Hello everyone,
due to an interesting topic that has come up around our house construction plans and is causing us some serious questions, I’d like to put this question out there:
Which standard should we build to (Energy Saving Regulation, KfW 55, KfW 40, or KfW 40 plus)?
We are not ideologues, meaning our decisions are mainly based on two criteria:
1) Cost-effort (i.e. which option pays off over the long term)
2) Future viability
-> We are in our early/mid-30s and therefore expect the house to last a long time
-> We expect energy prices to rise
What has happened?
-> We were determined that if we build, it will only be a KfW 40 plus house. Assumption: Insulation has reached its peak development, with little potential left. The top level of insulation has been achieved. The development potential still lies with heat pumps and storage systems.
Therefore, we wanted an air-source heat pump, with as large a solar system as possible (9.99 kWp), plus an appropriate battery storage. Controlled ventilation would be a must in all variants. Goal: to produce all the electricity we need ourselves and end the year with a net zero balance. In other words, no electricity costs or any other energy expenses.
The following challenge then arose:
In our region, there are virtually no general contractors or shell contractors who offer this kind of solution at all. The only company we could build with relatively easily is the well-known one from Bad Fallingbostel. We’ve already had several discussions there, but I’m not entirely convinced. Sure, there are many advantages, but also some things that bother me.
Now we have gone on another tour through local providers.
The consensus: about 70% build to Energy Saving Regulation or KfW 55 standard. One company showed such incompetence in the first meeting and then zero customer service afterward that we can no longer imagine that they can deliver a house with a functioning heating system. One company is now insolvent. Another offers a maximum of KfW 55 (without any option to upgrade). Another would basically build anything for us but thinks anything above KfW 55 is nonsense.
In short: Our idea faces absolutely no support (except in Bad Fallingbostel). And now we are starting to wonder which path might actually be the right one (based on the points mentioned above).
I hope I’m not starting a debate that ultimately ends up as a “matter of belief.” The problem is that every scenario can apparently be made to "look good" with the right calculations.
I look forward to your experiences, opinions, and perhaps calculations on this topic.
Best regards
CarinaJ
due to an interesting topic that has come up around our house construction plans and is causing us some serious questions, I’d like to put this question out there:
Which standard should we build to (Energy Saving Regulation, KfW 55, KfW 40, or KfW 40 plus)?
We are not ideologues, meaning our decisions are mainly based on two criteria:
1) Cost-effort (i.e. which option pays off over the long term)
2) Future viability
-> We are in our early/mid-30s and therefore expect the house to last a long time
-> We expect energy prices to rise
What has happened?
-> We were determined that if we build, it will only be a KfW 40 plus house. Assumption: Insulation has reached its peak development, with little potential left. The top level of insulation has been achieved. The development potential still lies with heat pumps and storage systems.
Therefore, we wanted an air-source heat pump, with as large a solar system as possible (9.99 kWp), plus an appropriate battery storage. Controlled ventilation would be a must in all variants. Goal: to produce all the electricity we need ourselves and end the year with a net zero balance. In other words, no electricity costs or any other energy expenses.
The following challenge then arose:
In our region, there are virtually no general contractors or shell contractors who offer this kind of solution at all. The only company we could build with relatively easily is the well-known one from Bad Fallingbostel. We’ve already had several discussions there, but I’m not entirely convinced. Sure, there are many advantages, but also some things that bother me.
Now we have gone on another tour through local providers.
The consensus: about 70% build to Energy Saving Regulation or KfW 55 standard. One company showed such incompetence in the first meeting and then zero customer service afterward that we can no longer imagine that they can deliver a house with a functioning heating system. One company is now insolvent. Another offers a maximum of KfW 55 (without any option to upgrade). Another would basically build anything for us but thinks anything above KfW 55 is nonsense.
In short: Our idea faces absolutely no support (except in Bad Fallingbostel). And now we are starting to wonder which path might actually be the right one (based on the points mentioned above).
I hope I’m not starting a debate that ultimately ends up as a “matter of belief.” The problem is that every scenario can apparently be made to "look good" with the right calculations.
I look forward to your experiences, opinions, and perhaps calculations on this topic.
Best regards
CarinaJ
Building anything better than the energy saving ordinance will probably never be economical.
So it’s about the green mindset or other motivations.
However, I wouldn’t build with someone who improves a KfW 55 house to a KfW 40, as that is pointless.
If you want an energy-efficient house, then work with an architect who considers all aspects. Otherwise, it’s not worth the effort.
So it’s about the green mindset or other motivations.
However, I wouldn’t build with someone who improves a KfW 55 house to a KfW 40, as that is pointless.
If you want an energy-efficient house, then work with an architect who considers all aspects. Otherwise, it’s not worth the effort.
Hello everyone,
I have a few basic questions that I need to ask. We would like to have a mechanical ventilation with heat recovery system (for comfort reasons—I have allergies, and due to past experiences with well-insulated houses and working full time). Naturally, we were considering a centralized mechanical ventilation system with heat recovery. Does that still make sense? If you build according to the energy saving regulations, my understanding is that it would result in a properly insulated house with a gas heating system.
