The only light that doesn't put out much heat is an LED.
Eh, CFL lights don't put out all that much either though.
I'm running dual 150's. Simple yet effective setup. I think the lumens, total amount combined from both units is like 32k or 36k. Which is perfect for me.. as I never have more than three plants going.. when I grow. I grow for my personal usage and enjoyment only.
I also got two 125watt CFL bulbs. I don't really count in the lumens the plants get from these.. but i think its right around 12k combined.. maybe a little more. But they work great for side lighting.
My temps are around 80-85`F when running the conversion bulbs (mh spectrum bulbs); during flowering, temps stay steady between 73`F-78`F. Humidity stays right between 40%-55%.. which is acceptable. Wish I could get them lower than that.. especially during flowering. I'd like to have around 25-35% humidity when I flower my babies..
maybe some day I can achieve that.
back to the drawing boards.
peace.