Assistance Program found some dramatic results (Florida ECAP). Natural light from Solar Tubes resulted in:
· Reduced eye fatigue and headaches · Delivery of more useable light · Decreased Thermal Heat load · Natural changes in light levels that matched the normal functional rhythms of the human body · A necessary change from the monotonous illumination of artificial light
As much as we want to discuss the energy savings or reduced environmental impact of certain technologies, it is good that we remember the human benefits of removing artificial systems from our lives. As with the use of rainwater for our gardens instead of treated water, natural light from solar tubes has many benefits beyond the obvious savings in electricity. |