Energy saving retrofit in a heritage district: The case of the Budapest

Planning an energetic retrofit for heritage buildings faces several limitations, as multiple protection guidelines narrow down the possible energy efficiency interventions. The present study introduces an energy saving but at the same time heritage respecting retrofit methodology, using the European Union directives as a baseline. The case study area in Budapest, Hungary contains traditional apartment houses, built around the turn of the 19th-20th century. Their physical and energetic state are deteriorated, resulting in demolitions, which endanger historical values. Concerning climate, according to the Koppen-Geiger climate classification, Budapest belongs to the humid continental climate group 'Dfb', and heating energy is the most significant part of households' energy usage. After investigating the limitations of heritage protection, the authors introduce combinations of structural and engineering system upgrade scenarios, aiming to reach the European Union nearly zero-energy level. The retrofits' effect on the buildings' energetic characteristics were surveyed. The results were compared to find optimum solutions balancing between heritage preservation and energy efficiency. The calculation results show that reaching nearly zero-energy level is possible with heritage respecting solutions. The traditional apartment houses have high energy saving potential, heating and domestic hot water energy can be reduced by 69% with certain upgrades. The methodology and results are based on numerical analyses. The paper introduces an estimation method for the energy saving potential of the above building stock, using simply accessible data. The significance of the typology-based and fast estimation is that it can be used for efficient decision support when planning a large-scale retrofit.