ᐅ kfw40plus monolithic solid construction – tips and experiences?
Created on: 8 Mar 2016 17:25
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bellamuc
Hello everyone,
we are planning to build a house in the Allgäu region. Since it will not be small and includes three residential units, we would like to take advantage of the kfw40plus subsidy. Photovoltaics are already planned extensively (covering the entire roof), so that is settled. Additionally, there will be a hydronic fireplace stove.
I definitely want to build with solid construction and prefer no external insulation. Ideally, I would like a purely monolithic wall made of materials like aerated concrete or expanded clay blocks (so without insulated blocks such as Cariso).
The house will be built on a hillside, with the basement partially exposed on one side and used as living space. Therefore, I would prefer a masonry basement if it is not counterproductive to achieving the kfw40+ standard.
I have received various opinions from construction companies and architects (including passive house planners). It seems everyone tries to sell me the solution they are familiar with.
How can I calculate whether, for example, a 42.5cm (17 inches) thick Ytong wall can meet the kfw40+ standard and which additional measures I need to take (windows, roof, basement floor, other energy-related measures...)?
Maybe there are other factors I can adjust so that the masonry can be as thin as possible (perhaps even 36.5cm (14 inches) plus plaster)? Of course, all this should not cost more than what the subsidy and heating cost savings justify.
Some say that the 0.07 W/(m·K) Ytong or Poroton blocks are so fragile they break easily in your hands… I should rather use 0.08 W/(m·K) blocks and make the wall thicker… there are so many opinions.
Is there anyone here who has really built purely monolithic solid and met the kfw40+ standard?
Any tips?
Greetings from Munich.
we are planning to build a house in the Allgäu region. Since it will not be small and includes three residential units, we would like to take advantage of the kfw40plus subsidy. Photovoltaics are already planned extensively (covering the entire roof), so that is settled. Additionally, there will be a hydronic fireplace stove.
I definitely want to build with solid construction and prefer no external insulation. Ideally, I would like a purely monolithic wall made of materials like aerated concrete or expanded clay blocks (so without insulated blocks such as Cariso).
The house will be built on a hillside, with the basement partially exposed on one side and used as living space. Therefore, I would prefer a masonry basement if it is not counterproductive to achieving the kfw40+ standard.
I have received various opinions from construction companies and architects (including passive house planners). It seems everyone tries to sell me the solution they are familiar with.
How can I calculate whether, for example, a 42.5cm (17 inches) thick Ytong wall can meet the kfw40+ standard and which additional measures I need to take (windows, roof, basement floor, other energy-related measures...)?
Maybe there are other factors I can adjust so that the masonry can be as thin as possible (perhaps even 36.5cm (14 inches) plus plaster)? Of course, all this should not cost more than what the subsidy and heating cost savings justify.
Some say that the 0.07 W/(m·K) Ytong or Poroton blocks are so fragile they break easily in your hands… I should rather use 0.08 W/(m·K) blocks and make the wall thicker… there are so many opinions.
Is there anyone here who has really built purely monolithic solid and met the kfw40+ standard?
Any tips?
Greetings from Munich.
You write that with a 0.07 W/(m²·K) material, for example Ytong, a wall U-value of 0.16 W/(m²·K) can be achieved. I assume you mean this based on a thickness of 42 cm (17 inches)? That already makes me wonder... is that enough? I found a guideline stating that a U-value of at least 0.15 W/(m²·K) must be met. Is there any way to compensate for this slight lack of insulation performance?
And again, my question: I was told that the 0.07 W/(m²·K) blocks, whether Poroton or Ytong, are very porous and need extensive reinforcement afterwards. Can anyone confirm this?
What do you mean when you say I’m “sitting at the source”? A photovoltaic calculation is a standalone project. My conditions are the roof, orientation, budget, and the requirements that must be met, for example self-consumption rate and feed-in restrictions. All of this also has to be economically viable. I can calculate that. For “my” system, I’m going way beyond the target. The system has about 500% more capacity than required, and the battery is around three times larger than needed. However, no one can tell me to what extent, or if at all, this positively affects the calculation and achievement of the KfW 40+ standard. The contractors I consult refer to an internal, complex calculation that only happens after signing a contract; the energy consultant and passive house planner want payment upfront for the calculation, with an uncertain outcome.
And again, my question: I was told that the 0.07 W/(m²·K) blocks, whether Poroton or Ytong, are very porous and need extensive reinforcement afterwards. Can anyone confirm this?
