Dean, with all due respect, when I built the shop in 07, I put in T5 High Bays, I have a 50' X 80' with 18' ceiling. I have 14- 6 tube x 4' fixtures off the ceiling, a mezzanine full width x 8' out one end with three 4 tube x 4' fixtures under it, one 4 tube ... Login to read more.