Our preference would be to have underfloor heating throughout the house and the mechanical ventilation with heat recovery. How is this usually implemented?
I often see houses with solar panels as well. Does that make sense, or is it rather pointless? I assume it often doesn’t pay off because the electricity consumption of the mechanical ventilation system is not high enough for the solar panels to be worthwhile. Is that correct? Or are there any combinations (perhaps including water heating) where it would be beneficial?
Thank you for the insightful contributions. Even though this means we will have to rethink a lot and spend time reading and learning new things.
Regards,
Carina
I have a few basic questions that I need to ask. We would like to have a mechanical ventilation with heat recovery system (for comfort reasons—I have allergies, and due to past experiences with well-insulated houses and working full time). Naturally, we were considering a centralized mechanical ventilation system with heat recovery. Does that still make sense? If you build according to the energy saving regulations, my understanding is that it would result in a properly insulated house with a gas heating system.
Our preference would be to have underfloor heating throughout the house and the mechanical ventilation with heat recovery. How is this usually implemented?
I often see houses with solar panels as well. Does that make sense, or is it rather pointless? I assume it often doesn’t pay off because the electricity consumption of the mechanical ventilation system is not high enough for the solar panels to be worthwhile. Is that correct? Or are there any combinations (perhaps including water heating) where it would be beneficial?
Thank you for the insightful contributions. Even though this means we will have to rethink a lot and spend time reading and learning new things.
Regards,
Carina
It’s quite interesting how confident everyone is here that it “will never” pay off. As if everyone swallowed a crystal ball.
You assume rising energy prices. I do too, mainly because of inflation. Electricity prices are primarily made up of taxes and less by changes in generation costs. Gas is different; it is a globally traded commodity and linked to oil prices. It’s highly volatile and currently at a low, so many believe this is a good deal for the next 30 years. Time will tell. Gas prices of €60 can easily become €100.
You also say insulation has reached its limit and you’d rather focus on the building services systems. I don’t see it that way. The common insulation material in structural walls is EPS (expanded polystyrene), with a thermal conductivity of around WLG 032, typically 035. Mineral wool insulation falls between 040 to 035. However, the current state of the art includes vacuum insulation panels, with thermal conductivity from WLG 007 down to even 002. These are available on the market but quite expensive. The advantage is they are about 5 to 10 times thinner than comparable insulation. In a structural wall, this means a KfW 55 standard can be achieved with a wall thickness of about 20-22cm (8-9 inches) compared to 35-37cm (14-15 inches) otherwise. That’s a significant gain in living space, which translates directly into money.
More insulation reduces the building’s heating load, allowing for smaller heating systems. This saves investment costs, for example, a smaller heat pump or shorter geothermal boreholes (if applicable). The facade will outlast any technical systems and will not be changed quickly. In 20 years, your heating system might need replacement, but the insulation will again help reduce costs when installing a new system. Just a suggestion not to reduce the topic to “Today I pay €60 gas, you pay €50 electricity.”
Regarding subsidies, that depends on the individual situation. Here, we have to build at least to the KfW 55 standard (or at least meet that level, not necessarily go through the KfW program), as nothing else is allowed in new development areas in this city. Controlled ventilation systems are standard anyway, so upgrading to KfW 40 is just a small step if you add just 2-4cm (1 inch) more insulation to the structural wall. That can be worthwhile. For two residential units, subsidies double, making it even more attractive. Some also appreciate KfW loan conditions because they are credit-rating independent, unlike typical bank loans. However, since the beginning of this year, KfW conditions have become less attractive for us, so we plan to skip the KfW certification and the associated loan and subsidy. But this is just a snapshot; a year ago it was different.
KfW 40+ costs about €40,000. That’s a fair point when you consider the large step from Energy Saving Ordinance standards to KfW 40: roughly €10,000 more for insulation, €10,000 for ventilation systems, €10,000 for photovoltaics, and €10,000 for battery storage. Approximately. In return, there’s a €15,000 repayment subsidy (but you have to take the full KfW loan for that), or €30,000 with two units... plus energy savings, a higher quality house (better resale value), possible income from photovoltaics or savings on household electricity, and the intangible comfort of controlled ventilation.
You assume rising energy prices. I do too, mainly because of inflation. Electricity prices are primarily made up of taxes and less by changes in generation costs. Gas is different; it is a globally traded commodity and linked to oil prices. It’s highly volatile and currently at a low, so many believe this is a good deal for the next 30 years. Time will tell. Gas prices of €60 can easily become €100.
You also say insulation has reached its limit and you’d rather focus on the building services systems. I don’t see it that way. The common insulation material in structural walls is EPS (expanded polystyrene), with a thermal conductivity of around WLG 032, typically 035. Mineral wool insulation falls between 040 to 035. However, the current state of the art includes vacuum insulation panels, with thermal conductivity from WLG 007 down to even 002. These are available on the market but quite expensive. The advantage is they are about 5 to 10 times thinner than comparable insulation. In a structural wall, this means a KfW 55 standard can be achieved with a wall thickness of about 20-22cm (8-9 inches) compared to 35-37cm (14-15 inches) otherwise. That’s a significant gain in living space, which translates directly into money.
