ᐅ Air-to-water heat pump including ventilation system vs. ground-source heat pump including ventilation system
Created on: 31 May 2018 08:51
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Bauer2018
Hello dear forum community,
We are currently planning the heating system for our new build (135 sqm [1450 sq ft] living area, KfW 55 standard). So far, we thought we wanted an air-to-water heat pump with a central ventilation system featuring heat recovery. The KfW application has been submitted and approved for the air-to-water heat pump.
Now we had a meeting with a heating contractor who strongly recommended a ground-source heat pump. This also sounds logical to us... better annual performance factor (seasonal coefficient of performance), since deep underground it never gets too cold... therefore, there is no “risk” of the electric heating element kicking in with the air-to-water heat pump, which would drastically reduce the seasonal performance factor.
In terms of price, both systems are fairly similar after subsidies (the ground-source heat pump is 1500 Euros more expensive after BAFA support).
With the ground-source system, there is the option of a decentralized ventilation system that only exhausts air centrally from the kitchen, bathroom, guest toilet, and utility room, while fresh air is supplied through mechanical openings in the windows (this option would even be 1500 Euros cheaper than the air-to-water heat pump).
Now the questions:
1. Does anyone have experience with these heating systems and can explain why they chose one of the two options?
2. Would I need to change the KfW application if I decide on the ground-source heat pump, even though it offers a better seasonal performance factor?
3. We definitely want a ventilation system with heat recovery, but the decentralized solution sounds a bit odd to me... does anyone have this? Would it be better to go with the central system?
Thank you very much for your answers :-)
Bauer2018
We are currently planning the heating system for our new build (135 sqm [1450 sq ft] living area, KfW 55 standard). So far, we thought we wanted an air-to-water heat pump with a central ventilation system featuring heat recovery. The KfW application has been submitted and approved for the air-to-water heat pump.
Now we had a meeting with a heating contractor who strongly recommended a ground-source heat pump. This also sounds logical to us... better annual performance factor (seasonal coefficient of performance), since deep underground it never gets too cold... therefore, there is no “risk” of the electric heating element kicking in with the air-to-water heat pump, which would drastically reduce the seasonal performance factor.
In terms of price, both systems are fairly similar after subsidies (the ground-source heat pump is 1500 Euros more expensive after BAFA support).
With the ground-source system, there is the option of a decentralized ventilation system that only exhausts air centrally from the kitchen, bathroom, guest toilet, and utility room, while fresh air is supplied through mechanical openings in the windows (this option would even be 1500 Euros cheaper than the air-to-water heat pump).
Now the questions:
1. Does anyone have experience with these heating systems and can explain why they chose one of the two options?
2. Would I need to change the KfW application if I decide on the ground-source heat pump, even though it offers a better seasonal performance factor?
3. We definitely want a ventilation system with heat recovery, but the decentralized solution sounds a bit odd to me... does anyone have this? Would it be better to go with the central system?
Thank you very much for your answers :-)
Bauer2018
I am still not so sure about the supposedly minor additional costs. It sounds like the offer for the air-to-water heat pump includes a central ventilation system (probably a combined unit, but the piping is what costs the money, not the device), whereas the ground-source heat pump does not. That easily amounts to a difference of €10,000 in value.
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Bauer201831 May 2018 12:39Of course, I know that the ventilation system is independent of the choice of heating system. However, with the ground-source heat pump, there would be the option of a decentralized ventilation system... though I’m somewhat skeptical about that. Ventilation would then be ensured through window rebate vents.
The small price differences result from subsidies from BAFA. For the air-source heat pump, there is a grant of 2,500 euros, and for the ground-source heat pump, 5,000 euros. This leads to the slight additional cost of about 1,500 euros.
What exactly does the type of soil mean?
How can I tell if the ground will recover quickly?
Best regards
Bauer2018
The small price differences result from subsidies from BAFA. For the air-source heat pump, there is a grant of 2,500 euros, and for the ground-source heat pump, 5,000 euros. This leads to the slight additional cost of about 1,500 euros.
What exactly does the type of soil mean?
How can I tell if the ground will recover quickly?
Best regards
Bauer2018
montessalet31 May 2018 12:56I would always recommend a ground-source heat pump if it is allowed. The additional costs are manageable nowadays (which was very different 20 years ago). Our existing house has a ground-source heat pump. The follow-up costs are really very low, and the heating works completely without any issues. A unit like that outside would simply bother me—apart from any potential noise disturbances, which are completely absent with a ground-source system.
montessalet schrieb:
I would always recommend a ground-source heat pump if it is allowed: the additional costs are manageable today (which was quite different 20 years ago). No offense, but that statement is simply not accurate in such a general way. The feasibility of a ground-source heat pump largely depends on accessing the heat source and the related costs. These can vary significantly by region, especially for deep drilling. For example, about six months ago, I shared my drilling quote here from the Franconia region. The drilling alone was around 15,000 euros (approx. $16,000). The heat pump unit itself is comparable in cost, but the drilling is not. Even if you deduct a 5,000-euro (approx. $5,300) subsidy from that 15,000 euros, you are still left with about 10,000 euros (approx. $10,600) in additional costs that do not pay off quickly.
Regarding regeneration capability: the ground regenerates through rainfall and moisture – this is how a geologist once explained it to us. If the soil poorly absorbs rainfall (such as clay) and/or it rarely rains, this can become problematic. This has already been an issue for a few clients of our architectural firm. Despite warnings, they insisted on a ground-source heat pump and are now struggling because, under these conditions, the ground cannot provide enough energy.
Don’t get me wrong: I would also recommend a ground-source heat pump if it makes economic sense here and the circumstances are right. Unfortunately, they often aren’t. The idea that ground-source heat pumps are a universal solution that works everywhere simply is not true, and I want to raise awareness of that. In most cases, however, it is a good solution if the additional drilling costs stay within a reasonable range. The local situation matters a lot here, too. Can you manage with just one borehole because you’re allowed to drill deep enough? Or do you have to split it up, for example with 4 or even 6 boreholes, which is considerably more expensive?
Bauer2018 schrieb:
The small price differences result from the subsidies provided by BAFA. For the air-to-water heat pump, there is a subsidy of 2,500 euros, and for the ground-to-water heat pump, 5,000 euros. This explains the small additional costs of about 1,500 euros.To my knowledge, there is no subsidy for air-to-water heat pumps in new buildings, and if there was one, it was around 1,500 euros, right? With smart grid support, there is an additional 500 euros on top, if I remember correctly. Please double-check that.Regardless: could you share the figures without subsidies for the air-to-water heat pump (excluding controlled residential ventilation) and the ground-to-water heat pump (excluding controlled residential ventilation), including the ancillary costs for the development of the heat source in the case of the ground-to-water heat pump?
I am still not quite clear on how the calculations add up here.
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