I had heat issues in a closet, space was 2' x 4' but actual growing area is 2' x 2'. Under a 400w HPS I had heat issues and burned my ladies a little bit. Don't have the ability to take the actual temp of the closet, but with the HPS it was noticeably uncomfortable for me to stand in there. No fans.
I'm running a CMH now, and heat is no longer a major concern for my setup.