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How to nail a vapor barrier. Which side to lay the vapor barrier against the insulation. Types of vapor barrier materials. Installation of vapor barrier. Video: Ondutis vapor barrier installation technology

IN winter period, when it’s frosty outside, but inside the house it’s cozy and warm, unnoticeable steam forms in the rooms. And this steam must leave the room freely. To accomplish this task, a vapor barrier is installed. You need to know which side to lay the vapor barrier on the floor, walls or ceiling.

Why do you need a vapor barrier?

Paro insulating material used for normal moisture circulation indoors. If you ignore the vapor barrier, then moisture in the air can enter the insulation and gradually destroy the material.

If the construction of buildings is carried out from a material that is already insulated, then the vapor barrier will serve as protection against the entry of harmful substances into the premises.

Insulation is a heat-insulating material. Depending on the origin of the feedstock, it is divided into:

• organic thermal insulation - the basis is wood, plants, animal hair;
• inorganic thermal insulation - mineral wool, fiberglass, concrete.

Installation of the vapor barrier layer is carried out to preserve comfortable temperature inside the house, preventing air from entering through the cracks of the building.

When using insulation that absorbs moisture well, you cannot do without a vapor barrier. In its absence, moisture is absorbed into the structure of the insulation and there it turns into water. With time thermal insulation characteristics insulation material will decrease. After a certain period, it will be possible to observe the appearance of fungus and mold. The use of a vapor barrier creates a kind of shield between the insulation and the internal air of the apartment.

Correct installation of a vapor barrier will allow the insulation to last a long time and effectively.

Types of vapor barriers

IN modern construction vapor barrier is successfully used to protect organic and inorganic thermal insulation materials. It comes in the following types:

• Film.

Film– a blind vapor barrier material that retains moisture and does not allow moisture to pass through. Due to its low cost and excellent waterproof characteristics, the film is used not only in the construction industry, but also for domestic needs. Films vary in thickness, number of layers, and surface quality. It can be smooth on the outside and rough on the inside. Water always remains on the surface of the film.

This type of vapor barrier material consists of a polymer film and polypropylene and has limited vapor permeability. Water vapor contained in the insulation immediately evaporates.

resistant to elevated temperatures external environment due to its metallized outer layer. Vapor barrier should be installed in rooms with high humidity and temperature. The material is capable of reflecting infrared radiation.

Permits moisture in two directions. Convenient to use when insulating large surface areas.

The thermal insulation and vapor barrier characteristics of a structure depend on the choice of material. Careful approach to selection necessary products will provide comfort and coziness of the premises and help extend the service life of the entire structure.

Principles of installing vapor barriers to different surfaces

Manufacturers of vapor barrier films, focusing on consumer desires, produce their products in different directions:

• for work on and under the roof;
• on vertical wall surfaces;
• on the floor.

Vapor barriers can be installed on any surface. When using vapor barrier material on wooden structures use a film with a membrane. Polymer or bitumen mastic can be used for any type of surface. On concrete walls It is recommended to install a vapor barrier with a metal outer layer.

Its use will be much more effective if the working side is prepared in advance. Preliminary work depends on the characteristics of the material with which the building is built.

During construction wooden house, to begin with, soak everything wooden surfaces insect repellents and harmful bacteria. Only after completing a set of preparatory work do they begin installing the vapor barrier layer.

Most quality material for insulation wooden floors– breathable membranes. The body of the membrane consists of a layer of anti-condensation fibers that absorb and accumulate moisture. There are single-sided and double-sided membranes. In the latter option, moisture is absorbed from both sides at once, so the double-sided breathable membrane can be laid with either side to the floor.

When conducting overhaul All outdated insulating coatings are dismantled. Surfaces are thoroughly cleaned and impregnated with special disinfectants. Then you can lay the vapor barrier. Concrete surfaces They do not require special treatment with special means; they just need to be cleaned.

Features of installation on various surfaces

Installation of a vapor barrier layer is not particularly difficult; it must be done carefully preparatory work and know the main stages of installation.

Laying on the floor

Film – best option insulating the floor from moisture. On the ground floor, the insulation layer below is protected by a device, and closer to the premises - by a roll of insulating film, which is laid overlapping. The joints are taped with metallized tape or tape.

If it is interfloor or attic floor, then the film unfolds smooth side down to protect against water vapor coming from the slab or floor logs.

Ceiling insulation

Used in rooms with increased content moisture in the air. These can be bathrooms, showers, baths, saunas. The vapor barrier is securely overlapped and the joints are sealed. The reflective side of the material is directed indoors. Particular attention is paid to the corners of the room, the insulation should be slightly overlapping the walls around the entire perimeter of the room.

Vertical surfaces

For such surfaces use diffusion membranes, which allow air to pass through rather than moisture. The walls must “breathe”, so impermeable film is not used. In case of external work, the product is laid with the smooth side facing the insulation. When installing, the film is slightly stretched.

Roof mounting

The purpose of the vapor barrier is to protect the rafters from mold and prevent the formation of condensation in the insulating layer. Installation is carried out with an overlap and sealing of the seams. The main condition is to ensure the tightness of the roof in conjunction with the vertical elements of the building.

Basements, balconies and underground structures

Balconies, basements and underground rooms are in contact with cold outside air. For balconies, dense foamed polyethylene is used, the reflective side of which is directed indoors. For other structures, membrane film is used.

