Sorry to ask a primary question. I simulate the building model using Ideal loads air system with outdoor air. In the beginning, I considered the districting cooling and heating energy as the cooling and heating energy requirements. However, when I sum all zones cooling and heating energy (Output:Variable:Zone Ideal Loads Zone Total Cooling Energy),the result has a big difference from district cooling and heating as follow.

I can understand the zone total cooling energy is bigger than district cooling because the outdoot air.But in the winter, the outdoor air should also enlarges the zone total heating energy which ought to bigger than district heating. However the result is opposite. In additional, If the district cooling and heating is the heating and cooling energy requirements, then how to statistics each zone' s heating and cooling energy requirements.