comparing result of energy plus output and design builder output

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Dear all, I am working on thesis. I have started with previously found some simulation results that was done in energy plus. So I am using those as base and also for verification as I am using Design builder for my work. I have applied exactly same inputs for all models. But some models shows 0% difference and some shows 10%. But I expected if some show 0% difference, other should show same or close result. Can anyone help why this is happening. I you need more info, I can provide that. Is there any allowable difference when using two different software? For some input I could not use same, but close one.

Regards Tamanna