How to properly install vapor barrier. Method of laying vapor barrier. Types of vapor barrier materials

The roof structure is a complex system. It consists of several layers of dissimilar materials, each of which performs its own unique function.

To provide comprehensive protection buildings from influence environment quality performance is required for all installation work, as well as the correct choice of base and insulating materials. This whole process is briefly called.

Standard Composition roofing cake includes:

Inner finishing layer;
The design of the crate;
Counter-breech;
(does not apply to a cold attic);
(about);
ventilation shafts or gaps;
Roof covering.

Why do you need a roof vapor barrier? Vapor barrier layer protects the roof from the penetration of water vapor into the thermal insulation. The fact is that insulating materials for the most part have porous structure, since the air contained in them performs the function heat insulator. When in contact with a colder environment, the vapor turns into condensate, which lingers in voids.

This can lead to a violation of the functionality of the heat-insulating material, as well as the occurrence of decomposition and decay processes in the summer. In winter, freezing water expands, thereby breaking bonds between cellular elements.

The main characteristic of a vapor barrier material is vapor permeability, depending on the density of the material. The values of this indicator can be found in the passport of the packaged building material.

Release form of vapor barrier films - roll. Vapor barrier can be made from various materials. Some of them have additional positive properties that increase the efficiency of the operation of the interior of the building. Installing a vapor barrier on the roof is not as difficult as it seems at first glance, but it requires a careful approach and accuracy.

Types of vapor barrier

Single layer polyethylene films

They are made of low-density polyethylene, which provides an increased degree of steam penetration. This material often has defects associated with the ingress of foreign particles during manufacture. The cheapest type of insulating material.

Reinforced polyethylene films

Compared to single-layer polyethylene, reinforced vapor barrier has little greater thickness, as it includes a reinforcing frame. It is made up of polymer twisted threads located in mutually perpendicular directions. The mesh is fastened to the polyethylene base by warm pressing.

This technique does not affect the waterproofing and mechanical properties of the material, but may reduce the degree of vapor barrier.

Anti-condensation film

Made from two layers: smooth and hairy. The smooth layer is attached to the surface to be insulated. The fleecy layer is created from cellulose fibers. Steam, falling on such a surface, clings to the fibrous structure, thereby preventing moisture from dripping onto the underlying structures. pitched roofs. Excess water is removed together with air through the ventilated space.

Polymers with a foil layer

They are made of penofol or foamed polypropylene, covered with a thin layer of metal. Due to the reflective properties of metal surfaces, such a vapor barrier performs an additional function protection against heat loss.

Membranes (film for roof vapor barrier)

Membrane vapor barrier materials are divided into five main classes:

Type A. It has increased resistance to moisture and wind. Fits between roofing and thermal insulation layer. Manufacturing technology - spunbond. Such a vapor barrier does not allow moisture to flow through the cracks. roofing material, as well as from the resulting condensate. The absence of a laminating layer allows the use of such membranes in roof structures with a slope. over 35 degrees. To remove excess moisture, it is necessary to arrange ventilation holes from a double crate located between the membrane and the insulation.
Type AM. Unlike Type A has a multilayer structure. It is located between the insulation and the roof, to provide adequate protection from negative atmospheric influences. The most common is a three-layer construction, consisting of two layers of spunbond with a diffuse film located between them. It acts as a waterproofing, as it allows steam to pass through, but retains water. Laying is carried out directly on the heat-insulating layer, which reduces labor costs for the device of the ventilation gap.
Type B. Double layer material. It consists of a layer of vapor barrier film and spunbond. It is used to protect the insulation from the internal vapors of the building. Applies only in insulated roof structures.
Type C. It is made similarly to type B membranes. It has a stronger and thicker spunbond layer, which provides better protection of the insulation from moisture. It is used in insulated and non-insulated, pitched and flat roofs .
Type D. Consists of polypropylene fabric, protected on one side with a laminating polymer coated. The structure of the material allows it withstand significant mechanical stress. This causes it to be laid between the insulation and the attic floor screed, as well as in non-insulated roof structures.

Which side is the vapor barrier for the roof?

