Is a heat pump a sensible option in a multi-family house?

A heat pump uses up to 75% free environmental energy from the air, ground, water or waste heat, thereby significantly reducing running costs. It operates efficiently and requires little maintenance.

The most important advantages at a glance:

• Up to 60% lower heating costs compared to oil or gas heating systems
• The value of a renovated property increases
• Reduced or even zero CO₂ costs compared to heating with gas and oil
  
• Investment costs for the heat pump can be added to the basic rent (if structural measures are required)
• High tenant satisfaction: 8 out of 10 tenants rate climate-friendly heating as an important decision-making criterion

How well do heat pumps really work in apartment buildings? The LowEx-Bestand research consortium, led by Fraunhofer ISE, investigated the use of heat pumps in renovated apartment buildings. The aim was to develop practical concepts for heating, hot water and ventilation and to evaluate their efficiency in real-world operation.

The study shows that heat pumps can also be implemented in existing buildings in a technically and economically viable manner, especially in combination with renovation measures. Five system solutions were investigated – from centralised to combined to apartment-specific heat pumps. Centralised systems with combined space heating and hot water preparation proved to be particularly efficient.

Further key findings of the study:

• Emissions savings > 50% compared to gas condensing boilers
• Heat pumps remain more economical in the long term, even with rising gas prices
• PV-thermal combinations (PVT collectors) are an efficient heat source for densely populated urban areas
• Heat pumps are a viable component of the heating transition in multi-family housing stock.

In principle, all common types of heat pumps are suitable for multi-family dwellings. Air source heat pumps are the most flexible option for multi-family dwellings, as they do not require drilling, can be operated in modular cascades and can also be installed in densely built-up areas (e.g. in the attic). Where there is plenty of land available, ground source heat pumps offer the highest long-term efficiency.

In order for the heat pump to operate efficiently, certain technical and organisational requirements must be met.

1. TECHNICAL REQUIREMENTS

• Heating system with the lowest possible flow temperature (< 55 °C)
• Good thermal insulation or renovation schedule
• Sufficient space for outdoor unit, storage tank and pipes
• Ideally, hydraulic balancing has already been carried out

2. PROPERTY & RESIDENTIAL PROPERTY OWNERS' ASSOCIATION

The installation of a heat pump in an apartment building is a structural alteration and usually requires a majority vote.
The costs are usually distributed according to co-ownership shares.

3. NEIGHBOURHOOD & NOISE PROTECTION

When installing outdoors, statutory noise protection guidelines must be observed. Careful planning of the installation location and soundproofed devices help to avoid conflicts with neighbours.

Multi-family homes are diverse. This increases complexity, but also opens up more technical possibilities than single-family homes. For example, multiple heat sources such as geothermal energy, waste water, waste heat or outside air, as well as heat pumps and heating systems, can be combined in a multi-family home.

Solution family 1 describes central heat pump systems for the entire building, solution family 2 describes the combination of centralised and decentralised solutions, solution family 3 describes the use of heat pumps for specific residential units, solution family 4 describes the installation of heat pumps in individual flats, and solution family 5 describes single-room heat pumps.

The use of a heat pump in an apartment building offers many advantages, but also presents planners and owners with particular challenges. In addition to correct dimensioning, space, sound insulation, heating circuit connection and coordination within the owners' association play a major role.

1. TECHNICAL INTEGRATION INTO EXISTING SYSTEMS

In order for the heat pump to work efficiently, heating surfaces and hydraulics must be coordinated. Often, replacing individual radiators or performing a hydraulic balance is sufficient to lower the heating curve and significantly increase efficiency.

For gradual renovation, a bivalent heating system that combines a heat pump with an existing gas or oil boiler is recommended. This ensures that heating requirements can be reliably met at all times.

2. SPACE PROBLEM AND INSTALLATION LOCATION

An important consideration for multi-family dwellings is the available space – both for the outdoor unit and for the buffer storage tank and pipes.

Outdoors:

If there is sufficient space on the property, the air/water heat pump can be installed there. It is important to ensure adequate sound insulation and visually appealing integration into the surroundings.

Installation on the roof:

If the building is structurally sound, the heat pump can be installed in the roof. This location usually offers optimal air flow conditions and frees up valuable floor space. However, installation is more technically complex and requires careful vibration decoupling.

Installation in the cellar:

In many cases, the basement is also a suitable location, especially for split units or brine/water heat pumps. It is important that the air ducting or refrigerant line can be installed without major modifications.

3. NEIGHBOURHOOD CONFLICTS

Heat pumps are significantly quieter than they used to be, but noise levels are still an important consideration, especially in densely built-up residential areas. Outdoor units should be positioned so that the sound does not radiate towards bedrooms or neighbouring properties.

Soundproofing hoods, low-reflection walls or vibration-isolated bases can further reduce the noise level.

The power requirement is determined by the heating load of the building.
A correctly dimensioned heat pump runs smoothly and cycles less frequently, which reduces wear and tear and electricity consumption.

Technical solutions for performance adjustment:

• Inverter heat pump: continuously adjusts its output
• Cascade connection: multiple devices work together flexibly
• Multi-stage heat pumps: achieve higher flow temperatures when there is a high heat demand

The costs depend on size, system and effort.

The following table provides a rough guide:

FACTORS AFFECTING COSTS

• Building standard and heating load
• Type of heat pump (air, brine, water)
• Number of residential units
• Cost of heating distribution and storage
• Subsidy amount and bonus programmes

Heat pumps are currently one of the most efficient and climate-friendly heating solutions for multi-family homes.
With careful planning, a tailored heating system and the right type of heat pump, you can achieve high efficiency ratings, low operating costs and long-term value appreciation.