Then why would you use it Marlo........
Covering your floor is more important than the ceiling since your bulb ends point down.
Any light hitting the ceiling with base up bulbs is reflected off something to begin with. The bulb end does kick out much more light than I thought according to my cave man style white board tests..
If the canopy is perfect in a vert grow, the walls should be all shadows, but we all know this rarely happens. I plan to upgrade my white walls for next run to return something from a less than perfect canopy.....
I tend to ask myself what would Heath Robinson do? The answer is he covers everything in reflectix. It also helps deaden sound along with everything else mentioned.