72ºF is quite cool for ambient / cool end temps. I'd not worry about the humidity the cool end is alway higher than the warm. From the sound of it my guess is that your room temp is quite cool? (69-72 ish?) The simple solution is to raise the room temps up to the correct ambient temps 80 usually the best way is a oil filled heater. Racks also do best with higher ambient temps so it isn't really am issue as you will need one later anyway.

It is possible to run with out doing this but it is difficult and expensive, I run a rack in a cool room temp and unless there is some pressing reason why this is the only way I advise against it.