Selection of heat pump in new construction via general contractor

Hello dear community,

I am currently comparing various offers from GU for our house construction (KFW 40 with QNG).
Now I am asking myself how much importance I should place on the offered heat pump and ventilation system.
Questions:
- Are there significant quality differences here that one should urgently pay attention to?
- Does a heat pump without an outdoor unit (see GU1) have any disadvantages?
- I have also heard that the heat pump from GU1 uses some "older" refrigerants, should one be careful about that?
- How useful could a brine/water heat pump possibly be? I want to commission a soil survey for the plot soon and am considering directly including appropriate services for the suitability of such a heat pump. (1675€) Sensible?
- Actually, we find the cooling function via the underfloor heating quite interesting, but apparently not compatible with QNG funding. Are there experiences / "workarounds" regarding this?
- In general: Would you simply go with the standard heat pump from the GU or try to integrate a heat pump of your choice into the offer?

GU1:
Our efficient houses are heated with air/water heat pumps from Tecalor (Stiebel Eltron) with integrated, central ventilation systems. (*THZ 5.5 eco or THZ 504) The heat pumps/ventilation systems have heat exchangers for heat recovery. It is a state-of-the-art complete system for heating and ventilating residential buildings. The residual heat extracted from the exhaust air is used both to support heating and to preheat the supply air (fresh air).

GU2:
For a KFW efficiency house 40, depending on the house size, an exhaust air heat pump type Nibe F730/F735, an air/water heat pump type Nibe 2120, or a brine/water heat pump type Nibe 1255 each with a ventilation system including highly efficient compressor technology is installed. The exhaust air module with energy recovery is mounted directly on the heat pump. Through controlled indoor ventilation, moisture and odors are constantly removed from the polluted rooms and replaced by fresh filtered air.

A general contractor builds you a house with "his" subcontractors, the trades run smoothly because it is always built that way. If you force the general contractor to make deviations and use other manufacturers, the risk of errors increases. has had experience with the general contractor's heating engineers.

- Are there significant quality differences here that one should urgently pay attention to?

Both are top suppliers of heat pumps.

- I also learned that the heat pump from GU1 uses some "older" refrigerants, should one be careful about that?

Both use older refrigerants that will eventually be banned. What that means in 10 years is hard to say.

- How sensible could a brine/water heat pump possibly be? I want to commission a soil survey for the property soon and am considering including corresponding services to assess the suitability of such a heat pump right away. (1675€) Sensible?

A soil survey is definitely sensible. You are responsible for what you build on. Brine/water is only cheaper if you want to install a horizontal trench collector on your property yourself. And you don’t want an outdoor unit. A deep borehole will cost about 20-30k extra, depending on the depth of the borehole and the number of drill holes.

- Actually, we find the cooling function via underfloor heating quite interesting, but it is probably not compatible with QNG funding. Are there any experiences / "workarounds"?

Do you have photovoltaic on the roof? Why not simply install a split air conditioning unit per floor. The advantage is a much better cooling performance if you’re already collecting too much electricity (more self-consumption), you can dehumidify with it, and quickly heat additionally in winter. With the cooling function, there is always a risk of condensation, and it only gets a few degrees cooler. The extra cost for a cooling function easily covers a split air conditioning system. I have often read in energy forums that many regret not installing an air conditioning system right away.

A controlled ventilation system is sensible. It saves a lot of energy and can bring humidity back into the house (enthalpy exchanger). With a central controlled ventilation system, think about filters in the supply and exhaust air so that the enthalpy exchanger stays clean for a long time. Small filters in the exhaust air outlets are also sensible. This keeps the ducts clean for a long time. However, filters must be changed regularly; otherwise, the system has to work harder.

Probably, the KFW 40 house could also be heated only with split air conditioning systems. That would be a very cheap option, but it is still quite rarely implemented.

Best regards,
Jan

Do you have photovoltaics on the roof? Why not simply install one air conditioning split unit per floor. The advantage is a much better cooling performance, especially if you already generate too much electricity (more self-consumption), you can dehumidify and quickly heat in winter. There is always a risk of condensation with the cooling function, and it only cools a few degrees. The additional cost for a cooling function is easily enough for a split air conditioning system. I have also often read in energy forums that many regret not installing an air conditioning system right away.

A controlled residential ventilation system makes sense. It saves a lot of energy and can bring humidity back into the house (enthalpy exchanger). For a central controlled residential ventilation system, think of filters in the supply and exhaust air to keep the enthalpy exchanger clean for a long time. Small filters in the exhaust openings are also useful. This keeps the ducts clean for a long time. However, filters must be changed regularly, otherwise, the system has to work harder.

You could probably heat the KFW 40 house only with split air conditioning units. That would be a very inexpensive option, but it is still rather rarely implemented.

Best regards, Jan

Thank you very much for the detailed answer! I assume an air conditioning system is unfortunately not compatible with the QNG funding. With KFW 40 without QNG, an air conditioning system is probably possible, right? That would indeed be an interesting consideration.

Exhaust air heat pump type F730/F735, an air/water heat pump type Nibe 2120 or a brine/water heat pump type Nibe 1255

But those are three different price categories. I would definitely not go for an exhaust air heat pump. Brine-water heat pumps are basically the better technology, but they rarely pay off in EH40. I find 20-30k for the drilling a bit overestimated. We have a single 80m drilling at our place, you are building somewhat bigger but Hamburg is also a bit warmer. However, the big crew still has to come once. And regarding the Tecalor, you have to think about whether you want a combined unit for heating + controlled residential ventilation or rather two separate units that you can replace independently later.

I am currently comparing various offers from GU for our house construction (KFW 40 with QNG).

So you want to commission a GU without a tender? - that is hardly advisable: Only people with too much money go to a construction company without a knowledgeable secondary expert. The best way to a GU is that they apply for the tender of the construction project. GUs as contractors are good, GUs instead of tender usually come with a learning fee.

Generally: Would you simply follow the standard heat pump of the GU or try to integrate a heat pump of your choice into the offer?

My Steinemantra clearly applies to heat pumps as well.