The main definition of a Powerhouse is a building that shall produce at least the same amount of energy from on-site renewables as the energy used during construction, manufacturering of materials, renovation, demolition and operation exclusive energy used during manufacturering of equipment such as PCs, coffee machines etc. In addition the exported energy shall in average not have less quality than the imported energy. This implies that produced and exported electricity can offset corresponding amount of imported energy for both electricity and thermal purposes, while produced and exported thermal energy cannot offset imported electricity. The building shall also as a minimum fulfil all the requirements of the Passive House standard according to NS 3701.

The first Powerhouse renovation building will be built at the Kjørbo site in Bærum, and start of construction was in March (2013). For the Powerhouse Kjørbo project, PV panels will balance the energy needed during it’s lifetime. The two buildings will thus export more electricity than it will use for operation. A geothermal heat pump, in addition to waste heat from the data/server room, will cover the heating and cooling demand. There will be no export of thermal energy. In a broader environmental perspective, an aim of this project is also to achieve the classification “Outstanding” in the BREEAM-NOR environmental certification scheme.

The heated useful floor area of the two office buildings at Kjørbo, which will be renovated to plus-energy standard, is about 5.180 m2, distributed on 3 or 4 floors. Energy efficiency measures and materials with low embodied energy have been crucial for obtaining the energy goal. A very efficient ventilation concept has been developed.

Powerhouse Kjørbo is a ZEB pilot building, i.e. a pilot within the Research Centre on Zero Emission Buildings (www.zeb.no). Therefore an aim is also very low greenhouse gas emissions during the building’s lifetime.

Calculations indicate that the energy balance during the building’s lifetime, and within the defined definition, fulfils the goal of plus-energy.

The aim of the Norwegian research centre on Zero Emission Buildings(ZEB) is to develop competetive products and solutions of buildings with zero emission of greenhouse gases related to their production, operation and demolition.

However, to develope solutions and concepts for zero emission buildings it is first necessarry to develop a sound definition of ZEB (for single buildings, and also cluster of buildings). During the first 3 years of the centres running, significant work have been done to adress different issues related to the ZEB-definition, among them defining CO2 factors for various energy wares. Work done in the International Energy Agency (IEA), and European organisations in light of the revised Energy Perfomance Buidling Directive (EPBD) have been an important basis for the ZEB-defintion work. Experience from the design process of 7- 8 ZEB pilot building projects comprising approximately 100 000 m2 floor area has also been an important background for the agreed ZEB-definiton. The ZEB-definition consist of nine points