All apartments and houses by law must have an energy certificate here. There's a high level EU directive but the details are by country. https://en.wikipedia.org/wiki/Energy_Performance_of_Building...

However, it has its pitfalls and critics. Anyway, there the energy consumption is calculated from areas and insulation U values and so forth.

Don't know what would be the actual biggest problems against launching something similar elsewhere like in USA.

Probably one could build a software product to estimate these things. Especially easy during construction if the drawing data can be used directly. If things are drawn with CAD that is. But it might be relatively easy to estimate even from photos of paper drawings...

Estimates done from the design are pretty common, and BIM programs (Building Information Management) like Revit integrate all of the construction details into the design model, so they are able to automate some of those calculations. But BIM programs are not great design tools (not sure if that's an inherent conflict or if there simply aren't any good ones) so they are not popular for smaller jobs like single-family homes where you can use drawings produced directly from a tool that provides a better user experience for design.

Unfortunately, the drawings don't give you any assurance that the construction details are done correctly. Corner-cutting aside, a contractor may depart from the design with good intentions and accidentally create a thermal bridge that sucks heat in or out of your house.

Drawing estimation, outside vs inside temp + heating energy monitoring, heat camera pictures and some kind of other measurements could probably create a reasonable certificate that would be reassuring to house buyers. Or even if the owners are the same but there was some significant renovation being done, one could do that to see if the renovation was done properly.