The KIWI in Lerberg, to the west of Oslo, can rightly call itself Norway’s greenest supermarket. The building with the striking curved roof is the product of an architectural competition which was won by the renowned A-Lab architects. But the shop is not just an eye-catching building for KIWI, it also sets a standard for ecological sensitivity. The focus of the design was on maximum energy efficiency and a minimal CO2 footprint, resulting in full wooden construction. The walls are made of cross-laminated timber (CLT) and the signature roof structure was created using Kielsteg. The Kielsteg wooden construction elements gave the designers a lot of architectural freedom. Despite the need for a high load rating, to allow for the green roof and snow, the required roof span of 40 m, divided in two 20 m sections was achieved using only one row of internal supports, and with relatively low-profile roof elements, only 80 cm high. The 2,200 m² of green roof fits gently into the natural surroundings. The roof vegetation also helps maintain biodiversity and creates a habitat for many insect species.