ᐅ Assessment of Wall Construction – Steel Frame Prefabricated House
Created on: 26 Nov 2018 17:23
M
MarkusK8
Hello everyone,
We are currently considering choosing a prefab house supplier for the construction of our single-family home, which uses prefabricated steel frame modules.
From the perspective of the future homeowner, this offers several advantages for us:
Therefore, the question is whether anyone here could evaluate the wall construction used. A KfW40 standard is promised, which is said to be achieved as standard.
Exterior wall (from inside to outside) (U=0.091):
Roof (flat roof from inside to outside) (U=0.134):
Floor (elevated on point foundations from inside to outside) (U=0.132):
What matters to me in evaluating the construction is not necessarily whether this is the absolute best setup in terms of insulation, since we cannot influence that and KfW40 is fully sufficient for us, but rather whether it contains any pitfalls or no-gos that might lead to expensive renovations later on.
Also, any potentially critical questions that could be asked to the manufacturer about the construction would be of interest to me.
Here are a few additional conditions:
Best regards,
Markus
We are currently considering choosing a prefab house supplier for the construction of our single-family home, which uses prefabricated steel frame modules.
From the perspective of the future homeowner, this offers several advantages for us:
- Very short construction time on the plot itself, which is located far from our current residence.
- More house for the same budget.
- The necessary deep foundation and earthworks will be significantly cheaper, as a slab foundation is omitted (point foundation possible) and the house’s weight is comparatively low.
Therefore, the question is whether anyone here could evaluate the wall construction used. A KfW40 standard is promised, which is said to be achieved as standard.
Exterior wall (from inside to outside) (U=0.091):
- Gypsum board 12.5mm (0.5 inches)
- OSB board 12mm (0.5 inches)
- Subframe 75mm (3 inches)
- ISUM foil
- Zinc
- Isopan F90 PIR panels (120mm) (5 inches)
- Zinc
- Air gap
- Zinc
- Facade cladding (60mm) (2.5 inches)
- Zinc
Roof (flat roof from inside to outside) (U=0.134):
- Gypsum board 12.5mm (0.5 inches)
- OSB board 12mm (0.5 inches)
- Installation level 50mm (2 inches)
- ISUM foil
- Air gap
- PU foam (100mm) (4 inches)
- Steel (2mm) (0.08 inches)
Floor (elevated on point foundations from inside to outside) (U=0.132):
- Parquet flooring (14mm) (0.5 inches)
- Rigid foam XPS (40mm) (1.5 inches)
- MDF (20mm) (0.8 inches)
- ISUM foil
- Zinc
- PU foam (120mm) (5 inches)
- Zinc
What matters to me in evaluating the construction is not necessarily whether this is the absolute best setup in terms of insulation, since we cannot influence that and KfW40 is fully sufficient for us, but rather whether it contains any pitfalls or no-gos that might lead to expensive renovations later on.
Also, any potentially critical questions that could be asked to the manufacturer about the construction would be of interest to me.
Here are a few additional conditions:
- Construction location: southern Bavaria
- A shallow pitched roof will be added on top of the flat roof for the building permit, but it will have no further function.
- A decentralized ventilation system with heat recovery is to be installed.
Best regards,
Markus
The grid for the posts is about 3m x 3m (10ft x 10ft). In between, there is a framework made of I-beams that holds the insulation panels. This is one of my concerns, as a non-expert, since it seems to me that this could create a typical thermal bridge.
If interested: There is a documentary about this type of house in the Kabel Eins media library (just search for KabelEins Containerhaus).
To be honest, I’m not sure if it’s allowed to mention names or post links here…
If interested: There is a documentary about this type of house in the Kabel Eins media library (just search for KabelEins Containerhaus).
To be honest, I’m not sure if it’s allowed to mention names or post links here…
MarkusK8 schrieb:
Honestly, I’m not sure if it’s allowed to mention names or post links here... Interesting to read from someone who just agreed to the terms and conditions yesterday 😉
MarkusK8 schrieb:
If interested: There is a documentary about a house like this on the KabelEins media library (just search for KabelEins container house). I took a quick look. It reminds me of container homes, Flyinghomes, or whatever they’re called.
I actually like these houses: modern, minimalist, and similar to houseboats.
I think few people consider them seriously because a) they often don’t fit into residential zones, and b) there’s the question whether the climate inside remains comfortable over the years.
Also, most already seem to have a kind of issue with drywall (gypsum board).
M
Mottenhausen27 Nov 2018 13:55The U-value matches the wall construction. The dew point is reached well toward the outside, so the inner vapor barrier is not an issue. Moisture stays inside and in vapor form.
