JPH11504088A5 - - Google Patents

Description

[Document name] Statement
Detailed Description of the Invention
[0001]
Vapor barrier for building insulation
The present invention relates to a vapor barrier that is installed on the interior side of a building to insulate it, particularly as an insulating measure in new construction or renovation of a building.
[0002]
In order to reduce carbon dioxide emissions from building heating equipment, insulation measures are used in the construction of new buildings and in the renovation of existing buildings. For economic reasons, always considered by building owners, cost issues are also taken into account. Furthermore, the appearance of the building is an important factor, which also represents a certain limit to what can be done practically. Therefore, for example, this form of insulation is only implemented in buildings with a framing that is visible through an insulating layer applied to the inside. Furthermore, an acceptable moisture content in the framing timber must be ensured, especially under winter conditions, by possible vapor diffusion and a vapor barrier installed on the interior side. In contrast, in summer, rainwater that passes through the wooden posts and brickwork joints must be dried inward to ensure the long life of the framing timber.
[0003]
Similar problems also occur with the semi-perfect rafter insulation of high-pitched roofs with vapor-tight coverings (such as plank roof structures). Therefore, tests conducted by the Fraunhofer Institut für Bauphysik have shown that, particularly for north-facing roofs, when a vapor barrier with a water vapor diffusion resistance characteristic value ( _Sd -value) of less than 10 m is installed on the inside, the plank drying rate is not sufficient in summer to achieve harmless wood dampness conditions. Therefore, a vapor barrier installed on the inside is no longer able to sufficiently release moisture accumulations that occur, for example, due to convection.
[0004]
In view of the above-mentioned problems, the object of the present invention is to devise a vapor barrier to be installed on the indoor side, which is adapted for use under various conditions and is arranged in a position that ensures the diffusion of water vapor between the space air and the interior of the building component, so as to prevent, as far as possible, damage to the building materials used caused by moisture. This object is achieved by the features recited in the characterizing part of claim 1.
[0005]
Application of the features recited in the dependent claims provides further developments and embodiments of the invention.
[0006]
According to the present invention, the vapor barrier installed on the indoor side can also be called a "humidity-responsive vapor barrier" and is basically made of a material that has water vapor diffusion resistance properties that depend on the ambient humidity and also has sufficient tensile strength and compressive strength for use in the structure under construction.
[0007]
In the form of a film or as a coating on a carrier material, the vapor barrier material has a water vapor diffusion resistance characteristic value ( _Sd -value) of a diffusion equivalent air gap width of 2 to 5 m when the relative humidity of the air surrounding the vapor barrier is 30% to 50%, and for example a diffusion equivalent air gap width of less than 1 m when the relative humidity is 60 _% to 80%, which is typical of summer humidity.
[0008]
This results in a higher water vapor diffusion resistance characteristic value under winter conditions than under summer conditions. In this way, it is desirable that the summer drying process does not allow the moisture content to reach values that would be dangerous under winter conditions and would damage the materials used and the building itself.
[0009]
In addition to the applications described above in the prior art problems, the vapor barrier of the present invention can also be used on metal roofs and wood support structures, further improving thermal insulation performance as well as reducing construction costs.
[0010]
As vapor barrier materials having the desired properties, polyamide 6, polyamide 4, or polyamide 3 can be used, as known in particular from BIEDERBICK, K., "Kunststoffe-kurz und bundig", Vogel-Verlag Wurzburg. These polyamides are inserted as films and inherently possess the desired characteristics regarding water vapor diffusion resistance. Furthermore, polyamides provide the strength required for construction, so they can be used without additional strength-related costs. The thickness of the film is between 10 μm and 2 mm, preferably between 20 μm and 100 μm.
[0011]
However, other materials which do not have sufficient strength may also be used and may be applied to a suitable carrier material which preferably has a low water vapor diffusion resistance characteristic value, the characteristics required for the vapor barrier according to the invention being essentially provided by the coating.
