Installation of vapor barrier membranes. Must read

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 confuse 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 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

Paro insulating- which do not allow steam or water to pass through and are not membranes
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 the 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.

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.
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 barrier 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:

In cold climates (most of Russia), vapor barrier is always installed only on the inner, “warm” side - be it a roof or a wall
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.
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.
Vapor-permeable membranes (super-diffusion, windproof) are always installed on the outer, cold side of the structure.
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.
Instructions can be found on the manufacturer's website or on the roll of the film itself.
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.
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

Thermal insulation of frame buildings is very important, since heat must be retained inside the building. The technology involves the use of up to 75% insulation in the construction of walls. But this material loses its thermal insulation properties if moisture gets into it from the inside. To ensure the dryness of the entire building, a vapor barrier is used for the walls of the frame house.

What is the vapor barrier of a frame house?

This term means the use porous membranes, with the help of which excess moisture is removed from the inside and does not enter from the outside. Thus, the house can “breathe” and does not turn into a closed greenhouse. Partial air exchange is provided by wooden structures, which allow 35% of the air volume to pass through them.

Some people, when making a vapor barrier with their own hands, install ordinary plastic film instead of a porous membrane. This is wrong, as it begins to accumulate water and cause the wood to rot.

Unlike polyethylene, vapor barrier film has a more complex structure and consists of multiple porous layers. One side is smooth (it is adjacent to the insulation), the other is rough. This feature is needed for better collection of moisture and its further removal.

There are films in which both sides are the same, so they can be installed in any order. Before installation, it is better to read the instructions and find out what type of membrane you have.

There are also membranes with specific purposes. They are intended for vapor barriers only in specific conditions. For example, exclusively in non-residential premises, in harsh climates, with high humidity (baths, saunas).

What is the difference between vapor barrier for frame houses

The vapor barrier of a frame house is carried out practically according to the same scheme as for other buildings, but there are also some differences. So, load-bearing structures do not have an insulation function, and this is a significant difference. The “pie” of the wall looks like this:

External decorative finishing (siding, lining).
Waterproofing film.
Wooden frame.
Thermal insulation layer.
Vapor barrier film.
Lathing.
Interior finishing materials.

The vapor barrier material is quite easy to install. It is necessary to properly lay and secure it. To do this, you can use tape and galvanized nails or a construction stapler. But there are also some subtleties:

seal all membrane ruptures with tape so that there are no gaps;
minimize the number of folds;
seal all seams properly and check for integrity;
where the wood comes into contact with the vapor barrier, apply a special antiseptic;
a diffusion membrane can be in direct contact with the insulation; for another type, you need to leave a gap of 5 cm;
The sides of the membrane cannot be swapped, as it will lose its properties.

If you make a mistake somewhere and make a mistake, the vapor barrier of a frame house will be ineffective, and it will have to be changed along with replacing the insulation, which will cost a tidy sum. Very often, those who like to do everything with their own hands try to install the membrane faster, so they perform the installation sloppily. Because of this, the vapor barrier only lasts for 2-3 years, and then it has to be replaced.

As for the rules for laying the material, this must be done from top to bottom. There should be between layers overlap of at least 10 cm, glued with a special vapor barrier layer. You also need to carefully glue the places where the film is adjacent to the wood.

When a vapor barrier is not required

There are insulation materials that do not collapse, despite the lack of vapor barrier. Therefore, builders may not use it. But then another way to remove moisture from the room is needed.

Thus, polyurethane foam and polystyrene foam do not allow moisture to pass through, so it is necessary to install a forced air exhaust, otherwise moisture will accumulate in the room and contribute to the development of mold. Also, there is no need to carry out vapor barrier in houses without insulation.

Vapor barrier schemes in a frame building

Depending on the design of the house, different vapor barrier schemes may be used. Let's look at them below.

Double vapor barrier

In the case of double-sided wall decoration non-breathable materials(plastic, tile, oilcloth) water can collect inside, since there is nowhere for it to escape. To avoid this problem, a ventilation gap is provided between the cladding and the wall. It must ensure air circulation and release to the outside.

Elimination of excess moisture in a frame house is carried out in the following ways:

The membrane is fixed to the frame posts, after which interior finishing work is done.
A vapor barrier membrane is installed, then a sheathing is installed to secure the facing materials. This allows for a ventilation gap of about 5 cm.

The second option is best suited for residential buildings, since the likelihood of moisture accumulation inside the walls is higher there. And the construction of structures without a ventilation gap is permissible only in buildings for non-permanent use. There, as a rule, simple ventilation or a supply and exhaust system is installed to get rid of high humidity.

