Reports are available at Annex 30 Publications.


The objective of annex is a survey of the availability, technology, economy, ecology and possible R&D trends of heat pump systems to retrofit low energy efficient space and tap water heating systems in existing residential buildings, taking into account that heat pumps are able to drastically reduce fossil energy consumption and the related greenhouse gas emissions. Space heating systems include first of all hydronic systems including heat sources, heat pumps and distribution systems but also air-to-air heat pump air-conditioners without heat distribution system. Heat pumps for retrofit should include electric heat pumps with zero or low GWP working fluids and gas-fired systems including ab- and adsorption.

Project manager and participating countries

Germany is the envisaged Operating Agent. The other participating countries are: France and the Netherlands.


The objectives will be achieved by common studies performed by the participants for each country /organisation:

Task 1 – State of the Art, Market Analysis

Statistical information on the present status of retrofitting of existing buildings in all participating countries and past and present R, D&D projects directly related to the objectives of the annex. An analysis of the present heat pump technology economically applicable for retrofit of existing buildings in the different climatic regions.

Task 2 – Matrix of Heat Pumps

Development of a catalogue of existing buildings with already improved standard, insulation and medium temperature heat distribution systems applicable for the present generation of heat pumps (air-to-air-, air-to-water-, water-to-water and earth coupled heat pumps).


Collection and analysis of practical applications of heat pumps in existing buildings (case studies and demonstration projects).

Task 3 – Improvement of Components and Systems

Conditions of the development of new heat pump systems for retrofit applications should include

  • electric heat pumps with HFC-refrigerants
  • electric heat pumps with zero or low GWP
  • working fluids, including natural refrigerants, Rankine- and Stirling systems
  • gas-fired heat pumps including Ab- and Adsorption- and Vuilleumier-Systems

Heat sources include:

  • air (air-to-air-systems, air-water-systems)
  • earth coupled systems (earth –collectors and –probes)
  • solar collectors
Task 4 – Overcoming Economic, Environmental and Legal Barriers

The task should include information on the economy and ecology (energy-efficiency and greenhouse gas emissions) of retrofit heat pump systems compared with conventional heating and cooling systems as well as governmental or utility promotion and support programmes. System optimising including heat source with given heat sink (distribution system)