Boundaries, along with metrics, decide the definition of zero energy buildings. NZEB definitions are energy accounting methods whereas balance boundaries are physical thresholds for energy accounting.
Balance boundaries basically define the eligible location of supply side RE generation technologies. Renewable energy sources outside the boundary cannot be Defining the boundary is equal in importance to defining the NZEB itself. Usually, defining the type of NZEB also delineates its boundaries and vice versa, drawing the boundary controls whether a building can be site, source, cost or emissions NZEB.