If the house is held high-quality ventilation system, the vapor barrier layer has virtually no beneficial effect. It is then needed only to prevent the possible accumulation of moisture inside the wall.

External building insulation and vapor barrier

As already mentioned, the vapor barrier layer should not be in direct contact with the wooden frame. Therefore, for the outside, first the wall is covered with wooden slats, the thickness of which is 25 mm. The distance between the slats is 1 m.

Next, a membrane is stuffed onto the slats rough side out, after which the sheathing is installed again. And only after that the house is insulated with heat-insulating materials, the waterproofing layer is fixed and the finishing is done on the outside.

Thanks to such a complex design, the vapor barrier of a frame house creates the necessary microclimate in the room.

As for the disadvantages of the technology, the structure will dry out for several years. In addition, all joints and grooves must be carefully sealed and treated with a sealing compound. An important requirement is the need to use exclusively hydrophobic materials for insulation.

Floor vapor barrier

The floor must be insulated and this must be done in parallel with steam and waterproofing. Firstly, moisture will constantly flow from the basement or basement. Secondly, indoor humidity can also damage the thermal insulation structure.

Installed on the subfloor waterproofing layer. Tightness is ensured by overlapping the film and gluing the joints with tape for this material.
Insulation in the form of rolls or slabs is laid between the floor joists, after which the entire structure is sheathed with a vapor barrier layer. It is also made one-piece by fastening the film overlapping with tape.
In the logs, ventilation gaps are made between the vapor barrier layer and the floor using boards that are secured with self-tapping screws.
At the final stage, a tongue-and-groove or edged floorboard is laid on top of all these structures, and a finishing coating is placed on top of it.

If you plan to make a vapor barrier for floors in a frame house, please note that it is only relevant if insulation that allows air vapor to pass through. Foam plastic does not allow air to pass through, so installing a membrane is irrelevant for it. It is best to choose mineral wool for floor insulation, the density of which is 37-57 kg/m3. m. It is very light and provides air exchange.

Ceiling insulation

Almost all ceilings of frame houses are insulated using mineral wool. Expanded clay, expanded polystyrene and ecowool are less commonly used.

Insulation is done like this:

First, a vapor barrier membrane is secured to the bottom of the beams using a stapler, after which boards are stuffed onto it. The interval between them is 40 cm.
Next, the entire ceiling is insulated with mineral wool. Important make overlaps on the walls so that there are no areas through which heat will escape. The seams should not be continuous, that is, the slabs are laid in a checkerboard pattern.
If you plan to insulate the attic, line it with another vapor barrier layer. All film joints are sealed. If there is no heating in the attic of a frame house, this stage can be eliminated. Next, they lay out the floor in the attic.

If the ceiling is correctly assembled and insulated, moisture will not collect either from below or from above.

Proper roof insulation

The principle of insulating the roof of a frame house is similar to the rules for walls, with the exception of some features.

A waterproofing layer is installed on top of the rafters, which is additionally secured with a lath on which the roofing material is supported. There is a large free space between the rafters themselves. Rigid insulation boards are laid there.
A gap is made between the slabs and the waterproofing layer so that moisture can be removed and the structural element itself can be ventilated with air. On different sides of the house they draw conclusions from this gap.
It is very important to maintain the tightness of the waterproofing. If the insulation comes into contact with water, it will quickly begin to deteriorate.
The inside of the rafters is sheathed with a vapor barrier membrane, after which it is stuffed again lathing for installation of internal facing materials.

If the attic is properly insulated and insulated from excess moisture, you can even install heating there. This will make it a full-fledged living space, and not a collection point for unnecessary things.

So, it is important to select and install vapor barrier membranes correctly. This will allow them to fulfill their function - to prevent the insulation from coming into contact with water, and also to remove excess moisture from the room.

Watch a video in which professional builders talk about the technology of vapor barrier for a frame house.

In order to maximize the service life of a frame house, it is important to pay special attention to its vapor barrier during the construction stage. From this article you will learn what materials are best to use to avoid the unpleasant consequences of exposure to moisture, and you will also become familiar with the most common mistakes in the process of laying vapor barrier materials.

Choosing a material for vapor barrier

Let's look at specific examples of each material, its advantages and disadvantages.

Reinforced polyethylene

A well-known, but already rarely used material, which was previously used to create a vapor barrier in wooden houses. Today, its use practically does not give the desired effect and reliability.

Advantages:

Among the advantages, one can highlight only the affordable cost of the material.

Flaws:

Maximum care when installing. Polyethylene should not be stretched or stretched in order to avoid its deformation and ruptures. In addition, if it is strongly stretched, it can easily lose its functionality and integrity during the annual temperature change.
Often, improper use of film turns a frame house into a steam bath, does not allow the walls to “breathe” normally, and accumulates moist air inside the house, making living in it uncomfortable and unpleasant.

