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 So this argument is no longer valid.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
Acof1978 schrieb:
You’re probably right. But this is how it is for us. In this case, it’s not ecological. We chose it consciously. We don’t want to use the fireplace for heating, and since we only use it a few days a year (I estimate about 20), it doesn’t make sense for us to use it for heating purposes.
You are also right about the ecological footprint.
As I said, we made conscious decisions for this, just like for a rainwater harvesting system and a photovoltaic system. It’s a matter of give and take. An electric cargo bike for commuting is also coming soon, which will replace car trips. Isn’t it the other way around? If you use the fireplace so rarely anyway, it doesn’t hurt to make use of the heat as well :-)
rdwlnts schrieb:
What energy standard are you building to? With KfW40, the room quickly turns into a sauna with a maximum stay of 15 minutes. But then again, what wouldn’t you do to have a regular lifelong chat with the chimney sweep.We are building to KfW 55. Heating is not done with the fireplace.
Myrna_Loy schrieb:
We have forest nearby, so I know how fast it grows. I also know how much work it is to turn a 15 m (50 feet) beech tree into firewood. And all that just for the appearance? I don’t bake a cake just to look at it and then throw it away.Of course, I thought about what you wrote and consulted our stove installer. Apparently, I misunderstood him. Here is his response:
"The heat emitted by the firebox into the combustion chamber should not be lost through the chimney. I apparently did not explain this clearly enough. Around the firebox, heat storage stones will be installed, which then store this radiant heat and keep the system warm even when there is no longer a fire in the stove. This way, we achieve a high efficiency and make very good use of the fuel wood. I would not recommend a firebox with a water heat exchanger, and not only because of the very high costs."
Well, the house is warm even without a fireplace. The additional heat is actually too much. Or do you want to be cold first? At least the temperature increase is buffered.
However, you have to turn off the underfloor heating, and the screed starts to cool down (warm air rises), meaning the actual thermal mass of the house then requires the heat pump to work harder by temporarily increasing the flow temperature.
A highly efficient underfloor heating system is not controlled and runs continuously, day and night. The fireplace slightly reduces the overall heating demand from the heat pump, but it makes the heat pump less efficient over the annual cycle. And it still gets too warm when using the fireplace. Therefore, partial ventilation is necessary, and the heat pump heating demand rises again.
There are now artificial fireplaces that are indistinguishable from real ones. And they cost less than 10–15k€ (about 11,000–16,500 USD).
If the wood is not properly dried, it actually releases more CO2 than coal.
Fine dust is also released as a side effect.
We simply need to stop constantly burning things, and a fireplace cannot be justified reasonably.
However, you have to turn off the underfloor heating, and the screed starts to cool down (warm air rises), meaning the actual thermal mass of the house then requires the heat pump to work harder by temporarily increasing the flow temperature.
A highly efficient underfloor heating system is not controlled and runs continuously, day and night. The fireplace slightly reduces the overall heating demand from the heat pump, but it makes the heat pump less efficient over the annual cycle. And it still gets too warm when using the fireplace. Therefore, partial ventilation is necessary, and the heat pump heating demand rises again.
There are now artificial fireplaces that are indistinguishable from real ones. And they cost less than 10–15k€ (about 11,000–16,500 USD).
If the wood is not properly dried, it actually releases more CO2 than coal.
Fine dust is also released as a side effect.
We simply need to stop constantly burning things, and a fireplace cannot be justified reasonably.
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