When working with vapor barrier materials, it is necessary to find out which side the product should be laid in relation to the insulation. The location of the vapor barrier will determine the degree of moisture absorption by the insulation and its service life. The instructions for the product indicate how to install it correctly. But what if there are no instructions? In this case, the installation method is determined independently, taking into account the following points:

• if there are sides on the vapor barrier material different color, then the lighter one is placed next to the insulation;
• the outer side of the product has a rough surface;
• if in doubt, take a glass with hot water and placed on the vapor barrier area. Condensation forms on the waterproof side.

A polyethylene film is laid with either side facing the insulation, while a diffusion film has one smooth surface, which should lie towards the insulation. By preventing the insulating layer from getting wet, it allows moisture to pass through the smooth side without hindrance.

• By placing the barrier with its smooth side facing the thermal insulation, the influx of steam and the formation of rotting processes in wooden structures are eliminated;
• when installing a thermal insulation layer outside the building, the insulating layer is placed outside the room;
• the film should fit tightly to the insulating layer;
• when sealing joints, use wide adhesive tapes and tapes;
• when working with windows and doorways, it is necessary to leave a small supply of vapor barrier film;
• The film should be protected from direct sunlight;
• Before starting work, the most critical places are determined - areas of interaction between warm and cold air.

When performing work on installing a vapor barrier film, it is important that the product is attached correctly. Otherwise, the error will lead to ineffective thermal insulation.

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Construction work, regardless of purpose, cannot be done without an insulating layer, due to which the quality and service life of the building significantly increases. The most important insulating material is vapor barrier, which ensures the correct microclimate in the under-roof space, as well as in wall structures. Working with it does not cause any particular difficulties, however, every developer should know how to properly attach a vapor barrier.

Types of insulating materials and technology for their construction

There are several types of vapor barrier, and in each specific case it is necessary to take into account the presence of certain characteristics of the material.

The most common materials for vapor barrier include:

• pasting, for the installation of which it is used adhesive composition. The integrity of the insulating layer is ensured by the tight fit of the material to the surface of the structure;
• painting;
• grouting materials.

When working with film, it does not matter how the vapor barrier is attached, that is, it can be turned with either side to the base and nailed with small nails or staples. Facial and inner side This type of insulation fiber is absent, which greatly simplifies working with it.

Installation of film depending on its type

It should be remembered that the film is attached depending on a certain gap and its limit level stretches. Since the material has an impenetrable structure, air freely penetrates through the gap into the insulated space. This type of material has a slightly modified copy - with a rough front side, which serves for the timely release of steam to the outside. If necessary, it is permissible to lay two layers of film, with the glossy side facing each other.

As a more modern insulation, manufacturers offer it, which has wide application possibilities. When laying it, the front side must face outward to allow air to flow to the structural elements and release moisture from them.

To determine the correct placement of the material, just look carefully at its canvas - there is a special mark there. Such films are available in two types: single-sided and double-sided, which are used depending on the characteristics of the work being performed.

Vapor barrier films are offered with reflective properties, and they are also called penofol. On one side of this material a foil layer is applied, due to which the film is widely used in baths and steam rooms. In addition, it is necessary during the construction frame houses, where main construction material– these are galvanized metal profiles. Such insulation is fastened quite quickly and simply, but when working with structures endowed with special properties and characteristics, some difficulties may arise.

Preparation of the primary base for vapor barrier material

Developers who do not have sufficient experience construction work, often wonder which side to lay the vapor barrier so that it reliably protects the roof from negative factors. To answer it, you should pay special attention to the entire stage.

Initially, a primary base must be prepared, where the insulation layer will be attached. In most cases, this will require ordinary lumber that has been cleaned, dried and primed.

This type of insulation does not require special tension, but the film should not sag in the spaces between the elements of the main structure. Under no circumstances should you use staples, nails or other fasteners that could perforate the material or compromise the integrity of the canvas. Experts recommend attaching such insulation to a strong adhesive tape, which ensures a high-quality connection of the film to the primary base.

The material is supplied to the market in rolls, so it is very convenient to work with it when cutting strips required length. To form a complete layer of material, a slight overlap should be made when placing the cut pieces.

Thanks to this type of insulation, a number of actions are carried out that have a positive effect on the building as a whole:

• evaporation of residual and excess moisture is carried out without the formation of condensation in the under-roof or inter-wall space;
• microclimate is regulated as in interior spaces, and in the roofing structure;
• the service life of individual building elements and the entire house or cottage increases.

Installation allowed vapor barrier materials right on top of the roof. In this case, solutions made from bitumen, special varnish and mastic are more suitable. This installation is relevant in the case of arranging some roof structures, most often used for the construction of high-rise buildings and those covered with soft roofing material. Grout insulation materials can be used as a base for cement mortar, poured according to construction requirements.

Self-installation of insulation film

So, initially, you need to determine how much film will be needed to complete the work. If you skip this stage, it may turn out that there is not enough material, or too much, which is fraught with additional material costs. To correctly calculate the material consumption, you need to have a clear idea of ​​the total area, and to the obtained value add about 15% for the reserve that will be used to overlap the material, as well as replace damaged pieces (read also: " "). It is impossible to complete the work without special tools, so you also need to take care of their preparation in advance. Stock up on a pencil, tape measure, utility knife, adhesive tape, stapler and other equipment necessary for construction.

