Which side the vapor barrier is laid on. Proper work with vapor barrier: which side to lay

In every room there is a circulation of air currents. In order to avoid excessive humidity and stuffiness in the room, a vapor barrier is necessary. In this article, we will tell you how to lay the vapor barrier on the floor, walls, ceiling, consider which side to lay the vapor barrier to the insulation, and also give photo and video instructions.

For which premises

In the cold season, the temperature in the room is much higher than in the street, respectively, and the humidity there is much higher, the accumulated vapors are trying to escape from the house. Even in the presence of high-quality thermal insulation, protection from moisture in the form of a vapor barrier material is required. Its function is to prevent the penetration of moisture into the structure through existing cracks, gaps and holes. Waterproofing material protects the insulation from interaction with moisture from outside at home, and the vapor barrier - from the inside.

Vapor barrier materials are divided depending on vapor permeability into limited and complete.

Vapor isolation is required:

• in multilayer structures for fencing;
• in the presence of pitched or flat roof for the insulation of which bulk or fibrous materials were used;
• in rooms with high humidity;
• in structures insulated from the inside;
• in seasonal buildings.

Vapor barrier protection is used not only in the construction of residential facilities and other structures, but also in addition to materials that absorb moisture, as well as to isolate communication lines.

In order for the procedure to have the expected result, the vapor permeability of the multilayer structure must increase from a warm surface to a cold one. For this reason, the vapor barrier is mounted from the inside of the roof, walls and ceilings.

The sequence of layers for wall insulation:

• roofing layer;
• diffusion membrane;
• material for insulation;
• vapor barrier, with an overlap glued with a tape;
• tightly glued vapor barrier to the surface of the walls.

Nuances

Hardware stores offer huge selection materials for vapor barrier, and depending on the manufacturer, they all have their own characteristics. In the manufacture, the convenience of installation, humidity and climatic conditions of operation, the functional purpose of the room are taken into account. Today, many manufacturers produce material that prevents fire, steam penetration, and helps to remove excess moisture.

In our country, for a long time, polyethylene film was produced as an insulator against steam, but the high level of competition and the requirements for the material prompted Russian manufacturers to develop special construction insulators. Today, we can safely list several manufacturing companies that produce vapor barrier material based on polyethylene foil, metal-coated films and laminated film vapor barriers, which not only successfully cope with the assigned functions, but are also resistant to ignition.

In order to choose best option material, you need to consult with a professional who is knowledgeable in all the intricacies of installation, who knows which side to lay the vapor barrier, which material to choose specifically for your room, and the like. As a rule, beginners in the construction business rely on cost, manufacturer and area of ​​\u200b\u200buse when choosing, but this is not enough to perform high-quality insulation.

List distinctive features much more extensive and requires a more responsible and professional approach. An example is roof insulation, in which the planned structure, layers, slope, climatic conditions and indoor temperature play an important role. Already starting from this, preference is given to an insulator with high, medium or low vapor permeability.

Video

How to ensure good roof vapor barrier, taking into account the features of all structural elements:

Often, trained specialists are engaged in laying. Based on the opinion of professionals, several rules can be deduced:

1. For effective vapor barrier, it is necessary to have supply and exhaust ventilation inside the building.
2. Protection of the insulating material from interaction with moisture, both from the inside and outside.
3. The work of laying the vapor barrier exclusively on the warm side of the insulation.
4. Mandatory fixation of the material at the joints and in places of contact with surfaces using a special tape and glue.

In any case, the installation must be completely sealed. In the event of a violation of technology, you will have to redo everything anew, which will entail large financial losses.

To carry out high-quality insulation, it is necessary to have at hand many special tools, many of which are determined by the characteristics of the material.

Vapor barrier, as a rule, is laid in a pie, which consists of the following layers:

1. Draft floor.
2. Waterproofing.
3. Insulation.
4. Vapor barrier.
5. Finishing material.

But in some cases, the vapor barrier is laid on both sides of the thermal insulation. Much easier to do the job in a new building. If you are making repairs, then first of all you will need to completely remove the old coating up to the subfloor.

Even if it is planned to lay a floor heating system, it is recommended to lay vapor barrier and insulation between the pipes of water floor heating.