Various types of mastic

They are special mixtures that are applied to the floor and walls of the house before creating the exterior decoration. They allow you to create a reliable vapor barrier layer on the outside of the walls of a frame house. Bitumen-kukersol mastic is one of the most popular. Its application does not require the creation of wall sheathing. It can be applied in several layers, but each of them must dry thoroughly.

Advantages:

They allow air to pass through well and allow the walls of a frame house to “breathe.”
Affordable price.
Wide range of mastics to choose from.
Mastic reliably retains moisture and preserves the house frame and insulation from destruction.

Flaws:

Maximum accuracy during the application process.
Requires application to previously prepared walls with a cleaned surface.
Apply a very thin layer, avoiding the appearance of uneven areas.

Ruberoid

This is a modern and affordable building material that allows you to create a reliable vapor barrier layer. Suitable for creating an external vapor barrier layer for the walls of a frame house. Requires preliminary lathing of bars around the perimeter of the entire wall no wider than 50 by 50 cm.

Advantages:

Relatively low cost.
Availability of material.

Flaws:

Be careful when working to avoid uneven joints and poor-quality seams.

Of the above materials, the most unsuccessful and undesirable for vapor barrier of a frame house is polyethylene. It does not allow air to pass through and can turn your home into a real steam bag with high humidity. In winter it will be cold and damp, and in the warm season it will steam like in a bathhouse.

Vapor barrier films

The optimal material for creating a vapor barrier layer for the walls of a frame house. Due to their functional features they are also called vapor barrier membranes. They reliably protect the house from the penetration of unwanted moisture into the insulation and into the room itself, and also ensure comfortable living in a wooden building for many years.

Flaws:

The only drawback is the rather high cost of this material, but it also fully pays off during the operation of the frame house, because you don’t need to worry about replacing the insulation, as well as about the destruction of the wooden frame of the entire house, because special membrane films will provide it with long-term maximum protection from moisture from the outside sides and a pair - from the inside.

Advantages:

Long service life.

Easy to install.

Reliability.

High functionality.

Ondutis vapor barrier films have proven themselves to be excellent in the building materials market for paraisolating the walls of a frame house.

Installation of vapor barrier from outside

The most important feature of installing a vapor barrier from the outside is to avoid a common mistake when installing double insulation, which most often contributes to rotting of the frame and accumulation of moisture inside the insulation.

Stages of vapor barrier outside

Laying is done between the insulation and the wall.
It is especially important to ensure that there is a special air gap between them.
Films with a special adhesive layer are placed with the inner surface side on the insulation. It is important to ensure that the windproof membrane remains on top.

The following films are suitable for vapor barrier on the street side: A100, A120, A120 Smart. They reliably protect the outer surface of the wall from moisture and wind, allow moisture to pass through and ensure a normal microclimate inside the frame house.

Installation of vapor barrier from the inside

Stages of vapor barrier from the inside

Vapor barrier membranes are laid on top of the rest.
You can attach it directly to a wooden frame, having previously treated it with an antiseptic.
On partition walls, the material is applied on both sides with an obligatory overlap.
The joints are additionally treated with sealed tape with moisture-resistant capabilities.

For a long service life of the insulation in a frame house, you need to pay attention to such an element of the overall design as the vapor barrier of the frame house and its quality. It is important to monitor this already during the construction of the building. Although many still ask the question: is vapor barrier necessary for a frame house?

Is vapor barrier necessary in a frame house? Well-thought-out and equipped vapor barrier of the internal walls of a frame house is needed for warm and at the same time damp rooms. A large amount of moisture and steam is generated in a frame house, which must be removed from the structure to maintain optimal humidity, high quality and the appearance of a do-it-yourself frame house.

Moisture, in the process of its formation and accumulation, tends to escape through the walls or ceiling. First of all, moist air rises, so a vapor barrier between floors will stop the movement of air and prevent the insulation from getting wet. If the correct vapor barrier of a frame house is not installed, the humidity will quickly destroy or cause quite serious damage to the construction site, and will also create an unfavorable microclimate.

Vapor barrier of walls and ceiling.

A vapor barrier from the inside of a house is a barrier designed to protect the surface of walls, floors and ceilings from moisture, therefore ideally protecting them from subsequent wetting.