It is better to secure the canvas before insulation of the room begins. In order for the insulation system to function effectively, experts recommend checking the correct location of the film in relation to the structure. The material needs to be slightly stretched. Make sure there are no wrinkles on it.

Regardless of which side the vapor barrier is laid on, it is imperative to maintain an overlap of at least 50 mm between the two slabs of material - this is the only way to guarantee the integrity of the insulating layer. To connect each strip, you need to use adhesive tape, the structure of which allows you to securely fasten the insulation without damaging it. To completely prevent damage to the interlayer during subsequent operation, carefully inspect the strips of material - if there are even small defects, it is better to replace the damaged material with a whole sheet. The highest quality insulating layer will be obtained if the strips are laid with a slight overlap not only among themselves, but also on the walls (150 mm is enough), as shown in the photo.

Now let's take a closer look at how to correctly place the selected insulating film based.

Despite the fact that all insulating materials perform the same function, the requirements for their placement do not provide for a single pattern. This fact is explained by the fact that each type of insulation requires a special fastening that ensures reliable fixation of the material to the structure.

When choosing special types of films that are produced without the inside and front sides, the work is greatly simplified. In other cases, if the material is placed incorrectly, the opposite protective effect will be created.

An example is the function membrane film– it consists in passing wet vapors out and preventing moisture from penetrating inside. If the developer confuses which side to attach the vapor barrier, then a reverse reaction will result, which is fraught with rapid destruction wooden elements. Thus, moist air from the street will be drawn into the room, in which additional fumes will accumulate that have not gained access to the outside. In a word, such a system will lead to a significant reduction in the service life of the building.

Features of installation of roofing and wall vapor barriers

Performance insulation works can be placed at the basis of the entire construction, since in the absence of such a protective layer the frame structure or rafter roofing system will not be able to fully perform its functions, which means it will be subject to rapid wear and tear.

Depending on the availability and use of thermal insulation, the installation of vapor barrier materials will be determined. If there is no insulation in the under-roof pie, attention should be paid to how to lay a vapor barrier: it is laid as a layer between the sheathing and the rafter system. Thus, the rafters are protected from the accumulation of moisture, due to which fungus and mold will appear over time.

Using attic space like a second residential floor, roof structure must be installed with high-quality insulation with help mineral wool or foam boards. The latter material is dangerous due to the release of chemical particles as a result of strong heating.

So, when performing thermal insulation, a double vapor barrier layer is installed, which will protect not only rafter system, but also the insulation itself. According to special requirements, we pre-check correct location sides of the film - this is the only way to be sure of the complete safety of the building material during operation.

If the installation of insulating material is carried out to wall structures, then the installation requirements are completely different. In this case, you need to determine the purpose of the walls in the building, and also pay attention to what they are made of. The most popular are interior partitions, with the help of which a living space is delimited into several zones. Such walls are usually built from frame structures with double-sided lining.

For filling interior partitions you will need insulation and soundproofing materials, necessary for a high-quality and comfortable microclimate in the house. This design does not require insulation equipment, only if it does not border the kitchen or bathroom, where steam is constantly generated and moisture settles on the walls.

How to properly attach a vapor barrier, more details in the video:

Let's look at how to properly install a vapor barrier in this case.

Inside the partition itself, where the insulation material, it is necessary to build protective layer, which would prevent penetration humid air. The function of such protection is assigned to a vapor barrier film laid on both sides of the thermal insulation so that there are no gaps. To make the fabric complete, you need to connect its individual elements with adhesive tape - it works well not only with two, but also with several insulation elements. The insulating material itself required quantity carefully cut from the roll; in case of even minor damage, you need to replace it with a new one.

So, installing a vapor barrier is a mandatory stage of any construction work, which will result in a high-quality structure that will last a long period of time.

This article was brought to me by the total ignorance on the part of both builders and buyers, as well as the phrase “vapor-hydro insulation” or “hydro-vapor insulation” that is increasingly flashing in commercial offers - because of which then all the pandemonium begins, lost money, problematic designs, etc.

So, you've probably heard about waterproofing, windproofing and vapor barrier - that is, about films that are placed in insulated roofs and frame walls to protect them. But then, a complete “steam and hydrodisorder” often begins.

I will try to write very simply and easily, without immersing myself in formulas and physics. The main thing is to understand the principles.

Steam or hydro?

Let's start with the fact that the main mistake is to mix steam and moisture into one concept. Steam and moisture are completely different things!

Formally, steam and moisture are water, but in different states of aggregation, respectively, having a different set of properties.

Water, aka moisture, aka “hydra” (hydro from ancient Greek ὕδωρ “water”) is what we see with our eyes and can feel. Tap water, rain, river, dew, condensation. In other words, it is a liquid. It is in this state that the term “water” is usually used.

Steam is the gaseous state of water, water dissolved in the air .

When an ordinary person talks about steam, for some reason he thinks that it is necessarily something visible and tangible. Steam from the nose of a kettle, in a bathhouse, in a bath, etc. But actually it is not.

Steam is present in the air always and everywhere. Even now, as you read this article, there is steam in the air around you. It is the basis of that same air humidity, which you have probably heard about and more than once complained that the humidity is too high or too low. Although no one saw this moisture with their eyes.

In a situation where there is no steam in the air, a person will not live long.

Taking advantage of the different physical properties of water in liquid and gaseous states, science and industry have received the ability to create materials that allow steam to pass through, but at the same time do not allow water to pass through.

