18 May 2017

P.1.5.4 Retrofitting fossil-based heating systems with air to water heat pumps in multifamily houses


We have studied three pilot projects of replacing fossil-based heating systems by air to water heat pumps in
multifamily housing in Geneva, Switzerland. The pilot projects are being realized by the local public utility
Services Industriels de Genève (SIG), under its energy program portfolio éco21.
The project is implemented with an owner of 600 buildings in Geneva, who has a legal obligation to reduce
energy consumption and/or increase the part of renewables in its building stock. Feasibility studies revealed the
difficulties of the task: solar is not technically possible (due to complicated old roof, building being under
historical heritage protection, no place available for water storage), geothermy, wood and biomass are not
authorized by law (due to water and air protection regulations). Air to water heat pumps are therefore the only
solution for integrating renewable energy supply into the buildings.
The challenge is important: buildings are old, there is few place and an old distribution system, investment costs
are high, which requires energy consumption to be highly efficient. Due to the age of the buildings and the
restrictions to insulate the buildings envelope, the distribution temperatures are not always compatible with the
ones needed for the high efficiency of the air to water heat pumps. In two cases, the boilers were also replaced
and the systems were made bivalent. The three pilot projects demonstrate technical and economic difficulties and
solutions for integrating air to water heat pump solution in existing multifamily houses, which can be used for development of renewable heat program and energy contracting in Geneva and other locations.