my 100w cfl kicks out some heat too, when my fan is off the plastic cover gets hot as hell. i duct taped the fixture to the hood of my new growbox and left it for an hour to see how much heat it produced when i had returned the tape had softened its grip because of the heat i guess. but with the fan on its consistantly about 70 degrees. my new box is sweet i have two 27w on three of the sidewalls on y splitters and on the fourth wall, above the fan, is another y splitter with two 42w cfls.and the hood has a 100w cfl fixture.if there still is a light problem i will swith the 27w with 42w bulbs but that will make the box even hotter probly in th 80s and im not sure wether my fan can chill that.