That is, this is a kind of sieve that can let steam through, but will not let water in a liquid state.

At the same time, particularly smart scientists, and then manufacturers, figured out how to make a material that would conduct water only in one direction. How exactly this is done is not important to us. There are few such membranes on the market.

Vapor-permeable membrane - allows steam to pass in both directions, but does not allow moisture to pass through

So, a construction film that is impervious to water, but allows steam to pass equally in both directions is called waterproofing paro permeable membrane. That is, it allows steam to pass freely in both directions, but water (hydra) does not pass through at all or only in one direction.

Paro insulation - this is a material that does not allow anything to pass through, neither steam nor water. Moreover, at the moment, vapor barriers membranes- that is, materials that have one-way permeability to steam have not yet been invented.

Remember as “Our Father” - there is no universal “vapor-hydro membrane”. There is a vapor barrier and vapor-permeable waterproofing. These are fundamentally different materials - with different purposes. Using these films in the wrong places and in the wrong places can lead to extremely tragic consequences for your home!

Formally, vapor barrier can be called vapor barrier, since it does not allow water or steam to pass through. But using this term is a recipe for making dangerous mistakes.

Therefore, once again, in frame construction, as well as in insulated roofs, two types of films are used

1. Paro insulating- which do not allow steam or water to pass through and are not membranes
2. Waterproofing steam permeable membranes (also called windproof, due to extremely low air permeability or super-diffusive)

These materials have different properties and using them for other purposes is almost guaranteed to lead to problems with your home.

Why do we need films in a roof or frame wall?

To understand this, you need to add a little theory.

Let me remind you that the purpose of this article is to explain “at a glance” what is happening, without delving into physical processes, partial pressure, molecular physics, etc. So I apologize in advance to those who had five in physics :) In addition, I’ll immediately make a reservation that in reality all the processes described below are much more complicated and have a lot of nuances. But the main thing for us is to understand the essence.

Nature has decreed that steam in a house always flows in the direction from warm to cold. Russia, a country with a cold climate, has an average heating period of 210-220 days out of 365 per year. If you add to it the days and nights when it’s colder outside than in the house, then even more.

Therefore, we can say that most of the time, the vector of steam movement is directed from inside the house, out. It doesn’t matter what we are talking about - walls, roofing or lower floors. Let's call all these things in one word - enclosing structures

In homogeneous structures, the problem usually does not arise. Because the vapor permeability of a homogeneous wall is the same. The steam easily passes through the wall and exits into the atmosphere. But as soon as we have a multilayer structure consisting of materials with different vapor permeability, everything becomes not so simple.

Moreover, if we talk about walls, then we are not necessarily talking about a frame wall. Any multi-layer wall, even brick or aerated concrete with external insulation, will make you think.

You've probably heard that in a multilayer structure, the vapor permeability of the layers should increase as the steam moves.

What will happen then? Steam enters the structure and moves through it from layer to layer. At the same time, the vapor permeability of each subsequent layer is higher and higher. That is, from each subsequent layer, steam will come out faster than from previous.

Thus, we do not form an area where the saturation of steam reaches the value when, at a certain temperature, it can condense into real moisture (dew point).

In this case, we will not have any problems. The difficulty is that achieving this in a real situation is not easy.

Vapor barrier of roof and walls. Where is it installed and why is it needed?

Let's look at another situation. Steam has entered the structure and moves outward through the layers. I went through the first layer, the second... and then it turned out that the third layer was no longer as vapor-permeable as the previous one.

As a result, the steam that gets into the wall or roof does not have time to leave it, and a new “portion” is already supporting it from behind. As a result, before the third layer, the vapor concentration (more precisely, saturation) begins to increase.

Remember what I said before? Steam moves in a direction from warm to cold. Therefore, in the region of the third layer, when the steam saturation reaches a critical value, then at a certain temperature at this point, the steam will begin to condense into real water. That is, we got a “dew point” inside the wall. For example, at the border of the second and third layers.

This is exactly what people often observe when the outside of their house is covered with something that has poor vapor permeability, such as plywood or OSB or DSP, but there is no vapor barrier inside or it is made poorly. Rivers of condensation flow along the inside of the outer skin, and the cotton wool adjacent to it is all wet.

Steam easily enters the wall or roof and “slips through” the insulation, which usually has excellent vapor permeability. But then it “rests” on the outer material with poor permeation, and as a result, a dew point forms inside the wall, right in front of the obstacle to the steam path.

There are two ways out of this situation.

1. It takes a long and painful time to select materials for the “pie” so that the dew point under no circumstances ends up inside the wall. The task is possible, but difficult, given that in reality, the processes are not as simple as I am describing now.
2. Install a vapor barrier from the inside and make it as airtight as possible.

It is along the second path that they go in the west, making a hermetically sealed obstacle in the path of the steam. After all, if you don’t let steam into the wall at all, then it will never reach the saturation that will lead to condensation. And then you don’t have to rack your brains over what materials to use in the “pie” itself, from the point of view of the vapor permeability of the layers.

In other words, installing a vapor barrier guarantees the absence of condensation and dampness inside the wall. In this case, the vapor barrier is always installed on the inner, “warm” side of the wall or roof and is made as airtight as possible.

Moreover, the most popular material for this “they have” is ordinary polyethylene 200 microns. Which is inexpensive and has the highest resistance to vapor permeation, after aluminum foil. Foil would be even better, but it's hard to work with.