Consider an example of laying rolled material:

• The film must be fully stretched over the floor surface.
• Between the insulation and the vapor barrier, it is recommended to leave from 7 to 15 cm of the ventilation gap. If a diffuse membrane is used, then such gaps are not needed.
• The direction in which you lay the material does not really matter.
• But the side of laying the vapor barrier plays an important role. As a rule, company inscriptions should be on top. If the film does not have an inscription, then the metallized side is laid up, and the rough side is placed on the insulation. If a simple plastic film is used, then there is no difference.
• Regardless of the material chosen, the canvas is overlapped up to 20 cm. They are fastened together with adhesive tape.
• If the base is wooden, then on top you can additionally fill the slats in increments of 50 cm or fix the vapor barrier with a stapler.

Another vapor barrier option is to use liquid rubber. For its use, it is not worth preparing the floor surface in a special way. Rubber is distributed over the surface with a roller or spatula manually. The only thing you need is to remove all debris from the surface before starting work. In this case, it is best to vacuum the floor.

As a result, the rubber will completely prevent the penetration of moisture under flooring. The air in the room will be light, you can forget about the smell of dampness and mold forever.

The technology for applying liquid rubber is especially relevant when working with wooden floors.

Can be used to insulate walls different material. So, if roll material is used, then the installation is carried out in a horizontal position. Laying starts from the floor to the ceiling. In this case, each subsequent strip is mounted with an overlap. The joint is glued with adhesive tape or other special compound. It is important that the connection is completely sealed.

If there are places where the material is adjacent to a stone or concrete surface, the film should be glued. It is important to achieve tightness. If you are building a wooden frame on the wall, then the film is stapled to the wooden bars.

As for the vapor barrier of the ceiling, it overlaps the vapor barrier of the walls up to 20 cm. The presence of a vapor barrier on the ceiling will save finishing material long time. As a rule, vapor barrier can be laid both from the bottom of the ceiling and from above from the side of the attic. In this case, the following pie will turn out:

1. Vapor barrier.
2. Thermal insulation.
3. Vapor barrier.

This work must be done even with concrete ceilings. With a temperature difference, the accumulated condensate can, after a while, provoke the appearance of mold and fungus, which is not so easy to fight.

The installation process begins with preparatory work:

• The surface is cleaned of construction debris and old finishing material.
• All existing gaps and imperfections of the base are covered with.
• The ceiling is primed and dried.

The vapor barrier process looks like this:

• As mentioned above, the vapor barrier is overlapped with the wall one. Attached to the ceiling with a stapler.
• It is good if it is possible to process the joint of the vapor barrier with rails.
• The joint is preliminarily glued with waterproof tape.
• On the ceiling, it is enough to overlap up to 10 cm.
• There is no need to stretch the material strongly. But at the same time, sagging should not be allowed. Otherwise, condensation will accumulate on the film and the polyethylene may break through.

Remember that the vapor barrier on the ceiling cannot be pierced. So ideal option is laying a film on a wooden frame.

Video

In the provided video, you can clearly see the intricacies of vapor barrier work:

Photo

In the photographs, you can take a closer look at the individual details of the vapor barrier process:

Scheme

The provided diagrams will help you understand the principle of the work:

A vapor barrier is necessary to protect the insulation from intense attacks of household fumes. A competent arrangement of this barrier affects the frequency of repairs, the service life of finishes and structures, and the formation of a microclimate in the equipped housing.

In order for the protection to cope with difficult duties, you need to clearly know how to lay a vapor barrier, how to build a reliable barrier from it in the way of vaporous moisture that destroys building materials.

Vapor barrier is called a thin, almost weightless film material that blocks moisture from accessing the body of the roofing pie and truss system. This barrier is set up inside heated rooms to prevent wetting and subsequent rotting of thermal insulation and wooden frame roofs.

If you do not arrange a vapor barrier, moisture accumulated in the thickness of the insulation will contribute to heat loss. After all, water is an excellent conductor, passing through itself both electrical and thermal waves. Then, instead of the task assigned to thermal insulation, which consists in warming the house, wet material will create a feeling of dampness and dank cold in the rooms.

In addition, the accumulation of moisture in the roofing cake will invariably lead to the settlement of colonies of fungal microorganisms. As a result of their vital activity, wooden elements roof structures in the shortest possible time they will lose their bearing capacity and become completely unusable. The same will happen with the insulation and other components of the system.