The principle of installation of vapor barrier materials depends on which side is the layer responsible for the repulsion of water vapor:

We figured out which side to lay the vapor barrier on the roof, now we will analyze in detail how to properly lay the vapor barrier on the roof.

Vapor barrier for the roof: how to properly install using special technology

Laying the vapor barrier on the roof is carried out as follows:

Laying can be done vertically and horizontally. In the second option, the installation of the roof vapor barrier is carried out starting from ridge part roofs. Each subsequent strip is superimposed on the previous layer. with an overlap, the value of which should not exceed 10 cm.

CAREFULLY!

When joining elements, a mandatory seam sealing, which provides optimal protection against moisture ingress into the gap between them. Most often, gluing is done with one- or two-sided adhesive tape or adhesive tape. In roofs with a slope of up to 3o degrees, additional fixation with wooden planks.

The vapor barrier is attached to the wooden truss elements with the help of galvanized nails or a construction stapler.
When installing films and membranes near roof hatches, you need to use a special vapor barrier apron which is included as standard.
At the joints with ventilation pipes, film and membrane structures are wrapped down, wrapped around the pipe and tightly fixed with construction tape.
After laying the vapor barrier layer, it is necessary to nail wooden blocks. The rules for laying vapor barrier on the roof dictate the following rule - the step between the bars of the crate should be 500 mm. In this case, a ventilation gap is formed, and additional fastening of the vapor barrier layer is carried out. Now you know how to lay a vapor barrier on the roof, you can move on to the issue of waterproofing.
If the vapor barrier for the roof was damaged, then small cuts or holes can be stick with special tape for vapor barrier membranes.

Roofing pie scheme

Gluing joints with adhesive tape

The final version of the vapor barrier

NOTE!

A tightly stretched film is the key to good vapor barrier.

Hydro and vapor barrier of the roof - what's the difference?

Useful video

And now we invite you to familiarize yourself with the video instruction on the vapor barrier of the roof:

Conclusion

Vapor barrier is the lightest and thinnest layer of the roof. But neglect of its structure can nullify all material and physical efforts to create quality roof. So don't neglect it important element, it will significantly increase the life of the entire building.

In contact with

First of all, you must follow the manufacturer's instructions, which clearly describes which side to lay the windshield. If there is no such instruction, there are a number of general recommendations applicable to windproof films:

wind protection spreads to the insulation with the “fleshy” side, unless otherwise indicated in the instructions;
if both sides are the same, the film is attached with the manufacturer's logo on the outside;
wind protection without markings and distinctive qualities of one of the sides can be placed in any convenient way.

Often, manufacturers roll rolls so that the wind protection is as easy to lay as possible - in the course of unwinding the roll.

Windproof films different kind, stacked differently:

Simple windscreen. These are perforated single-layer films that can be laid on either side of the insulation, as they have bilateral vapor permeability.
Wind and moisture protection. These are two-layer films that are laid with the moisture-repellent side out. This side is smooth, often with manufacturer's markings or painted in a different (non-white) color.
Superdiffusion membranes. Such material has a multilayer structure with high water resistance and vapor permeability. It is necessary to lay the membrane on the outside of the insulation and only with the marked side out.

Floor wind protection

On internal ceilings, the film is spread over the insulation with the marking outward, and with the plain side inward.

And in order to protect the wooden floor from blowing cold wind from the open basement of the columnar foundation, the film is laid on the subfloor without gaps close to the insulation. In this case, it is laid with the inscriptions down.

How to install windscreen on a roof

Single-layer windproof films are laid under the roof on either side. But two-layer - only the smooth side up.

Some films and membranes are UV resistant due to a special coating. The manufacturer must specify this parameter. Such wind protection is attached to the rafters with the colored (protective) side up.

