Workers stand at the entrance to an office block in Sandvika that will be renovated to become "energy positive"

Office blocks rennovated to be 'energy positive'

A radical refit will mean two office blocks by the Oslo fjord will generate more power than they use from 2014.

The 110 million krone (£12.8m) project in Sandvika, near Oslo, is being undertaken by the Powerhouse alliance to show that the world's energy-squandering building sector can do more to fight climate change.

Geothermal and solar energy generated on site will make the 1980s buildings "energy positive" in a tiny step to cut demand from the building sector that burns about 40 per cent of world energy and emits a third of man-made greenhouse gas emissions.

So far, most focus in green energy has been on new buildings, not refits, but about 80 per cent of existing buildings in developed nations will still be standing in 2050, by which time governments are planning deep cuts in emissions.

Svein Richard Brandtzaeg, chief executive of Norwegian aluminium group Norsk Hydro, which is a partner in the Powerhouse alliance, believes there is “huge global potential" in renovations.

"We believe this is the first time in the world that a normal office block is being renovated to such strict standards," he said.

The three and four-storey blocks, which has space for more than 200 workers, will use a heat-retaining black wooden façade, an interior design that makes air flow without fans, and high-grade insulation to cut energy use by up to 90 per cent.

Backers say it will make long-term economic sense by eliminating bills for heating and lighting. An energy-positive refurbishment in Norway, where winter cold pushes up heating bills and scant sunlight makes solar panels inefficient, would show that they can be achieved anywhere in the world.

"We see it ... as a big possibility for us to take a strong market position," Brandtzaek said.

The on-site electricity will more than cover lighting and heating and the energy used to produce and recycle building materials but it will not cover energy used by equipment brought by the tenants, from computers to coffee machines.

One problem faced by the team is that tall elm and ash trees shade the coastal site where workers are tearing out insulation and other fittings this month.

"There aren't optimal conditions for solar energy," said Fredrik Daehli, project manager at construction group Skanska.

The European Union says that new buildings owned by public authorities will have to be "near zero energy" from 2019 and other new buildings from 2021 and California has a "net zero energy" standard by 2020 for residences.

The UN Environment Programme says the building sector has the biggest potential of any sector – from industry to transport – for big and money-saving cuts in emissions of greenhouse gases that are released by burning fossil fuels.

In rich nations, the rate of renovations would have to triple from 1 per cent of buildings a year to meet goals of cutting greenhouse gas emissions by 80 per cent by 2050, said Peter Graham, head of the Global Buildings Performance Network.

Meanwhile, emerging economies led by China and India need stricter codes for new buildings and cities, he said.

"For Europe and the United States more than 80 per cent of the existing building stock will still be around in 2050. In China and India, 80 per cent of the buildings in 2050 have yet to be built," he said.

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