tion - which side to the heater should be laid + Video

So, finally the walls of the house are insulated. Traditional and inexpensive mineral wool is chosen for this. The work was entrusted to builders who take cheap. Only, as it turned out, and they do it anyhow. In all the rooms, the tooth on the tooth still does not fall, in addition the roof together with the walls began to dampen. After all, such unfortunate builders, most likely, do not even know basic things. And you just need to properly put a vapor barrier. How a vapor barrier is made and which side to the heater needs to be laid down, let's talk in this article.

tion - which side to the heater should be laid + Video

What are building membranes

To begin with, consider in more detail what kind of vapor barrier there is and depending on its purpose. Based on its purpose, the membranes used in construction work can be of the following types:

  • vapor-permeable membranes;
  • membranes with vapor barrier properties.

In order to protect the mineral wool from moisture penetration, a layer of vapor barrier material is laid inside it. When warming the roof or the room under the roof, such a film is laid without fail. The vapor barrier must be on the bottom, under a layer of mineral wool. If you have to insulate the walls on the inside of the building, you must also provide a barrier to water vapor. At the same time it is impossible to use the material having a time or perforation. In more detail about warming of walls from within look material: Than to warm walls from inside of the apartment or the house and how to make it correctly.

The vapor permeability coefficient of this layer should be as low as possible. It is preferable to use, for example, a film of polyethylene (can be reinforced). Not be superfluous and foil aluminum coating on such a film. Do not forget - when using vapor barrier, humidity in a warmed room will increase many times. Therefore, we must consider a good ventilation system.

There are special films on which an anti-condensate coating is applied. Moisture does not accumulate on them. They are usually underlain by materials susceptible to rust. This is profiled, galvanized, metal (not having a protective coating on the inside). The film prevents wet vapor from reaching the metal. To do this, on its inside there is a rough fabric layer that collects moisture. Laying the film with anti-condensate coating should be the fabric side down, at a distance of 2 to 6 centimeters from the layer of mineral wool.

tion - which side to the heater should be laid + Video

Anti-condensing film.

Construction membranes that allow evaporation to pass through are used to insulate walls from the outside, protecting them from wind gusts. And they are also used in pitched roofs and untight facades as an additional protection against moisture. From vapor-permeable films requires microscopic pores and perforations. Moisture that accumulates in the insulation should pass freely through them into the ventilation system. The more water evaporation goes, the better. Because then the heater dries quickly, and the effect of its use is higher.

Permeable films can be of the following types:

  • Pseudodiffusion type membranes pass less than 300 grams per square meter of water vapor per day.
  • Diffusion-type membranes have a vapor permeability coefficient from 300 to 1000 grams per square meter.
  • For membranes of superdiffusion type, this indicator exceeds 1000 grams per square meter.

Since pseudodiffusion membranes are well protected from moisture, it is convenient to use them under the roof as the outer layer. In this case, it is necessary to provide an air gap between the film and insulation. But with the facade insulation such membranes are not suitable - they miss steam too badly. After all, when it is dry outside, dust can enter the membrane pores from the ventilation. So the film stops “breathing”, and the condensate as a result is deposited on the insulation.

And how to put a vapor barrier of diffusion or superdiffusion type? Much easier, as evidenced by experience. Such a membrane has rather large pore openings, and clogging them is not so easy. Therefore, laying it, do not take care of the air gap for ventilation from the bottom. This makes the task easier - you don’t have to mess with mounting the batten and counter rails.

There are diffusion films not only ordinary, but also voluminous. They are designed so that the interlayer for ventilation is located inside the membrane. Due to this, condensate does not reach the metal roof. The principle of operation of such a film is the same as that of the anti-condensate film. The difference is that the volume membrane removes moisture from the insulator. After all, if the metal roof is inclined at a small angle (from 3 to 15 degrees), then the condensate formed from the bottom side cannot flow down. He slowly but surely undermines the galvanized coating, gradually destroying it completely.

tion - which side to the heater should be laid + Video

Bulk diffuse membrane.

