Yes they do give off quite a bit of heat. The ballast gives heat off too. I dont know what your ventilation set up is now, but, you could always invest in some better intake and exhaust fans. You can also by an air cooled reflector. The dryer duct hose goes directly into the hood thats housing the light. That way it removes a lot of the heat before it ever gets into the garden. I am growing in a closet 2' deep by 4' width and I have a 400 HPS bulb in there. My fans take out the heat rather quickly.
Let me know what ventilation set up you have.