The vapor barrier is always installed as the first layer, if we consider the roofing pie from the side of the equipped space. Since the air, which contains vapors of all kinds and of any origin, is warmer and lighter than itself, but in a less humid and colder form, the vapor, along with warm air currents, rushes upwards according to physical prescriptions.

According to the natural direction of steam movement, protection against it is installed in the upper areas of rooms with a characteristic high degree of humidity, along ceilings and slopes of equipped heated attics. The entire wall is protected by a vapor barrier if it separates two rooms with sharply different operating conditions.

As an example, let's take a partition between an ordinary living room and a home sauna or steam room. In this case, the vapor barrier is placed on the side of the bath facilities, and if they are located in the attic or on the second floor, then they are also placed on the floor as on the floor.

Barrier materials

Before proceeding with the analysis of the principles that determine how to properly and where to lay the vapor barrier, it is worth studying the materials used in this area and their defining characteristics.

The most ancient option, protecting roofing systems from moisture coming from inside the houses, was crumpled clay, laid in a dense layer on ceiling beams with flooring. In terms of insulating and environmental qualities, it is unlikely that it has still found competitors, but the method of constructing such a barrier is not always and everywhere applicable. True, in eco-houses preference is given to her.

Later, clay was replaced by glassine, which did not please with high insulating properties. In addition, it is too easy to accidentally break through, which creates significant complications during operation and does not bring joy during maintenance and during operation. So far, no one has completely abandoned glassine, it is used in budget buildings, sometimes roofing material is used instead.

The era of the reign of glassine was interrupted by polyethylene, which is ahead of its predecessors both in terms of technical data and technological indicators. It is easier to work with it, it is quite strong, but not sufficiently resistant to mechanical stress such as punctures and breakthroughs. And ordinary polyethylene can easily destroy traditional atmospheric phenomena: sunlight and low temperatures.

Due to the poor resistance of polyethylene films to phenomena that can critically damage them, improved materials began to be developed based on the above polymers. Their creators sought to reduce the disadvantages and enhance the advantages of polyethylene, which was also joined along the way by polypropylene.

As a result of the hard work of the developers of vapor barrier materials, the following options are now presented to the consumer:

• Reinforced films with a base of polyethylene and polypropylene. These are modernized versions of the predecessors of the same name, but with optimized resistance to UV rays and fluctuations in thermometer readings. They are used both in pitched roofs and in ceilings.
• foil membranes. Polymer films with a working side covered with aluminum foil. They are used where an increase in heat-saving qualities is required, for example, in steam rooms, because, with proper installation, they perform the function of a reflector that reflects heat waves.
• anti-condensation membranes. Universal roll materials that can play the role of both vapor barrier and waterproofing. On the side of steam movement, these materials are endowed with a rough surface, which excludes dew. The outward-facing side is smooth and water-repellent.

The listed species significantly, but not completely, pressed the position of glassine with non-reinforced polyethylene. To this day, obsolete vapor barrier materials are used in the insulation of floors, they are laid under filling thermal insulation such as expanded clay or dried earth. They are used in cold roofing structures of dachas and change houses, in the construction of which insulation was not pursued as a goal.

The principle of accounting for vapor permeability

Vapor permeability is an important characteristic in the construction business. It indicates how many grams of water contained in the air stream can pass through 1 m 2 of insulation or building material in one day. Literally all products used in construction have the designated quality, only their capabilities are radically different.

Both brick, and all types of foam blocks, and wood with varying degrees of intensity let steam through. If the structures made of them are not equipped with thermal insulation, then a barrier against vaporous moisture is not constructed. Evaporation will simply pass through the slopes and walls with ceilings to the outside, where they are deficient for the majority of the year.

If the structures are equipped with insulating material, there is an urgent need for the installation of a vapor barrier. In this more complex scheme usually combined options with different ability to transmit steam, and some of the building materials generally tend to accumulate moisture that is detrimental to them.

It is better not to let evaporation into the roofing cake of an insulated roof at all. And even if something managed to penetrate, then this moisture-saboteur should be removed at the most frisky pace by all methods available in construction. The list of methods is headed by the organization of ventilation of the under-roof space and the attic itself.

With a rational and correct construction of the roof structure, steam and condensate, formed due to the temperature difference outside the roof and inside the heated space, do not linger in the roof cake at all.

