Comfort factor

I just posted this as a Yahoo comment reply and it was rejected twice for 
violating community guidelines. I wonder if the suggestion of being able to 
do arithmetic offended them.

A weather station that gives indoor and outdoor temperature and humidity can 
tell you when ventilating with a fan at night will improve comfort, rather 
than running the A/C.

The best comparison is dew points. They can be determined closely enough by 
subtracting 1/3 of the difference between the RH and 100% from the 
temperature, for example 65F and 70% corresponds to a dew point of 55F.