ᐅ KfW 40 standard, ground-source heat pump worthwhile or better air-to-water?
Created on: 10 Feb 2025 19:22
I
itizniti
Dear forum members,
I have been considering the idea of building a house for several weeks now. The building will be around 160 sqm (1,722 sq ft) and will be located in Duisburg, a city not known for heavy snowfall or freezing temperatures. I already have a plot of land and am in discussions with two general contractors (GC). One GC follows the philosophy of monolithic construction using a ground-source heat pump, while the other initially planned an external thermal insulation composite system (ETICS / external wall insulation) combined with an air-to-water heat pump. I have now also asked the latter to provide a quote based on monolithic construction. Both GCs achieve an energy efficiency class of A+ with their building methods. Currently, I favor the second GC due to almost identical build quality and significantly lower costs; however, I would have to cover the drilling cost myself if I want a ground-source heat pump there.
This raises the question for me whether a ground-source heat pump is really worth it. The drilling costs amount to 12,000–13,000 euros. Fundamentally, I wonder if I will ever recoup that money by installing such a heat pump. Unfortunately, I lack practical experience regarding the energy consumption of both types of heat pumps. My current assumption is that winters will remain mild and electricity costs will continue to decrease.
I look forward to your experiences.
Best regards
P.S. GC1 plans to use the Vaillant flexoCOMPACT exclusive model 58/4 up to 5.28 kW ground-source heat pump, and GC2 proposes the Bosch CS5800iAW as the air-to-water heat pump, if that is of interest.
I have been considering the idea of building a house for several weeks now. The building will be around 160 sqm (1,722 sq ft) and will be located in Duisburg, a city not known for heavy snowfall or freezing temperatures. I already have a plot of land and am in discussions with two general contractors (GC). One GC follows the philosophy of monolithic construction using a ground-source heat pump, while the other initially planned an external thermal insulation composite system (ETICS / external wall insulation) combined with an air-to-water heat pump. I have now also asked the latter to provide a quote based on monolithic construction. Both GCs achieve an energy efficiency class of A+ with their building methods. Currently, I favor the second GC due to almost identical build quality and significantly lower costs; however, I would have to cover the drilling cost myself if I want a ground-source heat pump there.
This raises the question for me whether a ground-source heat pump is really worth it. The drilling costs amount to 12,000–13,000 euros. Fundamentally, I wonder if I will ever recoup that money by installing such a heat pump. Unfortunately, I lack practical experience regarding the energy consumption of both types of heat pumps. My current assumption is that winters will remain mild and electricity costs will continue to decrease.
I look forward to your experiences.
Best regards
P.S. GC1 plans to use the Vaillant flexoCOMPACT exclusive model 58/4 up to 5.28 kW ground-source heat pump, and GC2 proposes the Bosch CS5800iAW as the air-to-water heat pump, if that is of interest.
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nordanney11 Feb 2025 08:52itizniti schrieb:
I don’t fully agree with you regarding the choice of masonry, as I want to make sure that I don’t have to replace the external thermal insulation composite system (ETICS) boards in 30 years.In fact, this 30-year lifespan (or whatever is claimed) is a persistent myth. When installed properly (and maintained if necessary), an ETICS lasts just as long as the building itself. Having to replace the ETICS is actually an exceptional case. There are probably more older buildings with cracks in the facade than cases where the ETICS has failed.W
wiltshire11 Feb 2025 09:36At the Fraunhofer Institute for Building Physics, you can find quite a bit of information about the aging behavior of ETICS (External Thermal Insulation Composite Systems). A summary of a study from last year mentions more visual than technical defects appearing after only 20 years. There is no doubt that the material has proven itself.
I have the material for insulating the concrete foundations. In visible areas, we coated the surface with render. The render on the ETICS facade is quite susceptible to impact damage, and attaching anything to this wall is a hassle. First, the brittle render, then the flexible ETICS, and behind that the hard concrete wall.
The building materials used have not only a technical but for many people also an emotional component. We built with wood and occasionally get head shakes because the material is considered less durable. If I were to build with solid construction, I would much prefer the monolithic type over ETICS. To me, it reminds me too much of a Tupperware container – please take this as a subjective opinion and not offensive. Technically, all these options work. What is important is that you feel comfortable in your own home, and it makes sense to engage with your personal preferences and prejudices and take them into account.
I have the material for insulating the concrete foundations. In visible areas, we coated the surface with render. The render on the ETICS facade is quite susceptible to impact damage, and attaching anything to this wall is a hassle. First, the brittle render, then the flexible ETICS, and behind that the hard concrete wall.
The building materials used have not only a technical but for many people also an emotional component. We built with wood and occasionally get head shakes because the material is considered less durable. If I were to build with solid construction, I would much prefer the monolithic type over ETICS. To me, it reminds me too much of a Tupperware container – please take this as a subjective opinion and not offensive. Technically, all these options work. What is important is that you feel comfortable in your own home, and it makes sense to engage with your personal preferences and prejudices and take them into account.
N
nordanney11 Feb 2025 10:22wiltshire schrieb:
but also an emotional component for many peopleYep. Exterior thermal insulation composite systems (ETICS) are not just plastic. They can also be made from mineral wool, wood wool, straw, phenolic resin, among others. So it’s not always the assumed "hazardous waste."A rough opinion after now 3 years living in a KfW55 house, made with sand-lime bricks plus ETICS (mineral wool insulation) and a brine-water heat pump (NOVELAN WSV 6.2K3M, almost identical to Alphainnotec), with two 80m (260 ft) boreholes.
Electricity costs at about €0.27/kWh (27 cents per kWh) equal roughly €70 (about $75) per month for heating, summer cooling, and hot water, in a 171m² (1,840 sq ft) home, maintaining an indoor temperature of 21–22°C (70–72°F) during winter.
Air-water heat pumps perform very well in summer with low load, but during winter the load is high and they must work hard.
Brine-water heat pumps run consistently and quietly.
What do you think a motor/compressor prefers?
Down/high/down/high!?
Personally, I’m in favor of brine-water.
Electricity costs at about €0.27/kWh (27 cents per kWh) equal roughly €70 (about $75) per month for heating, summer cooling, and hot water, in a 171m² (1,840 sq ft) home, maintaining an indoor temperature of 21–22°C (70–72°F) during winter.
Air-water heat pumps perform very well in summer with low load, but during winter the load is high and they must work hard.
Brine-water heat pumps run consistently and quietly.
What do you think a motor/compressor prefers?
Down/high/down/high!?
Personally, I’m in favor of brine-water.
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