ᐅ Selecting a Heat Pump for a New Build Through the General Contractor

Hello dear community,

I am currently comparing various general contractor offers for our house construction (KFW 40 with QNG).
Now I am wondering how much importance I should place on the heat pump and ventilation system offered.
Questions:
- Are there significant quality differences here that one should definitely pay attention to?
- Does a heat pump without an outdoor unit (see GU1) have any disadvantages?
- I also learned that the heat pump from GU1 uses some "older" refrigerants; is this something to be concerned about?
- How practical could a ground-source heat pump (brine/water) be? I plan to commission a soil survey for the property soon and am considering including the necessary services to assess the suitability for such a heat pump (1675€). Is this worthwhile?
- We actually find the cooling function via underfloor heating quite interesting, but apparently this is not compatible with QNG funding. Are there any experiences or "workarounds" regarding this?
- In general: Would you simply go with the contractor’s standard heat pump or try to integrate a preferable heat pump into the offer?

GU1:
Our energy-efficient houses are equipped with air-to-water heat pumps from Tecalor (Stiebel Eltron) with an integrated central ventilation system (*THZ 5.5 eco or THZ 504). The heat pumps/ventilation units include heat exchangers for heat recovery. This 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 size of the house, either 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 is installed, each combined with a ventilation system including high-efficiency compressor technology. The exhaust air module with energy recovery is mounted directly on the heat pump. Controlled mechanical ventilation continuously removes moisture and odors from the occupied rooms and replaces them with fresh filtered air.

A general contractor (GC) builds your house using "their" subcontractors. The trades work smoothly because this is how they are used to building. If you force the GC to deviate and use different manufacturers, the risk of errors increases. @Tolentino has experience with the GC’s heating contractor.

Schnubbihh schrieb:

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

Both are top providers of heat pumps.

Schnubbihh schrieb:

- I also learned that the heat pump from GU1 uses some "older" refrigerants, is that something to be concerned about?

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

Schnubbihh schrieb:

- How practical might a brine/water heat pump be? I plan to commission a soil survey for the plot soon and am considering including proper tests for the suitability of such a heat pump. (€1675) Is that sensible?

A soil survey is definitely worthwhile. You are responsible for what is built on your land. A brine/water system only becomes cheaper if you plan to install a horizontal ground collector yourself on your property and don’t want an outdoor unit. A deep geothermal borehole will cost around 20,000–30,000 more, depending on drilling depth and number of boreholes.

Schnubbihh schrieb:

- We actually find the cooling function via underfloor heating quite interesting, but apparently it is not compatible with QNG funding. Are there any experiences or "workarounds"?

Do you have photovoltaic (solar panels) on your roof? Why not simply install a split air conditioning unit on each floor? This offers significantly better cooling performance, especially if you already generate excess electricity (increasing your self-consumption). You can also dehumidify and quickly heat in winter. There is always a risk of condensation with cooling via underfloor heating, and it only cools by a few degrees. The additional cost for a cooling function easily matches that of a split AC system. I’ve often read in energy forums that many regret not installing air conditioning right away.

A controlled mechanical ventilation system is useful. It saves a lot of energy and can return humidity into the house (enthalpy exchanger). For a centralized system, remember to include filters on supply and exhaust air to keep the enthalpy exchanger clean for a long time. Small filters on exhaust vents are also helpful for keeping ducts clean. Filters must be changed regularly; otherwise, the system has to work harder.

It might even be possible to heat a KfW 40 house solely with split AC units. That would be a very cost-effective solution, though it is still rarely implemented.

Best regards,
Jan

alles3d schrieb:

Do you have photovoltaic panels on the roof? Why not simply install a split air conditioning unit on each floor? This has the advantage of much better cooling capacity, especially if you generate excess electricity (increasing self-consumption). You can also use it to dehumidify and quickly provide additional heating during winter. With the cooling function, there’s always a risk of condensation, and it only lowers the temperature by a few degrees.
The extra cost for a cooling function easily covers the price of a split air conditioning system. I have often read in energy forums that many people regret not installing air conditioning right from the start.

A controlled mechanical ventilation system with heat recovery is useful. It saves a lot of energy and can bring humidity back into the house (enthalpy exchanger). For a central system, remember to include filters in both supply and exhaust air to keep the enthalpy exchanger clean for longer. Small filters in the exhaust vents are also effective at keeping the ductwork clean for a long time. However, filters need to be changed regularly; otherwise, the system has to work harder.

It’s probably possible to heat a KfW 40 house using only split air conditioning units. That would be a very economical option, but it is still quite rare in practice.

Best regards,
Jan

Thank you very much for the detailed response!
I assume that an air conditioning system is unfortunately not compatible with the QNG subsidy.
However, with a KfW 40 house without QNG, an air conditioning system would probably be allowed, right? That would actually be an interesting option to consider.

Schnubbihh schrieb:

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

These are actually three different price ranges. I would definitely not go for an exhaust air heat pump. Ground source heat pumps are generally the better technology but rarely pay off for energy standard EH40. I find 20-30m (65-98 feet) for the drilling a bit on the high side. We have a single 80m (262 feet) borehole; you are building somewhat larger, but Hamburg is also a bit warmer. The big rig still has to come out once.
Regarding the Tecalor, you really have to consider whether you want a combined unit for heating plus mechanical ventilation with heat recovery, or rather two separate devices that can be replaced independently later on.

Schnubbihh schrieb:

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

So you want to hire a GC without a formal tender process? – that is not advisable: Only those with too much money go to a construction company without an expert advisor. The best way to hire a GC is to have them bid on a tender for the construction project. GCs as contractors are fine, but GCs instead of a tender usually involve learning the hard way.

Schnubbihh schrieb:

Generally: Would you simply go with the GC’s standard heat pump or try to include a heat pump of your choice in the offer?

My Steinemantra clearly applies to heat pumps as well.

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