Heat pump retrofit projects for multifamily buildings –An obstacle run

The use of heat pumps in existing multi-family buildings (MFBs) represents an important underexploited potential to help decarbonize the building sector. However, challenges may arise. These could be legal, technical, administrative or financial. Awareness considerations are reviewed here in a Swiss context, including specific examples that can help addressing the situation. Proposed solutions are presented, as are identified paths to improved adoption of heat pump solutions.


Supplying sustainable heat for households plays a key role in the Swiss energy strategy. Heating and domestic hot water needs account for about 30% of national CO2 emissions and MFBs make up about 43% of the built environment. Heat pumps sold in Switzerland are increasingly used for retrofit projects but still only marginally for large buildings. Why is retrofitting large buildings with heat pumps still lagging behind? Mainly because it has long been considered unrealistic. The truth is, such projects are cross-disciplinary with a tendency to multiply the challenges.

There could be several regulatory and financial considerations related to heat pumps in MFBs. In some Cantons where a minimum of 10% or 20% of renewable energy is mandatory for heating system replacements, air-to-water heat pumps are often proved to be the only achievable solution in urban areas. Regarding funding, the situation differs in different parts of the country and range from no subsidy policy for heat pump retrofits to generous ones including the distribution system replacement. A lack of subsidies either stems from technology reluctance or, in contrast, because they are considered the most profitable option in the long run. The Swiss tenancy law is a barrier. Large buildings are mainly inhabited by tenants who do not contribute financially to heating system renewal even though they would benefit from cheaper resulting energy charges. Owners therefore lack an incentive to opt for a renewable solution. To help carry out projects, a successful energy contracting system has been implemented in Geneva by the local public utility SIG. Implementing a heat pump often requires constructive adaptations, which triggers a building permit application procedure for these works related to noise, environment and fire protection for example. This can become an administrative nightmare. Cultural heritage laws make it even tougher in old city centers, where patrimonial protection could be a barrier. This can, however, be overcome with a solution where coolers are ingeniously hidden underneath painted grids.

When it comes to technical considerations, these often are related to lack of silent standardized procucts with sufficient capacity. Capacity issues could be solved by cascading smaller products or by tailor made products. A relatively noisy heat pump impact can be limited through a wise implantation. Hydraulic integration schemes should be specifically developed with the manufacturer to reliably integrate the heat pumps with the constraint of existing heat and DHW distribution systems. The dimensions and weight of the heat pump and storage tank are critical since a lack of available space may compromise a project. Heat pump projects require technical engineering expertise and a solid understanding of laws and finance. The usual skills needed for small installations in single-family housed are often not sufficient.

To conclude, various challenges can stand in the way of large heat pump retrofit projects MFBs. However, realized examples of a variety of sizes and solutions, as presented by HPT Annex 50, should inspire and encourage more such projects. Environmental awareness and the desire to maintain property values are already driving owners to choose heat pumps even for larger buildings. The evolution of the regulatory framework following the energy transition strategies and the will to develop adapted tools and training prove that this topic has been identified as important.

Nicole Calame,
CSD Ingénieurs SA, Switzerland

The text has been shortened by the HPC team

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