Hello everyone. My partner and I are planning to build a house. About 140-150 square meters (1507-1615 square feet), 1.5 stories. After initially considering building a KfW 40 house, I quickly moved away from that idea. The general opinion seems to be that it’s not cost-effective (considering only the costs). So now we want to build according to KfW 55 standards.
Underfloor heating is planned throughout the entire house. However, despite extensive research, we are still uncertain about other details. For the standard KfW 55, a heat pump or a gas connection (then with a share of renewable energy) is mandatory, right?
What do you think is the best combination for KfW 55? I had originally planned on a ground source heat pump / geothermal system. But this seems somewhat oversized for a new build, doesn’t it? What technology would you recommend for an air-source heat pump?
Does it make sense to install a photovoltaic system (because of the additional electricity costs of the heat pump and generally) or solar thermal collectors? Would solar thermal still be mandatory if using a heat pump? With gas, solar thermal would be mandatory, right?
I’m also interested in your opinions on a controlled mechanical ventilation system. If yes, with or without heat recovery? I know the cost of the system does not pay off financially. But it’s a gain in comfort (no need to ventilate manually and you have fresh air). Does it offer any additional benefits? The filters would also reduce dirt like pollen, dust, etc. inside the house, right? Maybe someone has current experiences with these systems. I have read a lot, but mostly reports from 3-4 years ago.
Am I forgetting any important systems or options?
Underfloor heating is planned throughout the entire house. However, despite extensive research, we are still uncertain about other details. For the standard KfW 55, a heat pump or a gas connection (then with a share of renewable energy) is mandatory, right?
What do you think is the best combination for KfW 55? I had originally planned on a ground source heat pump / geothermal system. But this seems somewhat oversized for a new build, doesn’t it? What technology would you recommend for an air-source heat pump?
Does it make sense to install a photovoltaic system (because of the additional electricity costs of the heat pump and generally) or solar thermal collectors? Would solar thermal still be mandatory if using a heat pump? With gas, solar thermal would be mandatory, right?
I’m also interested in your opinions on a controlled mechanical ventilation system. If yes, with or without heat recovery? I know the cost of the system does not pay off financially. But it’s a gain in comfort (no need to ventilate manually and you have fresh air). Does it offer any additional benefits? The filters would also reduce dirt like pollen, dust, etc. inside the house, right? Maybe someone has current experiences with these systems. I have read a lot, but mostly reports from 3-4 years ago.
Am I forgetting any important systems or options?
As already mentioned, take some time to read through the forum. The same questions come up every 2-3 months.
Gas technology is well established, whereas heat pumps are still developing.
Over a 20-year period, the costs roughly even out regardless of which system you install.
KfW-55 is good, but the minimum standard of the energy saving regulation / building code is also sufficient.
What you save in initial costs will be offset by higher energy consumption, and vice versa.
Ventilation systems are only mandatory in passive houses. However, I wouldn’t want to live in a modern house without one. These buildings are simply constructed to be too airtight by design (regardless of whether it’s just the energy saving regulation / building code, 55, 40, or even lower).
Either you have the interest and time to ventilate yourself, or you let the technology take care of it.
Gas technology is well established, whereas heat pumps are still developing.
Over a 20-year period, the costs roughly even out regardless of which system you install.
KfW-55 is good, but the minimum standard of the energy saving regulation / building code is also sufficient.
What you save in initial costs will be offset by higher energy consumption, and vice versa.
Ventilation systems are only mandatory in passive houses. However, I wouldn’t want to live in a modern house without one. These buildings are simply constructed to be too airtight by design (regardless of whether it’s just the energy saving regulation / building code, 55, 40, or even lower).
Either you have the interest and time to ventilate yourself, or you let the technology take care of it.
I actually often agree with you, even more so now on the topic of KNX [emoji6]
But neither this...
nor this...
nor this...
is unfortunately true.
Just read the discussion above. If the infiltration airflow is less than the airflow needed for moisture control (and that’s not much), a USER-INDEPENDENT ventilation system is absolutely necessary. This can be found in DIN 1946-6.
If a planner, general contractor, or whoever does not point out that a ventilation concept is missing, they become liable for damages. And as you already said, even the Energy Saving Ordinance 2016 often results in buildings being too airtight for proper moisture protection.
