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The function that performs this calculation is here:

https://github.com/NREL/EnergyPlus/blob/9814fa5069b4cf52457ff0f9d18c7422f83eb33a/src/EnergyPlus/ThermalComfort.cc#L2442

Whether the zone is occupied is determined here:

https://github.com/NREL/EnergyPlus/blob/9814fa5069b4cf52457ff0f9d18c7422f83eb33a/src/EnergyPlus/ThermalComfort.cc#L2216

Basically it adds up all time periods that any zone is outside the range of the threshold (which is 0.2 C unless specified by the user) during occupancy.

A few things to check:

• Are you using hourly values,this may not match up because the algorithm does this for each timestep.

• Occupancy is when greater than zero

• Heating and cooling times are calculated separately

• Heating not met is when colder than the setpoint minus the threshold

• Cooling not met is when hotter than the setpoint plus the threshold

You also should think about checking against the output variables:

• Zone Heating Setpoint Not Met Time [hr]
• Zone Heating Setpoint Not Met While Occupied Time [hr]
• Zone Cooling Setpoint Not Met Time [hr]
• Zone Cooling Setpoint Not Met While Occupied Time [hr]
• Facility Heating Setpoint Not Met Time [hr]
• Facility Cooling Setpoint Not Met Time [hr]
• Facility Heating Setpoint Not Met While Occupied Time [hr]
• Facility Cooling Setpoint Not Met While Occupied Time [hr]

I hope this helps you figure out the difference.