Temp. shouldn't be the deciding factor in co2 enrichment, however temps are crucial being that you want to be at peak photosynthesis to utilize co2 enrichment which i beleive is at 80-85f (please correct me if i'm wrong), i personally go by a few rules when using co2, is you enviroment completely in check? ppm, ph, res temps, ambient temps, relative humidity, 40 plus watts per square foot? all of these must be very stable, no big fluctations in enviromental changes, also how many people and pets reside in your residence, you may be at peak saturation already, and last but not lease, co2 is not the magic remedy, it can definately increase your yeild but only in conjunction with a proper setup, good luck