Vapor barrier for use in the heat insulation of buildings

[0001] This application is a Continuation-in-part of U.S. patent application Ser. No. 08/945,146, filed Oct. 17, 1997, which is the U.S. national phase of PCT/DE96/00705 filed Apr. 18, 1996, which claims priority to German patent application serial number 195 14 420.1 filed Apr. 19, 1995.

[0002] The invention relates to a vapor barrier, which is arranged facing the room, for use in the thermal insulation of buildings, especially for thermal insulation procedures in new buildings and in the renovation of old buildings.

[0003] In order to reduce the carbon dioxide emission which occurs as a result of heating buildings, thermal insulation procedures are carried out in the construction of new buildings and in the renovation of old buildings. For economic reasons, which constantly have to be considered by the owner of the building, the question of cost also has to be taken into account here. Moreover, the external appearance of the building is a significant factor here which also represents a limit to what can actually be done. Thus, for example, thermal insulation procedures of this kind can be carried out only in buildings, which have a visible framework, by means of insulation layers which are located internally. An acceptable amount of moisture in the framework wood must also be ensured, especially under winter conditions, via the possible diffusion of vapor and also by the vapor barrier facing the room. In contrast to this, the moisture, which is due to rain and which penetrates through the joints between the wooden posts and the nogging, must also be able to dry out toward the inside in the summer months in order to ensure long life for the wood that is used in the framework despite the improved thermal insulation characteristics.

[0004] Similar difficulties also arise in subsequent full-rafter insulation on high-pitched roofs with a vapor-tight front covering, for example, roofing fabric on planking. Thus tests carried out by the Fraunhofer Institut fr Bauphysik in the case where vapor barriers were applied inside with a water vapor diffusion resistance (s_d value) which is less than a 10 m diffusion-equivalent air layer thickness, especially on roofs oriented toward the north, showed that the extent to which the planking dries out in the summer is not sufficient to achieve a wood moisture situation which is harmless. Thus vapor barriers which are applied facing the room can no longer adequately carry away moisture accumulations which are caused by convection, for example.

[0005] Proceeding from these known disadvantages, the problem for the invention is to create a vapor barrier which is arranged facing the room and which is capableunder different ambient conditions which are variable in useof ensuring water vapor exchange between the room air and the interior of the building component which will, as extensively as possible, prevent damage by moisture to the building material that is used.

[0006] According to the invention, a vapor barrier for use in the insulation of buildings is formed from a material which has a water vapor diffusion resistance dependent on an ambient humidity. At a relative humidity of an atmosphere surrounding the vapor barrier in the region of 30% to 50%, the material has a water vapor diffusion resistance (s_d-value) of 2 to 5 meters diffusion-equivalent air space width. At a relative humidity in the region of 60% to 80%, the material has a water vapor diffusion resistance (s_d-value) which is <1 meter diffusion-equivalent air space width.

[0007] Illustratively according to the invention, the vapor barrier is a film-forming composition capable of being sprayed or painted onto the inner walls of a room to form a film on the inner surface of the walls.

[0008] Further illustratively according to the invention, at least a second portion of the vapor barrier is comprised of a carrier material.

[0009] Additionally illustratively according to the invention, the carrier material is selected from the group consisting of particle board, chip board, oriented strand board, plywood paneling, gypsum board (standard or fiber reinforced), fiber board, cement board, cementitious wood wool board, calcium silica board, fiber insulation batts or slabs, foam insulation slabs, wall paper, carpet and cloth.

[0010] Illustratively according to the invention, the material is a film.

[0011] Further illustratively according to the invention, the film has a thickness of 10 m to 2 mm.

[0012] Additionally illustratively according to the invention, the film has a thickness of 20 m to 100 m.

[0013] Illustratively according to the invention, the material is applied as a coating to a carrier material. The carrier material is such that the characteristics of the vapor barrier are essentially provided by the coating.

[0014] Further illustratively according to the invention, the material is sandwiched between two layers of a carrier material. The carrier material is such that the characteristics of the vapor barrier are essentially provided by the coating.

[0015] Additionally illustratively according to the invention, the film is formed prior to application to an inner wall surface.

