ᐅ Air-to-air heat pump vs. air-to-water heat pump vs. trench ground collector – Differences
Created on: 12 Dec 2019 10:33
N
Neubau2020
Hello,
I am currently trying to decide how the heating energy should be generated.
Here in the forum, I came across the horizontal ground loop collector, which I find very interesting. In conversations with two prefabricated house suppliers, I mentioned that I am considering generating energy with a horizontal ground loop collector. Both times, the response was, "We’ve heard of horizontal ground loop collectors, but never installed one."
One offer included an air-to-water heat pump (Luxhaus KfW55), and the other included an air-to-air heat pump with controlled residential ventilation (Streif Haus KfW40). The house will have two levels, no basement, around 190 m² (2,045 sq ft), on a fairly flat plot with no special features.
I am wondering how the horizontal ground loop collector differs technically and in price from the air-to-water heat pump.
Is the technology inside the house the same, or are there other factors to consider, such as system size and design?
Is the main difference simply that instead of the external unit of the air heat pump, I install the trench and lay the pipes?
What is the price difference?
What about the long-term difference in energy consumption? The air heat pump needs to run continuously on electricity to draw in air—how does it work with geothermal energy from the horizontal ground loop in this regard?
Lastly, a question regarding the air-to-air heat pump:
The sales representative from Streif Haus said that if I wanted to switch from the air-to-air heat pump to an air-to-water heat pump, it would cost about 10,000 euros more. Is that a realistic estimate?
I am currently trying to decide how the heating energy should be generated.
Here in the forum, I came across the horizontal ground loop collector, which I find very interesting. In conversations with two prefabricated house suppliers, I mentioned that I am considering generating energy with a horizontal ground loop collector. Both times, the response was, "We’ve heard of horizontal ground loop collectors, but never installed one."
One offer included an air-to-water heat pump (Luxhaus KfW55), and the other included an air-to-air heat pump with controlled residential ventilation (Streif Haus KfW40). The house will have two levels, no basement, around 190 m² (2,045 sq ft), on a fairly flat plot with no special features.
I am wondering how the horizontal ground loop collector differs technically and in price from the air-to-water heat pump.
Is the technology inside the house the same, or are there other factors to consider, such as system size and design?
Is the main difference simply that instead of the external unit of the air heat pump, I install the trench and lay the pipes?
What is the price difference?
What about the long-term difference in energy consumption? The air heat pump needs to run continuously on electricity to draw in air—how does it work with geothermal energy from the horizontal ground loop in this regard?
Lastly, a question regarding the air-to-air heat pump:
The sales representative from Streif Haus said that if I wanted to switch from the air-to-air heat pump to an air-to-water heat pump, it would cost about 10,000 euros more. Is that a realistic estimate?
Teemoe86 schrieb:
Currently, when we shower the next morning, we turn up the underfloor heating a bit the evening before.How long have you been living there, and do you really have a heat pump? I believe this heat pump is not running optimally.
Teemoe86 schrieb:
If you shower every day instead of every other day, we would keep the bathroom temperature permanently at 23°C (73°F), since constantly turning the heat up and down wouldn’t make sense with such thermal inertia. We would rather keep the bathroom at a constant 23°C (73°F) and the rest of the rooms at 21°C (70°F). This would probably only need to be taken into account during the heating load calculation.
face26 schrieb:
None of the three options allow for that. Air-to-water heat pumps and ground-source heat pumps are limited by the slow response of underfloor heating, and with an air heat pump you can’t just quickly turn up the heater like a portable fan heater.
I haven’t followed everything, but if you currently live in an older house, you shouldn’t make direct comparisons. The experience in a modern new build is quite different. If you are still worried, you would need to use supplementary heaters.
Infrared heating is one option. But keep in mind that some women find standing in front of a bathroom mirror with infrared panels uncomfortable while doing makeup.
It does exist, but it’s completely uneconomical. A lot of investment that is never recouped. At the moment, we still live in an apartment with a regular gas boiler and radiators. So we will probably have to adjust to that.
Can anyone comment on the different energy consumptions of the three heating systems? Obviously, it depends on many factors (user behavior, insulation, size of the heated area, etc.). But there should be some kind of general trend, right?
S
Strahleman8 Jun 2020 10:02DerGuteTon schrieb:
Is a cooling function of an air-to-water heat pump any good? The cooling function can generally help keep the house a bit cooler during the peak of summer. However, this only works if it is started early and combined with very effective shading. You can expect around a 2-3°C (4-5°F) difference this way.
Unlike a ground-source (or brine-to-water) heat pump, using the cooling function on an air-to-water heat pump always involves a corresponding energy input.
The biggest issue, however, is humidity. That’s what really makes the temperature feel uncomfortable. And that can only be removed from the house with an air conditioning system. We initially planned to rely on the passive cooling of the ground-source heat pump. Now, however, we are likely abandoning that plan and, in coordination with our refrigeration technician (who is installing the heat pump), are laying copper pipes for a potential future installation of an air conditioning system.
DaSch17 schrieb:
Is there any information on the different consumption values of the three heating systems? Logically, this depends on many factors (user behavior; insulation; size of the area to be heated, etc.)... But there should be some kind of trend, right?You can’t really give any solid figures. Ground-source heat pumps are definitely the most efficient. A lot depends on the design and sizing. A poorly designed ground-source heat pump with a badly planned underfloor heating system is less efficient than a well-designed air-source heat pump.
Very generally, I would say:
Air-to-air heat pumps are not worthwhile in a KfW55 standard house (but be careful, the KfW55 label alone doesn’t give a clear indication of the insulation level). The investment savings there are quickly lost through higher consumption. In other words, you need a very, very well-insulated house with a very low heating load for an air-to-air heat pump to be worth it despite its lower efficiency. I would exclude it from the start.
Choosing between a ground-source heat pump and an air-to-water heat pump is a matter of calculation and personal preference. Generally, the investment for a ground-source heat pump is considerably higher. On the other hand, it offers higher efficiency and, with current subsidies, the difference becomes smaller. If you can provide some DIY work and enjoy it, and use a horizontal trench collector, you might even get a ground-source heat pump at no extra cost.
DaSch17 schrieb:
Is there any information about the different energy consumption values of the three heating systems? Assuming a standardized house built to the KFW55 standard and taking the air-to-water heat pump as the baseline at 100%, I estimate the following:
Air-to-water heat pump: 100%
Air-to-air heat pump: 200-300%
Ground-source (water-to-water) heat pump: 75%
Please note, these are not confirmed figures; this is simply my personal estimate. If anyone has a different opinion or verified data, I am interested.
Where do my assumptions come from?
Air-to-air heat pump: electricity directly generates heat at a 1:1 ratio
Air-to-water heat pump: 1 kWh of electricity produces 3-4 kWh of heat
Ground-source (water-to-water) heat pump: 1 kWh of electricity produces approximately 4-5 kWh of heat
What can also be seen here is that the smaller the total energy demand, the less impact the choice of heat pump has. This means an air-to-air heat pump (if at all) only becomes interesting when the total heating energy demand is very low (passive house).
Exactly when each system pays off can only be calculated based on the precise data of the individual building; everything else can only be a rough estimate.
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