Norway's Oslo Airport has received a smart-looking new terminal extension courtesy of local architects Nordic – Office of Architecture. Featuring an attractive curved form, the building is hailed as the "world's greenest terminal" by the firm and certainly boasts an impressive amount of sustainable and energy-efficient design.

Nordic designed Oslo Airport back in 1998 and its new extension has been in the works since 2009 before finally opening this week. It consists of a 300 m (984 ft)-long new building that provides an extra 115,000 sq m (1,237,849 sq ft) of floorspace, doubling the size of the existing terminal building.

The project has increased the airport's overall capacity from 19 million to an estimated 30 million passengers per year. Public transport links have also been improved and up to 70 percent of passengers can now potentially arrive by public transport.

Natural and recycled materials were used during the extension's construction and it includes curved glulam beams and recycled steel. Nordic also used concrete mixed with volcanic ash. This is said to be more environmentally-friendly than standard modern Portland cement-based concrete by its proponents, in part due to the lower temperatures required to mix it and an expected longer lifespan.

Indeed, it's a similar mix to that used to construct Ancient Rome's buildings, which have certainly stood the test of time.

In a nice touch, snow from the airport's runways will be collected during winter and stored to use as coolant in summer. The interior is mostly lit with natural daylight during the day thanks to extensive glazing. A panoramic window dominates the north end of the building, while additional windows and a skylight are also installed.

The shape of the terminal extension and its glazing promote passive solar heat gain, warming the interior naturally in the right conditions. Green walls and water features are installed inside and meant to invoke Scandinavian forests. Duty free retail units are conceived as organic stone forms associated with Norway's landscapes, and – judging by the photos – the interior looks spacious and light-filled.

The terminal extension has excellent insulation and has achieved Passive House-level performance, which is impressive as Passive House is a very stringent green building code. The building also achieved the world's first BREEAM "Excellent" sustainability rating (another leading green building code) for an airport building.

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