Hi leonardlluz, and thanks for answering.
No, they did not share anything. I proceeded in this way: I joined the top's height points with the polygons shapefile. The join was based on the location, set as "internal". I did the same with the bottom height. Then, in the attribute table I subtracted the bottom from the top, gaining the exactly value.
Anyway, the last one is not correct, because lots of buildings have incorrect heights (comparing with the point cloud), and some buildings have strange forms.
For now i resolved, changing manually just the buildings near my project's area, but I'm sure, that there will be a workaround to resolve this problem.
Thanks again, regards.