EP4628666A1

EP4628666A1 - External wall structure in a timber frame construction, in particular for a prefabricated house

Info

Publication number: EP4628666A1
Application number: EP25167961.9A
Authority: EP
Inventors: Klaus SCHMALBUCH; Janusz KERN
Original assignee: Saint Gobain Isover; Saint Gobain Isover SA France
Current assignee: Saint Gobain Isover; Saint Gobain Isover SA France
Priority date: 2024-04-03
Filing date: 2025-04-02
Publication date: 2025-10-08
Also published as: DE202024101616U1

Abstract

The invention discloses an external wall structure (1) in a timber frame construction, in particular for a prefabricated house, having a U value of at most 0.28 W/(m2K), wherein the external wall structure (1) has a layer structure from the inside to the outside in the form of at least one inner end board (3, 4), a first insulating layer (5) or an insulating/functional layer (16), a gypsum fibreboard (7), a supporting/insulating assembly (8) and a second insulating layer (11).

Description

FIELD OF THE INVENTION

The invention relates to an external wall structure in a timber frame construction, in particular for a prefabricated house.

PRIOR ART

In prefabricated house construction, external wall structures are prefabricated in a timber frame construction at the factory and transported to the construction site, where they are assembled to form the outer shell of a house. The external wall structures must meet structural, acoustic, and energy requirements.
A key value for energy efficiency is the U value in W/(m²K), which represents the heat transfer through an external wall in a timber-frame construction in terms of the wall area and the temperature difference between the outside and inside. Currently, a U value of at most 0.28 W/(m²K) is the minimum requirement for this construction.
In practice, a U value of at most 0.28 W/(m²K) can be achieved with an external wall structure comprising a supporting/insulating assembly having a wooden rafter construction, between which mineral wool or softwood fibreboards are arranged. On the inner face, the supporting/insulating assembly is followed by a first insulating layer or an insulating/functional layer, optionally with ducts for electrical installation, as well as an inner end board, made for example of plasterboard. The first insulating layer or insulating/functional layer is attached to the supporting/insulating assembly using an OSB board. The OSB board and the vertically extending wooden rafters of the wooden rafter construction ensure sufficient statics of the external wall structure. On the outer face, the supporting/insulating assembly is followed by a second insulating layer in the form of a softwood fibreboard and a cladding assembly.
A disadvantage of the known construction is the resulting relatively high wall thickness in order to achieve a U value of at most 0.28 W/(m²K).

OBJECT OF THE INVENTION

The object of the invention is to propose an external wall structure, in particular for a prefabricated house, which makes a low wall thickness possible while maintaining the U value of at most 0.28 W/(m²K).

DISCLOSURE OF THE INVENTION

The object is achieved by an external wall structure having the features of claim 1.
An external wall structure according to the invention in a timber frame construction, in particular for a prefabricated house, has the following layer structure from the inside to the outside:

at least one inner end board,
a first insulating layer or an insulating/functional layer,
a gypsum fibreboard,
a supporting/insulating assembly and
a second insulating layer.

