not enough to really worry about

you can touch CFL's even after they have been on for hours without getting burned

I would guess that you wouldn't need too much for ventilation

don't take my word for it tho
Revanche21 Reviewed by Revanche21 on . Amount of light vs. heat generated Growing in 2ft x 1ft footprint, 3ft vertical space (6sq ft). Want to run 12 30watt CFLs. Temps between 72 and 78F currently running 6 23watt CFLs. I know CFLs do not create much heat, but that many is bound to create some. Anyone have any guesses as to how much? Options are 50 or 70CFM fans. Think 50CFM would be enough to suck out a lot of the heat? Rating: 5