heat = energy
light = energy
Whats the law? Energy never dies or ceases to be, it just changes forms.

white = reflection of light energy
black = absorbtion of light energy

Why then, would you want to waste that potential energy. Wasted wattage, wasted resaources. Wanna lock in that heat for whatever your reason? I did too. Theres this stuff called reflecti-x (lowes). Its reflective insulation. 97% light reflective, 7 layer insulation - fairly sturdy i suspose.

Check my cab in signature for pics of the stuff, its lined in it. I trap the heat in my cab in the top section via reflecti-x and a 1/4" plexi glass heat sheild w/ a 2" gap up front. Fans are expelling the hot air which is trapped and held away from the plants keepin the overall box temp lower.

4 PC fans cfm rating for the entire cabinet, sucks. 4 PC fans for the now smaller sized lighting area, good. I reduced the size area i NEED to move the air from (where its hot) and the 2" gap in the front allows for air flow from the bottom.

Hope it helps?