That brings up a good point... you might consider scheduling your grows so that during the hot period of June-August, you concentrate on propagating clones, doing maintenance on the room, and starting seeds, and leave the HIDs turned off entirely. A grow buddy of mine is doing that actually! It's not a bad way to save the frustration of dealing with heat problems, and then when September brings the cooler days, you will be ready to go.
My last piece of advice is to cool your house as much as possible the way I do it:
Every evening at about 6 when the outdoor temps drop below what your house has heated up to over the course of the day, OPEN all the windows and get fans going... leave them open all night (run your lights only at night too) and then at dawn, shut them and draw the curtains. You will be amazed how much $$$ this saves on a/c too. HEAVY curtains that can darken a room should be used on any windows with S/W exposure!
Good luck...