Background and central aspects of the topic
About one third of energy consumption in Germany is accounted for by space heating and hot water. This is why, from an energy and climate policy perspective, the reduction of the energy consumption for space heating and hot water is of great importance. Considerable saving effects are seen particularly in the stock of residential, office and administration buildings. In order to efficiently use investment resources and funding for this purpose, robust and realistic data are required with regard to the saving potential that could be tapped using various technologies (e. g. heat pumps, solar thermal systems, ventilation systems with heat recovery, digital system control and regulation, window replacement, façade insulation). Based on this, the legislator can initiate tangible and effective policy measures to promote energy saving and increased efficiency.
The results of scientific studies on energy savings and greenhouse gas emission reductions differ from each other – in some cases even to a significant degree. This is why it is of great importance to differentiate between the different levels of consideration and also between the different objectives and intended purposes of the energy consumption values: With regard to individual buildings or cases, it must be taken into account that the calculated saving potentials for building refurbishment are based on a number of assumptions (e. g. reference values for heat transfer coefficients, air exchange rates and room air temperatures, user behaviour, heat transfer due to adjacent unheated rooms as well as location-related climate data). The energy demand determined on the basis of theoretical technical and physical calculations of the energy expenditure of a building serves to provide information about the efficiency of the examined building and to furnish an official proof. When measuring energy consumption, however, the aim is to obtain information about the actual amount of energy consumed and the costs incurred. Moreover, it should be noted that the quality of the construction work has a significant influence on the actual energy consumption as well.
Objectives and approach
Against the background of the great importance of energy savings in the residential, office and administration building sector and the deviations between calculated and realised saving effects of the individual technologies, the TA project will examine the cost-benefit ratio of the technologies and energy-efficient building refurbishment measures that are particularly significant for the energy transition. Moreover, the extent and causes of deviations between realised and previously calculated saving potentials will be investigated in order to make – on this basis – a reality-based assessment of the technologies involved and to derive more effective policy measures. The TA project will be carried out in three phases:
- Based on a literature evaluation of relevant published studies, expert opinions and evaluation reports, an overview of expected and realised saving effects, costs and cost-benefit ratios of relevant technologies and measures for energy-efficient building refurbishment will be provided in a first step. This evaluation will be complemented and deepened by expert interviews.
- In a second step, the saving effects and costs will be compared as cost-benefit relations. Furthermore, the extent and causes of deviations with regard to the identified saving effects will be compared. Using the example of significant scientific studies, it will be explained systematically how the energy saving effects were determined in order to point out relevant differences. With regard to the costs of the different technologies, both the acquisition costs and the costs of the use phase will be taken into consideration.
- In a third step, the results of the preceding work steps will be discussed within the framework of a workshop with scientists from universities and research institutions.
In January 2020, as part of the first project phase, an external expert study on energy saving effects and cost-benefit ratios for energy-efficient building refurbishment was commissioned by the German Bundestag. It encompasses the areas of heating, ventilation and air conditioning technology as well as refurbishment measures. Based on this, the results of the expert interviews and workshops were incorporated into the preparation of the final report, which is currently going through the process of approval by the group's TA rapporteur group.