apart from using an a/c sytem you can put a pane of glass in the top that keeps the light in a seperate space than where the plants are but this migt only give you 4-5 degrees difference. if your willing to drop some dough than a good set of super leds will completely eliminate all of your heat issues no question. but you need ones with the right spectrum and 2-3 watt diodes to be a great grow light, and they can get pricey depending on where you get em