ᐅ Wall construction for KfW 40 standard (monolithic or with external thermal insulation composite system) for a single-family house
Created on: 24 Dec 2025 06:44
M
Markusba
Hello experts,
with our new bungalow construction project, we are still undecided about the wall structure (here only wall structure for KFW40).
Originally, we were planning: Poroton + ETICS (external thermal insulation composite system). After initial discussions with the shell builder, he recommended considering a monolithic wall structure.
Therefore, I would be interested in your opinions on this.
The U-value is almost identical; the costs seem to be slightly lower for the monolithic structure (prices are from websites: hopefully they are somewhat accurate!).
In single-family house construction, I mostly see a monolithic wall structure.
Thank you 🙂
with our new bungalow construction project, we are still undecided about the wall structure (here only wall structure for KFW40).
Originally, we were planning: Poroton + ETICS (external thermal insulation composite system). After initial discussions with the shell builder, he recommended considering a monolithic wall structure.
Therefore, I would be interested in your opinions on this.
The U-value is almost identical; the costs seem to be slightly lower for the monolithic structure (prices are from websites: hopefully they are somewhat accurate!).
In single-family house construction, I mostly see a monolithic wall structure.
Thank you 🙂
| | Poroton T16 42.5cm (17 inches) + Hasit 242 (light plaster) | Poroton T14 24cm (9.5 inches) + EPS 20cm (8 inches) | |
| U-value W/(m²K) | 0.13 | 0.12 |
| Material costs /m² | 160€ for Poroton + 30€ for mortar | (60€ for Poroton + 30€ for mortar) + (30€ EPS + 30€ mortar) |
| Labor costs /m² | 80€ for Poroton | 80€ for Poroton + 70€ for EPS |
| Total | 270€/m² | 300€/m² |
| Advantages | - higher sound insulation - simpler construction (fewer trades involved) → less prone to errors - lower tendency for algae/mold growth - easier connections (windows, etc.) - easier to plaster - more impact resistant | - better thermal insulation |
| e.g. from Schlagmann or Wienerberger including a good range such as load-bearing insulation, window fastening reinforcement) |
Either I am reading your table incorrectly, or the costs for the lightweight plaster on the left side are missing. That is really expensive! You should get a quote for it.
I am also surprised that with the filled Poroton blocks you don’t achieve a good result using regular plaster. We manage it with the unfilled ones.
I am also surprised that with the filled Poroton blocks you don’t achieve a good result using regular plaster. We manage it with the unfilled ones.
This is a common misconception, but the filling in Poroton blocks does not increase the overall insulation of the block. The filling only allows for fewer chambers and thicker webs to be used, resulting in better soundproofing and compressive strength compared to the similar unfilled block.
Tolentino schrieb:
This is a common misconception, but the filling in Poroton blocks does not increase the overall insulation value of the brick.
The filling only allows for fewer chambers and thicker webs, which results in better sound insulation and higher compressive strength compared to the comparable unfilled brick. That may be true; at least Schlagmann markets the unfilled blocks with a thermal conductivity (λ) of 0.08 (0.075 can be found with other manufacturers as well) and the filled ones with 0.06.
You mean lambda.
Yes, but those also have lower compressive strength.
According to the manufacturers’ classification, T8/U8, the filled blocks each have higher compressive strength.
You are right that there are also filled blocks with better insulation. However, there is no unfilled equivalent for those. So if manufacturers sorted by compressive strength, the filled ones would always have better insulation.
It’s a bit confusing.
Yes, but those also have lower compressive strength.
According to the manufacturers’ classification, T8/U8, the filled blocks each have higher compressive strength.
You are right that there are also filled blocks with better insulation. However, there is no unfilled equivalent for those. So if manufacturers sorted by compressive strength, the filled ones would always have better insulation.
It’s a bit confusing.
M
MachsSelbst26 Dec 2025 21:49Make it monolithic and keep in mind that the masonry is only part of the building.
I have a Ytong block with a U-value of about 0.23, and according to the heat calculation, just as much heat is lost through my windows as through the block... even though the window area is only 20% of the wall area.
If it’s possible to do without plastic on the wall, I would always avoid it.
I have a Ytong block with a U-value of about 0.23, and according to the heat calculation, just as much heat is lost through my windows as through the block... even though the window area is only 20% of the wall area.
If it’s possible to do without plastic on the wall, I would always avoid it.
Hello everyone, thanks for the helpful contributions 🙂.
I happened to meet a general contractor over the holidays.
@familie_s: That is really expensive, I only included it because it improves the U-value by 0.01 🙂 so it won’t be done.
The contractor also mentioned that soundproofing needs to be considered, not only for the wall itself but especially for the building connections.
As always, with 1) ETICS (external thermal insulation composite systems) over-insulation is easily possible, 2) with monolithic construction it's rather difficult, as there are more thermal bridges; however, soundproofing is significantly better with 2) monolithic construction.
Regarding cost, he said the two options don’t differ much, depending on whether the builder offers it “as part of their standard portfolio” – as you have already mentioned.
Is there actually a good source for details on building connections for monolithic wall construction (reveal areas, roller shutter boxes, etc.)?
I happened to meet a general contractor over the holidays.
@familie_s: That is really expensive, I only included it because it improves the U-value by 0.01 🙂 so it won’t be done.
The contractor also mentioned that soundproofing needs to be considered, not only for the wall itself but especially for the building connections.
As always, with 1) ETICS (external thermal insulation composite systems) over-insulation is easily possible, 2) with monolithic construction it's rather difficult, as there are more thermal bridges; however, soundproofing is significantly better with 2) monolithic construction.
Regarding cost, he said the two options don’t differ much, depending on whether the builder offers it “as part of their standard portfolio” – as you have already mentioned.
Is there actually a good source for details on building connections for monolithic wall construction (reveal areas, roller shutter boxes, etc.)?
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