Proper vapor barrier of a frame house is an event that is mandatory not only for baths and basements, but also for other premises built or finished using a special technology. Among the main buildings and structures where insulation is needed, the following can be noted:

Buildings that are insulated from the inside, especially if mineral wool or glass wool can be used as insulation. Insulation materials ideally retain overall heat, but do not remove moisture at all. It gradually accumulates in insulation, whereby the base gradually loses its main purpose, and the structure of the insulation is also lost.
Structures with multilayer wall insulation. These are frame buildings with special internal insulation, therefore, protection from steam is simply necessary here.
Frame houses with ventilated modern facades. The windproof membrane will act as a windbreak. The installed wind protection seriously doses and softens the directional flows of external air masses.

On a note

The advantage of a well-equipped vapor barrier from inside the house is its ability to normalize heat exchange in the room.

Basic vapor barrier mistakes

If you listen to the opinions of professionals, you can find out what difficulties and mistakes you may encounter when solving such an important issue as vapor barrier for the walls of a frame house. Among the most common shortcomings are:

Construction of external walls.

Installation of vapor barrier on the outside of a frame house. Steam will pass through the entire finish and accumulate in the insulation. The vapor barrier layer should be located inside the building; wind protection on the outside will be sufficient;
Installing a poor vapor barrier in a tiled bathroom. In this situation, water and steam penetrate inside through the tile joints. All this automatically leads to a violation of not only the tightness, but also the strength and reliability of fastening the finishing material in the frame house;
Lack of protection from moisture in walls insulated with mineral wool and its analogues. The absence of vapor barrier layers is permissible only if the walls are insulated with foam plastic;
Carrying out poor quality work. The processes associated with installing a vapor barrier in a frame house must be carried out as clearly as possible, following the instructions. Even the most minor shortcomings and neglect of the rules will lead to damage.

Frame houses are known for their microclimate that is comfortable for everyone. For its long-term preservation and to significantly increase the service life of the object, it is worthwhile to competently carry out all work and activities related to construction and subsequent professional finishing.

We insulate the ceiling.

Vapor barrier materials

Modern manufacturers offer a huge variety of vapor barrier materials. Which vapor barrier to choose for a frame house? The most popular of them include the following options:

Reinforced polyethylene. A material that is becoming increasingly rare and popular solely because of its affordable cost. It is used in a process such as vapor barrier of the floor of a frame house. When using it, maximum caution and strict adherence to instructions is required. Otherwise, the frame house may turn into a steam room, that is, humid air will accumulate in the house, making living not very comfortable.
Different options for mastic. These are special mixtures that are applied to the walls of the structure before the exterior finishing of the frame house. Bituminous kukersol mastic, which perfectly allows air to pass through, is popular and is sold at an affordable cost. Any type perfectly collects and retains water, completely preserving the frame of the house in its original form. This is only possible with proper installation of the vapor barrier of a frame house.

Vapor barrier of partitions.

Ruberoid. Suitable for finishing modern frame buildings. The main feature of the material is the need for preliminary arrangement of wooden sheathing 50 by 50 mm. Modern roofing felt is universal and affordable.
Vapor barrier films. This is a unique option with which you can create high-quality vapor barrier for the walls of a frame house. Vapor barrier films reliably protect the structure and insulation from moisture. All this ensures the most comfortable stay in buildings built using frame technology.

All of the listed materials not only provide an excellent level of protection, but are characterized by such positive properties and qualities as the possibility of long-term use, ease of installation, reliability during use and ideal functionality.

Vapor barrier for walls

To install the vapor barrier layer of modern frame buildings, you will need to prepare special tools and the necessary materials. Proper vapor barrier of a frame house requires a certain sequence of work. The tools that the frame house vapor barrier technology provides include:

Adhesive construction tape that has a special double-sided coating is construction tape;
Various measuring instruments and standard scissors;
You need metal staples, a hammer, and nails;
The main vapor barrier material.

Frame wall pie.

If the installation of a vapor barrier for a frame house is carried out by adhesion of the main layer, which protects against water and steam, to the main frame using nails, you need to purchase additional slats made of wood or galvanized material. At the same time, it is not necessary to paraisolate the internal walls of a frame house, because there is no temperature difference in the partitions, which means there is no movement of air from hot to cold.

Vapor barrier of the floor in a frame house is simply necessary to avoid getting the mineral insulation wet, which in this case loses its insulating properties. A vapor barrier layer is laid out on the logs, which must be glued at the joints. The counter batten is driven directly onto the top of the joists, and only then the floor covering is installed.

On a note

The installation of a vapor barrier for the walls of a frame house should be carried out after installing the outer layer of wind protection, as well as a layer of insulation.

