The easiest way to get the most out of the available light in your indoor grow room is to use reflective sheeting hung on the walls, to bounce it all around and back towards your plants.
Megalux Silver Mylar Sheeting is 95% reflective and does exactly that, which can have a significant impact on the yield you can achieve from your indoor garden.
Megalux Silver Mylar is 1.25 metres wide and 110 micron thick.