Hello everyone
We are currently taking the next steps toward building our own home. We have looked at several prefabricated houses and spoken with sales consultants from various providers. Based on this, we have created a top 5 list. Now I want to contact these 5 companies with our floor plan and the standards we want. This way, I hope the list will be reduced by 2-3 providers after receiving the first offers.
In my inquiry, I want to roughly outline what we have in mind. KFW55, KFW40, or KFW40+ is not yet very important—it will be one of these standards. Our floor plan does not differ much from the standard layouts offered by prefab house suppliers. Something like a simple 8x10 meter (26x33 feet) rectangular shape... To be able to compare the 5 offers reasonably, I want them all to be as similar as possible. Therefore, I would like to specify the heating system.
Now the question is, what is the right choice… I assume this is partly a matter of philosophy? The options are an air-to-water heat pump, an air-to-air heat pump, or a ground-source (geothermal) heat pump. I assume most have one of these three systems combined with solar panels on the roof.
My first thought was this: an air-to-air heat pump, since we would also have an automatic ventilation system in the house, making manual airing less or unnecessary. However, I have learned that all KFW-certified houses are so well insulated that they almost always have automatic ventilation. So this argument is no longer valid. Nevertheless, I still find the air-to-air heat pump interesting. We also want to install a wood stove in the living room. With an air-to-air heat pump, the indoor air is circulated throughout the house, so I could benefit from the wood stove’s heat everywhere, right? Perhaps even with heat recovery, which is usually included.
Another advantage of the air-to-air heat pump would be that if it ever gets too warm, we could install a fixed air conditioning unit somewhere in the house, and the whole house would benefit. The built-in cooling systems in these heat pumps usually aren’t as effective as promised.
Is it true that an air-to-air heat pump cannot provide domestic hot water? Then a second system would be needed just for hot water, which means more costs, two systems to maintain, and more space taken up. In the forum, I mostly see air-to-water heat pumps mentioned, probably combined with underfloor heating. That seems to be the most popular system. Is there a particular reason for this?
Geothermal heating combined with a heat pump seems to be the most efficient. But then I would also have underfloor heating, right? We actually didn’t want underfloor heating, but as I’m writing this, I’m starting to convince myself toward geothermal or air-to-water heat pumps…
How did you make your decision and why? Somehow, I don’t fully trust the salespeople, since they want to sell what makes more money, right? And since I’m not very technical in this area, I’m hoping to benefit from your experience.
Best regards Andreas_79
We are currently taking the next steps toward building our own home. We have looked at several prefabricated houses and spoken with sales consultants from various providers. Based on this, we have created a top 5 list. Now I want to contact these 5 companies with our floor plan and the standards we want. This way, I hope the list will be reduced by 2-3 providers after receiving the first offers.
In my inquiry, I want to roughly outline what we have in mind. KFW55, KFW40, or KFW40+ is not yet very important—it will be one of these standards. Our floor plan does not differ much from the standard layouts offered by prefab house suppliers. Something like a simple 8x10 meter (26x33 feet) rectangular shape... To be able to compare the 5 offers reasonably, I want them all to be as similar as possible. Therefore, I would like to specify the heating system.
Now the question is, what is the right choice… I assume this is partly a matter of philosophy? The options are an air-to-water heat pump, an air-to-air heat pump, or a ground-source (geothermal) heat pump. I assume most have one of these three systems combined with solar panels on the roof.
My first thought was this: an air-to-air heat pump, since we would also have an automatic ventilation system in the house, making manual airing less or unnecessary. However, I have learned that all KFW-certified houses are so well insulated that they almost always have automatic ventilation. So this argument is no longer valid. Nevertheless, I still find the air-to-air heat pump interesting. We also want to install a wood stove in the living room. With an air-to-air heat pump, the indoor air is circulated throughout the house, so I could benefit from the wood stove’s heat everywhere, right? Perhaps even with heat recovery, which is usually included.
