A common goal in the grow room is maximizing efficiency. If you have metal halide (MH) or high pressure sodium (HPS) grow lights, you can increase their efficiency by up to 40% by using a grow light reflector!
Grow light reflectors and hoods redirect wasted light back down onto your plants, ensuring they are seeing as much of the light you use as possible. Without a reflective hood, the top half of the MH or HPS grow light will be illuminating the ceiling. So you can further increase light coverage by using mylar and reflective wall coverings!