In addition, I pay special attention to the word hermetically sealed. In the west, when installing a vapor barrier, all joints of the film are carefully taped. All openings from communication wiring - pipes, wires through the vapor barrier - are also carefully sealed. The installation of overlapping vapor barriers, popular in Russia, without gluing the joints, can result in insufficient tightness and, as a result, you will get the same condensation.

Untaped joints and other potential holes in the vapor barrier can cause a wet wall or roof, even if there is a vapor barrier itself.

I would also like to note that the mode of operation of the house is important here. Summer country houses, in which you visit more or less regularly only from May to September, and maybe several times in the off-season, and the rest of the time the house is without heating, can forgive you some flaws in the vapor barrier.

But a house for permanent residence, with constant heating, does not forgive mistakes. The greater the difference between the external “minus” and the internal “plus” in the house, the more steam will flow into the external structures. And the greater the likelihood of getting condensation inside these structures. Moreover, the amount of condensate can ultimately amount to tens of liters.

Why do you need a waterproofing or superdiffusive vapor-permeable membrane?

I hope you understand why you need to make a vapor barrier from the inner wall - in order to prevent steam from entering the structure at all and to prevent conditions for its condensation into moisture. But the question arises: where and why to place the pair? permeable membrane and why it is impossible to install a vapor barrier instead of it.

Windproof, waterproofing membrane for walls

In American wall construction, a vapor-permeable membrane is always placed on the outside, on top of the OSB. Its main task, oddly enough, is not to protect the insulation, but to protect the OSB itself. The fact is that Americans make vinyl siding and other facade materials directly on top of the slabs, without any ventilation gaps or sheathing.

Naturally, with this approach, there is a possibility of external atmospheric moisture getting between the siding and the slab. How - this is the second question, heavy slanting rain, construction flaws in the area of ​​window openings, roof junctions, etc.

If water gets between the siding and the OSB, it can take a long time to dry there and the board can begin to rot. And OSB is a bad material in this regard. If it begins to rot, this process develops very quickly and goes deep into the slab, destroying it from the inside.

It is for this purpose that a membrane with one-way water permeability is installed in the first place. The membrane will not allow water, in case of a possible leak, to pass to the wall. But if somehow water gets under the film, due to one-sided penetration, it can come out.

Superdiffusion waterproofing membrane for roofing

Don't let the word superdiffusion confuse you. Essentially this is the same as in the previous case. The word superdiffusive only means that the film allows vapor to pass through very well (vapor diffusion)

In a pitched roof, for example, under metal tiles, there are usually no slabs of any kind, so a vapor-permeable membrane protects the insulation from both possible leaks from the outside and from blowing by the wind. By the way, this is why such membranes are also called windproof. That is, a vapor-permeable waterproofing membrane and a windproof membrane are, as a rule, one and the same.

In the roof, the membrane is also placed on the outside, in front of the ventilation gap.

In addition, pay attention to the instructions for the membrane. Since some membranes are placed close to the insulation, and some with a gap.

Why do you need to install a membrane outside and not a vapor barrier?

But why not install a vapor barrier? And make a completely vapor-tight wall on both sides? Theoretically, this is possible. But in practice, achieving absolute tightness of the vapor barrier is not so easy - there will still be damage from fasteners and construction flaws somewhere.

That is, some tiny amount of steam will still get into the walls. If there is a vapor-permeable membrane outside, then this minuscule has a chance of coming out of the wall. But if there is a vapor barrier, it will remain for a long time and sooner or later, it will reach a saturated state and again the dew point will appear inside the wall.

So - a windproof or waterproofing vapor-permeable membrane is always installed outside. That is, from the “cold” side of the wall or roof. If there are no slabs or other structural materials outside, the membrane is placed on top of the insulation. Otherwise, in the walls, it is placed on top of the enclosing materials, but under the façade finishing.

By the way, it is worth mentioning one more detail, for which films are used, and the wall or roof is made as airtight as possible. Because the best insulation is air. But only if he is absolutely motionless. The task of all insulation, be it polystyrene foam or mineral wool, is to ensure the stillness of the air inside it. Therefore, the lower the density of the insulation, the higher, as a rule, its thermal resistance - the material contains more still air and less material.

Using films on both sides of the wall reduces the likelihood of wind blowing through the insulation or convection air movements inside the insulation. Thus, forcing the insulation to work as efficiently as possible.

What is the danger of the term vapor and waterproofing?

The danger lies precisely in the fact that under this term, as a rule, two materials are mixed, with different purposes and with different characteristics.

As a result, confusion begins. Vapor barriers can be installed on both sides. But the most common type of error, especially in roofs and the most terrible in terms of consequences, is when the result is the opposite - a vapor barrier is installed on the outside, and a vapor-permeable membrane is installed on the inside. That is, we calmly let steam into the structure, in unlimited quantities, but do not let it escape. This is where the situation shown in the popular video comes into play.

Conclusion: never mix the concepts of vapor-permeable waterproofing membranes and vapor barriers - this is the right road to construction mistakes that have very serious consequences.

How to avoid mistakes with films in a wall or roof?

