Modern technologies The construction of roofs is very different from the methods of covering residential and commercial buildings a hundred years ago. More advanced and durable roofing materials retain heat better, protect more reliably from moisture penetration and make housing more comfortable to live in. However, complete tightness also has back side– “greenhouse effect” and the condensation caused by it, settling inside the roof structure. To protect the frame and insulation from destruction as a result of getting wet, a vapor barrier is performed on the roof. In this article we will tell you what vapor barrier materials exist, how they differ and how they are used in roofing pie.

Roof vapor barrier is a mandatory component roofing pie roof, on which the service life and safety of the finishing coating depend. She represents thin fabric or a film whose structure allows air to pass through, but blocks larger water molecules. Vapor barrier materials are used as part of a “warm” roof, since it is more prone to condensation due to heating of the under-roof space. Vapor barrier performs the following tasks:

1. Prevents getting wet thermal insulation material. Warm, moist air that rises to the top penetrates the insulation, increasing the thermal conductivity of the material, which leads to a decrease in its efficiency. And when it freezes, the water absorbed by the fibers of the thermal insulation crystallizes, which leads to the destruction of the insulating layer after several freeze-thaw cycles.
2. Protects the roof frame from rotting. Waterproofing protects rafter system roofs from the penetration of moisture from the outside, and vapor barrier materials reduce the formation of condensation, due to which microorganisms actively multiply, leading to wood rotting.
3. Increases service life roofing. Most topcoats are well protected from contact with moisture only with outside, while the lower surface often suffers from corrosion, which is formed as a result of the condensation process. A vapor barrier prevents rust from affecting the roofing material, extending its service life.

Note! Most modern roofing coatings require the installation of a vapor barrier, which provides protection against condensation and wetting. Only if this condition is met waterproofing material will last the service life stated by the manufacturer.

Quality requirements

Vapor barrier materials are an essential component of the roofing pie of a “warm” roof; they are attached to inner surface rafters with a construction stapler or adhesive. The material is cut into strips, which are overlapped so that condensation cannot penetrate through the joints. For efficient work vapor barrier required:

• Pronounced water resistance. Water vapor barrier must contain not only steam, but also water in order to reliably protect the “insides” of the roof from contact with water.
• Strength. High strength properties ensure resistance to mechanical damage during installation and operation.
• Long service life. Roof coverings last at least 15 years, since the vapor barrier cannot be replaced without dismantling the structure, it must have a service life no less.
• Non-flammability. To increase the safety of living in buildings with a high risk of fire, it is recommended to use non-combustible vapor barrier.

Important! Water vapor barrier is a material that combines the properties of waterproofing and vapor barrier coatings, that is, it does not allow water or steam to pass through, while remaining breathable.

Criterias of choice

During construction own home Non-professionals often wonder which hydro-vapor barrier is better, and how to choose the material suitable for a particular structure. Experienced craftsmen It is recommended to follow the recommendations of the roofing manufacturer, and also take into account the following criteria:

1. Climatic conditions of the region in which construction is taking place. For the right choice vapor barrier material, it is necessary to know the average annual temperature in winter and summer period to determine the difference between indoor and outdoor temperatures.
2. The nature of the use of the under-roof space. A heated attic can be located under the roof of the house, from which comes a large number of heated, moist air, or an uninhabited attic that provides natural air insulation for the roof surface.
3. Properties of roofing material. Finish coatings roofs have different composition, shape and installation method, therefore they require installation of a type of vapor barrier suitable for its properties.

Please note that the use of roofing felt, roofing felt or waterproofing material as a vapor barrier in combination with modern roofing materials is not allowed, since they do not allow air to pass through. Despite affordable price and high strength, they do not protect the frame structure from condensation, but rather stimulate its active formation.

Kinds

Modern vapor barriers for roofs are high-tech polymer membranes, the multilayer structure of which effectively protects against the penetration of water and steam, but at the same time allows air to pass through, which is necessary for ventilating the rafter frame. IN roofing works The following vapor barrier materials are used:

Important! Vapor barrier materials have 2 sides, one of which allows steam or water to pass through, and the other does not. Therefore, during installation it is important to properly fasten the sheet, otherwise the operation of the roofing pie will be disrupted.

