1.5 feet hieght doesnt give much room for plants. are you using that for clones? ya figure you hps will take up about 8 inches of that hieght and then the pots you are planting in will take more so by the time you get any plants in there they will be burnt by the light. also you will need fresh air in for the fan to be effective at all. I would probably go for flourescent lighting to save space and produce less heat and the a pc fan would do for fresh air. if you were to put your fan on a thermostatic outlet then it will controll your temps just fine with a little fan and I cant tell you the cfm. besides in that small of a space you really dont need to worry about cfm I wouldnt think.