Energy-optimization of historic buildings: A challenge for preservation of cultural values of buildings? Results from a screening of energy-performance of Danish historic multi-story residential buildings

Energy-optimization of historic buildings is often seen as a thread against preservation of historic and cultural values of buildings. Critics have claimed that efficient energy retrofitting is difficult to carry out on historic buildings, as technical interventions such as external insulation of facades and roofs, energy-efficient windows, and PV panels will ruin the architectural value of the historic buildings. However very few studies have actually identified how energy optimization in practice takes place in historic buildings, and how historic buildings are performing energy-wise, compared to ordinary buildings. This paper presents the initial findings from a project that aims to map the energy performance of historic buildings, and to understand how preservation values of the buildings are taken care of in practice. It is based on combining the Danish database of the SAVE-registration system (Survey of Architectural Values in the Environment) and the database of EPC (Energy Performance Certificates). The main result of the analysis is that residential multi-story buildings with high preservation values are energy-preforming at least to the same level as traditional buildings. This is a somehow surprising result, and the paper explains some of the reasons behind this, and how energy-optimization takes place in practice. Another main result is that “deep renovations” which are often hailed as a desirable strategy for energy optimization, hardly ever takes place in practice. Instead, almost all buildings with high SAVE-values and high EPC-scores have used a stepby-step approach to energy optimization. The paper will discuss the results in the light of the ambitions for reducing CO2-levels in the existing building stock, and current policy interventions, e.g. the new EU-directive on energy efficiency of buildings.