Sole/Water Heat Pumps

Hello,

we are currently planning our house. It will probably be a KFW-40 house. The question we ask ourselves is, what kind of heating is needed for this? Can a KFW-40 house even be achieved with a gas boiler?

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

Our house will be about 135-140 sqm. 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,

... It is presumably going to be a KfW-40 house. The question we ask ourselves is, what kind of heating is needed for this? Is it even possible to achieve a kfw-40 house with a gas boiler?

Probably not, unless an unfortunately uneconomical solar thermal system is "bought in". The sticking point is usually the allowable value for primary energy.

... We were recommended a brine/water heat pump (collector) from Nibe (NIBE F1145 PC/F1245 PC). Does anyone have experience with this? Is the pump sufficient for heating even in winter?

Almost any modern building can be heated adequately. Whether this is done actually energy-efficiently in operation, however, is a completely different matter. Various dimensioning calculations are required beforehand, which are often done inaccurately or sometimes not at all. Based on the result parameters, the choice of which heat generator (HE)/device, manufacturer is particularly suitable is then determined.

... Furthermore, we are considering installing a photovoltaic system on the roof. In my opinion, the investment costs are extremely high, so I wonder whether it is worthwhile or not.

Photovoltaics are significantly more economical for the builder compared to solar thermal systems, however only due to subsidies.

..., so that the roof faces west.

This results in yield losses. An exact dimensioning and balancing beforehand would certainly be advisable.

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

This can only be reliably answered after the calculation has been carried out; anything else would be looking into a crystal ball.

Best regards.

But how do I get such a dimensioning calculation done? Is it enough to have the heating load of the building determined? Actually, the construction company should know exactly what values the house needs, since they are not building such houses for the first time, meaning that it should not be necessary to carry out a separate calculation for each house. The south-facing location of the house is also known.

I have to correct myself. The roof would have a southwest orientation.

Just a personal question @ €uro: Is it allowed to know if you work in the industry or where you get your knowledge from?

Best regards

corner

....But how do I get such a dimensioning calculation done? Is it enough to have the heating load of the building determined?

The most sensible option is to commission an external planner who is independent from sales interests. At the very least, one should have the intended solution checked. The heating load alone is by far not sufficient.

....Actually, the construction company should know exactly what values the house requires, since they don’t build such houses for the first time,...

One would think so, but unfortunately that is not the case. As already mentioned, you usually get “warm” enough – actual energy efficiency, however, is mostly an unknown word. If the builders later notice this, corrections are partly very difficult.

.... meaning it does not have to be a separate calculation for every house.

In the case of a “standard house,” i.e., a kind of reuse project, at best only the geometric data of the building are identical, whereas climate location and user behavior are always individual. The latter have a significant influence on the final results and thus on the sensible technical solution.

.... May I ask whether you work in the industry or where you got your knowledge from?

A good question that should be asked more often in forums. I work as an MEP (Mmechanical, Eelectrical, and Pplumbing) planner, energy consultant, and as an expert witness/appraiser. In the latter capacity, I deal with many botched systems, as I call them. There are often significant discrepancies to the disadvantage of the client between the Energy Saving Ordinance or KfW certificates on paper and the practical reality.

Regards

Hello,

I have a question about geothermal collector systems. On the internet, it is said that approximately 1 to 2 times the heated living area is needed as collector area. However, two providers have now offered us a collector area that is smaller than the heated area. About half. The statement was that this area would be sufficient because conventional collector area is not used, but spiral pipes. It may be that more energy can then be absorbed from the ground, but the question I ask myself is: Does the ground not cool down too much then, and is there a risk of permafrost or ground on which grass no longer grows?

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

Thank you and best regards

corner

Hello,

... On the internet, one reads that approximately 1 to 2 times the heated living area is needed as collector area.

Unfortunately, you read a lot on the internet, where the truthfulness is sometimes questionable.
The collector area, length, and number of brine circuits are dimensioned according to the cooling capacity of the heat pump as well as the type of soil.
Diameter and length also depend on the hydraulic conditions, e.g. characteristic curve of the brine pump (residual delivery height).

... , because conventional collector area is not used, but spiral pipes.

For horizontal collectors there are now various types of construction, of course each with advantages but also disadvantages. Classic horizontal collector, trench collector (slinky), energy baskets, and much more.

... It could be that more energy can then be absorbed from the ground, ...

Or less! Sometimes the extraction capacity is not sufficient at all to cover the required heating load. Not rarely, the supply temperature to the heat pump in spring after or at the end of the heating period decreases significantly. Consequence: poor annual performance factor and an ice rink in the garden.

... the question I ask myself is: doesn’t the ground cool down too much and is there a risk of permafrost soil ....

Certainly, especially with shallow installation. The consequences for intended vegetation (garden) can be considerable, because not all native plants tolerate "cold feet" permanently.

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

Actually a good prerequisite for a horizontal collector.

Best regards