The 1500 m2 extension to the existing research facilities of the Norwegian Meteorological Institute is located just outside Oslo’s City Centre. It accommodates two contrasting uses on two distinct levels. A subterranean level houses the large server park of the Institute, whereas the upper level (which was built to Passive House standard) contains a canteen and meeting rooms for the employees. For the concrete in the lower floor, a ‘low carbon’ cement mix incorporating fly ash was used. The more irregularly shaped upper floor consists of a steel framework with timber infill. Space heating is largely provided by waste heat from the servers on the basement floor. Peak loads in the heating system are covered by local district heating. The waste heat is even used to heat the exterior access area to the building whenever outside temperatures drop below 15?°C.