ᐅ Heating and Ventilation Concept for a New KfW55-Energy-Standard Building with Heat Pump

Hello everyone,

We are currently planning a KFW55 single-family house, 140m2 (1,507 sq ft), and are completely overwhelmed when it comes to the heating system.

We would like underfloor heating, and since photovoltaic installation is mandatory for us, we are considering an air-to-water heat pump. To handle dehumidification and heat recovery, we plan to add a centralized ventilation system.
It would also be great if the heat pump could provide cooling in the summer, meaning active cooling.

This is our idea so far — does it make practical sense?
Is it advisable to include a buffer tank? Would that be more cost-effective than an electric storage system?
Is a split unit or monoblock better suited for this setup?
(There is a technical room in the basement.)
Which models are suitable, and do you have any recommendations?

Sorry for all the questions.

Generally a difficult topic. I can only speak from our experience: a 12.4kWh photovoltaic system with an 11kW battery storage, an air-to-water heat pump, a 920L (244 gallons) buffer tank with a fresh water station (drinking water is heated on demand), underfloor heating in all rooms, and a controlled ventilation system with an enthalpy heat exchanger.
Is all of this necessary?
That’s hard to answer and probably not always the optimal setup over the course of a lifetime. But since we are a household of four with very different daily and nightly routines, resulting in a highly uneven consumption of energy (heat, hot water, and electricity), this was the best solution for us (currently).
Once the kids have moved out, I can imagine replacing the buffer tank with a smaller fresh water station.
Since we also have smart home control for the house and photovoltaic system, things like increasing the flow temperature during photovoltaic surplus work quite well. The system is also linked to the weather station to incorporate possible weather changes into the scenarios.

The investment for all these extras is of course a topic of its own. It might pay off someday, but that was not our motivation – comfort was the keyword, I think.

WayneTrain schrieb:

So much for the concept—does it make practical sense?
Is it advisable to include a buffer tank? Is that more cost-effective than an electric storage system?
Is a split unit or a monoblock better suited?
(There is a utility room in the basement.)
Which units are suitable, any recommendations?

Any heat pump makes sense. An air-to-water heat pump is a more affordable option than a ground-source (brine-to-water) heat pump. An air-to-air heat pump would be impractical for a standard house without special energy efficiency measures.
Buffer tank? It’s unnecessary if the heat pump can run continuously.
Split or monoblock—either is fine in the end. Both are heat pumps; one has an indoor unit, the other does not.
Which units are suitable? That’s like asking, “I need a car, any recommendations?” I prefer Asian brands—they have a lot of experience and don’t have the complicated settings like the German products. However, there are fewer installers available for them (and more DIYers).
Active cooling should basically be possible with any unit. Just don’t expect too much from it. You might get around ±2°C (±3.5°F) temperature difference, but with increased humidity. If you really want cooling, then plan a dedicated air conditioning system from the start.

P.S. Far more important than all the points mentioned above is proper heating system planning. Many installers just do a rough job because “it’s always been done this way.” So have your system planned professionally according to your needs, preferably externally, ideally also with a waiver for the ERR.

Thank you for the feedback.

The idea behind the buffer tank was to store additional energy during sunny daytime hours. The feed-in tariff is hardly attractive anymore and is unlikely to improve in the future.

What would be a good point of contact for external planning? Who offers this service without also carrying out the construction, and what are the typical costs?

We are currently having the preliminary planning done and then plan to put the project out to tender with several builders. To make the best possible comparisons, it is ideal to have a detailed building specification.

Just use your largest buffer tank in the house, your screed. In winter, however, there won’t be much from the photovoltaic system to store anyway.