History of High Bay Fixtures and Recent Technology Changes

High-intensity discharge (HID) light sources, such as metal halide and high-pressure sodium fixtures, have long dominated the market for lighting indoor spaces with high ceilings. These "high-bay" spaces are typically found in warehouses, factories, large retail stores, and athletic facilities.

In recent years, technology changes (including the introduction of the T5 high output lamp), general improvements in fluorescent lamps and the emergence of high-intensity fluorescent high bay fixtures have made fluorescent lighting the most cost-effective choice for lighting high ceiling indoor spaces. These high-intensity fluorescent high bay systems are more energy-efficient than HID solutions and feature lower lumen depreciation rates, better dimming options, virtually instant start-up and re-strike, better color rendition, reduced glare, better “pupil lumens” (fluorescents produce a much greater amount of light within the visible spectrum of the human eye than the HID) and lower energy consumption.

HID fixtures produce intense light in such a small area that they are considered "point sources." The T5 fluorescent high bay fixtures use highly reflective aluminum specular reflectors (specular reflection is the mirror-like reflection of light from a surface, in which light from a single incoming direction (a ray) is reflected into a single outgoing direction), to direct the light emitted from the lamps in a much wider array than an HID fixture. The result is an overlapping of light emitted by neighboring fluorescent high bay fixtures that produces a very uniform light in a work area. HID fixtures, which are point source lights, produce very bright light in spots but have very poor light uniformity between the fixtures.

The T5 fluorescent high bay fixture can generate large amounts of light and are excellent for higher hanging heights. T5 high bays for use in industrial lighting applications are available in many configurations including 2-lamp, 4-lamp, 6-lamp, 8-lamp, 10-lamp, 12-lamp and 16-lamp fixtures. The advantage the T5 high bay fixture has over the T8 model is that each T5 lamp can produce approximately 5,000 lumens as compared to a T8 lamp which will produce approximately 3,000 lumens. As an example, a 6-lamp T5 high bay will produce approximately 30,000 lumens (6 X 5,000 lumens) and a 6-lamp T8 high bay fixture will produce approximately 18,000 lumens (6 X 3,000 lumens).