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Andreas_7926 Jul 2021 12:07Hello 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 So this argument is no longer valid.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
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RotorMotor26 Jul 2021 12:33What specific questions do you still have?
The internet is full of experiences.
Why don’t you want underfloor heating?
The internet is full of experiences.
Why don’t you want underfloor heating?
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Andreas_7926 Jul 2021 13:11I have now searched the internet for hours/days.
I was hoping for some experience reports from here.
How did you make your decision and why choose one option over the other?
Why no underfloor heating? I can’t really say exactly; it’s more of a feeling, not something concrete.
I was hoping for some experience reports from here.
How did you make your decision and why choose one option over the other?
Why no underfloor heating? I can’t really say exactly; it’s more of a feeling, not something concrete.
Andreas_79 schrieb:
In order to compare the 5 offers reasonably, they all need to be as similar as possible. Well, good luck with that! If you really want to compare the offers, they have to be identical, which means you need to specify ALL the details. However, very few general contractors (GCs) will agree to that, and you’ll probably need some technical support (an architect) for it.
Andreas_79 schrieb:
The options under consideration are an air-to-water heat pump, an air-to-air heat pump, or a geothermal (ground source) heat pump. Are you sure? It’s no coincidence that nowadays the air-to-water heat pump is generally regarded as the standard. Geothermal requires suitable geological conditions (do you already have a specific plot of land?), and air-to-air heat pumps are more typical for passive houses. So out of your three main candidates, one might naturally be eliminated through this selection process.
For more details, you can check out https://www.hausbau-forum.de/ 😀
Unfortunately, I can only share limited personal experience.
Radiant heat is the most comfortable form of warmth; the sun provides us with radiant heat. Underfloor heating basically works on this principle of radiant heat. Additionally, the floor itself is warmed and emits some convective heat as well. This makes underfloor heating quite pleasant.
In theory, underfloor heating combined with a heat pump can also provide cooling, but the cooling capacity is rather negligible. However, at least you have a cooler floor to walk on barefoot during summer. (This is an assumption.)
I see two disadvantages to underfloor heating: it is a very slow-reacting system, and individual room control makes little to no sense.
Air-to-air heat pumps work by heating the air, which usually also makes the air very dry. Personally, I have a hard time dealing with dry air (→ car heating in winter).
This would be an absolute dealbreaker for me, even though an air-to-air heat pump is probably by far the most cost-effective option. (In my opinion, cost is the only real advantage of air-to-air heat pumps.)
Radiant heat is the most comfortable form of warmth; the sun provides us with radiant heat. Underfloor heating basically works on this principle of radiant heat. Additionally, the floor itself is warmed and emits some convective heat as well. This makes underfloor heating quite pleasant.
In theory, underfloor heating combined with a heat pump can also provide cooling, but the cooling capacity is rather negligible. However, at least you have a cooler floor to walk on barefoot during summer. (This is an assumption.)
I see two disadvantages to underfloor heating: it is a very slow-reacting system, and individual room control makes little to no sense.
Air-to-air heat pumps work by heating the air, which usually also makes the air very dry. Personally, I have a hard time dealing with dry air (→ car heating in winter).
This would be an absolute dealbreaker for me, even though an air-to-air heat pump is probably by far the most cost-effective option. (In my opinion, cost is the only real advantage of air-to-air heat pumps.)
I would also like to read some experiences; the entire internet, including this forum, is full of them.
Regarding your specific points:
An air-to-air heat pump only makes sense in a net zero energy house; otherwise, it consumes a lot of electricity and can be uncomfortable.
With a heat pump (air-to-water or geothermal), a surface heating system is required. The most cost-effective solution is underfloor heating, but wall or ceiling heating also works.
Where does the aversion to underfloor heating come from? In a normally used single-family home, there is no reason to avoid it or to choose something else like radiators.
The most economical option is KFW55 + air-to-water heat pump + photovoltaic system, but with current subsidies, KFW40+ is probably not much different economically. For everything else, personal preferences are needed.
Regarding your specific points:
An air-to-air heat pump only makes sense in a net zero energy house; otherwise, it consumes a lot of electricity and can be uncomfortable.
With a heat pump (air-to-water or geothermal), a surface heating system is required. The most cost-effective solution is underfloor heating, but wall or ceiling heating also works.
Where does the aversion to underfloor heating come from? In a normally used single-family home, there is no reason to avoid it or to choose something else like radiators.
The most economical option is KFW55 + air-to-water heat pump + photovoltaic system, but with current subsidies, KFW40+ is probably not much different economically. For everything else, personal preferences are needed.
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