Copenhagen: Modern retrofitting of a historic buildning

Investigators have used the renovation of the Fæstningens Materialgård, a cluster of buildings which played an important role in the expansion of Copenhagen’s defenses at the end of the 18th century and which are now protected by Denmark’s Heritage Agency, to study how to reduce a structure’s CO2 emissions without compromising its historic value. Since these buildings are now used as offices, investigators not only had to address issues of historic preservation and environmental sustainability, but also to create an attractive working environment.

The process began at the discussion table. Representatives of different groups—landlords, technical engineers, construction engineers, conservation architects, and conservation authorities—gathered to consider possible renovations from a variety of different perspectives. Participants were forced to articulate not only which retrofits they found acceptable but also why they held certain opinions. After a year’s work, they had narrowed their initial list to a set of renovations that would be acceptable to all. The thoroughness and high quality of the discussions make the project’s first phase particularly notable.

Investigators then used a simulation model to determine the reductions in CO2 emissions that would result from the proposed renovations. They concluded that they could achieve 20 percent lower emissions per person using the office space (12 to 13 percent lower emissions overall), even as they improved indoor air quality significantly. After the opportunity arose to use a district cooling system for the building complex, investigators found that they could increase emissions reductions to 40 percent per occupant (approximately 25 percent overall).

Those renovations will now be made to the buildings at Fæstningens Materialgård, and the projections of the initial study will be tested by measuring CO2 emissions after the project has ended. In general, investigators have agreed to renovations that cannot be seen. Thus waterborne cooling systems were acceptable but not airborne cooling systems, replacing window glass but not entire windows, sealing building gaps but not installing exterior insulation, a centralized control system but not rooftop solar panels. The entire renovation project will be completed in two phases, the first beginning in fall 2009 and the second in fall 2010.

The study at Fæstningens Materialgård and the subsequent renovation should prove that it is possible to make substantial reductions in CO2 emissions without detracting from a building’s historic value and that even protected buildings can contribute to the goal of CO2 neutrality. Nevertheless, certain retrofits, most notably the installation of a centralized control system, would be difficult to justify in economic terms. If, however, the price of electricity continues to climb, even a centralized control system would become a sound investment for ordinary house-owners.