Another advantage of the air-to-air heat pump would be that if it ever gets too warm, we could install a fixed air conditioning unit somewhere in the house, and the whole house would benefit. The built-in cooling systems in these heat pumps usually aren’t as effective as promised.
Is it true that an air-to-air heat pump cannot provide domestic hot water? Then a second system would be needed just for hot water, which means more costs, two systems to maintain, and more space taken up. In the forum, I mostly see air-to-water heat pumps mentioned, probably combined with underfloor heating. That seems to be the most popular system. Is there a particular reason for this?
Geothermal heating combined with a heat pump seems to be the most efficient. But then I would also have underfloor heating, right? We actually didn’t want underfloor heating, but as I’m writing this, I’m starting to convince myself toward geothermal or air-to-water heat pumps…
How did you make your decision and why? Somehow, I don’t fully trust the salespeople, since they want to sell what makes more money, right? And since I’m not very technical in this area, I’m hoping to benefit from your experience.
Best regards Andreas_79
H
hampshire5 Aug 2021 13:25hanse987 schrieb:
Manual ventilation is not very frequent, is it.Currently, we even open only once (in the morning and close again in the evening (for most)).hampshire schrieb:
That is the difference between wood and coal.The timelines are obviously different. However, the timeline of a centuries-old tree is also very different from that of a fireplace fire. The claim that burning a tree solely for aesthetic reasons is carbon neutral is and remains a myth.
In terms of calorific value, wood—especially if too wet—is inferior to coal. Considering all effects together (there are many more), the advantage of wood over coal diminishes significantly.
R
RotorMotor5 Aug 2021 14:59So, better to burn coal in the fireplace then? 😎
I'm not sure if that looks very nice and if it really benefits the environment.
I'm not sure if that looks very nice and if it really benefits the environment.
H
hampshire5 Aug 2021 16:00rdwlnts schrieb:
The timeline, of course, varies. But the timeline of a centuries-old tree is very different from that of a log fire. I'll assume you really don't understand and suggest thinking in terms of geological ages. The age of a tree is irrelevant. A few million years, however, is very relevant. Coal is a long-term carbon storage from a climate completely different era. The CO2 you release from coal cannot really be offset, whereas the CO2 from burning wood can be, provided you regrow biomass simultaneously. CO2 from fossil fuels is not compensated by plant growth. That is the significance of the timeline.
rdwlnts schrieb:
The climate neutrality of burning a tree purely for aesthetic reasons is and remains a myth. Burning wood is not climate neutral. If you consider a small cycle and produce the biomass annually that you remove and burn, the climate impact is limited (assuming this biomass would not have grown otherwise). Of course, from a climate perspective, it would be better to avoid energy consumption—whether wood or other sources—purely for enjoyment. However, I will not become a fundamentalist about that.
rdwlnts schrieb:
In terms of calorific value, wood—especially when wet—is inferior to coal. Taken together with all other effects (and there are many more), the advantage of wood over coal shrinks considerably. There are certainly excellent energetic properties of coal—no question. But the very fact that we are releasing ancient CO2 stores into the atmosphere in large quantities disqualifies coal as an acceptable energy source—regardless of whether its energy density is better than wood’s, wet or dry. You are mixing different levels here and aligning with current trends. There is no longer a valid argument for coal if climate-friendly energy is the focus. It’s that simple. Wood is different—although wood consumption also has problematic effects.
Andreas_79 schrieb:
In the forum, I mostly see air-to-water heat pumps, so probably underfloor heating. This seems to be the most popular system. Is there a particular reason for this?Air-to-water heat pumps are relatively affordable (especially compared to groundwater or brine-to-water heat pumps), fully sufficient for a single-family home (for both heating and hot water), and straightforward to install. I also initially considered groundwater or brine heat pumps for their efficiency. However, in the end, they are so expensive that they simply don't pay off.
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