The project is one of Denmark’s largest transformation projects ever. The original plan was to demolish the old Høje Taastrup City Hall and build new housing on the site. However, the developer, Ikano Bolig, decided to reuse as much of the existing building stock as possible, and thus Denmark’s largest transformation project of its kind got underway.

An additional floor is being added on top of the town hall, and townhouses are being built on the roof. In addition to the transformation of the existing structure, the project also includes the construction of approximately 130 townhouses ranging from 80 to 115 m² in size and featuring 2 to 5 bedrooms, as well as a 1,500 m² grocery store. This has necessitated comprehensive structural assessments of the load-bearing structures, which were carried out using, among other tools, ABC’s in-house digital tool, ABConcept.

In addition, there is a comprehensive redevelopment of the 100,000 m² city hall site, where green spaces and running trails are being created, shared storage sheds, a 1,500 m² grocery store, and where the old heating plant, located centrally on the site, is being converted into a community center.

Originally, the old city hall was to be demolished. An early estimate showed that it would take approximately 600 fully loaded trucks to remove the construction waste after demolition, not to mention the new building materials that would need to be produced for the new construction. Instead, the decision was made to retain as much of the existing building structure as possible.

Load-bearing structures are often the elements of a building with the highest CO₂ impact, so by reusing the building, the project not only avoids unnecessary transportation to and from the construction site but also reduces emissions associated with producing these new, CO₂-intensive building materials. The client’s goal was to achieve a CO₂ calculation of 2.5 kg CO₂e/m²/year for the project.

Both load capacities and sustainability data for the various structural elements are embedded in the tool, allowing the project team to quickly see how different choices affected both the constructability of the concept and the building’s carbon footprint as a result of design changes.

ABConcept thus reported which structural elements were being utilized at more than 100% capacity due to the new structures built on top of them. Using these analyses as a starting point, engineers and architects were able to discuss various design proposals, such as whether to reallocate volumes or reinforce existing structures where the design had already been finalized.

This provided opportunities to test different building geometries and design proposals on a well-informed basis very early in the process. The analyses allowed for the testing and discussion of various designs, including different placements of rooftop townhouses, and created a far more informed basis for decision-making.