How to efficiently plan heating for a new building?

Hello,

we have decided on a monoblock air-to-water heat pump with propane and a 600-liter buffer tank with drinking water treatment.

A few bullet points to justify our decision.
- Monoblock heat pumps are supposed to work more efficiently than split systems, we have short pipes and more space inside.
- I have also heard about the buffer tank problem. Ultimately, we simply did not dare to omit the buffer tank. In the end, the fear was just too great.
- Because of the fresh water station, I think the risk of legionella is also eliminated and you do not have to expect high electricity costs due to the enormous electrical heating. For showering and such, 40°C is sufficient.
- As far as I am informed, a thermostat must be installed in every room over 4m² (or so) in a new building. Basically, I also consider thermostats to be pointless, since new buildings are so well insulated that significant temperature differences cannot be achieved anyway.

I also consider two heat pumps to be complete nonsense.
Geothermal heat pumps are certainly interesting but very complex. Usually, they are about COP 1.0 more efficient than air-to-water heat pumps. The question is only: How long do you have to heat to recoup the additional costs?
There is also a cooling function with heat pumps. However, I find this option very risky, since the condensate risk is already enormous. Sure, with sensors, etc., all this could work, but who guarantees that the sensors will always work that well and will not be miscalibrated after a few years.

Unfortunately, I have no practical experience yet. The house is still under construction.

my recommendation goes towards a ground source heat pump. It should be somewhat more efficient than the air source heat pump.
However, you need a ground borehole for this.

The question is whether a (rather small) energy saving compared to one in the upper single digits to low double digits is worth it. But it is definitely more visually appealing (no outdoor unit).

- Monoblock heat pumps are supposed to operate more efficiently than split systems,

Unfortunately, that is a myth.

600 liter buffer tank with potable water treatment.

So a combination tank?

- Because of the fresh water station, I think the legionella risk is also eliminated and you don’t have to expect high electricity costs due to the enormous heating with electricity. 40°C is also sufficient for showering and so on.

The legionella risk in normal use in a single-family house at a storage temperature of around 50 degrees (and possibly a legionella program once a week) is negligible. There are actually no cases in Germany. However, your electricity demand will actually be higher than without this large buffer. Because you always have to keep 600 liters at temperature. With a 200 liter tank, it is only 1/3 of the amount of heat.

- As far as I am informed, in a new building a thermostat has to be installed in every room over 4m² (or so).

Yes, BUT you can relatively easily get exempted from that.

There is also a cooling function with heat pumps. However, I find this option very risky because the risk of condensate water is enormous. Sure, with sensors etc. all this could work, but who guarantees that the sensors always work so well and don’t become miscalibrated after a few years.

You can also cool using experience values. That works well.

Hello,

So a combi storage tank?

Yes, with a combi storage tank.

It is quite possible that the electricity demand will be slightly higher due to the buffer tank. I am also not entirely sure if this is the best solution. Since we have a 16 kWp photovoltaic system, I talked myself into it.

The thermostat exemption is new to me. For me it's already too late, but out of interest, how does that work?

What do you mean by cooling with experience values?

It is quite possible that the electricity demand will be somewhat higher due to the buffer tank. I am also not entirely sure if this is the best solution. Since we have a 16 kWP photovoltaic system, I have reassured myself.

With photovoltaics, it will be more relaxed.

The thermostat exemption is new to me. For me, it's already too late, but out of interest, how does that work?

By having the person who plans the heating write an appropriate statement and you apply for an exemption with that.

What do you mean by cooling with experience values?

There are sources on the internet that share their own experiences with the cooling function. These are especially users of the Geishas etc., i.e. the Panasonic monoblocks, as the cooling function has always been integrated there and thus does not entail an additional cost. Many report that up to about 18 degrees flow temperature there are no problems, most settle at 20 degrees. BUT: Please remember that using the cooling function greatly increases the humidity inside the house. It then feels like a cool sauna. That makes sense, since the air conditioner not only cools but also dehumidifies directly, which does not work with underfloor heating cooling.

Can anything still be changed? Instead of a combination tank, I would prefer to use 2 separate tanks. Combination tanks often cause problems. The separation of hot water and heating water with the different temperature levels does not work as well as advertised by the manufacturers. In addition, they are often integrated as a hydraulic separator, which creates additional problems.