A vapor barrier for the exterior walls of a wooden house is needed when insulating with mineral wool. This insulation is very susceptible to moisture. Due to its high hygroscopicity, it is able to accumulate water in itself. In this case, the heat-shielding properties of the material are significantly reduced. To prevent unpleasant consequences, it is necessary to protect mineral wool from moisture from all sides.
What is vapor barrier for?
To protect against water outside, wind and waterproofing is used. It prevents weathering of the insulation and atmospheric precipitation. Also usually provide an air ventilated layer with a thickness of about 50 mm, which allows you to drain dangerous condensate from the surface of the insulation.
But when designing a cake for the walls of a house, it must be taken into account that moisture can also come from inside the building. This is especially true for a wooden structure or any other built of vapor-permeable materials (for example, frame). To protect against moisture from the inside, vapor barrier is used. It is needed to prevent the movement of vapors inside the walls of the house and does not allow mineral wool to collect moisture.
What material to choose
A wide variety of materials for the vapor barrier of a wooden or frame house is presented on the construction market. All of them are divided into two large groups:
- films;
- membranes.
Also, a new material has appeared, which is a coating coating. It is a liquid rubber. The solution consists of polymers and is used in a liquid state. After applying the surface, allow to dry. The result of the work will be a film that is impervious to steam or liquid. But for the walls of a wooden or frame house, such vapor barrier is not applicable. It will become a modern alternative to the usual materials in the construction of a building made of brick and concrete.
For this case, traditional insulation with roll materials is needed. Before starting work, it is necessary to find out how the films differ from the membranes, and from which it is better to make a vapor barrier when insulating with mineral wool.
Vapor barrier films
The use of materials of this type has become popular for quite some time. As the easiest option, builders use the usual polyethylene film. Polyethylene in this case can be smooth or perforated. Experts recommend using the first type for a vapor barrier. The thickness of the material must be at least 0.2 mm. For vapor barrier of the walls of the house, it is recommended to choose two-layer films.
Polyethylene materials have a fairly large number of disadvantages. The disadvantages include:
- low tensile strength, the material is easily damaged during installation;
- low term of operation;
- prevention of air movement (a greenhouse effect is created), it is necessary to pay increased attention to the ventilation of the building.
If holes or cracks appear in the film during installation, the protective ability will be significantly reduced. For this reason, it is necessary to carry out work carefully even with reinforced films. the advantage of polyethylene is low cost and high availability (you can buy it in almost any hardware store).
The second option is polypropylene films. They are similar in appearance and properties to polyethylene, but are devoid of a number of disadvantages:
- increased strength;
- extended service life;
- resistance to overheating;
- reduced risk of cracking.
The disadvantages include a higher cost and the same low air permeability as propylene.
The vapor barrier of the walls of a wooden house made of polypropylene can have a special anti-condensation coating. On the one hand, the material has a rough surface. Moisture is delayed here, and then evaporates. When using such a film, it is necessary to provide a gap between the wall and the skin of the house from the inside.
For rooms where it is required to provide increased efficiency of heat conservation, films with an aluminum layer are often used. Such materials are able to reflect heat back into the building, which ensures high thermal insulation. This vapor barrier is suitable for the walls of a bath or sauna.
Vapor barrier membranes
The best option for protecting the insulation from moisture from the inside is a vapor barrier membrane. It is important not to confuse it with other materials with similar names:
- vapor diffusion membrane;
- superdiffusion membrane.
These materials are used only for waterproofing and are mounted on the outside of the insulation. They are designed to prevent moisture from entering the insulation, but do not prevent the movement of steam. This possibility is necessary so that the vaporous liquid does not accumulate inside the mineral wool. When installing waterproofing instead of a vapor barrier, serious problems may arise during the operation of the building.
Vapor barrier membranes are manufactured by many companies. Often they are found in the range of products of companies engaged in the manufacture of mineral wool or waterproofing protection. The material is a non-woven fabric and has the following positive characteristics:
- reliable barrier to steam dangerous to a heater;
- good air permeability, does not lead to the greenhouse effect in the building;
- safety for human health;
- environmental friendliness.
The disadvantages include a relatively high cost. When choosing which membrane is needed, you should pay attention to its strength. There are species that do not have good resistance to tearing, they need to be mounted with extreme caution.
When laying, it is important to strictly monitor which side of the material is facing the insulation. It is necessary to strictly adhere to the manufacturer's recommendations.
Mounting technology
During the construction of a wooden house, vapor barrier is fixed from the inside, while wind and waterproofing is fixed from the outside. An exception may be in cases where the insulation is fixed from the side of the room. But this option is not desirable with new construction. This is because, according to the rules, the insulating material must be fixed on the side of cold air. Deviate from this only if there are good reasons.
Before starting work on the insulation of the walls of a wooden house, it is necessary to clean the surface from dirt and dust. To fix the vapor barrier material, it will be necessary to prepare metal staples or nails. All fasteners must be protected against corrosion by a zinc coating.
A special tape is needed to glue the joints of the material webs. When installing the film to save money often use construction tape.
When performing the installation of films and membranes outside and inside the room, several rules must be observed:
- the canvases are attached to the wall in any direction, with a pattern on themselves;
- the overlap of one web to another should be at least 10 cm;
- the width of the tape for gluing joints - at least 10 cm;
- near the window openings it is necessary to provide a small margin taking into account deformations (it is a fold);
- next to the horses, the material must be reliably protected from sunlight (polyethylene is especially unstable to them).
The vapor barrier of the walls of the house is fixed with braces on a cleaned surface. After that, the frame rails are installed on the material for sheathing and installation of insulation. Proper protection of mineral wool from all types of moisture will extend the life of the entire building.