why heating gas line doesn't appear in the fuel breakdown graph in the simulation result in design builder?

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hello, i want to compare the energy consumption of 3 model atrium building. the first model has one central atrium. the second model has two central atrium with the same area and volume in compare to model one,and the third has four central atrium with the same condition to model 1 and 2. when i run the simulation, no "heating gas" line appears in the fuel breakdown graph.can anyone help me?