Many growers think that white paint is the best reflective lining for grow room walls. We have tested a lot of grow lights in a lot of different environments to see what works best. We can tell you definitively that matt white paint is as effective as the standard reflective lining in grow tents but no better.
For once the best solution is actually a very easy and cheap solution - standard silver mylar from your grow shop.
The reason: It's a good reflective surface and it's directional. Directional means that the light comes from the grow light at the top of the grow tent, reflects off the grow room wall and is directed onto the bottom of the tent. The diagrams below show the test of a matt white surface and a silver mylar surface.
The test is a simulation of the grow light at the top of the tent and the plant canopy at the bottom. When the light is spread wide it must reflect off the grow area walls and be directed onto the grow. Let's see what surface type does this job most effectively.