How to install windscreen on walls

On the walls, the wind protection is placed outside directly on the insulation (marked or colored side out). It is necessary to provide a ventilation gap between the film and the exterior finish. In order for the wind protection to provide a sufficient level of protection against moisture, it must be mounted horizontally from the bottom up with an overlap of at least 10 cm. Inside, a vapor barrier is laid on the walls - it is very important

Until recently, glassine served as the only type of vapor barrier. Cut, attached, fixed - that's all! And only a few decades ago, a more convenient polyethylene film appeared, and more complex and reliable materials began to be made on its basis. Yes, modern options They delight not only with strength characteristics, but also with resistance to temperature and ultraviolet changes, and with their versatility. But, at the same time, they are upset by the more complicated instructions for their use: they should be connected along a clearly defined line, and only special tape should be used, and - most importantly! - the laying side must be chosen correctly.

Therefore, it is not surprising how often panic questions can be found on the Internet, such as how and which side to put the vapor barrier to the insulation, and what to do if the parties are still mixed up? Is it really necessary to disassemble the entire structure? We can assure you: you don't have to. And with the definition of which side is "correct", let's take a closer look - you will be very surprised!

What is the essence of roof vapor barrier?

Moisture protection of the insulation is one of the most important problems of thermal insulation, and we will now tell you why.

By itself, water is an excellent conductor of heat, because it is not without reason that it is used in heating and cooling systems. And, if the roof insulation is not sufficiently protected from the steam from the room, then this will not end well. Even in the warm season, you will not know about the problem, because. such steam will be easily vented due to heat and good ventilation. And in hot countries, where there is no sub-zero temperature, they don’t think about the vapor barrier of the insulation at all, because the problem is imperceptibly solved by itself. But in Russian latitudes, due to the temperature difference in the cold season, steam rises and penetrates the insulation, concentrating in the form of water when it meets the so-called "dew point".

At the same time, the top layer of insulation in the roofing cake freezes and creates one more condition for getting wet from the inside. The efficiency of the insulation itself is significantly reduced, and the changed structure contributes to the development of fungus and corrosion. Moreover, at in large numbers moisture can even seep back into the room and damage, thereby, the interior finish. This is exactly what a vapor barrier is for.

And in order to understand how to properly mount the vapor barrier, you first need to understand the design itself. So, the insulation is protected from two sides by completely different films that perform opposite tasks. From below, from the side of the living room, a vapor barrier is installed that will not allow steam to pass through, and from above - a vapor-permeable membrane, which, on the contrary, will release excess steam from the insulation, if it is “cotton-wool”, and protect it from roof leaks:

But where is the logic, you ask? How can steam get into the insulation if there is a vapor barrier in front of it? In fact, not a single film or membrane protects 100%, and there are still poorly glued joints and other construction errors. And therefore, some minimum amount of steam will still be in the heater, and it is important to competently bring the steam out without harm:

Look carefully at the diagram: do you see where the condensate appears in a well-equipped roof? That's right, not from the side of the room, but quite a bit from the side of the roof, on the other side of the insulation, and it is easily removed by a windproof anti-condensate film or membrane. But condensation should not appear on the vapor barrier, and none of its rough side can cope with it, because. it has a different structure, and we will prove it to you now.

Types of vapor barrier materials: A, B, C and D

In order to understand which side of the vapor barrier should be laid and why, for example, it suddenly turned out to have both sides smooth, you must first determine its type. After all, not every species generally has two different sides!

Type A insulation: only for steam outlet on the other side

For example, type A cannot be used as a roof vapor barrier because in the end all the vapors will end up in the insulation. After all, the main task of such isolation is precisely to provide them with unhindered passage, but not to let rain water on the other side.

Such insulation is used in roofs with a slope angle of 35 °, so that water drops can easily roll off and evaporate (and the ventilation gap between such insulation and the insulation helps them evaporate).

Vapor barrier B: classic double-sided installation

But B is a real vapor barrier material. Vapor barrier B has a two-layer structure, which allows you to avoid condensation, due to the fact that moisture is absorbed into its villi in the morning and disappears during the day.

That is why type B vapor barrier is always placed with the smooth side towards the insulation (film side), and the rough side outward. Vapor barrier B is used only in insulated roofs, because for non-insulated, it has too little strength.

Type C membrane: for enhanced water vapor protection

Vapor barrier type C is a two-layer membrane of increased density. It differs significantly from type B in the thickness of the vapor barrier film layer. It is used in the same place as type B vapor barrier, but in itself is more durable.

