Do you have any ducting going to the holes in the walls to extract the hot air? If you get duct (homedepot it's 2.50 I believe) put 2 of those bad boys with fans on the inside of your growing unit to blow thehot air through the holes you will have better results. Do you hve any pics of your grow area.. It might help leading you in the right direction with the heat issues.
Have fun be safe
enjoy the buzz