In the following, the term "thickness" refers to the direction of the normal to the outer wall. The other dimensions perpendicular to the normal are referred to as width and height.
It has surprisingly been found that the use of gypsum fibreboard in combination with the supporting/insulating assembly and the inner end board can provide excellent statics, while meeting the acoustic and energy requirements, in particular a U value of at most 0.28 W/(m²K).
The external wall structure may comprise one or more inner end boards. Gypsum boards, either plasterboard or gypsum fibreboard, having thicknesses of 10 to 20 mm, preferably 12.5 to 18 mm, are particularly suitable for this purpose.
In a first embodiment, the external wall structure comprises a first insulating layer. The first insulating layer may be a softwood fibreboard or, preferably, a compression-resistant rock wool board, the bulk density of which is preferably between 80 and 120 kg/m³.
Alternatively, the first insulating layer may also be constructed with a wooden substructure with interstices filled with glass wool. Because the substructure takes over the structural requirements, the bulk density of the glass wool is preferably 15 to 30 kg/m³.
In an alternative embodiment, the external wall structure comprises the first insulating layer in the form of an insulating/functional layer. The insulating/functional layer may comprise a construction based on a softwood fibreboard or a first mineral wool board. Furthermore, the insulating/functional layer preferably has at least one duct, particularly preferably a plurality of ducts, for electrical installation. The ducts can be used as cable ducts. These are accessible by drilling through the inner end board, in particular plasterboard, and the softwood fibreboard or mineral wool board.
Preferably, the first insulating layer or insulating/functional layer has a thermal conductivity λ of at most 0.042 W/(m²K) in the case of a softwood fibreboard. In the case of compression-resistant rock wool boards or glass wool according to the alternative embodiment, a thermal conductivity λ of at most 0.035 W/(m²K) is preferred. The thermal conductivity is determined in accordance with DIN 4108-4:2020-11.
A first insulating layer or insulating/functional layer having a thickness of 30 to 80 mm, preferably 40 to 60 mm, particularly preferably 50 mm, is preferred.
The gypsum fibreboard is preferably between 10 and 20 mm thick, particularly preferably 12 to 15 mm thick, especially preferably 12.5 mm thick. Gypsum fibreboard at this thickness provides sufficient rigidity both for the structural integrity of the external wall and during transport. By virtue of the significantly higher bulk density of the gypsum fibreboard by comparison with an OSB board constructed using the conventional prior art, the construction according to the invention also has advantages in summer thermal insulation.
The supporting/insulating assembly preferably comprises a wooden rafter structure with a plurality of vertically extending wooden rafters. The wooden rafters preferably have a thickness of up to 160 mm.
In particular, the thickness of the wooden rafter construction, which acts as a thermal bridge, is significantly reduced by comparison with the state of the art. The additional space can be used as living space or to reduce the external dimensions of the prefabricated house. However, the measures according to the invention do not detract from the insulation value (U value).
The wooden rafters are preferably 60 to 100 mm, preferably 75 to 85 mm, and particularly preferably 80 mm, wide.
Between the wooden rafters is a mineral wool layer of the same thickness as the wooden rafters, preferably in the form of so-called clamping felts. The clamping felts are clamped between the wooden rafters and, by virtue of the resulting compression, are resistant to sagging. The clamping felt is preferably made of glass wool. The bulk density of the glass wool is preferably 15 to 30 kg/m³.
The mineral wool layer of the supporting/insulating assembly preferably has a thermal conductivity λ of not more than 0.035 W/(m²K).
The second insulating layer preferably has a thickness of 60 mm to 80 mm, particularly preferably 80 mm.
A softwood fibreboard may be used as the second insulating layer. A second mineral wool board is preferably used because of its improved insulating properties and to prevent build-up of moisture. The second insulating layer may, in particular, comprise mineral wool boards suitable for use as flat roof panels. The second mineral wool board preferably has a thermal conductivity λ of at most 0.031 W/(m²K).
In preferred embodiments, a vapour barrier is arranged between the first insulating layer or insulating/functional layer and the gypsum fibreboard. Particular preference is given to using a moisture-variable vapour barrier having a variable S_d value of 0.3 to 5 m, for example a polyamide film (PA film) having a layer thickness of between 20 µm and 100 µm. The PA film may for example consist of PA 3, PA 4, PA 6, PA 6.6, PA 4.6 or a combination thereof, particularly preferably of PA 6 or PA 6.6 or a combination thereof. Alternative moisture-variable vapour barriers suitable for this purpose are known. These consist for example of ionomers, EVOH, PVOH, or generally a polar material. The S_d value is determined in accordance with DIN EN ISO 12572:2017-05.
In one embodiment, the external wall structure may be supplied ex works without a cladding assembly. In an alternative embodiment, the external wall structure is supplied ex works with a cladding assembly, which is attached to the second insulating layer by means of suitable fasteners or to the gypsum fibreboard and/or the wooden rafters by means of screws penetrating the second insulating layer.
The cladding assembly preferably comprises a vertically extending batten with an air gap in between and a plaster base layer.
The height and width of the external wall structure, especially the external wall structure prefabricated ex works, are selected appropriately and in accordance with the project. The height is typically between 2.20 m and 3 m, for example, 2.50 m. The width is for example from 600 mm to 5 m, preferably from 1 m to 3 m.
With the proposed measures, the external wall structure, without any cladding assembly that may be provided, has a wall thickness of up to 360 mm, preferably up to 340 mm, even more preferably up to 330 mm and especially preferably up to 320 mm, while still being able to meet the required acoustic and energy specifications.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention will become apparent from the drawings, in which:

Fig. 1: shows a prior art external wall structure,
Fig. 2: shows an outer wall structure according to a first embodiment of the invention and
Fig. 3: shows an outer wall structure according to a further embodiment of the invention.

In the drawings, the features are merely shown schematically. Like reference signs are used for identical or equivalent components. For the avoidance of repetition, repeated description is omitted in the following.

EMBODIMENTS OF THE INVENTION

In the drawings, the inner face of an external wall structure is marked with A and the outer face with reference sign B.
Fig. 1 shows an external wall structure 100 according to the prior art.
On the inner face, there is an inner end board 118 in the form of plasterboard. The plasterboard has a thickness of 12.5-18 mm. It is followed by a first insulating layer 102, for example in the form of a softwood fibreboard. The first insulating layer 102 has a thickness of 50 mm. An OSB board 104 is provided as a load carrier, via a vapour barrier 116. The OSB board 104 has a thickness of 15 mm. An adjoining supporting/insulating assembly 106, with a wooden rafter construction and insulating materials in the form of softwood fibreboards 114 arranged in between, comprises a number of vertically arranged wooden rafters 112. The supporting/insulating assembly 106 provides the required statics. The supporting/insulating assembly 106 has a thickness of 220 mm. A second insulating layer 108 in the form of a further softwood fibreboard is attached to the supporting/insulating assembly 106. The second insulating layer has a thickness of 80 mm. A cladding assembly 110 is attached to the second insulating layer 108. In the case of a second inner end board 118 (not shown), there is a further 12.5-18 mm of thickness.
Fig. 2 shows a first embodiment of an outer wall structure 1 according to the invention.
The external wall structure 1 comprises an inner end assembly 2, which in Fig. 2 comprises a first inner end board 3 and a second inner end board 4, each preferably in the form of plasterboard. The plasterboards each have a thickness of 12.5 mm by way of example.
The inner end assembly 2 is followed by a first insulating layer 5, for example in the form of a softwood fibreboard, preferably in the form of a mineral wool board. The first insulating layer 5 has a thickness of 50 mm by way of example.
An essential feature of the invention is the use of a gypsum fibreboard 7, which contributes significantly to reducing the thickness D of the external wall structure 1 by comparison with the prior art. The gypsum fibreboard 7 is formed with a thickness of 12.5 mm by way of example.
A supporting/insulating assembly 8 is attached to the gypsum fibreboard 7, and comprises a number of wooden rafters 9 arranged vertically and spaced apart, at a distance of 565 mm by way of example, and interposed mineral wool layers 10, preferably in the form of clamped felt. The supporting/insulating assembly 8 is formed with a thickness of 160 mm by way of example.
A second insulating layer 11, with a thickness of 80 mm by way of example, to which a cladding assembly 12 is attached, is attached on the outer face. In the illustrated embodiment, without any limitation to the invention, the cladding assembly 12 comprises a vertically extending batten 13 with a rafter spacing of 570 mm by way of example and air gaps 14 located in between for rear ventilation, as well as an outer cladding 15. The outer cladding 15 is, by way of example and preferably, a cement fibreboard, which can serve as a support plate, for example for plaster.
Instead of the two-layer inner end assembly 2 shown in Fig. 2 with the first inner end board 3 and the second inner end board 4, merely a first inner end board 3 may be provided.
A vapour barrier may be provided between the first insulating layer 5 and the gypsum fibreboard 7, as is described below with reference to Fig. 3.
Fig. 3 shows a second embodiment of the outer wall structure 1 according to the invention.
The external wall structure 1 here comprises, by way of example but in a non-limiting manner, an inner end assembly 2 which comprises merely a first inner end board 3. Instead of the first insulating layer 5 described with reference to Fig. 2, in this embodiment an insulating/functional layer 16 is provided comprising a first mineral wool board 17 into which a number of parallel ducts 18 are milled. The spacing of the ducts 18 from one another is preferably selected in such a way that, when the inner end assembly 2 is drilled through using a socket cutter having the diameter of a standard socket, at least one duct 18 is always encountered. The insulating/functional layer 16 is formed with a thickness of 50 mm by way of example. The thicknesses of the other layers may be as described with reference to Fig. 2.
A vapour barrier 6, which is preferably moisture-variable, is located between the insulating/functional layer 16 and the gypsum fibreboard 7. Alternatively, the vapour barrier 6 can be omitted.
In the two embodiments according to Fig. 2 and Fig. 3, the battens 13 may be replaced with a screw connection. Preferably, even with the screw connection, the air gap 14 remains between the second insulating layer 11 and the outer cladding 15.

