I think the idea of vented the hoods would really help with heat, since one my plants did get heat stress when I moved I changed the lighting from a flourescent to the 400MH. It happened within hours and I had to raise the light up. I am more concerned though about the heat when it goes into flowering because then I want to use the 600W HPS. I have to figure this ventilation and temperature thing out, because when I increase my crop I plan on using both of the 400W MH. I was given these three lights, with digital ballast, thinking everything would be set, but I am finding out there is a lot more to it then lights and soil, lol.