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) |
ypg schrieb:
I would no longer want to use external thermal insulation composite systems voluntarily if there are other options available.And why would you avoid external thermal insulation composite systems?Noise? Moisture? Algae growth on the facade?
Markusba schrieb:
Is there a good source for the building connections (window reveals, roller shutter boxes, etc.) for a solid wall construction? Yes, the manufacturer or supplier of the wall system has the full range.
Also, the 12.5cm (5 inches) modular grid is very helpful—it almost eliminates the need for cutting and avoids poorly executed gaps, which are always problematic both thermally and acoustically.
With this modular dimension, you get a homogeneous wall structure.
Our general contractor refused to accept any custom dimensions.
Markusba schrieb:
And why would you no longer use ETICS?
Sound? Moisture? Algae growth on the façade?- Environment
- Limited or complex possibilities for fixing attachments to the façade
- Window reveals become narrower, resulting in a slim interior window sill
- Algae growth
A
Allthewayup5 Jan 2026 14:27We used the Poroton T6.5 (I think that’s the name) with a thickness of 36.5cm (14.4 inches) and are very satisfied. Overall, we almost reached Passive House standard. So why do you need 42.5cm (16.7 inches)?
A neighbor of mine, who built with ETICS (External Thermal Insulation Composite System), asked me last summer to help install the outdoor lights. That was fun (not), despite having the proper mounting materials. If the insulation gets soaked due to insufficiently sealed drill holes, you have a lot of work to dry it out before mold starts to grow or the plaster detaches.
Thinking about our cantilevered porch roof, the patio cover, and all the outdoor lights, I’m really glad. Of course, you can do all of this with ETICS as well, but with significantly more effort and the associated costs.
A neighbor of mine, who built with ETICS (External Thermal Insulation Composite System), asked me last summer to help install the outdoor lights. That was fun (not), despite having the proper mounting materials. If the insulation gets soaked due to insufficiently sealed drill holes, you have a lot of work to dry it out before mold starts to grow or the plaster detaches.
Thinking about our cantilevered porch roof, the patio cover, and all the outdoor lights, I’m really glad. Of course, you can do all of this with ETICS as well, but with significantly more effort and the associated costs.
Markusba schrieb:
For our new bungalow project, we haven’t made much progress regarding the wall construction yet (here only wall construction for KFW40 standard).
We were initially considering Poroton blocks plus external thermal insulation composite system (ETICS). After initial discussions with the shell builder, he recommended maybe considering a monolithic wall design. It certainly wouldn’t hurt you to not only discuss your initial talks with the shell builder but also to engage the community by presenting your overall house design first, instead of just asking about details. Even if you want to keep the bungalow style, it’s still worth questioning it.
Why do so many newbies or rare forum users tend to ask 1. only about details instead of the whole project, 2. about final details first, and 3. also direct those questions to (potential) contractors—people who have an interest in you following their advice?
Allthewayup schrieb:
We used the Poroton T6.5 (I think that’s the name) in 36.5cm (14.4 inches) thickness and are very satisfied. Overall, we almost reached Passive House standard. So why do you need 42.5cm (16.7 inches)? [...] When I think about our cantilevered porch roof, the terrace canopy, and all the outdoor lights, I’m really glad. Of course, all that could also be done with ETICS, but with considerably more effort and associated costs. You “need” castle walls because the mindset “more is better” is hard to overcome. ETICS is often chosen because it is cheaper for contractors: they use the same blocks for load-bearing interior walls also on the exterior; insulation boards can be installed by low-skilled laborers; the material is inexpensive, benefiting the industry. At some point, lobbyists realized you can’t recycle all PET bottles into park benches because there isn’t enough park area for that. So they decided to give the average homeowner a subsidy to stick this special waste underneath the plaster. A subsidy for widely scattered landfills, so to speak.
Allthewayup schrieb:
A neighbor who built with ETICS asked me last summer to help mount the outdoor lights. It was a real joy (not), despite the proper mounting supplies. If the insulation ever gets soaked through inadequately sealed drill holes, you have a huge amount of fun drying it out before it starts rotting or the plaster loosens. My advisees opt for ETICS wall assemblies practically only when building multi-family houses or condominium buildings (which is rare, as almost all of my advisees’ projects are single-family homes). For tenants or condominium owners who should generally avoid tampering with the exterior walls anyway, prioritizing pure cost arguments can be understandable. For a self-occupied home, I would not approach this from an investor’s perspective.
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