All about vapor barrier film

Conserving thermal energy in a building and reducing heating costs is becoming a hot topic in the face of rising energy tariffs and the price of gas supplies. The use of special materials makes it possible to reduce thermal energy leaks through the insulated facade, windows and ceiling by up to 30%. To maintain the energy-saving characteristics of the thermal circuit, a vapor barrier film is used.

The vapor-moisture insulating film is a barrier for water vapor entering the structure of the building from the inside of the room. The film counteracts the formation of condensate moisture on the heat insulator and structural elements, protects structures from the appearance of mold fungi and thus increases the service life of the building.

The atmosphere of the room contains a decent amount of moisture, because in it people are engaged in cooking, washing in the shower, and so on. When the temperature outside is lower than in the building, the moist air will begin to "break" out.

When there is no vapor barrier in structures, moisture remains in the heat insulator. Excessive dampness leads to a decrease in the quality of the insulation. In addition, corrosion processes begin, which lead to sad consequences: wooden components become infected with fungus, and metal components are corroded. The principle of operation of a vapor barrier film is based on the protection of insulated structural elements of the structure from the influence of water vapor.

The vapor barrier film is mainly intended to carry out protective functions, since it protects the wooden structural elements of the roof or attic rooms from the interference of weather factors, the penetration of moisture, it saves heat in insulated roofs, when laying floors it can serve as a substrate for parquet or laminate. This material also serves as an anti-condensation protection, as it removes excess steam from the structure, preventing condensate moisture droplets from getting back inside.

Based on all of the above, it can be stated that the use of a vapor barrier film is very widely practiced in various types of cladding work when arranging roof structures, attic floors, ceilings between floors, laying floors, thermal insulation of walls and carries many rather useful functionalities that increase the service life of the finished object.

Companies specializing in the manufacture of vapor barriers produce material that differs in structure, cost, characteristics and purpose, thanks to which the following types of vapor barrier are currently available on the market:

• ordinary polyethylene;
• membrane insulation;
• reinforced polyethylene;
• foil vapor barrier (reflective tape is perfect for vapor barrier PVC windows);
• liquid rubber;
• burlap.

However, if we talk about the key materials from which the hydro-wind-vapor barrier is made, then there are two of them:

• polyethylene;
• polypropylene.

The most affordable polyethylene films, only they have a significant drawback - this is a short period of use. They tear easily. It is required to work with such protection extremely carefully. One hole can make all your work worthless. Polyethylene films are available non-perforated and perforated. For vapor barrier, experts advise using non-perforated materials.

Polypropylene films have much higher strength properties. Their cost, along with this, is slightly higher. They better withstand temperature fluctuations, can be used as windscreens, perfectly withstand ultraviolet rays and electromagnetic radiation, are less likely to crack and more difficult to break.

Now they began to produce polypropylene films based on viscose and cellulose. This layer has a matte, slightly loose surface, is able to hold back impressive amounts of moisture, which subsequently evaporates. When using polypropylene with a similar anti-condensation base, it is imperative to leave a gap for the circulation of air masses to evaporate moisture.

There are many companies that specialize in the manufacture of one or the other types of vapor barrier material (universal, non-combustible, etc.), but the best are the following manufacturers:

• Izospan (Russian company);
• Yutafol, Yutavek (a company from the Czech Republic - Juta);
• Technonikol (Russian manufacturer);
• Tyvek (American company DuPont);
• Nanoizol (Russian manufacturer);
• Eurokron (a company from Russia);
• Izolon (Ukrainian manufacturer);
• Rockwool (Danish company);
• Megaflex (Russian company);
• Ondutis (Russian manufacturer);
• Klober (Germany);
• Fakro (Poland);
• Delta (German company Dorken).

When choosing this material, you need to pay attention to important points.

The vapor permeability level of the film determines the ability of the vapor barrier to provide a screen to protect against moisture-saturated atmosphere and is measured in grams per square meter per 24 hours. The lower the level of vapor permeability of the insulating film, the preferable. This means that the film intensively retains steam and will thoroughly protect the heat insulator, cladding, and structural components of the structure from getting wet.

At the same time the film should to a certain extent allow the passage of air masses, so that the "greenhouse effect" does not form in the structures. An anti-condensation film made of polypropylene with a non-woven hygroscopic layer and diffusion, with good air permeability, vapor barrier membranes are endowed with optimal characteristics of vapor permeability.

Durability is one of the complex characteristics that must be analyzed before purchasing a water vapor barrier. It depends on the stretching and tear strength of the film, its ability to withstand particularly high and low temperatures, corrosive environments, and the effects of ultraviolet radiation.

