CFL's give off little to no heat, which is why they work so well in other applications. You could set one up and check the temperature, but I wouldn't think it would raise the temperature at all. Some people use heat lamps clipped a distance (to be determined with your environmental factors) from the enclosure. I use heat tape regulated by a thermostat draped over the top of mine which probably isn't the best idea but gives me a steady 72/78 night/day. Until I find something better!