What do you mean when you say I’m “sitting at the source”? A photovoltaic calculation is a standalone project. My conditions are the roof, orientation, budget, and the requirements that must be met, for example self-consumption rate and feed-in restrictions. All of this also has to be economically viable. I can calculate that. For “my” system, I’m going way beyond the target. The system has about 500% more capacity than required, and the battery is around three times larger than needed. However, no one can tell me to what extent, or if at all, this positively affects the calculation and achievement of the KfW 40+ standard. The contractors I consult refer to an internal, complex calculation that only happens after signing a contract; the energy consultant and passive house planner want payment upfront for the calculation, with an uncertain outcome.
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Bauexperte11 Mar 2016 15:50bellamuc schrieb:
You mentioned that with a 0.07 material, for example Ytong, you could achieve a wall U-value of 0.16. I assume you mean this is based on a 42cm (17 inches) thickness?Yes.bellamuc schrieb:
That makes me wonder... is that sufficient? I found a requirement stating that at least a 0.15 U-value must be met. Can the small difference in insulation value somehow be compensated?A single-family house is made up of more than just the sum of its four walls and roof; when all factors (masonry, insulation, windows, thermal bridges, etc.) are taken together, the required U-value must be achieved.bellamuc schrieb:
And again my question: I was told that the 0.07 block, whether Poroton or Ytong, is very porous and therefore needs extensive reinforcement afterward. Can anyone confirm this?I know that our construction companies grumble when they have to install hollow bricks. But it can’t be that bad; otherwise, they would simply refuse to work with these bricks – whether filled or unfilled. Aerated concrete, on the other hand, is very easy to handle; it doesn’t crumble, otherwise many single-family houses here in Germany would eventually fall apart.Could it be that the companies you are referring to typically work with a different type of block (perhaps sand-lime brick) or are not yet familiar with KfW 40 requirements?
bellamuc schrieb:
What do you mean by "I have access to the source"? A photovoltaic calculation is a standalone project. My parameters are roof, orientation, budget, and the requirements that must be met, such as self-consumption rate and feed-in restrictions. All this should also be economically viable.Oh – learned something new; I thought that due to your work, you also had contacts to energy consultants. If not, try asking the energy agency or look for energy consultants in relevant associations. A second quote never hurts.Best regards, Bauexperte
Yes, I have also started to suspect that the construction company I inquired about is not yet experienced with the KfW 40+ standard. However, according to their own information, both primarily build with Ytong.
I just discovered the KfW 431 program. Here, 50% of the "construction supervision" costs are reimbursed, and there is a list of certified energy consultants provided. Apparently, there are 36 consultants within a 5km (3 miles) radius. I have reached out to one of them. Let’s see what comes of it.
And once again: my original question was whether it is possible to compensate for a less efficient wall with other components, such as a better-insulated basement than usual, improved insulation beneath the slab, a better-insulated roof, or higher-performance windows... or with energy measures like a 200% plus-energy house. Of course, the house does not consist of only one wall—but I am being led to believe that the wall must meet a U-value of 0.15 in any case. If it is higher, the wall is automatically disqualified!?
So apparently, that is not the case?
I just discovered the KfW 431 program. Here, 50% of the "construction supervision" costs are reimbursed, and there is a list of certified energy consultants provided. Apparently, there are 36 consultants within a 5km (3 miles) radius. I have reached out to one of them. Let’s see what comes of it.
And once again: my original question was whether it is possible to compensate for a less efficient wall with other components, such as a better-insulated basement than usual, improved insulation beneath the slab, a better-insulated roof, or higher-performance windows... or with energy measures like a 200% plus-energy house. Of course, the house does not consist of only one wall—but I am being led to believe that the wall must meet a U-value of 0.15 in any case. If it is higher, the wall is automatically disqualified!?
So apparently, that is not the case?
bellamuc schrieb:
Hello everyone,
we are planning a house in the Allgäu region. Since it won’t be small and includes 3 residential units, we would like to take advantage of the KfW 40 Plus subsidy. Photovoltaics are already extensively planned (the entire roof), so that is settled. Additionally, there will be a water-heated wood stove. Hello,
we are in almost the same situation, or rather considering everything from all angles.
We are also planning KfW 55 and 3 residential units.
That alone is already quite a challenge (residential building class III, 3 ventilation systems, ...).
We want to build monolithically as well and do not want exterior insulation.
On Wednesday, we had a very comprehensive meeting with our architect and structural engineer. But a lot is still uncertain or not yet decided.
Currently, we have a team consisting of an architect, structural engineer, verification engineer, and KfW energy consultant.
We also consider questions like what about 40 or 40 Plus.
The subsidy is indeed significant.
At the moment, I am researching all programs offered by BAFA that might be applicable.
Important to note: the 50% subsidy for the energy consultant is only available from April 1, 2016.
We are happy to exchange our experiences here in the usual way. With a project like this, it is easy to get frustrated if you overlook or don’t know something in advance.
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