After you have insulated the walls of the house, during which an inexpensive mineral wool was selected , a problem may arise in which some areas of the walls become damp. In order to eliminate such negative consequences, a vapor-permeable membrane must be used.
Application features
The process of wall insulation and arrangement of roof structures involves the use of such films that are placed under a layer of mineral wool. If you are faced with the task of warming from the inside, then it is necessary to provide a barrier for water vapor. It is not recommended to use a material that has perforation or pores. The vapor permeability coefficient for this layer should be minimal. It is preferable to use a film of polyethylene, which can be reinforced.
A foil coating based on aluminum will not be superfluous. Do not forget that when using a vapor barrier, you need to think about the presence of a ventilation system. There are also special films on which anti-condensation coating is applied. Such a vapor permeable membrane cannot form condensate on its surface. The material is usually lined with layers that are susceptible to corrosion. These include galvanized sheet, corrugated board and metal tile (the latter does not have a protective inner coating).
The film will not allow wet fumes to reach the metal. To do this, from the wrong side there is a rough fabric layer, which is necessary to collect moisture. It is necessary to lay the film with anti-condensation coating with the fabric side down, backing off about 2-6 cm from the layer of mineral wool. Those building membranes that can pass evaporation are used when insulating walls from the outside, they protect materials from gusts of wind and can fit into pitched roof structures. Their use is also advisable in unpressurized facades, when it is necessary to lay a protective layer against moisture. For vapor permeability, the films have perforation and microscopic pores. The moisture that builds up in the insulation must pass through them into the ventilation system.
The main types of vapor-permeable waterproofing membranes
The vapor-permeable membrane is of several types. It:
- material of presdiffusion type;
- diffusion membrane;
- superdiffusion membrane.
The first variety is capable of passing about 300 g of vapor per day. This indicator is relevant for each square meter. If we are talking about a diffusion membrane, the vapor permeability coefficient can vary from 300 to 1000 g / m 2 . In superdiffusion membranes, this indicator exceeds 1000 g / m 2 . For the reason that prediffusion membranes protect against moisture, they can be used under the roof as an outer layer. Provide an air gap between the insulation and the film.
For facade insulation, such materials cannot be used, since they do not allow steam to pass through well. After all, when the street is dry enough, dust can get into the pores from the ventilation. This will cause the film to stop “breathing” and the condensate to settle on the insulation layer.
Vapor Permeable Membrane Reviews
The vapor permeable membrane must be laid according to a special technology. If we are talking about a diffusion or superdiffusion membrane, then the pores are quite large, so they become clogged pretty soon. This necessitates the presence of an air gap for ventilation from the bottom. According to users, you don’t have to bother with installing crates and counter-rails. On sale you can find not only diffusion films, but also their volumetric variety. As buyers emphasize, the ventilation layer is located inside. Due to this, condensate is not able to penetrate inside the roof of metal. The principle of operation of such a material is the same as that of an anti-condensate film. However, there are differences. As emphasized by home craftsmen, a volumetric membrane is able to remove moisture from the insulation. After all, if the metal roof has a slight slope ranging from 3 to 15 °, then condensate from the bottom side will not be able to flow down. It will undermine the galvanized coating and gradually completely destroy it.
How to install the membrane - from the inside or outside of the insulation?
The vapor-permeable waterproofing membrane must be laid according to a certain method. If it is necessary to insulate the facade, then the film for the removal of steam should be located on the outside. Whereas if the roof is to be insulated, then a film with an anti-condensate coating of volume or diffusion type is laid on top of mineral wool. In this case, it is necessary to follow the technology that is used in the arrangement of ventilated facades. If the roof does not have insulation, then the film layer should be below, under the rafters. When thermal insulation of the upper ceiling of rooms under the attic, a vapor-permeable membrane must be laid at the bottom of the insulation. A vapor-permeable waterproofing membrane should also be used for internal wall insulation. In this case, it should not have perforation, but it should be laid on top of mineral wool, inside the room.
How to lay the membrane - inside out or face?
As practice shows, for many people it remains a mystery which side to lay the vapor-permeable membrane. If the film will have the same wrong side and front side, then the question is immediately removed. However, it is not always possible to find double-sided films for sale. If we are talking about the anti-condensation variety, then the inside will be the fabric side, and during installation it should be facing the inside of the room. The metal coating on the foil membrane should also be turned here.
If a vapor-permeable diffusion membrane was purchased, then you should read the instructions. In it, the manufacturer usually indicates the technology of laying the material. However, the same company can produce single and double-sided films. You can determine the outer and inner sides by color. If the membrane has two sides, then one of them is painted in a brighter shade, usually the outer side of the material.
How to choose a membrane
If you need a wind-moisture-proof vapor-permeable membrane, then you can pay attention to the “Isospan A” option that is most often purchased by customers, which is designed for laying in the under-roof space. It is used to protect wall and roof elements from condensation and wind during the construction of a building. The membrane should be located under the roofing or wall cladding on the outside of the insulation. The outside is a water-repellent smooth surface, while the inside has a rough anti-condensation structure. It is designed to retain moisture, followed by evaporation in the air stream. This windproof vapor permeable membrane is easy to use, it is characterized by high mechanical strength and environmental safety. There are no harmful substances in the vapors, and the properties of the material can persist for a long time. The material is resistant to bacteria and chemicals.
Features of laying the material "Izospan A"
The wind-vapor-permeable membrane "Isospan A" is used as a windproof membrane for the arrangement of thermally insulated roofs, the angle of which should not be less than 35 °. As an external coating, profiled sheets or shingles can act.
Features of the Megaflex membrane
Do you need a vapor permeable membrane? Which is better, you must decide before visiting the store. One of the types of such materials is Megaflex, which is a three-layer structure. The two outer layers are micro-perforated, and the inner layer is a reinforced film. Reinforcing mesh gives the material strength, while double-sided lamination provides waterproofing properties.
The material has microperforation, which guarantees the ventilation of water vapor coming from the interior. This moisture-proof vapor-permeable membrane is able to protect the under-roof space from moisture, dust and soot, protect materials from external moisture and internal condensate. If protection from the wind is necessary, then the “Megaflex D 110 Standard” variety should be used, which is rolled out with horizontal panels with an overlap of 15 cm.
Conclusion
A hydro-windproof vapor-permeable membrane that protects materials from moisture, wind and vapors must be present in insulated roofs and ventilated facades. In the first case, the gap is equipped with the construction of a counter-lattice, while when insulating the facade, the gap can be obtained by installing horizontal profiles or racks.