Good call pollux. I agree with antoine, I would also recommend using a reflector/hood. It doesn't have to be a huge hood, just big enough to reflect all the light downward instead of it just bouncing around. Especially if you get a decent little hood with ducting holes on it... hook a duct fan to it and vent that hot exhaust out of the area completely. If you could do that, you'll lower the ambient temperature significantly. Just to give you an idea, I have a 1000w HPS that I was using in a nice glassed hood/reflector with ducting holes... just sitting there by itself, with no fan pulling air through it, the ambient temp about 10" from the bulb was 145F. Hot! I flipped the ducting fan on, and after 60 seconds, the temp had dropped to 90F!!! 55 degree reduction in one minute. The room was also noticably cooler just circulating air past the bulb. Not even exhausting the air from the room. Hope this helps and good luck!
Mr. Bond