According to Sheldon in the Big Bang Theory the optimum temperature is 23'C (73.4'F), he was close but slightly out according to Cornell University, the best temperature for the best productivity is 22'C (71'F).
At 20'C (68'F) it can cause of 44% more errors and/or half as productive as when the temperature was 25'C (77'F).
For sleep however the best range for sleeping is 15.6-19.44'C (60-67'F). (Although remember our bodies need to drop 1 degree to fall asleep as well). Apparently a constant 66'F (18.9'C) helps burn calories.
Remember that computer screens and other electronic devises give off heat, and not the good kind.
the best kind of heat is the natural sun so sitting by a window will have a lot more benefits than sitting in a cubicle.
Have a humidifier for indoor ventilation, this will also keep the air moist and stop your skin from drying out too much, the more natural option is to open the window however you may want to avoid this if you live in a polluted or high pollen area.