The solution to the problem lies in the technologically verified arrangement of the components of the insulation system, which “line up” as the vapor permeability decreases as follows:

• Vapor barrier. A polymer film with the least ability to transmit moisture suspended in the air. In the data sheets of most of these materials, vapor permeability is indicated in hundredths and tenths of one gram, which the film can pass through itself in 24 hours. True, there are options with a permeability of several units.
• Thermal insulation. Mainly wadded and non-extruded foam materials with higher vapor permeability than the previous layer. When choosing a heater for an attic or ceiling, this factor must be taken into account.
• Waterproofing. Polymer film with a vapor permeability exceeding that of the insulation, in last resort equal to him.

The insulation system arranged in this way is perfectly protected from the accumulation of steam and condensate. Even if the vapor barrier still allows a certain amount of fumes to pass through, they will not linger in the insulation. After all, its ability to pass steam is higher. Then, on the path of the steam, there will be waterproofing, which is even less likely to retain evaporating water from its inside.

When a certain amount of evaporation enters the thermal insulation thickness of a well-arranged roofing pie, the protective mechanism of the roofing system comes into play. Moisture is removed along with the ventilation streams running through the ducts, or flows into the gutter along the outside of the anti-condensation film.

Features of fastening vapor barrier materials

For the construction of a vapor barrier, an abundant range of polymer films is now being produced, fundamentally performing the same function, but differing in degree of effectiveness. Well-founded recommendations for choosing products from a manufacturer with an impressive reputation should be followed, because. in addition to production experience, he also has a need to maintain a decent quality of the brand.

Good advice, which all manufacturers will certainly give out, is to acquire a complex of basic and Supplies one firm. This rule must also be followed for the sake of perfect compatibility of films and adhesive tapes, their reliable adhesion and normal subsequent operation.

In the case of laying and fastening the vapor barrier, the following rules should be observed:

• The panels of the vapor barrier film are laid from top to bottom. Each subsequent strip must overlap the previous strip from the side of the room. So it is necessary that the evaporation that has penetrated into the roofing pie during condensation can simply drain towards the eaves.
• The vapor barrier is rolled out according to the factory winding. Nothing needs to be turned over, everything is thoroughly thought out by the manufacturer for the convenience of working on the roof. The roll with the material should be on top, the rolled panel on the bottom.
• The vapor barrier is connected into a solid carpet with one- or two-sided adhesive tape. In places of roof penetrations, the fastening of the vapor barrier film is supplemented by the installation of rails around ventilation and sewer risers, chimneys. The panels are laid with an overlap of 10 - 20 cm.

Skylights are equipped with a vapor barrier similar to roof penetrations. The insulating carpet at the site of their location is cut according to the envelope principle. Cut corners unfold lengthwise window slopes outward and cut again in fact so that the material can cover the insulation and fix its edges.

Steam protection does not require connecting the panels with adhesive tape if the ceiling covering from the attic side is insulated with backfill thermal insulation. In such schemes, a film of polypropylene or polyethylene is loosely laid on concrete slabs with an overlap of 20 cm. There is no special need to attach the panels to the structure in this case, because the film will be pressed down by an insulating layer.

Waterproofing in such systems for insulation is not used at all, it is installed along the slopes, but the ventilation device is presented with high requirements. In addition to standard roofing ventilation ducts must be built dormers and the installation of roof aerators is desirable.

A vapor barrier for equipped heated attics is built along the rafters from the inside. Material panels are installed only perpendicularly rafter legs unlike waterproofing, which on steep roofs can be laid along the rafters.

Vapor barrier in attics is laid either over all areas of the roof structure, including gable areas, or only along pitched planes. In the first case, to remove warm air masses, usually saturated with moisture, a mechanical combined ventilation system is constructed, which includes both supply and exhaust devices.

In the case of laying a vapor barrier only along pitched planes, vapor diffusion will occur through the gable walls if they are made without insulation. For ventilation, it is not necessary to build an artificial system; natural devices will cope with the removal of steam and exhaust air: ventilation windows, roofing vents, conventional aerators.

Another significant difference from the process of laying waterproofing is that the vapor barrier is built without breaks in the areas of hip and ridge knots. Before attaching the vapor barrier panels to each other, they are fixed to the rafters with metal brackets.

Polymer films on wooden truss frames are laid without "tightness". So it is necessary that, with the linear movements characteristic of wood, the lumber does not break the insulating carpet. The adhesive tape for connecting the panels is unwound directly from the factory roller and glued as it is unwound. Double-sided is attached first with the back side, then turned to the master.

