I live in a 2- story home with 2- zone heating. Bedrooms are on the 2nd floor. During the day we set the 1st floor thermostat to about 66 or 67 degrees. In the evenings the thermostat for the 1st floor is set to 58 degrees as the entire family will be asleep upstairs. (I live in the northeast.)

What would be the ideal, (most efficient) setting for the 1st floor thermostat in the evening? My concern is that perhaps we are using more energy to re-heat the 1st floor in the mornings, so perhaps we should only reduce the setting by 2 or 3 degrees.

Also, during the day we greatly reduce the upstairs setting as the 1st floor is heated and the heat naturally rises to the 2nd floor.

Any thought on the subject will be appreciated. Thanks for looking...