Sequence of wall vapor barrier

The slats and the frame itself are carefully treated with special disinfection compounds.
The walls are measured.
According to the obtained dimensions, elements of vapor barrier materials are cut out. In this case, an overlap of 10 mm must be taken into account.
The material is being fixed. The fasteners are installed strictly along the perimeter, and slats and a construction stapler are used here. It all depends on the base used. Installation must be done from bottom to top. Elements of materials must be positioned strictly horizontally. At the joints you need to use tape, and it is important to overlap the material itself.

The vapor barrier of the walls and interfloor ceilings of a frame house was carried out according to all the rules and after that it is worth taking care of the presence of ventilation in the frame house with your own hands. By the way, vapor barrier of the partitions of a frame house is not required, therefore in the internal adjacent rooms the temperature does not differ from each other. But ventilation should pass between the finish and the protection layer. This will help prevent condensation from accumulating in the interior of the overall pie of the structure.

Basalt wool insulation.

Vapor barrier of interfloor ceilings

The division of a frame house by interfloor ceilings carries with it the division of the volume of premises into parts. Temperature and humidity may vary in these frame buildings. Thermal air vapor will rise upward, thereby forming condensation on parts of the floors. To protect load-bearing structures and insulation from moisture, a vapor barrier is installed between floors.

Interfloor pie.

It is very important to make a vapor barrier according to all installation rules. The vapor barrier of interfloor ceilings is overlapped by approximately 100 mm. The joints must be taped with special tape so that even small gaps are not left. Only in this case will the vapor barrier perform its functions.

Correct vapor barrier

To achieve optimal results when working with vapor barriers and in the process of vapor barrier work, it is worth using special insulating membranes that at the same time protect from wind. Vapor barrier of a frame house with a membrane on the outside will help release moisture to the outside.

If you do not secure high-quality protection on all sides of the installed insulation, the structure will get wet and lose its basic thermal insulation qualities. If there is no vapor barrier, and the installed insulation layer is tightly covered only with external finishing materials, the cotton insulation will get wet very quickly and, accordingly, will immediately lose its advantageous features.

Experts strongly recommend that builders and owners do not save on purchasing building materials, as this will require material investments over time. High-quality materials, as well as proper vapor barrier in a frame house, will ensure the most comfortable microclimate in the room and will preserve the general operational characteristics of the building for a long time.

Vapor barrier in a wooden house. Everyone who builds a frame wooden house asks about this first of all! I have already written about vapor barrier and waterproofing, but I decided to separately cover the topic of combating vapor, since errors in vapor barrier are very critical for the future home.

What is vapor barrier
Which side should the vapor barrier be laid?
Vapor barrier for the walls of a frame/wooden house
Vapor barrier of partitions
Vapor barrier of interfloor ceilings
FAQ. Film Frequently Asked Questions

What is a vapor barrier?

Vapor barrier- this is any film with low vapor permeability, which is installed in a frame house from the INSIDE in order to prevent steam from entering the insulation and keeping the latter from constantly getting wet.

Do not confuse it with waterproofing, which is installed outside and is needed to protect the wooden frame from moisture! Special membranes are used there.

Do you need a vapor barrier for a frame house?

Yes. The technology of frame house construction requires the presence of vapor barrier materials in the walls, floors and ceilings! We must create a complete vapor barrier circuit, which is why frame houses are often called “thermos houses.”

Why do you need a vapor barrier film:

prevents the insulation from getting wet (does not allow moisture to reach it)
stabilizes the climate in a frame house

For this, a special vapor barrier material is used; spunbond and other films are not suitable.

Which side should the vapor barrier be laid?

But you take a regular vapor barrier film, then you won’t need to look at either side. But if you have already taken a specialized vapor film, then look at the instructions. EVERYTHING is written there. Just don't be lazy or force the builders.

Apart from the manufacturer, no one knows how to properly install a vapor barrier from his production; each of them has its own notes. But it’s logical that the part with his brand should be inside and we could see it, they tried their best for us!

U Izospana-B it's simple. The surface is rough inside, moisture remains on it, the smooth side of this vapor film is placed against the insulation.

This is where the questions about how to install a vapor barrier end. You can go to the website of the manufacturer of the vapor barrier film and look at the exact information there, for example, on the Yutafol website (isospan does not have a normal website).

Vapor barrier for the walls of a frame house

In the walls of a wooden or frame house, steam is insulated BEFORE the wall, that is, inside. You can't lock it from the outside, the walls will rot.

Vapor barrier of frame house partitions

Partitions do not need to be vapor-insulated, except for wet rooms. It's really better to put PE film on the inside! But not on both sides of the wall.

If you are worried that the insulation will generate dust and get into your lungs, place a vapor-permeable membrane in the partitions on both sides!

