Scan back thru some of the recent posts. You will find several on lighting, a couple of them discuss lighting in a steel building of your size. What is the eave height? How high will the bottom of the lights be above the floor? What are you referring to by "bay lights"?
Industrial and commercial lighting is largely divided into "high bay" and "low bay" lighting. GENERALLY, "high bay" is lighting that is positioned ABOVE 20ft off the floor. It could be as low as 15 ft, depending on the fixture, but this is uncommon. "Low bay" lighting is that which is mounted below 20ft.
Hiigh bay lights generally are a very focused light, due to the height, there is a need to get all of the light to the floor, so it is tightly focused and doesn't spread out much. The fixtures must be fairly close together and if too low, will give alot of glare and also cause shadows and dark spots.
Low bay lights have much more spread to the light. Due to this, the lighting is ineffective above 20ft, it simply doesn't reach the floor, but if mounted properly, the light will spread out and overlap with light from other fixtures and reduce the effect of shadows and dark areas.
You generally have a choice of Flourescents, T12 (obselete technology, bulbs are 12/8's of an inch in diameter, the "common" flourescent bulb) T8 (bulb is 8/8's or one inch in diameter, current technology that is common, lots of light, electronic ballast that generate little or no noise) and T5 (5/8 inch diameter lamps, high output, and the only flourescent type used in high bay lighting, T12 and T8 being exclusively low bay). Other lighting types are Metal Halide (MH) the round fixtures with a bright bulb you see in Lowes and Wal-Marts and similar stores, these are available in both low and high bay designs. Sodium, which is the orange street light bulb, generally useless for anything other than industrial applications, and Mercury, the bluish lights use for years for street and security lighting. Not very bright and fast becoming obselete.
There are a few oddball fixtures on the market, such as the "sportlite" which use 8 small u shaped flourescent lights in a single fixture, largely designed to replace MH high bay fixtures in sporting arenas and gyms and such.
Charles
High bay T5 fixture
Sportlite shown rotated 90 degrees, bottom of light is to the left.
