Its gonna get hot, that fan will blow on the light heating up the air as it goes by and if theres no exchange with new air it will just keep getting hotter, also your plants will run out of co2, i just had this prob, youll have to put a louvered vent or somethin on your door so as to block light but also allow airflow or if thats not an option get some dryer vent tubing and a couple computer fans for some cold/new air exchange