Additionally, such a vapor barrier is used in non-insulated roofs to protect the wooden elements of the attic floor and in flat roofs to enhance the protection of thermal insulation. Vapor barrier C must also be laid with the rough side inside the room.

Polypropylene insulation D: for heavy loads

The newfangled type D vapor barrier is a particularly durable polypropylene fabric, in which one of the sides is a laminating coating. This can withstand significant mechanical stress. It is used not only to insulate the attic floor as a waterproofing layer, but in the insulated roof to protect it from leaks. Moreover, type D vapor barrier is indispensable for rooms with especially high humidity.

Here are the cases and where all these types of insulation are needed:

Does vapor permeability change when changing sides?

All of the above modern barriers are divided into the following types:

for one-sided installation, which need to be rolled out only on a certain side, and it is recommended not to confuse them;
and for double-sided use, usually with membranes that can be laid on either side.

You will be interested to know that for the first time membranes, which already had such properties as modern roofing, were used in astronautics! And from there they began to be used in construction and in many areas of the national economy. And until recently, there were not as many problems with their installation as they are today.

And now there is a strong opinion among the townsfolk: if you lay the vapor barrier to the roof insulation on the “wrong side”, then the whole structure will not last long. Actually right choice side affects only the service life interior decoration roofing cake, because the rough side has the same abilities as the smooth one and has exactly the same vapor permeability. But how much it retains droplets of condensate there is a little-studied question.

Let's deal with such concepts as condensate - this is important. There is a catch here: for some reason, most ordinary people are sure that if high-quality vapor barrier is used, then there will be no condensate at all. Or vice versa, it will quickly evaporate on its own. In fact, condensate is formed from the moisture that rises in the vapor state.

There is such a thing as a “temperature limit”, i.e. that specific condition under which the air temperature and humidity are sufficient for the vapor to come out in the form of droplets. For example, at a temperature of 15 ° C and an air humidity of about 65%, condensation will already begin to form. But if the air humidity reaches 80%, then the condensate will appear already at a temperature of 17 ° C.

In other words, the entire process of water vapor formation appears as a result of the so-called "partial pressure" difference. All the water vapor that is contained in the air is trying to go outside - to a colder street through the enclosing structures of the roof, but on its way they meet a barrier in the form of a vapor barrier. If the air in the house warms up faster than the surface of the vapor barrier, then the moisture from the air will fall on it in the form of condensate. Here, the difference between an insulated roof and an uninsulated one is clearly visible: any vapor barrier that is laid on a heater will warm up much faster than something that is in direct contact with the cold elements of the roof.

If there is no vapor barrier layer at all, or it is not enough, then water vapor penetrates into the roofing pie and meets a “cold front” there, which turns steam into condensate, and under special circumstances also into ice. And it all happens inside the roof! This ice will not bother you until spring comes and the outside air warms up, thereby warming the roofing elements. Then the accumulated ice will melt and form whole smudges on the slopes inside the house.

But with a properly equipped roof, condensate should not appear at all, and therefore, in fact, the difference between a smooth and rough side is not significant, at least in this aspect.

What is the difference between an anti-condensation film and an "anti-condensation side"?

As we have already said, most modern manufacturers emphasize that their vapor barrier films have a so-called “anti-condensation side”:

The “anti-condensation” side differs from the usual “anti-condensation” side by the presence of a fleecy layer that absorbs a small amount of condensate and holds it until it evaporates.

Due to this, the risk of wetting the surface of the film is much lower, which prolongs the life of the interior finish of the roofing cake. That is why the rough side should always be directed inside the living room or attic, and the smooth side should be leaned against the insulation. But is it really so?

Practice shows that if condensation forms inside the roofing cake, then the fleecy side of the film cannot help in this regard, and there is not much difference whether these drops stick to the film or flow down. The fact that they exist at all is bad in itself. The anti-condensation side of the vapor barrier and the anti-condensation waterproofing film on the other side of the insulation are two completely different things!

Therefore, let's summarize: the "correct" side of the vapor barrier is not equivalent in terms of the properties of the anti-condensation film: it does not remove water vapor, does not destroy moisture drops and does not solve the problem with condensate.

