After you have insulated the walls of the house, during which inexpensive mineral wool has been chosen, the problem may arise that some areas of the walls are damp. In order to eliminate such negative consequences, you need to use a vapor-permeable membrane.
Application Features
The process of wall insulation and arrangement of roof structures involves the use of films that are laid 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 to water vapor. It is not recommended to use material that has perforations or pores. The vapor permeability coefficient of this layer should be minimal. It is preferable to use polyethylene film, which can be reinforced.
Aluminum-based foil coating will not be superfluous. We should not forget that when using a vapor barrier, you need to think about the presenceventilation system. There are also special films on sale, on which an anti-condensation coating is applied. Such a vapor-permeable membrane cannot form condensate on its surface. The material is usually placed under layers that are susceptible to corrosion. This includes galvanized sheet, corrugated board and metal tiles (the latter does not have a protective inner coating).
The film will not allow wet fumes to reach the metal. To do this, on the wrong side there is a rough fabric layer, which is necessary to collect moisture. It is necessary to lay the film with an anti-condensation coating with the fabric side down, stepping back 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 non-hermetic facades, when it is necessary to lay a protective layer against moisture. For vapor permeability, the films have perforations and microscopic pores. Moisture that accumulates in thermal insulation must pass through them to the ventilation system.
Main types of vapor permeable waterproofing membranes
Vapour-permeable membrane can be of several types. This is:
- pre-diffusion type material;
- diffusion membrane;
- super diffusion membrane.
The first variety is capable of passing about 300 g of fumes per day. This indicator is relevant forevery square metre. If we are talking about a diffusion membrane, then the vapor permeability coefficient can vary from 300 to 1000 g/m2. For superdiffusion membranes, this figure exceeds 1000 g/m2. Due to the fact that pre-diffusion membranes protect against moisture, they can be used under the roof as an outer layer. It is necessary to provide an air gap between the thermal insulation and the film.
For facade insulation, such materials cannot be used, since they do not pass steam 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 will settle on the insulation layer.
Vapour-permeable membrane reviews
The vapor-permeable membrane must be laid using a special technology. If we are talking about a diffusion or superdiffusion membrane, then the pores here are quite large, so they will become clogged pretty soon. This necessitates the presence of an air gap for ventilation from the bottom side. According to users, you don’t have to bother with installing the crate and counter-rail. On sale you can find not only diffusion films, but also their bulk variety. As buyers emphasize, a layer for ventilation is located inside them. Due to this, condensate is not able to penetrate inside the metal roof. The principle of operation of such a material is the same as that of an anti-condensate film. However, there are also differences. As emphasized by homemasters, the 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 the 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?
Vapour-permeable waterproofing membrane must be laid according to a certain method. If it is necessary to thermally insulate the facade, then the steam removal film should be located on the outside. Whereas if the roof is to be insulated, then a film with an anti-condensate coating of a volumetric or diffusion type is laid on top of mineral wool. At the same time, 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 at the bottom, under the rafters. When insulating the upper ceiling of rooms under the attic, a vapor-permeable membrane must be laid below the insulation. A vapor-permeable waterproofing membrane should also be used for internal wall insulation. In this case, it should not have perforation, but should be laid on top of mineral wool, inside the room.
How to lay the membrane - inside out or face down?
As practice shows, for many people it remains a mystery which side to lay the vapor-permeable membrane. If the filmwill 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 on sale. If we are talking about an anti-condensate variety, then there will be a fabric side from the inside, and during installation it should be facing the inside of the room. The metal coating on the foil membrane should also be drawn 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-sided 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 colored in a brighter shade, usually this is 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 Izospan A option most often purchased by customers, which is designed for laying in the under-roof space. It is used to protect against condensation and wind elements of walls and roofs during the construction of a building. The membrane should be located under the roofing or wall cladding on the outside of the thermal insulation. The outer side is a water-repellent smooth surface, while the inner side has a rough anti-condensation structure. It is designed to retain moisture, followed by evaporation in the air stream. This windscreenvapor-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 be preserved for a long time. The material is resistant to bacteria and chemicals.
Features of laying the material "Izospan A"
The wind-vapor-permeable membrane "Izospan A" is used as a windproof membrane in the arrangement of thermally insulated roofs, the angle of which should not be less than 35 °. Profiled sheets or shingles can act as an external covering.
Features of the Megaflex membrane
Do you need a vapor permeable membrane? Which is better, you need to 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 micro-perforations, 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, to protect materials from external moisture and internal condensate. If wind protection is needed, then the Megaflex D 110 Standard variety should be used, whichrolled out with horizontal panels with an overlap of 15 cm.
Conclusion
A hydro-windproof vapor-permeable membrane that protects materials from moisture, wind and vapor must be present in insulated roofs and ventilated facades. In the first case, the gap is equipped by constructing a counter-lattice, while when insulating the facade, the gap can be obtained by installing horizontal profiles or racks.
