An office building of about 2000 m2 heated floor area is being designed for the Norwegian Defense Estates Agency (Forsvarsbygg). The building will be located at Haakonsvern, about 15 km from the centre of Bergen, Norway. The design aims at meeting the ZEB criterion of net zero energy balance for building operation during a year. The energy for operation of the plug loads (computers, printers, etc.) is not included in the balance.