Skanksa is nearing completion of a net-positive “Powerhouse” office building in Trondheim, Norway. Powerhouse Battørkaia, expected to be finished in February, will return electricity to the grid and is being built on a fossil-free construction site. The 18,200-sq-meter building features a sharply angled solar roof to maximize energy generation and a large circular opening to enable sunlight to reach interior offices, says Rune Stene, head of Skanska Technology, Norway, and managing director of Powerhouse, a collaboration of companies, including Skanska, committed to building energy-positive buildings. Seawater is a source of heating and cooling. Skanksa also spent two years developing a concrete mix with lower emissions than conventional concrete, a company spokesman says. “Materials are where the biggest changes will come in the next five to 10 years. … I don’t think we will use different materials—I still see concrete, steel, wood, glass and so on being widely used. But it will be a race to produce versions that require less carbon,” says Stene.