The building sector plays a significant role for the energy consumption in every country. New domestic buildings are often built with an envelope and heating system aimed at a low energy usage and with a potential for application of renewable energy technologies, such as heat pumps. For multifamily buildings, the challenge to apply heat pump technologies and renewable energy is more complex due to technical aspects as well as economical. While in some countries multi-family houses are often owned by local cities, communities or housing corporations, in other countries ownership is private and divided into separate flats.

Multifamily houses bring along a range of heat demand characteristics. Firstly the share of domestic hot water demand on the overall heat demand varies due to varying building standards as well as different climates. Secondly, the temperature level of the heating system is influenced by these aspects as well as by the installed heating transfer system. Henceforth, dealing with the variety of heat demand characteristic bears the challenge on the way to a broader spread of heat pumps in multifamily buildings.

Heat pumps – those powered by electricity, as well as those using fuel – have a significant potential for reducing the specific CO2 emissions for the heat supply in multifamily buildings. However, this potential is connected with special demands on both sides: the domestic hot water preparation and the heat transfer system (heat sink) as well as the utilization of environmental energy at site (heat source).


This Annex will focus on solutions for multi-family houses with the attempt to identify barriers for heat pumps on these markets and how to overcome them. In respect to the demand of the participating countries new buildings and retrofit will be considered as well as buildings with higher specific heating demand.

Particularly the following issues will be elaborated:

  • How to stimulate an increased use of heat pumps in multi-family houses
  • Enhancement of heat pump systems and/or heat pump components for their adaptation in multi-family buildings (scalable power range, high-temperature heat pumps, double stage compressors, inverter technology, etc.)
  • Development and demonstration of concepts for application of heat pumps in energetically renovated buildings and in buildings without improved building envelope
  • Finding the optimal bivalence temperature for bivalent or hybrid systems
  • Demonstration and monitoring of technical solutions (in prototype or market phase)
  • Identification of needs on the characteristics of HP components and figuring out, which are neither fullfilled by market available products nor a scope in ongoing research and development projects; making recommendations for future research and development needs
  • Presenting recommendations for the optimal (multi) heat source and operating mode (fuel driven, electric driven, hybrid) solutions depending on building type and ecologic-economic situation and climatic zone (weather, design temperature)
  • Close cooperation with companies in all relevant technology areas, as well as with the housing societies


Task 1 – Market overview, barriers for application, system classification

⇒ Country Reports: Market structure, market players, products, available systems and configurations, legislation, energy supply scenarios etc.

⇒ Product (system) analysis and classification (with regard to different multifamily building types)

Task 2 – Modeling and simulation of systems, economic models

⇒ Collection of existing and development of new models

⇒ Definition of the systems to be studied through simulations

⇒ Simulation of various systems in wide range of operating conditions (type of buildings / insulation, climates, applications, energy scenarios, heat sources etc.)

⇒ Sensitivity analysis and application matrix

Task 3 –  Technology development, evaluation and system assessment

⇒ Heat pumps with better modulation or cascaded systems

⇒ Heat pumps for higher supply temperatures

⇒ Compare centralized vs. decentralized systems

⇒ Compare different sources, e.g. facades, ground, air, waste water

⇒ Identification of “best solutions” depending on building, climate or other criteria

Task 4 –  Demonstration and monitoring

⇒ Reach a common definition on system boundaries and performance evaluation figures

⇒ Definition of field test procedures

⇒ Collection and analysis of measurement data

Task 5 –  Dissemination and communication

⇒ Provide information for a broad audience spectrum on the Annex results

⇒ Website and dedicated Wikipedia page

⇒ Workshops for target groups such as installers and planners

⇒ Final report


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