Fear has big eyes; in fact, with films in a wall or roof, everything is quite simple. The main thing to remember is to follow the following rules:

1. In cold climates (most of Russia), vapor barrier is always installed only on the inner, “warm” side - be it a roof or a wall
2. Vapor barrier is always done as hermetically as possible - joints, openings of communication penetrations are sealed with tape. In this case, special adhesive tape is often required (usually with a butyl rubber adhesive base), since simple tape can come off over time.
3. The most effective and cheapest vapor barrier is 200 micron polyethylene film. Preferably, the “primary” one is transparent; it is easiest to glue the joints on it with ordinary double-sided tape. Purchasing “branded” vapor barriers is usually unjustified.
4. Vapor-permeable membranes (super-diffusion, windproof) are always installed on the outer, cold side of the structure.
5. Before installing the membrane, pay attention to the instructions for it, since some types of membranes are recommended to be installed with a gap from the material to which it is adjacent.
6. Instructions can be found on the manufacturer's website or on the roll of the film itself.
7. Usually, in order to avoid mistakes with “which side” to mount the film, manufacturers roll the roll so that when “rolling out” it outside By design, you automatically installed the correct side. For other uses, before starting installation, think about which side to place the material on.
8. When choosing a vapor-permeable membrane, you should give preference to high-quality “first and second echelon” manufacturers - Tyvek, Tekton, Delta, Corotop, Juta, Eltete, etc. As a rule, these are European and American brands. Membranes from third-tier manufacturers - Izospan, Nanoizol, Megaizol and other “isols”, “brains”, etc. as a rule, they are much inferior in quality, and most of them are of unknown Chinese origin with the brand of a trading company stamped on the film.

about the author

Hello. My name is Alexey, you may have met me as Porcupine or Gribnick on the Internet. I am the founder of the Finnish House, a project that has grown from a personal blog into a construction company whose goal is to build a high-quality and comfortable home for you and your children.

A vapor barrier is a layer that protects insulation or building structures from the penetration of wet steam, which in turn leads to the accumulation of condensation on them, loss of useful properties and rotting under the influence of moisture. To create a vapor barrier, completely impenetrable double-sided films and sheets with one regular working surface can be used. It is extremely important to determine exactly which side to place the vapor barrier on the insulation; a mistake at this stage provokes accelerated destruction of building materials and significant financial costs. The main guideline is the manufacturer's instructions, but often this document is not available upon purchase; the choice is made taking into account the type of vapor barrier film and installation conditions.

For ordinary or double-sided reinforced polyethylene, this problem is not relevant; in other cases, the working surface is a vapor-impermeable surface. Most often, the vapor barrier is laid with the smooth side facing the insulation, and the protected side facing the source of steam penetration. Depending on the type of materials it is:

• Laminate on cardboard (it is not recommended to place it on critical objects).
• Reflective side of foil and aluminum roll coverings.
• A fleecy or rough surface of antioxidant films coated with viscose or cellulose.
• The vapor-tight side of the membranes is usually brighter.

Installation on different surfaces

1. Laying a vapor barrier on the floor.

Protection from steam and moisture is required when insulating floors or horizontal planes, or assembling timber structures. Reflective films that return heat to the house are considered optimal for flooring. When constructing or repairing the first floors, the insulation is protected with a layer of waterproofing, and on top - with rolled vapor barrier materials, laid overlapping (from 10 cm and above) with sizing with metallized tape. The situation is slightly different when arranging attic floors and interfloor ceilings: the films are turned with the impenetrable side down to protect against steam penetrating through logs or slabs.

2. Vapor barrier of ceiling structures.

Most often, the need to close the ceiling occurs in baths, saunas, kitchens, showers and other structures with high humidity. The greater the volume of vapors released and the higher their temperature, the more reliable vapor barrier is required from them. To protect steam room ceilings, dense aluminum, lavsan and antioxidant vapor barrier materials are well suited; for living rooms - the same, plus regular penofol. A prerequisite is an overlap of at least 10-15 cm and sealing of the joints; for reliability, the vapor barrier is fixed to the ceiling with a grid or staples. In this case, the reflective or vapor-tight side is directed exclusively into the room.

3. Vertical structures.

Installation of a vapor barrier when insulating walls is necessary when: using fibrous and cotton wool insulation, erecting frame wall panels, arranging ventilated facades; in the latter case, it also performs the functions of wind protection. In all the mentioned points, it is not recommended to choose completely impermeable films; the insulation must breathe; diffusion and superdiffusion membranes that allow air to pass through, but not moisture and steam, are considered the best option. For exterior work, the vapor barrier is laid with the smooth side facing the mineral wool or other insulation on the walls, and the rough side facing the street. The film or canvas should not sag, but excessive tension is also unacceptable. On internal vertical walls they are held in place by staples or upholstery with thin strips, the vapor-tight side facing the room.

4. Roof vapor barrier.

A vapor barrier is a mandatory layer when laying a roofing pie. It prevents the accumulation of condensation in the inner insulating layer and protects the rafters from fungus. The maximum possible tightness is required from the vapor barrier; preference is given to antioxidant and reflective types, the side impenetrable to vapor is directed into the attic. Overlap - from 15 cm, as well as gluing joints and seams. An important condition is the need to seal vapor barrier materials adjacent to vertical structures.

5. Other applications.

A vapor barrier is also needed when insulating basements and balconies (areas in contact with cold external surfaces. For basement and underground areas, membrane films are considered the best; the walls and ceiling of the basement must breathe, the floors are insulated from the ground side. For installing a vapor barrier when insulating balconies and loggias, preference is given to foamed polyethylene with a reflective side directed into the apartment. This is almost the only case when the materials are placed end-to-end and not overlapping, but sealing of adjacent areas is still required.