Vapor barrier of floor and ceiling in a frame house

You can vapor barrier the floor with film (standard), but you can do it a little lighter - underlayment under the laminate + plywood or OSB on the floor gives a good result. Or even linoleum. The floor is not where most of the steam goes; after all, steam mostly goes up!

The ceiling is more difficult. The ceiling needs to be vapor-insulated with film, because all the steam goes up. I have a text about what it looks like in my house - Installation of wooden sheathing on the ceiling.

Vapor barrier for ceilings in a frame house

The ceiling between floors does NOT need to be vapor-insulated, since there is warm air both below and above. But the top floor is a different matter, we work there in the same way as with the ceiling.

FAQ. Frequently asked questions about vapor barrier of a frame house

Vapor barrier. Inside or outside?

Inside of course! Steam goes from heat to cold.

Which vapor barrier to choose for the walls of a frame house

For walls and in general, the best vapor barrier for a frame house is an ordinary polyethylene film 200 microns thick (not thinner).

But if you really want it, you can buy Izospan or Yutafol vapor barrier, but for me, this is a waste of money. Americans usually use polyethylene without any brands.

Is it possible to have a frame house without vapor barrier?

In some climates, such as southern ones, it is indeed possible to build frame houses without a vapor barrier film. But these options are individual and you need to very clearly calculate the pies and dew point. I wouldn't experiment like that

Is it necessary to glue the vapor barrier and how?

Yes! The film can be glued using either special butyl rubber tape or glue. This is the only correct way, you can’t not glue the vapor barrier.

How to make a vapor barrier on video:

Thermal insulation in frame houses is the main means of heat retention. The walls consist of 75% insulation, for which special conditions must be created. It loses its positive properties under the influence of moisture entering from the inside. It is important that the thermal insulation fits tightly to the frame. To do this, it must always remain dry, which also requires vapor barrier of the frame house: walls, floor, ceiling and roof.

The use of vapor barrier in the insulation system of a frame house

Characteristics of vapor barrier

A vapor barrier is a porous membrane that can significantly reduce the negative process of moisture accumulation in thermal insulation. The porous layer allows the house to “breathe”, providing air exchange. In this case, the greenhouse effect is eliminated. Wooden structures allow up to 35% of air to pass through.

The mistake of many owners is to protect the frame house from the inside with plastic film. Over time, water accumulates under it, causing rotting of wooden structures.

Vapor barrier is not a film with many holes, but a complex multi-layer porous package. It is laid tightly with the rough side inside the house, and the smooth side against the insulation. This is necessary so that moisture can better settle on a rough surface and subsequently evaporate freely.

Features of laying vapor barrier when insulating a house

The film is the same on both sides. Then it makes no difference which side it faces the thermal insulation. In any case, before installation, you should read the instructions for the specific type of membrane.

Many membranes have a specific structure. They can have a specific purpose: for residential and non-residential buildings or for rooms with different humidity levels. The material is selected depending on the methods of use of buildings, the characteristics of the region, conditions of use, etc.

In rooms with a humid environment and elevated temperatures, membranes are needed that differ in properties from those used in ordinary homes. For example, reflective aluminum screens are used in saunas and baths.

Vapor barrier of bath walls and ceiling

Thus, the vapor barrier only partially protects the house structure from water vapor.

Features of vapor barrier of frame houses

Vapor barrier for the external walls of a frame house is done according to a scheme that is in many ways similar to other types of houses. The only difference is that the supporting structures do not perform the insulation function here.

The walls in cross section look like this:

external finishing with siding, lining or OSB boards;
waterproofing film;
frame;
thermal insulation;
vapor barrier;
sheathing;
interior decoration.

At first glance, it seems that it is not difficult to lay a vapor barrier, you just need to fix it by turning it in the right direction. Fixation is done using a construction stapler or galvanized nails, sealing the joints with tape.

Fastening the vapor barrier with a construction stapler

Basic rules to follow:

it is unacceptable to leave membrane ruptures;
the number of folds should be minimal;
gluing and sealing of seams must be of high quality;
the points of contact between the wood and the vapor barrier are treated with an antiseptic;
the diffusion membrane can be laid directly on the thermal insulation, in other cases a gap of about 5 cm is left between them;
It is not allowed to confuse the sides of the membrane during installation.

Any miscalculation will lead to the fact that the insulation will cease to perform its functions after a short time. As a result, the house will have to be insulated again. Not all owners or builders are able to show the necessary care during installation, and it lasts for 2-3 seasons, after which the insulation gets wet and stops working properly.

The installation technology involves laying the vapor barrier from top to bottom. The overlap is made at least 100 mm with sizing with tape intended for it. The connection to wooden structures should be carefully checked.