EXAMPLE

The commercial product Rigips "Die Harte" at a thickness of 12.5 mm has been found to be particularly suitable as inner end board 3.
"STEICOinstall" at a thickness of 50 mm has been found to be particularly advantageous for the insulating/functional layer 16.
The commercial product Rigips "Rigidur" at a thickness of 12.5 mm has been found to be a particularly suitable gypsum fibreboard.
The commercial product Isover "Integra ZKF 1-032" at a thickness of 160 mm has been found to be particularly advantageous as a clamping felt in combination with wooden rafters having a thickness of 160 mm.
The commercial product Isover "ULTIMATE AP SupraPlus-031" at a thickness of 80 mm has been found to be particularly advantageous as a second insulating layer.

Claims

External wall structure (1) in a timber frame construction, in particular for a prefabricated house, having a U value of at most 0.28 W/(m²K), wherein the external wall structure (1) has the following layer structure from the inside to the outside:
- at least one inner end board (3, 4),

- a first insulating layer (5) or an insulating/functional layer (16),

- a gypsum fibreboard (7),

- a supporting/insulating assembly (8) and

- a second insulating layer (11).
External wall structure (1) according to claim 1, characterised in that the inner end board (3, 4) comprises a plasterboard.
External wall structure (1) according to any of the preceding claims, characterised in that the first insulating layer (5) or insulating/functional layer (16) comprises a softwood fibreboard or a first mineral wool board (17).
External wall structure (1) according to any of the preceding claims, characterised in that the insulating/functional layer (16) comprises at least one duct (18), in particular a cable duct for an electrical installation, preferably a plurality of ducts (18), in particular cable ducts for an electrical installation.
External wall (1) according to any of the preceding claims, characterised in that the supporting/insulating assembly (8) comprises a wooden rafter construction with wooden rafters (9), each having a thickness of up to 160 mm.
External wall structure (1) according to any of the preceding claims, characterised in that the supporting/insulating assembly (8) comprises a mineral wool layer (10), particularly preferably in the form of clamping felts.
External wall structure (1) according to any of the preceding claims, characterised in that the second insulating layer (11) comprises a second mineral wool board.
External wall structure (1) according to any of the preceding claims, characterised in that a vapour barrier (6) is arranged between the first insulating layer (5) or insulating/functional layer (16) and the gypsum fibreboard (7).
External wall structure (1) according to any of the preceding claims, characterised in that the external wall structure (1) comprises a cladding assembly (12) which is attached to the second insulating layer (11).
External wall structure (1) according to any of the preceding claims, characterised in that the external wall structure (1) has a wall thickness of up to 360 mm, preferably up to 340 mm, even more preferably up to 330 mm and particularly