Small cab,few questions

So I'm thinking about a small grow (12"x12"x40") and I'll put in a 150w HPS, I have a few questions questions, how much heat the bulb will produce, will I need some kind of cooling for it? Would I have any problems if I wouldn't use a fan and does the fan has to be turned on all the time or just a few hours per day would be enough?

For the HPS light you will need some sort of ventilation for it. Put one fan blowing in and one blowing out. And you should keep the fans on at least as long as the lights are imo, i do 24/0 for fans and lighting. If heat is going to be an issue then do some research on CFLS, that's what i use

i have 6 23w cfls in a 2x2x3H and it hits 100 (insulated my box, 30 degrees outside of it...lol)now i pull air in. tricky in winter...lol

How do people set up cfls? Kingb420 > what were your yields? what strain?