Heat pumps in terraced houses: is it possible?

Terraced houses differ from detached houses and apartment buildings in their characteristic construction: shared walls, limited land area, and immediate proximity to neighbors. This has both advantages and disadvantages for heat pump technology.

Advantages in terraced houses:

• Significantly smaller exterior wall areas than in detached houses lead to less heat loss.
• According to Fraunhofer ISE, the average heating load of a terraced house is between 5 and 8 kW – about 30% lower than in single-family homes.
• This optimal size is easily covered by modern air-to-water heat pumps.

Special features to consider:

• Lack of space limits the choice of heat pump type.
• Sound propagation between houses that are close together is a sensitive issue.
• Neighborhood regulations on distances and noise protection must be observed.

In order for a heat pump to be installed in a terraced house in a way that is effective, practical, and, above all, does not cause problems with the neighbors, a number of requirements must be met:

1. CLARIFY SPACE REQUIREMENTS

Air source heat pumps require surprisingly little space. The outdoor unit requires a level surface measuring approximately 2x2 meters. Geothermal and groundwater heat pumps, on the other hand, have completely different requirements: These require large-area ground collectors or complex well drilling, which is often a deal-breaker in cramped terraced house layouts.

2. CHECK THE HEATING SYSTEM

An often underestimated point: Are the existing radiators suitable? Modern heat pumps in particular work more efficiently with low flow temperatures. For terraced houses, the following therefore applies:

• Optimal scenario: Flow temperature 30–35 °C (for underfloor heating or low temperatures)
• Realistic expectation for older buildings: 50–55 °C is often sufficient
• Perform a test: On frosty days, lower the flow temperature to a maximum of 55 °C – do all rooms get warm? Then your house is suitable

Hydraulic balancing of the heating system is mandatory during installation and significantly improves efficiency. This is particularly important if you want to operate your heat pump with radiators.

3. PERMITS

Different building regulations may apply depending on the region and municipality. It is best to check with the relevant local building authority or municipality to find out whether your planned heat pump requires a permit. You are also welcome to book our free consultation for an initial assessment.

In most cases, air-to-water heat pumps are standard for terraced houses. They extract heat from the outside air and do not require any complex drilling work. A major advantage is that they can also be installed in a basement, boiler room, or attic if necessary.

Although ground source heat pumps are theoretically more efficient, they are usually not practical for terraced houses. The reason: they require a lot of space for the ground collectors or ground probes and involve complex drilling. In densely populated areas, they therefore quickly reach their limits and are therefore less suitable.

If you only want to heat water with a heat pump, you might consider a hot water heat pump. These usually do not require any complex drilling and are therefore generally well suited for use in terraced housing estates.

Noise protection is the biggest issue in terraced houses. This is not only due to the noise emissions of a heat pump, but also to the special acoustics of terraced houses.

In a row of houses, sound reflections have a different effect than in isolated buildings:

• Reflection on facades: The sound is “trapped” between the house fronts and amplified.
• Courtyards and carports: These act as natural sound amplifiers.
• Operating conditions vary: Defrosting, full-load operation, and night operation produce different noise profiles.

A modern air-to-water heat pump generates 45–60 dB(A) at a distance of 1 meter, which is roughly equivalent to the noise level of a refrigerator. At night, at a distance of 3 meters, the value is already below 30 dB(A) – but sound propagation must be taken into account on the way there.

THE APPLICABLE LIMIT VALUES

In most countries, binding emission limits apply to technical installations, which vary in severity depending on the type of area (e.g., purely residential area, mixed-use area) and time of day. As a rule, the sound pressure level measured at the neighbor's nearest room requiring protection is decisive.

The values are measured at the nearest window of the neighbor's rooms requiring protection:

Typically, higher limits apply during the day than at night, as nighttime quiet hours are particularly protected.
The critical point for heat pumps lies in the nighttime limits, which are significantly stricter.

DISTANCE RULES FOR NOISE PROTECTION

The minimum distances to neighboring boundaries required by building regulations are not uniformly regulated internationally and vary depending on national and local building laws.

Minimum distances of around 2 to 3 meters are common, although in many countries it is not the distance itself that is decisive, but compliance with the permissible noise limits.

Beyond noise and the mere distance to the property line, there are several other aspects of neighbor law to consider. The so-called neighbor uses are particularly crucial:

• Bedroom windows: Is there a bedroom on the neighbor's side that faces directly toward the heat pump? This is the most critical scenario.
• Terraces and recreation areas: Outdoor seating areas need protection and can be problematic if incorrectly positioned.
• Ventilation openings: Open windows or ventilation systems at the neighbor's property increase the perception of noise.

Two identical distances to the neighbor can therefore be assessed completely differently in terms of their need for protection.

Yes, a heat pump also works in an older terraced house. Terraced houses from the 1980s and 1990s are often not fully energy-efficient, but they have smaller exterior wall areas than detached houses. Flow temperatures of 50-55°C are often sufficient here, and careful hydraulic balancing, realistic flow temperature control, and possibly retrofitting larger radiators can ensure optimum efficiency.

Government subsidy programs (building renovation)

• Basic subsidy: In many countries, 20–30% of eligible investment costs are subsidized.
• Replacement bonus: Additional subsidies for replacing a fossil fuel heating system with a heat pump.
• Technology bonus: Additional subsidies for particularly efficient systems or environmentally friendly refrigerants.
• Total possible: Depending on the state, subsidies of 30–40% of the investment costs are realistic.
  
• In some states, individual renovation roadmaps or energy consultations increase the subsidy rates even further.

This means that, after subsidies, the effective costs of an air-to-water heat pump in a terraced house can be significantly lower than the list prices, depending on the national subsidy framework.

Despite limited space, no underfloor heating, and initial skepticism from many heating engineers, Wolfgang Andrä took the plunge and switched from gas to an indoor air/water heat pump—with great success. In his 1996 terraced house in Weimar, an alpha innotec Paros 4 now reliably provides heat via existing radiators. Energy consumption has fallen by around 85 percent, and the system runs quietly, efficiently, and without compromising on comfort. For Wolfgang, one thing is certain: the decision to install a heat pump was absolutely the right one – even in a terraced house and in an existing building.

A heat pump in a terraced house is not only possible—under the right conditions, it is the most sensible heating solution for the future.