More insulation reduces the building’s heating load, allowing for smaller heating systems. This saves investment costs, for example, a smaller heat pump or shorter geothermal boreholes (if applicable). The facade will outlast any technical systems and will not be changed quickly. In 20 years, your heating system might need replacement, but the insulation will again help reduce costs when installing a new system. Just a suggestion not to reduce the topic to “Today I pay €60 gas, you pay €50 electricity.”
Regarding subsidies, that depends on the individual situation. Here, we have to build at least to the KfW 55 standard (or at least meet that level, not necessarily go through the KfW program), as nothing else is allowed in new development areas in this city. Controlled ventilation systems are standard anyway, so upgrading to KfW 40 is just a small step if you add just 2-4cm (1 inch) more insulation to the structural wall. That can be worthwhile. For two residential units, subsidies double, making it even more attractive. Some also appreciate KfW loan conditions because they are credit-rating independent, unlike typical bank loans. However, since the beginning of this year, KfW conditions have become less attractive for us, so we plan to skip the KfW certification and the associated loan and subsidy. But this is just a snapshot; a year ago it was different.
KfW 40+ costs about €40,000. That’s a fair point when you consider the large step from Energy Saving Ordinance standards to KfW 40: roughly €10,000 more for insulation, €10,000 for ventilation systems, €10,000 for photovoltaics, and €10,000 for battery storage. Approximately. In return, there’s a €15,000 repayment subsidy (but you have to take the full KfW loan for that), or €30,000 with two units... plus energy savings, a higher quality house (better resale value), possible income from photovoltaics or savings on household electricity, and the intangible comfort of controlled ventilation.
For the Energy Saving Ordinance, a mechanical ventilation system with heat recovery should be sufficient instead of solar panels. At least, that’s how the standard Energy Saving Ordinance house from our general contractor is designed. Although decentralized ventilation isn’t my preference, it’s still acceptable.
I would skip additional solar panels. Instead, I’d opt to space the underfloor heating pipes more closely so that the system works efficiently with the lower supply temperatures of a heat pump.
Why wouldn’t a central mechanical ventilation system with heat recovery make sense? If it is a desirable comfort feature for you. It was for us as well. Thanks to favorable KfW loan interest rates last year, opting for KfW 55 made sense for us. At the moment, it might not be worthwhile. If you do aim for KfW 55, look for certified energy consultants. Ours cost €2500 (about half of which KfW reimburses).
I would skip additional solar panels. Instead, I’d opt to space the underfloor heating pipes more closely so that the system works efficiently with the lower supply temperatures of a heat pump.
Why wouldn’t a central mechanical ventilation system with heat recovery make sense? If it is a desirable comfort feature for you. It was for us as well. Thanks to favorable KfW loan interest rates last year, opting for KfW 55 made sense for us. At the moment, it might not be worthwhile. If you do aim for KfW 55, look for certified energy consultants. Ours cost €2500 (about half of which KfW reimburses).
By the way, the statement about the KfW assessor mentioned at the beginning of the thread is incorrect. On one hand, the costs are covered halfway by the KfW, and on the other hand, specific services for the thermal insulation certificate are required for an Energy Saving Ordinance house, which are not free of charge. To be precise, KfW assessors and energy consultants who prepare thermal insulation certificates are usually the same person.
Facts. The current energy-saving regulation requires the partial use of renewable energy in new buildings. The most cost-effective solution for installation is a gas condensing boiler combined with solar panels for hot water production. The solar system can be effectively replaced by a controlled mechanical ventilation system with heat recovery. More is always better; less is not sufficient. The regulation also allows for district heating from renewable sources, biogas, or combined heat and power (CHP) systems. Where available, these are certainly the cheapest options in terms of initial investment.
It is also a fact that every house requires, in addition to plans and structural calculations, proof of compliance with the energy-saving regulation in the form of an energy demand calculation, which is carried out by a qualified engineering firm. This documentation is provided to the builder as proof and is part of the official house records.
Another fact is that when we talk about indoor climate, even a standard house built to the energy-saving regulation is very airtight. Therefore, it only makes sense to include some form of mechanical ventilation. The cheapest option is a bathroom exhaust fan, as this is where most moisture occurs, combined with trickle vents around the windows. A controlled mechanical ventilation system is a comfort option but uses electricity.
Karsten
It is also a fact that every house requires, in addition to plans and structural calculations, proof of compliance with the energy-saving regulation in the form of an energy demand calculation, which is carried out by a qualified engineering firm. This documentation is provided to the builder as proof and is part of the official house records.
Another fact is that when we talk about indoor climate, even a standard house built to the energy-saving regulation is very airtight. Therefore, it only makes sense to include some form of mechanical ventilation. The cheapest option is a bathroom exhaust fan, as this is where most moisture occurs, combined with trickle vents around the windows. A controlled mechanical ventilation system is a comfort option but uses electricity.
Karsten
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