ᐅ Ground source / water source heat pumps

Hello,

We are currently planning our house. It will probably be a KFW-40 house. The question we have is what kind of heating system is needed for this? Is it even possible to achieve a KFW-40 house with a gas boiler?

We were recommended a ground source heat pump (collector) from Nibe (NIBE F1145 PC/F1245 PC). Does anyone have experience with this? Is the heat pump sufficient for heating during the winter? Additionally, we are considering installing a photovoltaic system on the roof. In my opinion, the investment costs are extremely high, so I wonder if it is worth it or not.

Our house will be about 135–140 sqm (1450–1505 sq ft). The plot has a southwest orientation, so the roof faces west.

What heating system would you recommend for a KFW-40 house?

Thank you very much and best regards

corner

Hello,

corner schrieb:
... It is probably going to be a KfW-40 house. The question we have is, what kind of heating system is needed for that? Is it even possible to achieve a KfW-40 house with a gas boiler?

Probably not, unless an unfortunately not very cost-effective solar thermal system is included. The critical factor is usually the allowed value for primary energy.

corner schrieb:
... We were recommended a brine-to-water heat pump (collector) from Nibe (NIBE F1145 PC/F1245 PC). Does anyone have experience with this? Is the pump sufficient to heat the house in winter?

Almost any modern building can be heated adequately. Whether this is done in a truly energy-efficient way during actual operation is a different matter. Various sizing calculations are necessary beforehand, which are often imprecise or sometimes not done at all. Based on these calculation results, it is then decided which heat generator (HG)/ system or manufacturer is most suitable.

corner schrieb:
... Furthermore, we are considering having a photovoltaic system installed on the roof. In my opinion, the investment costs are extremely high, so I wonder if it is worthwhile or not.

Compared to solar thermal systems, photovoltaic is much more economical for the homeowner, but this is mainly due to subsidies.

corner schrieb:
..., so that the roof faces west.

This will lead to reduced yields. An accurate sizing and energy balance calculation beforehand would definitely be advisable.

corner schrieb:
... What heating system would you recommend for a KfW-40 house?

This can only be answered reliably after the appropriate calculations have been carried out; any other answer would be guessing.

Best regards

But how do I get such a sizing calculation done? Is it enough to have the building’s heating load determined? Actually, the construction company should know exactly what specifications the house requires, since they don’t build these types of houses for the first time—in other words, a separate calculation shouldn’t be necessary for every house. The south-facing orientation of the house is also known.

I need to correct myself. The roof actually faces southwest.

A quick personal question @ €uro: Is it okay to ask if you work in the industry or where you got your knowledge from?

Best regards

corner

corner schrieb:
....But how do I get such a sizing calculation done? Is it enough to have the building’s heating load determined?

The most sensible option is to hire an independent planner who is not tied to any sales interests. At the very least, the proposed solution should be reviewed. The heating load alone is far from sufficient.

corner schrieb:
....You would think the construction company should know exactly what values the house requires since they don’t build these houses for the first time,...

You would expect that, but unfortunately, that is often not the case. As already mentioned, usually the house will get warm enough – actual energy efficiency, however, is often a foreign concept. If the homeowners notice this later, making corrections can be very difficult.

corner schrieb:
....meaning it shouldn’t be necessary to do a separate calculation for every house.

In a "standard house," meaning a kind of repeat project, only the geometric data of the building may be identical; the climate location and user behavior, however, are always individual. The latter have a significant impact on the final results and thus on the appropriate technical solution.

corner schrieb:
....May I ask if you work in the industry or where your knowledge comes from?

A good question that should be asked more often in forums.
I work as a building services planner, energy consultant, and expert assessor.
In the latter role, I encounter many faulty systems, as I call them.
There are often considerable differences to the disadvantage of the homeowner between the energy saving regulations or certification documents on paper and the practical reality.

Best regards.

Hello,

I have a question about geothermal collector systems. Online, it is often stated that the collector area needed is about 1 to 2 times the heated living area. However, two suppliers have offered us a collector area that is smaller than the heated area—about half as much. Their explanation was that this area is sufficient because spiral pipes are used instead of conventional collector panels. It might be that more energy can be absorbed from the ground this way, but my question is: wouldn’t the ground cool down too much, potentially causing a permafrost condition or soil that no longer supports grass growth?

The soil on our property is marshland, so rather moist.

Thank you and best regards

corner

Hello,

corner schrieb:
... On the internet, it is said that roughly one to two times the heated living area is needed as collector surface.

Unfortunately, there is a lot of information online, and its accuracy is often questionable.
The collector area, length, and number of ground loop circuits are dimensioned according to the heat pump’s cooling capacity and the soil type.
Diameter and length are further determined by hydraulic conditions, for example, the characteristic curve of the brine pump (residual head).

corner schrieb:
... since traditional collector surface is not used, but spiral pipes.

There are now many different types of horizontal ground collectors, each with its own advantages and disadvantages. Classic horizontal collector, trench collector (slinky), energy baskets, and many more.

corner schrieb:
... It could be that more energy is absorbed from the ground then, ...

Or less! Sometimes the extraction capacity is simply not sufficient to cover the required heating load. It is not uncommon for the temperature of the brine return to the heat pump to decrease significantly in spring or at the end of the heating season. The consequences: poor seasonal performance factor and an icy surface in the garden.

corner schrieb:
... The question I ask myself is: doesn’t the ground cool down too much then, and is there a risk of permafrost? ....

Indeed, especially with shallow installation. The impact on intended vegetation (garden) can be considerable because not all native plants tolerate “cold feet” over a longer period.

corner schrieb:
... The soil on our property is marsh soil, so rather moist soil.

This is actually a good condition for a horizontal ground collector.

Best regards