A heater is not an option with lights on 24/7. Not to mention a waste of electricity and $$$$$ for my application. I got my temps. in a tolerable range. 76-79 lights on and off. The damper I installed too late is tied to my Central heating duct.It's the same temp as the living space. lights off,that is. I have a ceramic heater with a t-stat built in. This is the first time I have lost a cutting due to cold. Much less 3!!!!!! It's all good,though! Gonna take more and it won't happen this time! These cuttings won't be but about 2 weeks behind the rooted clones. Arggggggg!