Historical Evolution and Scenarios Up to 2050 of Heating Energy Consumption and CO<sub>2</sub> Emissions of Residential Buildings in Vienna

Abstract

Today, the building sector poses a major problem concerning fossil fuel energy consumption and the corresponding emissions of local pollutants and global greenhouse gases (GHG). In addition, an increasing number of people are living in urban areas, and it is becoming challenging to provide the necessary living space and energy for heating in fast-growing cities. Currently, urban areas host approximately 50 % of the global population and generate 70 % of GHG. The core objective of this study is to analyze the historical development and to derive scenarios for the possible future development of the overall CO<sub>2</sub> emissions in residential buildings in Vienna up to the year 2050, considering all relevant emissions from final energy, as well as the embedded emissions from the construction of new buildings, retrofitting, and rooftop apartment extensions. This study indicates the following key points: (i) The renovation of buildings by improving the thermal quality is the most favorable scenario strategy and produces the least CO<sub>2</sub> emissions. (ii) The transition to the sustainable heating of buildings requires at least a temporary "investment" in embedded CO<sub>2</sub> emission, e.g., in retrofitting and insulation of buildings to harvest reductions in CO<sub>2</sub> emissions in the long run, from a smaller amount of energy used for heating. The major conclusions of this study are as follows: (i) To implement the most favorable renovation scenario, strong policy measures are required, such as standards for new buildings and for building retrofitting, as well as subsidies to ensure an accelerated refurbishment rate of the old low thermal building stock. (ii) It is important to reduce the CO<sub>2</sub> emission of the final energy carriers, especially of district heating, by increasing the usage of renewable energy carriers such as biomass, solar, and geothermal.