With steel structures, temperature-related expansion and contraction along the steel beams is always a concern. However, I’m not sure how significant this is for the length or height of a typical single-family house. Radio and mobile phone signals are likely to be reliably shielded, which is more of an advantage than a disadvantage. Other than that, I can’t think of anything else.
What I wonder about is why it would be cheaper. The insulation used in the wall construction is certainly not less expensive than in conventional timber frame construction. Metal construction in general tends to be more expensive (at least that’s my assumption) compared to the carpentry-style manufacturing of prefabricated timber frame walls.
With steel structures, temperature-related expansion and contraction along the steel beams is always a concern. However, I’m not sure how significant this is for the length or height of a typical single-family house. Radio and mobile phone signals are likely to be reliably shielded, which is more of an advantage than a disadvantage. Other than that, I can’t think of anything else.
What I wonder about is why it would be cheaper. The insulation used in the wall construction is certainly not less expensive than in conventional timber frame construction. Metal construction in general tends to be more expensive (at least that’s my assumption) compared to the carpentry-style manufacturing of prefabricated timber frame walls.
C
Caspar202027 Nov 2018 14:06MarkusK8 schrieb:
In between, there is a framework made of steel beams that holds the insulation panels. This is actually one of my concerns because, as a layperson, I would expect it to act as a classic thermal bridge. This concern is likely addressed by the fact that KfW40 standards actually allow very few thermal bridges.
MarkusK8 schrieb:
As I said, we visited a bungalow where we didn’t notice anything unusual. The goal is to arrange a visit to a two-story single-family house soon.However, the manufacturer should be able to provide results or calculations regarding sound insulation. This is something that is often subjectively difficult to assess during a walkthrough (unless it is very poor). The wall construction does not contain much mass. In addition, the steel frame is connected throughout.
Of course, it also depends on your specific location, meaning the noise exposure in the area.
Do you have any information regarding the interior wall construction?
ypg schrieb:
Interesting to read from someone who just agreed to the terms and conditions yesterday Yes, I still had in mind that there was something about prohibited links 😀
Mottenhausen schrieb:
The U-value matches the wall construction. The dew point falls well outside, so with the interior vapor barrier, it’s not an issue. Moisture stays inside and in vapor form. Thank you very much for the assessment; that definitely helps to dispel these concerns.
Mottenhausen schrieb:
What I wonder is why it’s supposed to be cheaper. The wall assembly in terms of insulation materials is certainly not cheaper than classic timber frame construction. Metal construction in general is usually more expensive (at least that’s what I’d assume) compared to carpentry-made prefabricated timber frame walls. I think the main savings come from the production location in Bulgaria. In our specific case, the self-supporting structure also allows us to skip a concrete slab foundation, which saves a lot of money compared to deep foundation systems. That’s actually why we got interested in it. Combined with the lower investment costs for the heating system, this might be exactly the scale of savings that makes it possible for us to realize the project.
Our budget is very limited due to the expensive plot and the complex foundation work. However, the location is exceptional. So currently, we are trying to explore whether we can build a single-family house there that might be very simple in terms of standard but still has sufficient build quality. An alternative would probably be a prefabricated house from Danwood or similar. It has to compete with that.
Caspar2020 schrieb:
But the manufacturer should be able to provide results or calculations regarding sound insulation. That’s something that is often not subjectively noticeable through visual inspections (unless it’s really bad). There isn’t much mass in the wall construction. Also, the steel frame is connected in some way.
Of course, it also depends on your location and what kind of noise exposure there is.
Do you have information about the interior wall construction? I don’t have details on the interior wall build-up yet. That will be part of the next coordination round. Sound insulation to the outside is less relevant for us unless it is completely insufficient, as the house will be located in a quiet dead-end street with few neighbors. For me, impact sound insulation is important. We want to experience that in another customer house first.
MarkusK8 schrieb:
Container house So that’s where the wind is coming from. The construction seemed a bit unusual to me, but that explains it.
The manufacturer data for the container house seem reasonable from an energy perspective. The wall structure is unusual, but not critical. All materials used are vapor-tight, and the zinc sheet surfaces are ventilated, so if any condensation does occur somewhere, it can drain away.
The reflective foil used won’t make things worse, and there is enough insulation anyway.
The floor structure is somewhat unusual: the covering (parquet) is installed directly on XPS insulation, which is vulnerable to point loads. It would be better (and maybe it’s already installed?) to use cement- and fiberglass-coated XPS boards (such as WEDI, Jackodur, etc.).
An additional pitched roof or some other water drainage solution certainly wouldn’t hurt. A steel roof used as a flat roof will eventually fail, even with the thickest coatings.
Similar topics