I have tested the most popular grow tent and grow room lining materials to determine what is the most effective. The materials tested include white matt paint, white panda film, orca grow, diamond mylar and plain silver mylar.
The 4ft x 4ft or 1.2m x 1.2m test area was lined with the materials and an ARAY 8 500W LED grow light hung at 11" or 28cm over the test surface. I took 64 ePAR measurements with the Apogee Instruments MQ-610.
As you can see the simple and cheap option matt white paint performs much better than white panda film or the expensive Orca grow materials. However big improvement is possible by upgrading to Silver mylar.
Although white surfaces are highly reflective the light is reflected in all directions. In a grow tent or grow room situation where light is hitting the side walls the most effective solution is a shiny surface which reflects most of the light down onto the grow area.