But, if you are still in the process of building a roof, then for the sake of peace of mind, do as the manufacturer instructed in the attached instructions. If you have already laid the vapor barrier and doubt whether it is correct - forget it and do not worry anymore. But if you hope that the “correct” side of the vapor barrier will take on all the future shortcomings of the roofing pie, do not believe it.

Experienced roofers often state that they generally consider the epic about which side to attach the vapor barrier to, some kind of shamanism. Allegedly complicating the product, they increase its positioning in the market. But in fact, as we have already said, with a well-arranged vapor barrier, there should not be any droplets on the walls, otherwise even the lining on the walls will swell, and the wallpaper will fall off, since everything is so serious.

After all, this happens only with serious errors during the construction of the roof. In addition, if the vapor barrier itself will be between drywall and mineral wool, then with such complex design no point in messing around at all. By itself, drywall absorbs moisture well, and steam can hardly reach the internal vapor barrier. In this design, even a simple glassine is quite acceptable!

For example, some curious roofers even run their own vapor barrier tests to determine if the "wrong" side works or doesn't work:

And especially the quick-witted ones even say that with rough side polyethylene vapor barrier is obtained simply in the factory, when polyethylene is combined with nonwoven fabric: the film is glued with a rough layer, and the finished product really has two different sides. And it makes no sense to refine the second side so that it also becomes smooth by connecting with another layer of polyethylene: the vapor barrier properties will not change, and the manufacturing process becomes more expensive.

And therefore it is easier to give this meaning to the product itself. And in fact, quite a lot of people have already become convinced that, even if they mix up the sides of the vapor barrier, nothing like this happens, and the film works the same way on both sides, fully fulfilling its functions.

Therefore, in any case, just strive to implement roof protection from steam correctly, think through all the necessary details and not save on quality!

Last time we dealt with views and which is made from stone wool. Despite its ability to repel moisture, even this material needs protection. For this purpose, a vapor barrier is used. Today we will tell you how to properly install vapor barrier in heat-insulating walls, roofs and floors. For interfloor ceilings, where both floors are heated, such films are not needed.

How to put vapor barrier when insulating walls

Both sides of the vapor barrier are equally impervious to moisture and steam.

We will figure out how to properly lay the vapor barrier on the walls. There are two options for insulation:

internal;
external.

Of course, it is preferable to lay the thermal insulation outside the room, but in this case, a vapor barrier film is not required. The material used for insulation also matters. The film is needed only when it is necessary to protect the thermal insulation from moisture and steam. To figure out how to properly lay a vapor barrier film, you need to understand by what principle air circulates. He always moves out of the zone high pressure(where the temperature is higher) to a low pressure zone (where the temperature is lower). It turns out that the air, along with moisture, tries to leave the warm room and end up on the street.

Which side to put the vapor barrier to the insulation does not matter, since it does not let moisture in any form in both directions. Those who ask such questions are most likely confusing vapor barrier film with waterproofing ( diffusion membrane).

The scheme of laying the vapor barrier on the wall from the inside.

Therefore, in numerous forums, to the question of which side to attach the vapor barrier to the insulation, experts allegedly answer that it is rough. Where does the vapor barrier have a rough surface? It is completely smooth material on both sides. As it turned out, even the builders themselves confuse these concepts. In our previous article, we clearly explained .

Another frequently asked question about how to properly install a vapor barrier is the need for a ventilated gap. Some film manufacturers write that a ventilation gap is not needed at all, but it’s still not worth drawing hasty conclusions. When installing an insulating cake for walls from the inside, a ventilation gap is needed between the film and the finish, but is optional (although it does not interfere) between the film and the insulation. Here we are somewhat replacing the concept of a ventilation gap, since in the space between the film and the finish (especially the insulation), it is not always possible to achieve the necessary air circulation.

Let's leave these subtleties for now and call the buffer air zone between the materials the ventilation gap. Layers of insulation cake for walls, starting from the inside:

finishing;
ventilation gap;
vapor barrier;
insulation;
wall.

The ventilation gap will keep the finish dry, as a result, it will not have mold on it and it will last as long as it should.