[0012]
For example, film fiber reinforced cellulosic materials such as paper knits, films made from synthetic fiber spun structures, or perforated polyethylene films may be used as carrier materials or supports.
[0013]
The above-mentioned material may be used as a coating on a carrier material. Here, the coating is applied to one surface of the carrier material, but in special cases, it can also be sandwiched between two layers of carrier. In the latter case, the coating material is effectively protected from both sides, preventing mechanical abrasion. This ensures the desired water vapor diffusion of the coating material over the long term. By stacking the individual layers, structures with multiple layers can also be constructed.
[0014]
For coating the carrier material, various substances and materials can be used, thus for example polymers such as modified polyvinyl alcohol can be applied in a suitable coating process.
[0015]
Here, the water vapor diffusion resistance characteristic value, as measured according to DIN 52615, changes by more than the power of ten between the dry and wet state.
[0016]
However, dispersion synthetic resins, methylcellulose, linseed oil alkyd resins, bone glue, or protein derivatives are also used as coating materials for the carriers.
[0017]
If the carrier material is coated on one side, this coating is applied on the side that requires no or only minimal protection against mechanical influences, and the vapor barrier according to the invention is supported so that the protective carrier material faces the side facing the space or faces away from the space.
[0018]
In the following, the invention will be explained in more detail by using an example.
[0019]
Here, the vapor barrier according to the invention is formed solely from a film composed of polyamide 6. The experiments are carried out with a film thickness of 50 μm. The polyamide 6 used is currently manufactured by a company called 2MF-Folien GmbH, located in Kempten, Germany.
[0020]
According to the laboratory test method DIN 52615, the water vapor diffusion resistance characteristics of humidity- sensitive vapor barriers are determined in the dry range (3% to 50% relative humidity), the wet range (50% to 93% relative humidity), and two intermediate wet ranges (33% to 50% and 50% to 75% relative humidity). Figure 1 shows the test results for the diffusion equivalent air gap width ( _Sd -value) of a 50 μm-thick vapor barrier, depending on the average relative humidity commonly used in the test. Since the difference between the _{Sd -} values in the dry and wet ranges is more than ten times, it is expected that the diffusive flow will be clearly controlled by the vapor barrier under actual air gap conditions, which vary between 30% and 50% in winter and between approximately 60% and 70% in summer.
[0021]
Numerical analysis shows that high-pitched roofs with vapor-tight secondary roofs, even after the installation of complete inter-rafter insulation made of mineral fiber 10-20 cm thick, will become damp within 2-3 years, resulting in inevitable damage, regardless of the vapor barrier facing the interior. This situation is particularly critical during periods of high air humidity, ranging from 50% relative humidity in January to 70% relative humidity in July, when the shortwave radiation gain in the northerly direction is relatively small. Therefore, the impact of a moisture-responsive vapor barrier on the long-term humidity balance of such a structure under the climatic conditions of "Holzkirchen" has been estimated at a low level with the aid of a method that has already been repeatedly verified experimentally.
[0022]
Figure 2 shows the humidity fluctuations after the installation of a traditional vapor barrier and rafter insulation with a humidity-responsive vapor barrier facing the interior, when the roof is in moisture-wicking equilibrium around its perimeter, facing north, and pushing off from an uninsulated high-pitch roof (28° pitch) with planking, bituminized felt, and tile covering. The top graph in Figure 2 shows the evolution of the total moisture content of the roof over a 10-year period, while the bottom graph in Figure 2 shows the evolution of the moisture content of the planked wood over a 10-year period. The moisture content of the roof with the traditional vapor barrier rises sharply over the course of the seasons, with the wood moisture content (exceeding 20 M-%) already occurring in the first year and causing long-term changes, while no accumulation of moisture content is detected in the roof with the humidity-responsive vapor barrier. In summer, the wood moisture content constantly drops below 20 M-%, so there is no risk of moisture damage.
[0023]
Thus, moisture-responsive vapor barriers can increase the possibility of insulating high-pitched roofs on older buildings without significant risk of damage.