Building Height: Overall height from the lowest point of conditioned space to the highest point. Regardless of the projects varying height, and/or multiple project roofs, the building height should just illustrate the height of the projects thermal envelope.
If your project has a pitched roof, then the building height might include this height if the interior space is occupied attic space. If your pitch roof encloses unoccupied space, then do not include it in your building height calculation. In this case the highest point of conditioned space is the ceiling of the top floor, below the attic space.
If your project has below grade space, do not include height if space is similarly unoccupied or not conditioned.