Laying vapor barrier film on the roof

The scheme of laying vapor barrier for roof insulation.

The question of how to properly lay the vapor barrier is especially relevant for roof insulation, since it is here that the most mistakes are made, which subsequently bring many problems. Before explaining the layer layout, remember what we said about the direction of air flow and the main function of the vapor barrier. Our main goal is to protect the insulation from steam, so the film must be laid from the side warm room. You don’t need to think about which side to attach the vapor barrier to, absolutely all building films are wound into a roll so that they lie correctly when unrolled.

That is, take a roll, apply it to working surface, gradually unwind and nail the film with a stapler, everything is as easy as shelling pears. In the process of installing the film with a stapler, installing the counter-lattice and stuffing the trim, holes will in any case appear in the vapor barrier. Through these holes, steam will penetrate into the insulation, and the film itself does not protect 100%. Therefore, it is impossible to close the thermal insulation with a vapor barrier on both sides, it is necessary to give moisture the opportunity to escape. Between insulation and zone low temperature a membrane must be laid that releases steam, but does not allow the material to get wet.

Now we will tell you how to properly fix the vapor barrier using an example. Consider the roof insulation with mineral wool, layers from the inside:

vapor barrier;
mineral wool;
diffusion membrane;
a counter-lattice, thanks to which a ventilation gap appears;
roof finish.

In addition to the ventilation gap between the membrane and the roof trim, the gap between the same membrane and the insulation will not interfere (optional, but preferable).

The vapor barrier is laid tightly, it should not sag. At the joints, an overlap of about 10 cm is made, the joints are glued with adhesive tape.

You need either aluminum-coated construction tape, or a specialized double-sided adhesive tape for films, the second is preferable. Proper installation of vapor barrier:

first one tape is laid;
double-sided tape is glued along the edge;
the protective paper tape is removed - sometimes the paper is torn, small pieces may remain that must be removed;
the next tape of film is laid on top.

The double-sided adhesive tape connects the films very tightly, so that later it will not work to tear them apart.

How to install vapor barrier on the floor

The scheme of laying the vapor barrier when insulating the floor along the logs in wooden house.

Floor insulation is not much different from the roof, the only thing is that there is no rough finish. Thermal insulation is laid between the lags wooden house. Previously, a draft floor is stuffed from below, which should not be continuous, that is, between narrow boards there should be indents not less than their width. Thanks to these indents, the steam will have the opportunity to leave the insulation. Moisture enters the thermal insulation along with the air from the room, so the layers of the floor insulation cake in a wooden house should be laid as follows:

finishing floor;
vapor barrier;
insulation;
wind protection or waterproofing.

The gap between the insulation and the vapor barrier is not required, but whether it is needed between the finishing floor and the film is a moot point. Let's go back to the moment when we talked about replacing the concept of a buffer air zone with a ventilated gap. In fact, a ventilation gap is a space where there is a constant circulation of air, if this is not the case, then this is just a buffer zone.

The ventilation gap in the classical version can be observed in the roof structure and When the walls are insulated from the inside, it is still somehow possible to achieve circulation in the buffer air zone, with the floor it is more and more difficult. It is necessary to make holes in the floor, and there is no guarantee that the air will circulate there as we need and whether it will be at all.

Therefore, many craftsmen refuse the ventilation gap between the finishing floor and the vapor barrier, the same applies to walls. But if you look from the other side, the gap is still needed. Even if moisture condenses on the film, it will not be absorbed into the material in contact with it, respectively, it will not mold.

Proper installation of vapor barrier: results

To figure out how to properly install a vapor barrier, you need to know why it is needed and the principle of air circulation. The film is needed to protect the thermal insulation from moisture, which is in the warm air. The circulation of air flows occurs in the direction from a warm room to a cold street. Accordingly, the vapor barrier must be laid from the side of the room, preferably leaving a gap between the film and the finish. How to determine the sides of the vapor barrier? She has two sides: this and that, and both are the same. The film does not pass steam in both directions. Such questions are asked by those who do not understand the difference between a vapor barrier and a diffusion membrane (waterproofing).