Foil isn't as reflective as one would guess. Mylar or even matte white painted surface are better. It really surprises me, too. I guess the sheer size of these

Foil isn't as reflective as one would guess. Mylar or even matte white painted surface are better. It really surprises me, too. I guess the sheer size of these operations make it difficult or impractical. The cost must be greater than that of the wasted light. Too bad, because that is a lot of wasted light.