ᐅ No Heat Pump in a Single-Family Home After All?

Bauexperte schrieb:
The construction costs for solar utilization are in the six-figure range.

.. that is exactly the point ... and if you then have to repay this six-figure financing amount as a loan with principal and interest, plus maintenance and operating costs, you can just calculate where and how such a cost-benefit analysis ends up in the end ...

Hello, 1.5 years ago I conducted an energy assessment for a small house built in the 1950s. Honestly, the house is in terrible condition. Insulating by injecting insulation material into the cavity walls always resulted in calculations showing "saturated walls," so another approach was necessary.
Therefore, I planned the following measures:
- Sealing off radiator recesses
- Insulating roller shutter boxes
- Replacing windows, now with a U-value of 1.2 (so they are actually less insulated than the walls)
- Insulating the roof and top floor ceiling
- Insulating the basement ceiling
- Replacing radiators and pipes
- Installing solar support for heating and domestic hot water on the roof
- Equipping the existing fireplace with a water-based heat exchanger (theoretical efficiency 84%)
- A small gas boiler
- A large storage tank

The KFW approved the project through program 152 and the client received a favorable loan. The client is very satisfied; the gas boiler barely runs, only on days without sun when no one has time to operate the fireplace.

Best regards, Jürgen

What I want to say is that your architect’s idea works well. In comparison, a heat pump naturally requires quite a bit of electricity.

Wegener SV schrieb:
....-existing fireplace fitted with a water-bearing insert (theoretical efficiency 84 %)

Efficiency is always related to output and is merely a snapshot under laboratory conditions, nothing more. It is often misused for marketing purposes. What really matters is the heat generator’s coefficient of performance, since it is the energy consumed by the user that has to be paid for, not the power output!

Wegener SV schrieb:
...The KfW approved the project via program 152...

That only means their requirements/conditions have been met on paper. However, no actual economic viability for the user can be derived from this. Other interests are often the priority ;-) Also, a low interest rate is hardly synonymous with economic efficiency; for example, an initially mandatory grace period on repayments increases the overall financing cost, especially for investments that can sometimes exceed requirements. If you take it at face value, you might naïvely assume benevolent intentions ;-)

Wegener SV schrieb:
...On the other hand, such a heat pump naturally needs quite a lot of electricity.

If the demand is reduced beforehand, every heat generator will consume less! ;-)

Best regards

€uro schrieb:
An efficiency rating always relates to performance and is merely a snapshot under laboratory conditions, nothing more. It is often misused for advertising purposes. What truly matters is the heat generator’s performance factor because the operator pays for energy, not output! This simply means that the requirements/conditions on paper were met. However, actual cost-effectiveness for the operator cannot be derived from this. Other interests are at the forefront here ;-) Moreover, a low interest rate is hardly synonymous with profitability; an initial grace period on repayment alone increases the overall financing costs, especially when investments are sometimes excessively high due to the requirements. If one wants to keep it simple, they blindly believe in benefactors ;-) If the demand is lowered beforehand, every heat generator consumes less! ;-)

Best regards.

Regarding the efficiency rating, it clearly states "theoretical efficiency" there.

I am not a benefactor; I have done what one can do with a building like this. If the customer bought such a house with a specific budget for renovation, including the desired KFW loan, I strive to make the best out of it. Here, there is a difference between a practitioner and a theorist. Had he asked me before buying, I would have rather advised the customer against the purchase.

The energy demand was reduced as much as possible, but some things simply couldn’t be done. Therefore, we relied on solar energy and wood. Specifically, the customer also has access to wood at favorable prices.

The customer is satisfied; the gas heating hardly runs. From that perspective, I think I didn’t do too badly.

On the topic: if you have a house insulated to current standards, the system works. That was what was asked.

An air source heat pump is typically calculated by average building services professionals as 1 kW of electricity input producing 2 kW of heating output—at least those I know. Okay, one may consider that a lot or a little; personally, I don’t think air source heat pumps are great.

