Asset rating: disagreement between the results obtained from software for energy certification

The general practice for establishing the consumption in asset ratings of a building consists of entrusting the energy analysis of the shell of a building to calculating software. The building is the subject of an extremely complicated analysis, and there are many variables at stake, is it more correct to aim for a simplification of the problem, in the knowledge that behind every analytical formula there is the possibility of an evaluation error, or is it better to aim for calculation models that are more and more detailed in an attempt to succeed in predicting the real energy behaviour of