Possible mistakes

In addition to choosing the wrong side, violations of technology include:

1. Lack of overlaps or insufficient insulation of joints.

2. Pulling thin films, especially on structures exposed to temperature changes, leads to their rupture. But excessive sagging is also not required.

3. Lack of ventilation gaps for evaporation of condensate from the vapor-tight side of the film (a clear example of an error is the installation of internal cladding directly on the bottom layer of the roofing pie).

Before laying a vapor barrier, you should calculate its required quantity. The use of different types is undesirable, although there are no clear standards in this case. A common mistake is to buy rolls strictly according to the area of ​​the working surfaces without a 15% margin for overlaps and trivial damage.

There is only one option when it is not necessary to install a vapor barrier - when building a house from wooden beams, but this exception does not apply to absorbent insulating materials and floors; they always need protection. The work is carried out in the warm and, if possible, dry season, the films are protected in every possible way from getting wet. An important condition is that the vapor barrier is tightly connected to the insulation (ventilation gaps remain on the outer, reflective and impenetrable side), voids and sagging are unacceptable. All surfaces must be clean, grease-free and dry.

If you are in doubt about the correctness of the decision regarding which side to lay the vapor barrier against the insulation, you should read the instructions again. Reflective and rough planes are easy to determine, with membranes it is more difficult. Typically, the side facing down when unrolling the roll is considered to be the inside side. Experts advise paying attention to the coloring: lighter shades are observed on the sides adjacent to the insulation. But there is a variety in which it is the matte (usually fabric) surface that is vapor-tight. If this is not enough to identify the desired properties, then the canvas or film is rolled out a little on the floor, the tight-fitting side of the material will be the inner one.

Vapor barrier is the most important part of the insulation, which occupies a key place in its durability and reliability. The absence of such a layer will lead to the accumulation of moisture and slow destruction of the material, especially during the cold period, when significant temperature changes are observed. In this regard, many people are interested in how and which side to lay the vapor barrier to the insulation.

This material must be installed because it will protect against temperature differences

general information

A few decades ago, glassine was used exclusively as a vapor barrier. It was cut into even strips and then glued to the insulation. And only recently have more modernized materials appeared on the market, which are based on polyethylene film and can be used in the most extreme conditions with high humidity.

Modern options are characterized by the following advantages:

• high resistance to temperature changes and ultraviolet radiation;
• maximum strength;
• multifunctionality.

However, when installing such materials, additional difficulties arise that force beginners to figure out which side to lay the vapor barrier against the insulation. There are no particular difficulties in laying the vapor barrier layer, but nevertheless, questions about choosing the right side are increasingly appearing on various forums.

In this video you will learn how to properly install a vapor barrier:

Purpose of vapor barrier

Which side of the vapor barrier layer is laid to the insulation is one of the most pressing questions that people face when constructing private premises or renovating old homes. But before you start looking for answers, you should understand what such a layer is intended for and what its importance is.

As you know, water is the best conductor of heat, because it is not without reason that it is used as a coolant in heating and cooling systems. And if the thermal insulation of a room is not protected from moisture, this will cause serious deformation processes, the formation of mold, fungi and other problems.

The most serious troubles appear during the cold season, because if in the summer, with above-zero temperatures and good ventilation, any steam quickly escapes, then in the winter it will begin to rise, penetrating into the insulation. Exposure to negative temperatures will cause the upper part of the insulation in the roofing “pie” to begin to freeze, creating additional conditions for internal wetting.

Such phenomena will reduce the effectiveness of the insulation and negatively affect its structure, which, in turn, will entail the development of corrosion processes and the appearance of fungus. If radical measures are not taken, moisture will begin to seep into the room, damaging the finishing elements. To prevent such a course of events, it is necessary to install high-quality vapor barrier.

And in order to understand which side of the vapor barrier is laid to the insulation, it is important to study its design features. On both sides of the insulating layer there are different films, which are intended for opposite tasks. A vapor barrier is installed in the lower part, preventing the penetration of steam, and in the upper part, a vapor-permeable membrane is installed that can allow accumulated condensate to pass out.

A logical question arises: where does the steam come from if a vapor barrier is attached to the bottom of the insulation? Unfortunately, even the highest quality films are not able to provide 100% protection against condensation penetration, so certain amounts of moisture still penetrate into this layer.

Types of materials

When figuring out which side to lay the vapor barrier on, you need to learn about the main types of such materials. After all, people often wonder why a layer has the same or completely different sides. Conditionally existing varieties are divided into groups: A, B, C, D.

Vapor barriers are divided into 4 groups and each of them has its own specifics

Representatives of the first group are intended to remove condensate from the other side. They cannot be used as a vapor barrier, since they are characterized by high throughput and solve the opposite problem - they release steam to the outside, but do not allow rainwater to enter the room. Such thermal insulation is indispensable for roofing structures with an inclination angle of 35° or more. The fact is that on such a roof drops will easily roll down and evaporate.

Group B vapor barrier is a classic double-sided layer that has a durable structure and absorbs any moisture. During the day, the accumulated condensation comes out and disappears.

Because of this feature, such hydro-vapor barrier is always laid with the smooth side facing the insulation, and the rough side facing outwards. This option is suitable only for rooms with roof insulation, since in the absence of insulation its strength is significantly reduced.