[0016] Illustratively according to the invention, the formed film has a decorative surface structure.

[0017] Further illustratively according to the invention, the formed film has a printed color pattern.

[0018] Additionally illustratively according to the invention, the film is chosen from polyamide 6, polyamide 4 or polyamide 3.

[0019] Illustratively according to the invention, the carrier material is a fiber reinforced cellulose material.

[0020] Further illustratively according to the invention, the material is a polymer coating applied to a carrier material.

[0021] Additionally illustratively according to the invention, a polymer for the polymer coating is selected from the group consisting of polyvinyl alcohol, dispersed synthetic resin, methyl cellulose, linseed oil alkyd resin, bone glue and protein derivatives.

[0022] The invention may best be understood by referring to the following detailed description and accompanying drawings which illustrate the invention. In the drawings:

[0023] FIG. 1 illustrates the result for the diffusion-equivalent air layer thickness (s_d value) of a vapor barrier constricted according to the invention as a function of the average relative humidity which prevailed during an experiment; and.

[0024] FIG. 2 illustrates comparative humidity characteristics of inter-rafter insulation using a prior art vapor barrier and using a humidity-adaptive vapor barrier constructed according to the present invention.

[0025] The vapor barrier, which is applied facing the room in accordance with the invention and which can also be termed a humidity-adaptive vapor barrier, uses as an essential material one that has a water vapor diffusion resistance which is dependent on the ambient humidity and which has sufficient tensile and compressive strength for use in buildings as they are being built.

[0026] In the case of a relative humidity in the range between 30% and 50% of the atmosphere surrounding the vapor barrier, the material used for the vapor barrier, in the form of a film or as a coating on a carrier material, should have a water vapor diffusion resistance value (s_d value) of 2 to 5 m in terms of a diffusion-equivalent air layer thickness and a water vapor diffusion resistance (s_d value) which is less than 1 m in terms of a diffusion-equivalent air layer thickness in the case of a relative humidity in the range from 60% to 80% as is typical for the summer months, for example.

[0027] This leads to a higher water vapor diffusion resistance being achieved under winter conditions than under summer conditions. In this way, the drying out process in the summer can be encouraged without the supply of moisture under winter conditions being able to assume a value which can impair the materials that are used and the building itself.

[0028] In addition to the applications that have already been mentioned in connection with the disadvantages of the prior art, the invention can also be used with metal roofs or timber post constructions and can also lead to a reduction in building costs here along with an improvement in thermal insulation.

[0029] It is possible to use, for example, polyamide 6, polyamide 4 or polyamide 3 as a material for the vapor barrier which has the desired properties. These are known, in particular, from K. BIEDERBICK's work Kunststoffekurz und bndig, published by Vogel-Verlag, Wrzburg. These polyamides are used as films and they inherently have the required characteristics in terms of water vapor diffusion resistance. Moreover, they have the strength values that are necessary for use in buildings and they can therefore be used at no additional cost. The thickness of the films can be in the region from 10 m to 2 mm or, preferably, in the region from 20 m to 100 m.

[0030] In one embodiment, the vapor barrier comprises a film, which may be applied, for example, by painting, spraying, or the like, onto a wall in like manner to a paint, coating, or the like. For example, such a vapor barrier can be formed by painting or spraying a polyamide compound onto the inner walls of a room.

[0031] In another embodiment, the vapor barrier itself can comprise a wall paper, which can optionally be provided with a surface structure or print having a colored pattern. For example, such vapor barrier can be provided by using a polyamide film used like, and/or in place of, conventional wall paper previously known in the art.

[0032] Other materials can also be used which do not have adequate strength but which can be applied to suitable carrier materials. The carrier materials here preferably have a low water vapor diffusion resistance and the required characteristics of the vapor barrier in accordance with the invention are essentially produced by the coating.

[0033] Fiber reinforced cellulose materials, such as paper webs, membranes made from synthetic fiber spun fabrics or even perforated polyethylene films, may be used as materials for the carrier(s), for example. Other examples of suitable carrier materials for purposes of the present invention include particle board, chip board, oriented strand board, plywood paneling, gypsum board (standard or fiber reinforced), fiber board, cement board, cementitious wood wool board, calcium silica board, fiber insulation batts or slabs, foam insulation slabs, wall paper, carpet and cloth. The vapor retarding material itself may be applied to these carrier materials as film or membrane or as coating (via spraying, painting or other appropriate application methods).

