By Environment Correspondent Alister Doyle

SANDVIKA, Norway (Reuters) - Two office blocks by the Oslo fjord will generate more power than they use from 2014 after a radical refit meant 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 percent 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. Yet about 80 percent of existing buildings in developed nations will still be standing in 2050, by when governments are planning deep cuts in emissions.

"There is a huge global potential" in renovations, said Svein Richard Brandtzaeg, chief executive of Norwegian aluminum group Norsk Hydro which is a partner in the Powerhouse alliance behind the 110 million crown ($20 million) project near Oslo.

"We believe this is the first time in the world that a normal office block is being renovated to such strict standards," he said of the 3 and 4-storey blocks in Sandvika, south Norway, with space for more than 200 workers.

The renovation will use a heat-retaining black wooden facade, an interior design that makes air flow without fans, and high-grade insulation to cut energy use by up to 90 percent. Backers say it will make long-term economic sense by eliminating bills for heating and lighting.

And 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, hoping for new orders if successful. Aluminum will be widely used, such as in window frames.

NEAR ZERO ENERGY STANDARD

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. California has a "net zero energy" standard by 2020 for residences.

The U.N. 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 one percent of buildings a year to meet goals of cutting greenhouse gas emissions by 80 percent 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 percent of the existing building stock will still be around in 2050. In China and India, 80 percent of the buildings in 2050 have yet to be built," he said. Continued...