Depending on the type of insulation, sometimes a vapor barrier is not required. A similar decision is made when using polystyrene foam, ecowool and polyurethane foam. When using such thermal insulation, it is difficult for moisture to escape from the premises. Therefore, it is necessary to create their high-quality ventilation. In such a situation, forced air injection and exhaust is needed.

Vapor barrier is not required in houses without additional insulation when the walls are built of brick or foam blocks. It is also not used on interior partitions at home. The insulation absorbs steam if there is a temperature difference on the external walls.

Vapor barrier schemes for a frame house

Differences in house designs provide different conditions for removing moisture from the premises.

Double vapor barrier

If the wall is finished on both sides with poorly “breathable” materials (tiles, oilcloth, plastic), moisture may accumulate between them. To eliminate this negative effect, a ventilation gap is created between the wall and the cladding. At the same time, you need to make sure that air circulates in it and goes somewhere.

Basic vapor barrier schemes

Protection against moisture in frame houses is usually done in two ways:

The membrane is attached to the frame posts, and then the interior finishing is done (Fig. a below).
A horizontal or vertical sheathing is installed on top of the vapor barrier film, on which the cladding is attached. As a result, a ventilation gap of 4-5 cm is formed inside (Fig. b).

Methods for vapor barrier of frame house walls

The latter option is preferable to do if you live in a house permanently, when there is a risk of moisture accumulation between the walls. Without an air gap, it is allowed to construct buildings for temporary visits. They provide ventilation with the installation of a duct. It is imperative to vent from rooms with high humidity.

When equipping a house with effective ventilation, the role of vapor barrier is reduced. Here it serves only as additional insurance against moisture accumulation in the walls.

Vapor barrier for external insulation of a house

Vapor barrier cannot be laid on a smooth wooden surface.. First, 2.5 cm thick slats are placed on the wall in 1 m increments, and the membrane is stapled onto them. It should be facing the rough or fleecy side outward, and the smooth side facing the wall. Then the sheathing is stuffed on top, thermal insulation is laid on it, and a waterproofing film is stretched on top. After this, the final exterior finishing of the house is carried out.

External insulation of the house

The method provides a special microclimate in a house made of logs, timber or frame structure, since there is no need to cover the inside of the tree with finishing material.

The disadvantage of this option is the need to dry the structure, which takes several years. Additional work is also added to protect the joints with sealant and seal the grooves on both sides. For insulation, only hydrophobic materials can be used.

Vapor barrier of the floor in a wooden house

Hydro- and vapor barrier are needed for insulated floors due to the action of two factors:

moisture from the base or basement passing through the ground;
steam from the premises.

When insulating a floor, waterproofing is first laid in the space between the joists on the subfloor. The film strips are placed overlapping and glued with special tape.

Plates or rolls of insulation 15 cm thick are laid in the cells of the frame and then covered with a vapor barrier film. Overlapping and gluing of joints is also necessary here.

Boards 30 cm thick and with a pitch of 40-60 cm are placed across the logs. They are fastened with self-tapping screws or other suitable fasteners. Due to them, a ventilation gap is created between the floor and the vapor barrier.

A 25-30 mm tongue-and-groove floorboard or a 40-50 mm edged floorboard is tightly laid across the sheathing and secured. The finishing floor covering is installed on top.

Insulation of the first floor floor

The use of a vapor barrier for the floor is only effective in conjunction with breathable insulation. Polystyrene foam and similar materials are not suitable here. It is advisable to use mineral wool with a density of 37-57 kg/m3, since there is no load on it in the floor structure.

Insulation and vapor barrier of the ceiling

Up to 80% of frame houses are insulated with mineral wool. In addition to it, polystyrene foam, ecowool, expanded clay, etc. are used.

The ceiling is insulated as follows:

A vapor barrier film is stretched onto the beams from below and secured to them with a stapler. Then the board is filled in increments of about 40 cm.
Mineral wool is laid tightly on top of the entire ceiling. In this case, an overlap is made on the walls. If the slabs are 50mm thick, they should be laid in three layers to create a standard 150mm dimension. They are laid in a checkerboard pattern, and the top layer is covered with ceiling beams.
The top of the insulation is covered with a vapor barrier film if the attic is made warm. It is rolled out over the entire ceiling with an overlap of at least 10 cm and the joints are sealed. If the attic is unheated, such protection from above may not be necessary.
The floor is laid on top of the insulation. There should be a ventilation gap of about 5 cm between it and the vapor barrier.

A correctly laid ceiling “pie” prevents the accumulation of moisture in the insulation both below and above.