[0034] The material can be present as a coating on a carrier material. The coating here can be applied to one side of the carrier material but, in special cases, it can also be accommodated between two layers of the carrier material in a sandwich-like manner. In the latter case, the coating material is effectively protected from both sides firm mechanical wear and it can therefore ensure the desired water vapor diffusion properties over an extended period of time. Several such layer assemblies can also be assembled one above the other.

[0035] Different substances and materials can be used for coating the carrier material. Thus polymers, such as, for example, modified poly(vinyl alcohols), can be applied by means of suitable coating processes. The water vapor diffusion resistance, which is measured in accordance with DIN 52615, thereby varies by more than one power of ten between a dry environment and a damp one. However, dispersions of synthetic resins, methyl cellulose, linseed oil alkyd resin, bone glue or protein derivatives can also be used as a coating material for the carrier.

[0036] In the case where the carrier material is coated on one side, this coating can be applied to the side on which little or no protection is required against mechanical influences. The installation of the vapor barrier in accordance with the invention can take place in such a way in this case that the protective carrier material points toward the side facing the room or toward the side facing away from the room.

[0037] A vapor barrier in accordance with the invention can be formed from a film which comprises polyamide 6. Experiments were carried out with a film thickness of 50 m. The polyamide 6 films that were used are currently manufactured by the MF-Folien GmbH firm in Kempten, Germany.

[0038] Hygroscopic Behavior in Laboratory Tests

[0039] The water vapor diffusion resistance of the humidity-adaptive vapor barrier was determined in accordance with DIN 52615 in the dry range (3/50% relative humidity (RH)) and in the damp range (50/93% RH) as well as in two damp ranges lying in between (33/50% and 50/75% RH). The result for the diffusion-equivalent air layer thickness (s_d value) of the vapor barrier with a thickness of 50 m is represented in FIG. 1 as a function of the average relative humidity which prevailed in the test. The difference between the s_d value in the dry range and that in the damp range is more than one power of ten, so that under practical room air conditions which range between 30% and 50% in winter and between approximately 60% and 70% in summerit can be expected that the diffusion currents can be controlled significantly by the vapor barrier.

[0040] An Example of a Practical Application

[0041] As a result of the installation of full inter-rafter insulation made from mineral fiber which is 10 cm to 20 cm thick, computational studies have shown that high-pitched roofs with vapor-tight secondary roofs can become so damp within a few years that damage is unavoidable despite a vapor barrier facing the room. The situation is particularly critical with high room air humidity levels which vary, for example, from 50% RH in January to 70% RH in July while, at the same time, the short-wave radiation gain is relatively low via a northerly orientation. The influence of the humidity-adaptive vapor barrier on the long-term moisture balance of such constructions under the climatic conditions of Holzkirchen has therefore been estimated computationally below with the help of a method which has already been verified several times in experiments.

[0042] The humidity characteristics following the installation of inter-rafter insulation with a traditional vapor barrier and with the humidity-adaptive vapor barrier facing the room are shown in FIG. 2 in the case of a non-insulated, high-pitched roof (28 pitch), which is oriented toward the north, with planking, bitumen-treated felt and a tile covering, whereby the roof is in hygroscopic equilibrium with its surroundings. The profile for the overall humidity in the roof is indicated in the upper part of this diagram and the profile for the moisture in the wood of the planks is indicated in the lower part of this diagram, whereby these are over a period of ten years. The humidity in the roof with the traditional vapor barrier increases rapidly with seasonal fluctuations, whereby moisture values (>20% by mass) in the wood, which would give cause for concern on a long-term basis, already occur in the first year; by contrast, no moisture accumulation can be detected in the roof with the humidity-adaptive vapor barrier. In the summer, the moisture in the wood in this case is constantly below 20% by mass so that moisture damage does not need to be feared.

[0043] Thus the humidity-adaptive vapor barrier opens up the possibility of inexpensively insulating high-pitched roofs on old buildings with no great risk of damage.