The property, located at the corner of Lygten and Rentemestervej in Copenhagen’s Northwest district, just a stone’s throw from Nørrebro City Center and the train station, is a three-story commercial building with a basement, built in 1985.

The building was previously demolished and rebuilt, and is now scheduled for another renovation.

The building consists of two wings facing Lygten and Rentemestervej, respectively, with a connecting wing at the corner that links the two wings. The building was originally constructed for KONE Elevator, but until the current renovation, it housed KEA—Copenhagen Business Academy, offering IT and multimedia programs.

Lygten 37 is thus an existing building where commercial space is to be constructed from the ground floor up to the second floor, and from the third floor up to the fifth floor, a three-story addition will be built to house 75 student apartments. The student housing units are prefabricated modules manufactured in Lithuania, each with its own kitchen, toilet, bathroom, and balcony—this renovation and addition covers approximately 8,000 m².

At the corner of the existing building, a new connecting structure will be built to serve as a stairwell with an open entrance facing the courtyard. Open spaces for recreation will be primarily located in the courtyard, though a small number of the existing parking spaces will be retained. Car parking will be maintained in the existing basement, which will also be fitted out with storage rooms and mechanical and electrical equipment.

The existing building is a precast concrete structure with concrete facades and slabs, and concrete columns in the central load-bearing line. To avoid placing additional loads on the existing structures and to comply with fire safety requirements, the superstructure has been designed as a separate building spanning one of the existing wings.

The superstructure is built with a steel frame and rests on columns that extend down through the existing structure. From a structural standpoint, these are therefore two separate structures: an older structure consisting of the existing precast concrete elements and a new steel building.

The project is highlighted in the Danish Agency for Social Affairs and Housing’s “Guide to the Reuse of Load-Bearing Structures” (2023), prepared in collaboration with ABC and the Danish Technological Institute, as a green pilot project. The study shows that the transformation resulted in a 51% reduction in CO2 emissions compared to a similar new construction project. By reusing as much as possible, we avoid the production of CO₂-intensive structural elements. In the Lygten 37 project, this has been a key priority, resulting in such a significant CO₂ reduction compared to a complete demolition and new construction. This reduction potential was a decisive factor in the decision to build on top of the existing building, even from the early project phases. The report “Guide to the Reuse of Load-Bearing Structures” (2023) from the Danish Agency for Social Affairs and Housing states, among other things:

“By transforming the existing building at Lygten 37, 51% of total CO2 emissions were saved compared to rebuilding it from scratch.

The existing concrete structure covered approximately 6,680 m², including the basement, to which approximately 2,925 m² was added above one of the existing buildings, representing a 44% increase in floor area. When considering CO₂ emissions, it is evident that the emissions from the construction of the new areas account for approximately 50% of the total emissions that would have been generated had all 9,605 m² been built from scratch. This is despite the fact that the new areas account for only 30% of the transformed structure.

The primary reason for this is that the new floor area is constructed of steel, but also that it does not rest on the existing building below it. Instead, the new three-story building is supported and braced by a newly constructed steel frame that penetrates the existing structure. It is also worth noting that although the increase in square meters in this case has a relatively high CO2 footprint, the alternative solution would have been to demolish the existing building and build a new one from scratch.

To achieve a building with the desired square meters, this solution has therefore still resulted in a net reduction in CO2 emissions. The difference in CO2 emissions between new construction and renovation is not small enough to justify building the same number of square meters as a new structure."

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