Q: Years ago, there was there an option to use fiber optics to bring in natural light. Is that still available?
A: The system I remember from the mid ‘90s is the Himawari Solar Lighting System, which was invented by the late Dr. Kei Mori. The company introduced a new catalog last year. (By the way … If anyone is interested in buying a rather large “pre-owned” Himawari system, please contact me at email@example.com.) Today, there are several sunlight collection and fiber optic distribution systems on the market, such as the Parans system from Sweden and the Hybrid Solar Lighting system from Sunlight Direct, which combines sunlight and electrical illumination.
Q: Is HVAC system capacity decrease possible with daylighting because sunlight lumens produce less heat than manmade lighting? Why is there a reduction in HVAC system capacity with daylighting?
A: The general concept is that, by harvesting daylight, you are able switch or dim electrical lighting and reduce cooling load, thereby downsizing the size of the HVAC system. The preferred form of daylight is skylight rather sunlight since it has less heat for the same amount of lumens. Sunlight contains about 93 lumens per watt of radiant energy, while skylight from a clear sky has about 150 lumens per watt of radiant energy. As a point of comparison, a T5 fluorescent lamp is about 107 lumens per watt; an incandescent halogen lamp has about 20 lumens per watt.
Q: Isn’t using daylighting in museums harmful to fugitive organic materials?
A: All light causes cumulative, irreversible damage to fugitive organic materials whether produced by daylight or electric light. Shorter wavelengths, such as ultraviolet, are more “energetic” so they can cause damage at a greater rate. However, even longer wavelengths, such as infrared, can cause damage by raising the temperature of an object. Since we need light to see art objects, museums limit the duration and intensity of light exposure that objects receive based on wavelength and the object’s sensitivity.
Q: What would be a good ceiling height to get the most use of daylight from a side window?
A: The rule of thumb is that daylight penetrates twice the window head height, so you want to locate the window head as close to the ceiling as possible.
Q: Do have any rules of thumb that help determine which electric lighting control strategy is most cost advantageous?
A: Occupancy sensors provide the greatest savings, followed by dimming, then switching. Dimming has a higher upfront cost than switching due to the cost of dimming ballasts, so budget needs to be considered. Application is another consideration. Switching may work fine in a low-occupancy or non-critical application, such as a warehouse or lobby, and reap energy savings with low added cost.