Project: Multi-family house gas hybrid heat pump

Hybrid system in new apartments

New build apartment house

  • The couple would like to build an apartment building with six units. They want to rent out the flats, as the new building will serve as their retirement provision.

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  • The heating solution sought must be suitable for the cooler weather common at the location. The devices should fit together perfectly and function reliably throughout.

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Combination of appliances for cooler regions

The developers are a couple planning to build a new apartment block in a highland area. They are looking for a suitable heating system that can cope with the prevailing climatic conditions of the region. Read on to see what systems they choose.

Planning for the future

The developers are a couple in their fifties. Their two children have grown up and moved out. The new building will contain six rented flats and is intended to support them in their old age. They anticipate that their building will be popular amongst potential tenants as it is located in a highland area with beautiful landscapes. And they want all of the house and heating technology to run equally smoothly.

Project challenges

The regional climate features relatively low average temperatures, very cold winters and frequently cloudy skies. Therefore, it will not be possible to use renewable energies alone for heating and DHW heating.


However, the couple is obliged to use at least some renewable energy due to legislation concerning new buildings. Therefore, they are considering using a hybrid system in which all of the heat generators are perfectly coordinated.

New build apartment house

Reasons for choosing this new heating solution

The developers decide to combine a modern gas heating system with environmental heat. A pleasant side effect: this combination is eligible for subsidy. They also consider installing a photovoltaic system, which could supply the electricity needed to run the heat pump.

Last but not least, a ventilation system will provide a comfortable and healthy indoor environment at all times in all apartments and prevent mould from forming.

01. Environmentally friendly heating

Modern boilers use fuel more economically than earlier generations of appliances and emit less pollution. They are also powerful and have ample reserves to cope with peak loads. The heat pump heating system is pollution-free by design. This improves the ecological footprint of the overall system.

Environmentally friendly

02. Saving costs

The planned hybrid combination is eligible for subsidy so the developers can even save money on their purchase. Furthermore, the efficient utilisation of fuels cuts the running costs to a minimum, especially as the heat pump covers some of the work and only needs a small amount of electricity to do so.

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Product solutions for the building project

The developers’ building services planner recommended using WOLF products. He has been using these appliances for many years. The products are constructed from high-quality materials and his experiences with them have been positive. He appreciates the efficient and advanced technology, its intelligent design, simple installation and maintenance and that all WOLF products can be perfectly combined. 

All of the appliances are designed to be very compact and take up little space. Therefore, the available room in the new apartment block can be used for other purposes. One outstanding feature of the condensing appliance from an ecological point of view: it is already prepared to use hydrogen fuel at a later point in time. So its emissions can be reduced to near-zero in the future. Due to these many advantages, the couple are very happy to follow the recommendations.

WOLF Gas condensing boilers CGB-2 family

CGB-2 series gas heating systems

The WOLF CGB-2 38 kW gas boiler has sufficient output for the apartment block.

The appliance always adjusts itself perfectly to current demands. This saves fuel and improves its efficiency.

WOLF CHA heat pump

CHA monoblock heat pump

In addition to excellent efficiency, the extremely quiet appliance has the further asset that it can be run using the climate-friendly refrigerant R290. The landlords choose a 10 kW boiler.

WOLF decentralised living space ventilation CWL-D-70

CWL-D-70 mechanical ventilation unit

This model uses integrated filters and heat recovery to supply fresh, pollen-free air to all rooms without losing heat.

As the system is decentralised, the future tenants will be able to control their indoor climates separately.

Heat pump in the garden

Short checklist for the project

The developers must keep the following points in mind to ensure that everything goes to plan:

The building must meet the KfW standard for energy-efficient buildings to receive a heating technology subsidy. Therefore, it needs good thermal insulation and must be air-tight, amongst other things.

As the outer envelope is almost air-tight, a ventilation system must be employed.

The two heating appliances must be linked by a buffer cylinder.

If the heat pump heating system covers the DHW heating, the boiler can be switched off in the warmer seasons. This reduces the cost of fuel still further.

A good combination for all residential units

The couple have chosen a high-performance, efficient and environmentally friendly system. The hybrid solution is ideal for heating the planned new apartment block building in the challenging climatic conditions of the highland region whilst keeping costs low.

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