For example, inexpensive plastic films are capable of bursting already at the installation phase, and when used in unheated structures, they will slowly become unusable from frost. The optimal service life is shown by vapor barrier films made of nonwoven materials made of artificial fibers with a protective cover - they are quite stable to mechanical influences, capable of withstanding significant temperature fluctuations and ultraviolet radiation.

In the process of choosing a barrier for water vapor, be sure to find out how it should be installed: how the overlap should be and using which mounting tapes, close to the heat insulator, or instead with a ventilation gap. Such aspects of vapor barrier installation have a large impact on the cost of the film, on the composition of auxiliary materials and the cost of creating a roofing cake, walls or floors.

Vapor barrier films are roll material produced in the form of sheets of fixed length and width. Comparing the price of a roll of a vapor barrier from different manufacturers, most do not look at the fact that the cheaper film has a smaller width or footage. Before purchasing a vapor barrier film, multiply its width by length and calculate the price per square meter of material - this is the only way you will find out which vapor barrier is actually cheaper and which is more expensive.

When choosing a vapor barrier material, orient yourself - you need to make protection from steam for the roof, walls or floor of a room, a heated, unheated zone with an increased level of saturation of the atmosphere with moisture and fluctuating temperature. Besides, it is necessary to know exactly what building materials and facing materials will be used for various surfaces that need a vapor barrier.

In other words, first of all, the vapor barrier must meet the functional conditions of use, and then, from the limited list of suitable insulating films, you will have to choose an acceptable sample in terms of vapor permeability, service life, installation method and price.

The device of a vapor barrier film depends on the direction of use of the room, the type of surface of the fences and the type of material being practiced. There are quite a lot of vapor barrier and vapor-permeable films, in addition, their names have been invented tricky, sometimes it is difficult to understand for what purpose this or that film was created. However, the vapor barrier film differs from the vapor permeable film in the vapor permeability coefficient. So carefully look at the symbols on the packaging and read the instructions. The packaging with the vapor barrier material usually indicates how and which side to mount it.

Key rules to follow when installing a vapor barrier:

• the film must be laid from the warm side of the room;
• it is forbidden to cover the thermal protection with a barrier for steam from 2 sides, since it is required to create conditions for the escape of steam that penetrates into the heat insulator from the inside;
• steam barrier is tightly mounted, without slack;
• mating points are made with an overlap of approximately 10 centimeters, glued with 2-sided tape;
• a small gap should be left between the film and the cladding.

When insulating a heated room, when the heat insulator is located deep in structures with a lining of a thin sheet, this layer is mandatory:

• for the roof of used attics and attics;
• to protect the attic ceilings of the "cold" roof from the passage of water vapor;
• to protect the roof with slopes and walls of the frame structure from the passage of water vapor;
• to protect closed swimming pools, saunas, steam rooms from the passage of water vapor;
• to protect the heated loggia from the passage of water vapor when insulating all surfaces of the fences - outer cladding, floor and ceiling;
• for steam and anti-filtration waterproofing of the floors of the lower floor in a brick and timber house.

When protecting against steam penetration using a polyethylene film, it does not matter which side to lay it on, steam does not pass equally in any direction.

Films with an anti-condensate surface have a rough inner layer, which is able to retain excess moisture until conditions for its weathering arise. Films with a reflective surface can return some of the heat back, which makes it possible to save on heating. On a note! In order to correctly install such materials, it is required to leave an interval of 40-60 millimeters between them and the final cladding. If this is not done, the vapor barrier will remain, but the specific functions will not be carried out.

The film is fixed from the inside in a vertical, horizontal or inclined position to the wooden parts of the wall frame, to the floor beams and floor joists, to the rafter legs or an additional roof lathing. Along the width of the canvas, they overlap at least 150 millimeters. In the case of lengthening, the overlap is similar, and the seam must be fixed on the supporting component of the frame.

All seams and fittings must be taped with construction tape. The use of sealants and adhesives for vapor barrier films based on silicone, polyurethane or acrylic resins is prohibited. The protection of all surfaces of the fencing must be a continuous layer. Installation to timber structural elements is carried out by means of zinc-plated nails with a large head or staples. A block is stuffed on top of the fixation points - it "covers" the holes, forms the required interval for the correct functioning of the specialized surface and serves as a crate for fixing the final cladding.

On a note! Specific conditions at the water vapor barrier for timber beam ceilings. The installation of the film should be carried out at the bottom of the beams in order to completely protect all structural components from getting wet. All diagrams and technical solutions indicated by film manufacturers in their instructions are of a recommendatory nature.

For information on whether polyethylene can be used as a vapor barrier, see the next video.