And finally, I certainly don’t claim to know everything and am happy to learn something new every day.

Best regards from the beautiful Tecklenburger Land

Jürgen Wegener

Wegener SV schrieb:
...I am not a philanthropist ...

The recipient was someone else!

Wegener SV schrieb:
.. Here one distinguishes between practitioners and theorists. ...

As an expert witness, I am certainly not a theorist, if that was what was meant. On the contrary, the insights gained from practical installations are taken into account in my planning!

Wegener SV schrieb:
.. ..The client is satisfied, the gas heating hardly ever runs. Therefore, I think I didn’t do much wrong.

If a client is satisfied and there are no comparison options, you should leave it at that! ;-) If a gas heating system hardly ever runs, its justification should be questioned ;-) Nobody acquires something to hardly or never use it! First, existing installations are optimized before additional, sometimes uneconomical efforts are made. This distinction is usually not made by laypeople; sellers naturally recommend additional investment ;-) There’s probably some suspicion involved here ;-)

Wegener SV schrieb:
.. if you now also have a house insulated to today’s standards, the system works.

Merely “working” or just “providing warmth” could be said of almost anything. Today, due to the high investment costs, that is clearly not enough. A high investment must bring sustainable savings in operating costs—not just on paper, but in reality. This is usually where the paths of sellers diverge from those of true experts.

Wegener SV schrieb:
... An air-source heat pump is calculated by the average building services company with 1 kW of electricity input delivering 2 kW of heat output—at least those I know.

Whether these are really “specialist companies” is highly questionable. They likely just sell oil, gas, pellets, etc. Well-designed air-source heat pump systems achieve a seasonal performance factor of about 3.5. While this doesn’t reach the approximately 4.5 to 4.7 seasonal performance factor of brine (ground source) systems, it avoids the additional costs of source development.

Wegener SV schrieb:
... Ok, people may have different opinions on that, personally I don’t find air-source heat pumps very appealing.

Personal feelings are subjective, not objective. Therefore, they are hardly a suitable, independent guideline. Only facts count here—not one’s own, undoubtedly well-meaning, impressions.

Wegener SV schrieb:
..I certainly don’t have all the answers and like to learn every day.

The same applies to me; every measurement and investigation of practical installations contributes to gaining knowledge for future projects!

Best regards.

€uro schrieb:
The addressees were others!
As an expert, I am by no means a theorist, if that was implied. On the contrary, the insights gained from practical installations are taken into account in my planning!
If a customer is satisfied and there are no alternatives for comparison, you shouldn’t change that! ;-) If a gas heating system almost never runs, the question of its justification should be raised ;-) No one acquires something just to hardly use it! First, existing systems are optimized before additional, sometimes uneconomical efforts are made. Laypersons usually fail to make this distinction, and naturally, salespersons recommend additional investments ;-) Suspicious minds may think ill of this ;-).
Simply "functioning" or merely "providing warmth" could be claimed of almost anything. Today, given the high investment costs, this is clearly insufficient. High investments must bring sustainable savings in operating costs—not just on paper, but in reality. This is where the paths of salespeople and genuine experts typically diverge.
Whether they are "specialized companies" is highly questionable in my view. They probably only sell oil, gas, pellet systems... Well-planned air-source heat pump systems achieve an annual performance factor of about 3.5, and while they do not quite reach ground source systems with an annual performance factor of about 4.5 to 4.7, they do not require additional costs for source development.

Personal impressions are subjective, by no means objective. Therefore, hardly suitable as independent advice. Here, only facts count—not one’s own, certainly well-meaning, feelings.
The same applies to me; every measurement and investigation of practical installations contributes to gaining knowledge for future projects!

Regards.

€uro, you really are something! What you say is off-topic, but never mind—I’m the bad guy and you’re the hero.
A factual discussion with you seems pointless to me.
I will no longer participate in this discussion as I have more important things to do.

Enjoy yourself, Mr. Expert €uro.

Best regards, Jürgen Wegener