High- (above 25’) and low-bay (below 25’) lighting is used in “big box” retail, gymnasiums, sports facilities, warehouses (including cold-storage facilities), industrial facilities, and more. Occupancy can range from constant to occasional, and the quality of light can range from only enough for security to good enough for sales of clothing and home furnishings or television filming.The main difference among high- and low-bay lighting products is the distribution pattern and how much intensity is required to provide the desired amount of light at floor and eye level. High-lumen LEDs are now entering this market in increasing numbers, offering products to replace traditional high intensity discharge (HID) lighting systems.LEDs are particularly useful in cold storage and hazardous storage facilities. The long life of 50,000 hours and more means less time spent replacing lamps in hard-to-reach locations. Many products may double as outdoor area lights, the key being a watertight fixture, which may be useful in some facilities such as a food processing plant. With no ultra-violet (UV) or infrared (IR) light emitted to damage products LED lamps may be suitable for some retail areas, however color rendering index (CRI), which can be critical in color-sensitive applications, tends to be omitted from most LED lamp product information. The directionality of LEDs can be a benefit with high mounting heights when no light is desired on the ceiling, but this can also contribute to a very dark ceiling and cave-like atmosphere, which may not be the desired effect. Both general and aisle lighting distributions are available. As with most LED products, performance and quality vary widely. Careful research and small pilot demonstration installations are encouraged before committing to a large purchase.     

Interior high-bay interior lighting has traditionally been handled with high pressure sodium (HPS) or metal halide (MH) lighting, so these are generally used as the baseline in energy saving studies.

More recently, high-performance fluorescent systems using T8 or T5HO systems have been encouraged due to energy savings, the high quality white light they produce, long lamp life, and controllability allowing for occupancy sensor use and bi-level lighting, while eliminating the need for additional emergency lights in case the power supply is momentarily interrupted. The multiple lamps per fixture also mean it may not be critical to replace a failed lamp prior to scheduled group re-lamping, when it might be critical if there was only one lamp. Induction lamps are sometimes used.

As energy codes continue to reduce lighting power density thresholds and increase the required use of controls, some bi-level ballasts have become available for HID systems and the traditional probe-start ballast for MH is being phased out in favor of pulse-start ballasts, which improve lumen efficiency, lamp life, color stability, and lumen maintenance. The use of skylights has also increased.

As existing systems reach end-of-life, replacement with a different technology may be a common solution rather than re-lamping old ones. Codes will often then dictate that controls be added as well.

LED luminaires for high- and low-bay applications are available on the market now, for standard as well as hazardous location applications. Most LED products do not replace MH products more than 400W, although at least one distributor is advertising a 168W replacement for a 1000W HID lamp. The U.S. Department of Energy (DOE) used a 175W pulse-start metal halide as a baseline for high-bay LED studies in Round 13 of the CALiPER testing program(http://www1.eere.energy.gov/buildings/ssl/caliper.html) for comparing LEDs of 73-183 watts.

Advertising mounting heights ranging from 15'-44', and ambient operating temperatures between -18°F and 131°F it can appear that LED products are ready to replace HID, fluorescent and induction high-bay fixtures in manufacturing, warehousing, cold storage, commercial, retail and other large indoor spaces; this may be overly optimistic at this time. Light distribution patterns, quantity of light and rather high correlated color temperature (CCT or CT), usually above 4500K, are some of the factors that may not meet the needs of a given project. DOE testing through the CALiPER program continues to find some significant discrepancies between product performance and manufacturer claims, but some are quite close.

First costs are still steep and utility incentives are only slowly becoming available. Costs are high enough that getting free samples to test in your facility are not very likely, but a real-world application demonstration is highly recommended.

Glare must also be controlled, especially for forklift operators or others looking up toward the lights, or visibility and productivity may be compromised. While low- and high-bay luminaires come with a wide variety of light distribution, the LEDs at this time are not able to match the wide, “batwing” distribution of MH products. A major remodel hoping to use 1:1 replacements of MH fixtures discover that they require a new design with more fixtures due to the lower light output of LEDs. However any retrofit lighting project should be assessed in regard to occupant operations that may have changed since the original design for the best performance (for example, a room that used to be used for warehouse storage but now is used for machine operators or wholesale shopping requires very different lighting).

The high color temperatures that are predominant with LED lamps at this time may be “too blue” for many people, particularly if light from other sources is visible in the same “viewshed”.

Many companies in the product field are not well-known lighting companies but rather start-ups with little history to back them up, so determining high quality products with good reliability and service can be challenging.

Though LEDs can potentially be used with a variety of controls, those systems are not standardized and are undergoing rapid development at this time. Compatibility with existing or planned controls systems must be confirmed prior to purchase.

Designs that put no light on the ceiling might not feel as good as they sound. When parabolic fixtures became the fashion for fluorescent office lighting, the cave-like feeling was not always appreciated and was either mitigated with additional lighting or upgraded to newer “volumetric” lighting fixtures, which provide broader light distribution rather than just down onto work surfaces. In spaces where occupants are only passing through briefly, having all the light coming down might be acceptable.

Since most installations are only a couple of years old at best, proven performance in the field is not well established and most manufacturers will have newer versions of the early products in production now. The DOE has just begun testing these types of products in their CALiPER program and they observed, “The short record of performance and continuing rapid development of LED technology introduces uncertainty and can result in greater risk than with conventional high-bay luminaires. These factors may be of particular importance for commercial and industrial applications that require high-lumen sources. In order to reduce risk, it is advised that standardized testing, use of reputable manufacturers, learning from demonstration projects, and initial use of pilot or small-scale installations be employed.”

For anyone looking at installing a new lighting system with white light, the non-LED choices include pulse-start metal halide (PSMH), high performance fluorescent, induction, and possibly plasma systems.

Electronic ballasts are now available for pulse-start metal halide and offer enhanced lumen, maintenance (up to 60%), and longer dependable service life, enhanced color control (reduced color shift between lamps), higher efficiency (10-15% less energy consumption than magnetic ballast technology), reduction in noise (most electronic HID lighting systems are sound class “A” [<24 db]), and enhanced controllability (many systems are dimmable, driving additional energy savings).

High performance fluorescent systems may have lives in the same range as LEDs(46,000 hours and more) and sophisticated control systems are available. Both T8 and T5 systems cost less than PSMH, so they have no cost premium and therefore an instantaneous payback. Of the two, T8 systems have the best life cycle cost.

Plasma lighting may be entering the arena for very high light output applications.

High pressure sodium may still be used where color quality is not a priority due to its low cost, high efficiency, and long life.