On the inside, over the vapor barrier carpet, a crate is arranged, which serves as an additional material fastening element and the basis for installing the attic cladding. This technological gap at the same time will eliminate the formation of condensate arising from direct contact between the skin and the polymer film.

The installation of a vapor barrier along the slopes can be carried out both before laying the insulation, and after said work. However, the priority is the period after laying, so that if the roofing cake gets wet in the rain, it can be dried naturally.

Another strong argument for building a vapor barrier after the pie and roofing is laid is that it becomes possible to postpone this stage of work for a while before installing the sheathing. As a result Finishing work can be held in winter time, their implementation will not interfere with the rainy season.

Video about the rules for laying vapor barrier

A video with a detailed explanation of the rules for constructing a vapor barrier carpet and laying the components of a roofing pie in a visual form represents the essence of the process:

Vapor barrier is an important component of the roofing pie, the service life of the roof and the conditions in the equipped room depend on the competent device of which. Information about the features of its device is necessary for both independent craftsmen and owners who want to control the actions of a hired team of builders. armed useful information, you can eliminate a lot of trouble with the operation of the roof and the house as a whole.

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

This material is required to be installed, since it will protect against temperature differences.

general information

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

Modern options are characterized by the following advantages:

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

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

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

The purpose of the vapor barrier

Which side the vapor barrier layer is laid to the insulation is one of the most pressing issues that people face when building private premises or repairing old dwellings. But before you start looking for answers, you should understand what such a layer is intended for and why it is important.

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

The most serious troubles appear in the cold season, because if in the summer at a positive temperature and good ventilation any steam will quickly go outside, then in the winter it will begin to rise up, penetrating into the insulation. The impact of negative temperatures will lead to the fact that the upper part of the insulation in the roofing "pie" will begin to freeze, creating additional conditions for internal wetting.

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

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

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

Material types

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

Vapor barrier is divided into 4 groups and each of them has its own specifics

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

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

Because of this feature, such a hydrovapor barrier is always laid with the smooth side to the insulation, and the rough side outward. This option is suitable only for rooms with roof insulation, since in the absence of insulation, its strength is significantly reduced.

Before buying a vapor barrier, you need to find out the features of each group

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

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

Effect of side switching on vapor permeability

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

1. For one-sided mounting. Such material must be nailed with a specific side.
2. For double-sided mounting. In most cases, both sides of vapor barrier membranes are the same. Their main advantage lies in the maximum density and the possibility of masonry on either side.

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

Double-sided mounting is more practical

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

Pitfalls and myths

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

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

The formation of steam occurs at a difference in partial pressure. Any steam that appears inside the house tends to go outside, where there is a lower temperature. But on his way, he encounters a barrier - a vapor barrier layer.

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

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

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

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

Features of anti-condensation film

Many manufacturers of vapor barrier materials pay special attention to such a moment as the "anti-condensation side" of the film. It differs from the other part of the material in a special fleecy layer that can absorb a significant part of the moisture and hold it until it evaporates completely. Due to this specific feature, wetting of the insulation and the film practically does not occur, which positively affects the durability of the finishing part of the roof.

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

Nevertheless, at the stage of roof construction, it is better to follow the instructions from the manufacturer and place both the film and the anti-condensation side. But if the moisture-proof layer, heat and wind insulation are already installed, while there is a suspicion that some important points, there is no point in hoping that the "right" side or the most quality material from the leading brand Axton (Akhton) will hide these shortcomings.

Experienced craftsmen often argue that which side the vapor barrier will be placed on does not matter. Indeed, as already mentioned, any droplets, moisture and condensate are serious enemies of the roofing "pie", and with proper installation of insulation, they simply should not be. Otherwise, even lining and wall decoration will begin to deform, swell and fall off. And sometimes the consequences can be irreparable.

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

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

V winter period when it's cold outside, and inside the house it's cozy and warm, an imperceptible steam forms in the rooms. And this steam should freely leave the room. To accomplish this task, a vapor barrier is laid. You need to know which side to put the vapor barrier on the floor, walls or ceiling.

Why is vapor barrier needed?

Vapor barrier material is used for normal circulation of moisture inside the room. If you ignore the vapor barrier, then the moisture in the air can enter the insulation and gradually destroy the material.