Video instruction

Hydro-vapor barrier film is a film of combined action that provides moisture, wind and vapor barrier. In the article you will learn why a hydro-vapor barrier film is needed and where it is used, what is the principle of its operation and what types of films exist.

Why do you need a hydro-vapor barrier film?

The task of the hydro-vapor barrier film is to prevent steam from penetrating into the thermal insulation and bearing structures Houses. In the absence of hydro-vapor barrier films, the service life of the home is reduced and the need for repairs arises.

Indoor air contains a large amount of moisture because people cook, shower, etc. indoors. When the temperature outside is lower than inside the house, moist air will tend to flow out.

If a vapor barrier is not installed in the structures, moisture settles in the insulation. Excessive humidity leads to a decrease in the properties of the heat insulator. Corrosion processes also begin, which lead to disastrous results: wooden elements become infected with fungus, and metal ones are corroded by rust.

Where are hydro-vapor barrier films used?

The film protects the insulation from getting wet, wooden elements from rotting, and metal elements from corrosion. The use of film is necessary in the following designs:

• frame walls, wooden walls;
• ventilated facades;
• insulated roofs;
• irregularly heated premises, cottages;
• “warm” attics;
• multilayer interfloor ceilings, ceilings;
• rooms with high humidity and temperature (baths, saunas).

Types of hydro-vapor barrier films

Polyethylene films

Polyethylene films - materials, key feature which is reinforced with fabric or reinforcing mesh. This is done to give strength. There are two types of films:

• Perforated - they have micro holes that provide vapor permeability. However, this indicator does not correspond to the norm, therefore, when arranging an insulating pie, it is necessary to do ventilation gap;
• Non-perforated - materials used directly for vapor barrier. When installing them, tapes are used that are designed to connect individual panels.

It should be emphasized that there is another type of polyethylene films. This refers to materials laminated with aluminum foil. Their main advantage is good vapor barrier properties. Films are not suitable for rooms with a normal microclimate. But when arranging saunas and swimming pools, they are widely used.

Polypropylene films

Polypropylene films are materials that have been used for many years. At first they were brought from Finland, and then they began to be produced in Russia. The main advantage of such films is their excellent strength characteristics and resistance to exposure to sunlight. The materials under consideration have another significant advantage: the presence of an anti-condensation layer that absorbs and retains moisture. This layer has excellent performance because even in critical conditions it absorbs all the moisture, eliminating the formation of drops. And when the causes of condensation disappear, polypropylene films dry naturally.

Hydro-vapor barrier films Ondutis

• Ondutis RS. Used for vapor barrier of pitched and flat roofs(including those with a metal coating), buildings with a metal frame. Reinforced film weighing 100 g/sq. m, which is characterized by water resistance of more than 1000 mm of water column, vapor permeability of less than 10 g/sq. m, tensile strength: more than 250 N along and more than 200 N across the 50 mm strip.
• Ondutis D (RV) . Used for waterproofing floors in wet rooms, vapor barriers flat roofs and roofs with metal decking (insulated and non-insulated). Film weighing 85 g/sq. m, which is characterized by water resistance of more than 1000 mm of water column, vapor permeability of less than 10 g/sq. m, ultra-high tensile strength: more than 650 N along and more than 500 N across the 50 mm strip.

All modifications of Ondutis moisture and vapor barrier membranes reliably protect wall, roofing, interfloor and foundation structures of a house from moisture, wind, and condensation.

At the same time, the films are characterized by their low weight and convenient size for installation. This is a mechanically strong, durable, environmentally friendly, non-flammable material that helps save heat at home.

Thanks to its resistance to ultraviolet radiation And wide range operating temperatures (-40...+80 degrees Celsius), Ondutis hydro-vapor barrier films can be used as a temporary coating for 1.5-3 months. Smart series films in the form of panels with applied adhesive tape significantly simplify and speed up the process of installing hydro-vapor barriers.

