Energy Efficiency Class - How to Evaluate?

Which class on the energy certificate states only how much effort was put into prettifying the calculation of the demand. Case 1: Thick wall layers, ceiling insulation, and triple glazing are enough for a nicely low demand, even if there are thermal bridges everywhere through which your heat escapes in practice. Case 2: The certificate looks bad at first glance, because of only double glazing, etc., but a very thorough job was done during the renovation to ensure tightness, etc., and the actual consumption is lower than in case 1.