Energy efficiency: first energy-positive building renovation

Greener together

2 March 2017

Claudia Conway explains how a strategic alliance enabled the first energy-positive building renovation in the world

It would be rare to find a major office retrofit today that did not involve improving a building’s energy efficiency. But one project in Norway has gone beyond simple improvement: IPowerhouse Kjørbo outside Oslo now produces more than it uses, becoming the first ‘energy-positive’ building renovation, as well as the first to be awarded the BREEAM-NOR rating of ‘Outstanding’. Over its designed lifespan of 60 years, Powerhouse is set to produce enough renewable energy to offset all energy used in producing building materials and in the building’s construction, use and demolition.


The project redeveloped 2 typical office buildings of 3 and 4 storeys built in 1980. Although these themselves may have been unremarkable, an innovative alliance came together to renovate the buildings into an energy-positive site. The partners were:

ZERO is a non-profit foundation committed to limiting anthropogenic climate change, meeting the world’s growing energy demands without harming the environment, and working towards zero emissions. Asplan Viak was meanwhile to become the building’s occupier, seeing it as an ideal space to represent its work in sustainability.

Each member contributed its technical expertise to the success of the project. “The result is solutions that we would never have come up with individually,” said Kim Robert Lisø, chief innovation officer at Skanska Norway and managing director of the Powerhouse collaboration. The collaboration ran 4 workshops with these partners to begin the process, covering the following.

  • Project ambitions: this concentrated on technical aspects of the project such as building volume, site placement and low-impact materials.
  • Area efficiency and flexibility: this session concerned market testing, and was followed by smaller working groups focusing on their respective remits.
  • Bringing together all groups’ findings.
  • Finalising the solution and ensuring original objectives have been met.

Building information modelling was used extensively to manage safety, control quality, spot defects and keep all managers informed via a central database.

Sustainable energy

Solar photovoltaic panels meet the building’s power needs, producing about 225,000kWh annually, or 43kWh per square metre of heated useful floor area per year. Previously, the buildings’ energy consumption was 250kWh/sq. m/year, but now it can function on far less as a result of the various measures that keep the building well insulated but also naturally cooled.

The need for shafts, valves and automatic steering for the ventilation was reduced by well-insulated windows, exterior walls and roof. It was also supplemented by 10 energy wells that were bored 200m into rock beneath the buildings to cool them during the summer months and provide natural heat in the winter. The building has achieved a 60% greater airtightness than is required by Norwegian passive house standards for commercial buildings (NS 3701). Daylighting has also been carefully designed to minimise the need for electric lighting, and the artificial sources that are used are energy efficient.

The net result is that, once energy used for producing materials is deducted, the building produces a surplus of energy. It has surpassed expectations for energy production, thus increasing revenue for the buildings’ owners and demonstrating the value of sustainable buildings. More than 3,000 tour groups have been taken around the buildings at Kjørbo to date, reflecting the intense level of interest in creating ultra-efficient buildings.

The work continues

The Powerhouse collaboration is going on to work on further energy-positive projects, including a Montessori school near Oslo and another Powerhouse office building at the Brattørkaia development in Trondheim, which will be the most northerly energy-positive building in the world.

Powerhouse Kjørbo has shown that energy-positive development is possible even in cold climates such as in Norway, and that huge improvements can be made while retrofitting the sort of ordinary office building found around the world. It also exemplifies how collaboration between stakeholders, including nongovernmental organisations and suppliers, as well as a workshop approach can offer innovative solutions.

As the pressure increases for buildings to lower their emissions in a world where so many are expected to be in use well into the future, perhaps those considering refits should be looking north.

Claudia Conway is Editor of the RICS Property Journal.

Further information

  • Related competencies include Sustainability.
  • This feature is taken from the RICS Property journal (December 2016/January 2017).