Good question about the reflective material. I'm really not sure how much it helps, or if this diamond sheeting is better than standard mylar of even flat white paint. All I know is that I looked at the price, and figured I should just go for the diamond stuff because it really isn't expensive to line a cabinet as small as mine.
Peace
From what I know, the white sheeting diffuses light more than the shiny coverings. The shiny ones reflect direct light. Sounds like the direct light thing is a good idea, right? Heres the issue.
When you use reflective materials that dont diffuse light very well, you reflect colored light. When that reflective material is in a grow cab, its probably going to reflect a lot of GREEN light seeing as the plants are reflecting a lot of it. Guess what color light your weed plants DONT use...thats right...green light is not used by most plants. Thats why they look green, because they are reflecting all the green light and absorbing most of the other light, thus only the green makes it to your eye, and only the green light makes it to your reflective sheeting to be re-reflected to the plants.
Going by these facts, I would guess flat white is better.
Some can argue the point by saying "you reflect more lumen with shiny material". I have an answer for that too.
It is true. you do reflect more lumens with shiny stuff than with flat white stuff, BUT plants don't use all the light you measure when you take a lumen reading. Lumen readings measure the amount of light you can see. That is useless when you are dealing with plants.
Plants use more light than you can see. And they don't use some light that you can see. The light that a plant uses is called Photosynthetically Active Radiation (PAR). This can (and should) be measured apart from lumen to tell you just how much light your plants are actually able to use. Flat white always reflects usable light for your plants while high reflective sheeting like mylar and foil reflect exactly what you see and deliver much useless light.
So why do I have mylar in my own grow room? because its cheaper than black/white visqueen!
Hope this helps.