What you need to know about laying a vapor barrier - answers to popular questions

Mount the membrane

# 1 on the outside or inside of the heat insulator. If it is necessary to warm the facade, then a film for removal of steam is placed on the outside.

tion - which side to the heater should be laid + Video

# 2. But in the case of roof insulation, films with an anti-condensate coating, diffuse or bulk, are used. They should be put on the mineral wool on top, just as it is done in the ventilated facade.

# 3. If the roof is built without insulation, then a layer of film should pass below the rafters.

# 4. To insulate the upper ceiling of the room under the attic, we place a vapor barrier on the bottom of the insulator.

# 5. And the last option is internal wall insulation. Here the vapor barrier film (without perforation) should be mounted on top of the mineral wool, located inside the room.

How to lay the membrane - face or inside

# 1. As it turned out, many masters do not know which side to put the vapor barrier on. It is easiest if the film for vapor barrier has the same front and wrong side - the question is immediately removed. But not always - unilateral films are produced. For example, anti-condensate - their wrong side of the fabric, and when installing it should look inside the room. The metal coating on the foil membrane should also be turned there.

# 2. A manufacturer usually applies mounting instructions to diffusion films. It describes in detail which side of the membrane is placed. Carefully read this description: after all, the same company can produce films, both unilateral and bilateral. Sometimes it is possible to determine externally - by coloring. If the membrane has two sides, then one of them is colored more brightly. This is usually the outside of the film.

When do you need an air gap near the

# 1 membrane? At the bottom of all films for vapor barrier are usually satisfied with a gap for ventilation width of about 5 centimeters. This is done to get rid of condensate. The facing of the wall should not be allowed to come into contact with the membrane. If a diffusion-type film is used, then it is mounted directly on the insulation, moisture-resistant plywood or OSB. Here the air gap must be made from the outside of the membrane. In an anti-condensate membrane, the gap should be 4 or 6 centimeters on each side.

# 2. Warming of the roof, the gap for ventilation is done by constructing a counter-grill consisting of bars. And for the facade of the ventilated type, the gap is obtained when mounting racks or horizontal profiles, which are located perpendicular to the film.

What should be an overlap when entering parts of the membrane for each other

# 1. There is a marking along the edge of the vapor barrier films. It means what should be the overlap of paintings - usually from 10 to 20 centimeters. This is important when roof insulation of the roof - here the film must also protect against moisture. Overlap is calculated depending on the angle of the roof slope. So, an angle of up to 30 degrees requires an overlap of up to 10 centimeters, 15 centimeters is enough for angles from 20 to 30 degrees. If the angle of the slope is less than 20 degrees, the parts of the film should go behind each other by 20 centimeters, not less.

# 2. A diffusion-type membrane should overlap in the place where the ridge is also 20 centimeters. In the valley, the overlap will be 30 centimeters, and an additional strip along the slope is laid if the slope of the roof is small. Strip entry on both slopes should be from 30 to 50 centimeters. On the roof, the membrane also covers the side parts of the heat insulator. Its output goes either to the chute to drain, or on the drip.

Why and how are joints glued, and whether it is necessary

Some parts of the membrane need to be hermetically glued. This is done with self-adhesive tapes, one-sided or double-sided. They are made of ordinary or foamed polyethylene, butyl rubber or butylene, polypropylene. Such strips can repair the vapor barrier to produce, repairing the gaps and holes.

Which tape is best to use, recommended by manufacturers. Just do not take for these purposes the tape, especially the narrow. In this case, you can forget about tightness - stitches will be unstuck in a short time.

What kind of fasteners should be used

For mounting the membranes, you can take nails (provided they have a wide cap), or you can use an ordinary construction stapler. But the best fasteners are counters.


In order for the multi-layered building structure to serve for a long time, the membranes must be applied. Otherwise, the optimum ratio of temperature and humidity is not achieved. The main thing is to know how to choose the right and which side to lay the vapor barrier.

If the price of a building membrane is no more than 0.5 percent of the estimate, the insulation protection is a reasonable measure.After all, at the same time and in the rooms it will be comfortable, and the cost of energy will decrease.

Video: Waterproofing or Vapor barrier


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