And believing that manual ventilation is always an alternative is unfortunately wrong. I had to learn this too, as I thought the same. But user-independence is critical for moisture protection. In fact, courts apparently now also see it this way—that it is unreasonable for working people to ventilate twice a day! I personally see it differently, but that probably doesn’t matter [emoji6]
But neither this...
Mycraft schrieb:
...heat pumps are still in their infancy.
nor this...
Over a 20-year period, the costs roughly come out the same regardless of what you install.
nor this...
Ventilation systems are only mandatory in passive houses.
...
Either you have the time and willingness to ventilate manually, or you let the technology do it for you.
is unfortunately true.
Just read the discussion above. If the infiltration airflow is less than the airflow needed for moisture control (and that’s not much), a USER-INDEPENDENT ventilation system is absolutely necessary. This can be found in DIN 1946-6.
If a planner, general contractor, or whoever does not point out that a ventilation concept is missing, they become liable for damages. And as you already said, even the Energy Saving Ordinance 2016 often results in buildings being too airtight for proper moisture protection.
And believing that manual ventilation is always an alternative is unfortunately wrong. I had to learn this too, as I thought the same. But user-independence is critical for moisture protection. In fact, courts apparently now also see it this way—that it is unreasonable for working people to ventilate twice a day! I personally see it differently, but that probably doesn’t matter [emoji6]
You can see it however you want... but what I wrote reflects the current situation.
There are plenty of comparisons and projections regarding the 20-year timeframe.
DIN standards are guidelines, not mandatory requirements, so they can be followed but don’t have to be.
And it will still take years to decades before heat pumps are technically on par with established heating methods. There is plenty of experience and information about this available elsewhere on the internet and just about every neighborhood.
P.S. I read the discussion carefully before my initial post.
There are plenty of comparisons and projections regarding the 20-year timeframe.
DIN standards are guidelines, not mandatory requirements, so they can be followed but don’t have to be.
And it will still take years to decades before heat pumps are technically on par with established heating methods. There is plenty of experience and information about this available elsewhere on the internet and just about every neighborhood.
P.S. I read the discussion carefully before my initial post.
Mycraft schrieb:
You can see it however you want... but what I wrote reflects the current situation.Alright, I claim the opposite—so who is actually right?!There are plenty of comparisons and projections regarding the 20 years.Then please name some, with sources. Otherwise, it’s just what it is: a claim without proof. That’s unfortunately not how this works [emoji4]DIN standards are not mandatory but only guidelines, so you can follow them, but you don’t have to.When EU directives refer to DIN standards, they can become mandatory and legally binding. Just take a look at the Medical Device Regulation (MDR) and DIN 13485. So, that statement is not generally true, although it might be the case in construction. Yet even in construction, DIN standards are the basis for recognized rules of technology and are cited by courts to clarify liability issues in disputes. If you violate a DIN standard (like DIN 1946-6) and cannot prove that your solution, which does not comply with the standard, is correct, things look pretty bad. So yes, you do not have to comply, but that might not be very wise. Besides that, your general contractor, architect, or whoever is involved could be in quite a difficult position if they don’t point out the absence of a ventilation concept and the implementation of moisture protection measures (and the three additional ventilation levels).DIN standards thus do provide manufacturers with legal security in product liability matters.
Specifically regarding the ventilation concept—Google provides this answer on Wikipedia:
“The updated DIN 1946-6 standard ensures legal certainty in critical areas.
Since then, in Germany, it is necessary to prove whether adequate moisture removal can be guaranteed without active window ventilation. If a ventilation concept is created, the occupant has a legal obligation to follow it. If the architect or planner does not point out the absence of a ventilation concept or the failure to comply with DIN 1946-6, they are liable in the event of mold damage.
In Austria, this regulation does not explicitly apply. However, if a court case arises concerning related consequences, the standard of technology is referred to—which, due to a lack of an Austrian standard, can be found in the German standard.”
and further
“Nevertheless, even when the standard is followed, legal risks remain for planners and contractors. Even strict adherence to the requirements might mean that the necessary active window ventilation—as required by the ventilation concept—for producing a hygienic indoor climate is considered unreasonable. For example, courts increasingly regard twice-a-day airing by users who work full-time as critical or unreasonable.”
Theoretically, it might be true that you don’t have to comply, but either you or your construction company/planner face liability risks if you disregard it. It is not prescribed as law, though, that is true.