Insulation and vapor barrier of the roof

The roof is insulated like walls, but there are some peculiarities. Waterproofing is laid on top of the rafters. It is fixed with a lath on which the roof is attached. Afterwards, insulation boards are inserted between the rafters. It is better to take them rigid so that the material does not deform.

The slabs are installed with a gap from the waterproofing film. It is necessary for ventilation and removal of moisture that forms under the roof. For better circulation, two outlets are made from the gap - on different sides of the house. It is advisable to choose fireproof material.

Roof insulation

Waterproofing must be airtight, otherwise moisture will get on the insulation and it will lose a significant share of its useful properties.

From the inside, a vapor barrier is nailed to the rafters and sheathing is installed. The facing material is attached to it. These can be QSB boards, plasterboard, etc. For cladding, a frame made of profiles is installed, as for walls.

With high-quality insulation and reliable protection from moisture, a heating system can be installed in the attic. Then at any time of the year it will be a full-fledged living space.

Video: insulating a frame house

Installation of vapor barrier in a frame house is carried out taking into account the sequence, specifics of installation, as well as the features of the technology. If there is a non-residential premises under the roof, it may not be insulated, but thermal insulation significantly reduces noise during rain.

The correct selection and installation of vapor barrier membranes fully ensures that they perform useful functions in protecting a frame house from moisture.

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

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 confuse 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.

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

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

By taking advantage of the different physical properties of water in liquid and gaseous states, science and industry have been able to create materials that allow steam to pass through, but not 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.

So, a construction film that is impervious to water, but allows steam to pass equally in both directions is called waterproofing vapor 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.

Vapor barrier- 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

Paro insulating- which do not allow steam or water to pass through and are not membranes
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.

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.

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?

There are two ways out of this situation.

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.
Install a vapor barrier from the inside and make it as airtight as possible.

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.

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.

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 install a vapor-permeable membrane and why it is not possible to install a vapor barrier instead.

Windproof, waterproofing membrane for walls

Superdiffusion waterproofing membrane for roofing

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?

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.

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.

Moreover, this can happen both with the ceiling, and with the wall or roof.

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:

In cold climates (most of Russia), vapor barrier is always installed only on the inner, “warm” side - be it a roof or a wall
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.
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.
Vapor-permeable membranes (super-diffusion, windproof) are always installed on the outer, cold side of the structure.
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.
Instructions can be found on the manufacturer's website or on the roll of the film itself.
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.
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.
If you have any doubts about using the film, go to the manufacturer’s website and read the instructions or recommendations for use. Do not trust the advice of “sales consultants”. Refers mainly to “first and second echelon” materials. There are often a large number of errors in the instructions of third-tier manufacturers, since in fact they only sell films, without producing them or engaging in any development, so the instructions are written “on the knee”

PS If you are interested in a little more information about the differences in vapor permeable waterproofing membranes, I recommend reading this short document

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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 confuse 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.

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

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

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

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

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

Paro insulating - which do not allow steam or water to pass through and are not membranes
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 will immediately make a reservation that in reality all the processes described below are much more complex and have a lot of nuances. But the main thing for us is to understand the essence.

Single-layer design, no obstruction to the steam path

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.

Multilayer design, with increasing vapor permeability of layers towards the direction of vapor diffusion

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?

There was an obstacle in the way of the steam. Steam saturation has increased and condensation is likely to form

There are two ways out of this situation.

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.
Install a vapor barrier from the inside and make it as airtight as possible.

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.

The vapor barrier does not let steam into the wall and, accordingly, the likelihood of getting enough steam for condensation is greatly reduced

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.

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

Windproof, waterproofing membrane for walls

Typical arrangement of films in a frame wall

Superdiffusion waterproofing membrane for roofing

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

Location of films in an insulated roof

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?

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.

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.

Moreover, this can happen both with the ceiling, and with the wall or roof.

A dismantled wall without vapor barrier. Mold on the plywood, condensation flowed down, the insulation was thrown into the trash.

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:

In cold climates (most of Russia), vapor barrier is always installed only on the inner, “warm” side - be it a roof or a wall
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.
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.
Vapor-permeable membranes (super-diffusion, windproof) are always installed on the outer, cold side of the structure.
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.
Instructions can be found on the manufacturer's website or on the roll of the film itself.
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.
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.
If you have any doubts about using the film, go to the manufacturer’s website and read the instructions or recommendations for use. Do not trust the advice of “sales consultants”. Refers mainly to “first and second echelon” materials. There are often a large number of errors in the instructions of third-tier manufacturers, since in fact they only sell films, without producing them or engaging in any development, so the instructions are written “on the knee”
P.S. If you are interested in a little more information about the differences in vapor permeable waterproofing membranes, I recommend downloading and