Before purchasing a vapor barrier, you need to know the features of each group.

Membranes from group C are intended for maximum protection of insulation from water vapor. Their structure consists of 2 heavy-duty layers, which differ from the previous ones in increased density. Often this vapor barrier is used in non-insulated roofs to protect wooden elements and enhance the protective functions of the insulation. Unlike the previous type, the material is laid with the rough side in the lower (inner) part of the thermal insulation.

There is another type - polypropylene isopar group D. It is a modernized material consisting of especially durable polypropylene fabric with a laminate coating on one side. In addition to the main task of insulating the attic floor, such insulation can protect the roof structure from leaks, and in conditions of maximum humidity.

The effect of changing sides on vapor permeability

Depending on the installation method, the listed types may also differ from each other. In this regard, the following vapor barrier groups are distinguished:

1. For single-sided installation. Such material must be nailed on a specific side.
2. For double-sided installation. In most cases, both sides of vapor barrier membranes are the same. Their main advantage is maximum density and the possibility of laying on any side.

It should be noted that in the recent past, membranes with the properties of modern vapor barriers were used in astronautics. After that, they began to be modernized in every possible way and used for wide everyday tasks. And if once the installation of such material was not considered a difficult task, now various sites and forums are literally overflowing with discussions about performing such a task.

Double-sided installation is more practical

Today, there is a strong opinion that if the vapor barrier is attached to the roof with the “wrong” side, then the service life of the insulation and the roof as a whole will be noticeably reduced. However, according to experts, such masonry can only negatively affect the durability of the interior decoration, since the rough side has the same properties as the smooth side. In terms of vapor permeability, the layers practically do not differ from each other. But as for the quality of retention of condensate droplets, the situation here is different.

Pitfalls and myths

Many people mistakenly think that if there is a good vapor barrier layer, condensation will not appear in the room at all or will quickly come out. However, this is an erroneous statement, because any moisture that rises upward in the form of steam eventually becomes condensation.

There is also such a thing as a “temperature limit”, at which all moisture turns into a drop-like state. In most cases, this happens at a temperature of +15°C and a humidity of 65%. If the latter indicator rises to 80%, then condensation can occur at +17°C.

Steam formation occurs when there is a difference in partial pressure. Any steam that appears inside the house tends to go outside, where there is a lower temperature. But on its way it encounters a barrier - a vapor barrier layer.

If the room air is heated to a certain level, all the moisture in the air will turn into condensation and precipitate. With this phenomenon, the difference between a roof structure protected by insulation and an unprotected one is clearly visible. If the vapor barrier layer is located on the insulation, then it will warm up many times faster than without it.

In the absence of a vapor barrier, water vapor will begin to make its way directly to the roofing “pie”, where it will meet the cold front. Because of this, the steam is converted into condensate, and at low temperatures - into an ice edge. But all these processes take place inside the roofing structure, which negatively affects its functionality and durability.

And if in winter the ice formed does not pose any threat, then with the first rays of the sun it will begin to melt en masse, creating huge smudges on the slopes of the room.

True, if the roof is equipped correctly, then the occurrence of condensation will be practically excluded. And in this case, even incorrect placement of vapor barrier layers will not in any way affect the security of the roofing “pie”.

Features of anti-condensation film

Many manufacturers of vapor barrier materials pay special attention to such a point as the “anti-condensation side” of the film. It differs from the other part of the material in a special fleecy layer that can absorb a significant part of the moisture and retain it until it evaporates completely. Due to this specific feature, the insulation and film practically do not get wet, which has a positive effect on the durability of the finishing part of the roof.

Because of this, experts advise placing the rough side inside the home or attic, and the smooth side directly to the insulation. But in practice, things may look different. After all, if condensation appears inside the roof structure, then even a reliable fleecy surface is not able to completely retain it. The anti-condensation side of the vapor barrier layer and a similar film are significantly different from each other.

However, at the stage of constructing the roof, it is better to follow the instructions from the manufacturer and place both the film and the anti-condensation side. But if a moisture-proof layer, heat and wind insulation have already been installed, and there is a suspicion that some important points were missed during installation, there is no point in hoping that the “right” side or the highest quality material from the leading brand Axton will hide these shortcomings.

Experienced craftsmen often claim that it doesn’t matter which side the vapor barrier is placed on. After all, as already mentioned, any droplets, moisture and condensation are serious enemies of the roofing “pie”, and with proper installation of insulation they simply should not exist. Otherwise, even the lining and wall decoration will begin to deform, swell and fall off. Moreover, sometimes the consequences can be irreparable.

Such troubles occur only when there are serious shortcomings at the construction stage. And if the vapor barrier is located between the drywall and mineral wool, then there is no point in making such a complex structure at all. The drywall itself is able to absorb condensation, so steam will not have the opportunity to penetrate to the internal vapor barrier. In this situation, you can get by with ordinary glassine.

Installing a vapor barrier indoors is a rather painstaking and responsible process. But, unfortunately, many roofers pay great attention to those points that, in fact, do not play an important role for the effectiveness of protection against condensation. And the side of the masonry material is one of them. To prevent the development of putrefactive processes, the formation of fungus or deformation of the finish, it is enough to properly arrange the roof and follow the basic rules for maintaining this structure. In this case, it will serve for a long time and with high quality.