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

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

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

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

Using a heater that absorbs moisture well, vapor barrier is indispensable. In its absence, moisture is absorbed into the structure of the insulation and there it turns into water. Over time, the thermal insulation characteristics of the insulating material will decrease. After a certain period, it will be possible to observe the appearance of fungus and mold. The use of vapor barrier creates a kind of shield between the insulation and the internal air of the apartment.

Proper installation of the vapor barrier will allow the insulation to last a long time and efficiently.

Types of vapor barriers

V modern construction Vapor barrier has been successfully used to protect organic and inorganic thermal insulation materials. It is of the following types:

• Film.

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

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

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

Passes moisture in two directions. It is convenient to use when insulating a large surface area.

Thermal insulation and vapor barrier characteristics of the structure depend on the choice of material. A careful approach to the selection of the necessary products will ensure the comfort and coziness of the premises and help extend the life of the entire structure.

Principles of installation of vapor barrier to different surfaces

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

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

You can install vapor barrier on any surface. When using a vapor barrier material on wooden structures membrane film is used. Polymer or bituminous mastic can be used on any type of surface. On the concrete walls it is recommended to lay a vapor barrier with a metal outer layer.

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

During construction wooden house, to begin with, impregnate all wooden surfaces with special means from insects and harmful bacteria. Only after a set of preparatory work has been completed, they are accepted for the installation of a vapor barrier layer.

The best quality material for insulating wooden floors is breathable membranes. The body of the membrane consists of a layer of anti-condensation fibers that absorb and store moisture. There are single-sided and double-sided membranes. In the latter version, moisture is absorbed from both sides at once, so the double-sided breathable membrane can be laid on either side of the floor.

When conducting overhaul all obsolete insulating coatings are dismantled. Surfaces are thoroughly cleaned, impregnated with special disinfectants. Then you can lay the vapor barrier. concrete surfaces do not require special treatment with special equipment, it is enough to clean them.

Features of mounting on various surfaces

Installation of a vapor barrier layer is not particularly difficult, it is necessary to carefully perform preparatory work and know the basic steps of installation.

Floor laying

The film is the best option for insulating the floor from moisture. On the ground floor, the insulation layer is protected from below by the device, and closer to the premises - by a rolled insulating film, which is overlapped. The joints are glued with metalized tape or adhesive tape.

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

ceiling insulation

It is used in rooms with a high content of moisture in the air. It can be bathrooms, showers, baths, saunas. The vapor barrier is reliably overlapped with sealing of the joints. The reflective side of the material is directed into the room. Particular attention is paid to the corners of the room, the insulation should slightly overlap the walls around the entire perimeter of the room.

Vertical surfaces

For such surfaces, diffusion membranes are used that allow air to pass through, and not moisture. The walls must "breathe", so an impervious film is not used. In the case of outdoor work, the product is laid with a smooth side to the insulation. During installation, the film is slightly stretched.

Roof mounting

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

Cellars, balconies and underground structures

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

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

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

The polyethylene film is laid on either side of the insulation, while the diffusion film has one smooth surface, which should lie in the direction of the insulation. By preventing the insulating layer from getting wet, it allows moisture to pass unhindered through the smooth side.

• placing the barrier with a smooth side to the thermal insulation, the inflow of steam and the formation of the process of decay of wooden structures are excluded;
• when installing a heat-insulating layer outside the building, the insulating layer is placed outdoors;
• the film should fit snugly against the insulating layer;
• when sealing joints, wide adhesive tapes and tapes are used;
• when working with window and door openings, it is necessary to leave a small supply of vapor barrier film;
• the film should be protected from direct sunlight;
• before starting work, the most critical places are determined - areas of interaction between warm and cold air.

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

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, with a large amount of moisture, it 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 such insulation - just to provide them with unhindered passage, but not let rainwater through from 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 an uninsulated roof 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 of the interior finish of the roofing cake, because the rough side has the same abilities as the smooth side 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 get out - for more cold street through the enclosing structures of the roof, but encounter a barrier in the form of a vapor barrier on their way. 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 those who are especially quick-witted even say that with a rough side, polyethylene vapor barrier is obtained simply in the factory, when polyethylene is combined with a non-woven material: the film is glued with a rough layer, and the finished product really has two different sides. And it makes no sense to modify 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 the roof protection from steam correctly, think through all the necessary details and not save on quality!