And it will take years to decades until heat pumps are technically on par with established heating options.Okay, again a claim waiting eagerly for evidence. [emoji4]Hello everyone,
As an electrician, the DIN VDE 0100 standard is like law to me, even though it is only a DIN standard without legal basis. However, as already mentioned here, since it refers to the recognized rules of technology, it is practically elevated to the status of law.
Regarding home technology, I believe a gas heating system combined with solar thermal energy is a reliable choice.
In my opinion, a ventilation system is mandatory nowadays, regardless of the building method or standard. The risk of long-term mold issues is simply huge with current construction practices. And you can still open windows despite having a ventilation system.
The myth that a photovoltaic system helps with heating by using a heat pump is, in my opinion, exactly that—a myth. Especially problematic are air-to-water heat pump systems. In winter, I am essentially heating with electricity, and all the optimistic calculations by air-to-water heat pump enthusiasts don’t change that fact!
And before there are any arguments here, I have a 30kW photovoltaic system on my roof, which unfortunately generates electricity mainly when I don’t need it for heating. Since I drive a plug-in hybrid, I use it to charge my car at about €0.1/kWh (around 11 cents/kWh). The car consumes about 20kWh/100km (12.4 miles). That means my cost is approximately €2 per 100 km (about $2.20 per 62 miles).
By the way, I heat with liquefied gas, wood, and solar thermal energy, so I know what I’m talking about (despite having a large photovoltaic system on the roof). There is one thing I do: the water for the washbasins runs through an instantaneous water heater compatible with solar thermal systems. This means the water heater can handle water temperatures up to 70°C (158°F). In summer, I can wait until the solar thermal system heats up the storage tank and don’t have to use gas for heating. When the tank is hot, it supplies the warm water, and the instantaneous water heater does nothing. But when the tank is cold, the water heater heats the water up to 45°C (113°F). If the water comes out of the tank at 35°C (95°F), the water heater brings it up to 45°C (113°F).
As an electrician, the DIN VDE 0100 standard is like law to me, even though it is only a DIN standard without legal basis. However, as already mentioned here, since it refers to the recognized rules of technology, it is practically elevated to the status of law.
Regarding home technology, I believe a gas heating system combined with solar thermal energy is a reliable choice.
In my opinion, a ventilation system is mandatory nowadays, regardless of the building method or standard. The risk of long-term mold issues is simply huge with current construction practices. And you can still open windows despite having a ventilation system.
The myth that a photovoltaic system helps with heating by using a heat pump is, in my opinion, exactly that—a myth. Especially problematic are air-to-water heat pump systems. In winter, I am essentially heating with electricity, and all the optimistic calculations by air-to-water heat pump enthusiasts don’t change that fact!
And before there are any arguments here, I have a 30kW photovoltaic system on my roof, which unfortunately generates electricity mainly when I don’t need it for heating. Since I drive a plug-in hybrid, I use it to charge my car at about €0.1/kWh (around 11 cents/kWh). The car consumes about 20kWh/100km (12.4 miles). That means my cost is approximately €2 per 100 km (about $2.20 per 62 miles).
By the way, I heat with liquefied gas, wood, and solar thermal energy, so I know what I’m talking about (despite having a large photovoltaic system on the roof). There is one thing I do: the water for the washbasins runs through an instantaneous water heater compatible with solar thermal systems. This means the water heater can handle water temperatures up to 70°C (158°F). In summer, I can wait until the solar thermal system heats up the storage tank and don’t have to use gas for heating. When the tank is hot, it supplies the warm water, and the instantaneous water heater does nothing. But when the tank is cold, the water heater heats the water up to 45°C (113°F). If the water comes out of the tank at 35°C (95°F), the water heater brings it up to 45°C (113°F).
To put it simply: if you want to rebuild an old building, then by all means aim for KfW55 or worse.
The regulations are regularly becoming stricter, and your new build will already be outdated before you move in.
When every euro counts, there isn’t much room for flexibility, but you should be aware that you won’t be installing the latest state-of-the-art technology.
It also depends on who you ask. However, if your counterpart starts talking about “breathing walls,” it’s better to end the conversation.
The regulations are regularly becoming stricter, and your new build will already be outdated before you move in.
When every euro counts, there isn’t much room for flexibility, but you should be aware that you won’t be installing the latest state-of-the-art technology.
It also depends on who you ask. However, if your counterpart starts talking about “breathing walls,” it’s better to end the conversation.
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