How to choose a hydro-vapor barrier film

When choosing insulating films, take into account the design features of the house and the used Construction Materials: type and thickness of insulation, type of roof covering or external cladding walls You can read more about the nuances of choosing a vapor barrier film in the article “How to choose a vapor barrier film.”

Installation of hydro-vapor barrier film

The vapor barrier layer is one of essential elements roofing pie. It is necessary to protect the thermal insulation layer and the rafter system from excess water vapor. Steam from interior spaces the house always rises upward, passing through the insulation, it will cool down and settle there with condensation, and this in turn will lead to a decrease in the properties of the thermal insulation layer and swelling/rotting of beams and ceilings. But this will only happen if there is no vapor barrier film.

Choosing the best vapor barrier for the roof

• single layer film- most often it is simple polyethylene film, the cheapest and most unreliable material. This is not the most durable material on the market.
• reinforced - more strong material, due to the reinforcing middle layer - reinforced mesh. The top of this mesh was covered with polyethylene. This double-sided lamination ensures vapor permeability.
• universal - it is unique in that it is suitable for all structures and works with all types of insulation.
• unreinforced membrane is a multilayer material with high insulating properties, thanks to the foil layer, which copes with its functions perfectly.

Vapor control materials on the market

Hydro- and vapor barrier films Grand Line®

The line includes hydro- and vapor barrier films and superdiffusion membranes. Grand Line H98 film has a number of advantages - the laying pattern, installation side, and overlap boundaries are indicated on the roll. Made from primary raw materials.

Roof vapor barrier Folder

Folder products offer several types of material:

• Folder Steam Regulator - this material can provide controlled vapor transmission, maintain the level of vapor barrier and allow excess moisture to pass through as much as possible.
• Alum H90 - reinforced film with a foil layer that allows you to retain heat in the room and at the same time remove excess moisture.
• H98 - has a laminated layer, can be used with any thermal insulation material.

Hydro- and vapor barrier Tyvek®

The Tyvek line includes two vapor barrier membranes:

• Tyvek® AirGuard® Reflective - completely airtight. This membrane was developed to provide more efficient thermal insulation performance. The possibility of condensation entering is minimal.
• - this is a material with limited vapor permeability, thereby reducing the risk of condensation forming and entering.

Delta insulation materials

• DELTA-DAWI GP is a simple single-layer polyethylene film.
• DELTA-NEOVAP 20 is a film with a reinforcing layer, due to which the risk of damaging the vapor barrier becomes much lower.
• DELTA®-REFLEX PLUS / DELTA®-REFLEX- film with almost zero vapor permeability. This ensures that condensation does not get on the thermal insulation. This material also reflects heat back into the room.

Insulation from Icopal Fel"X

Insulation from Icopal Fel"X- this is a material consisting of three layers - polypropylene, SBS-modified bitumen and a non-woven base. These layers provide strength, waterproofing and protection to the roofing pie.

Hydro- and vapor barrier for roofing Izospan

The assortment includes several products:

• Izospan FS - consists of non-woven dense and metallized polypropylene film. Protects the structure from steam and also reflects heat into the building.
• Izospan B has two layers, the first layer is smooth, the second is rough, capable of holding condensation.
• Izospan D is a membrane that is a two-layer material. Performs the functions of hydro- and vapor barrier. The material is very durable and has high UV stability.
• Izospan DM - this material combines the functions of wind protection, waterproofing and vapor barrier. Consists of three layers.

Hydro- and vapor barrier Optima

One of economical materials. The line includes Optima B - vapor barrier, Optima C - provides vapor and waterproofing, and Optima D - a universal hydro- and vapor barrier material with increased strength.

Waterproofing TechnoNIKOL

A three-layer membrane has high vapor permeability, quickly removes moisture and protects the insulation.

Hydro- and vapor barrier Ondutis

It is a fabric with the addition of a UV stabilizer and a protective layer.

• Ondutis V (R70) Smart- classic film. Performs all necessary functions, protects the insulation and removes moisture.
• Ondutis D (RV) Smart— this film can be used as a vapor barrier on a warm roof and as waterproofing on a cold one.

How to properly install a vapor barrier - basic steps

• Vapor barrier sheets are laid from top to bottom perpendicular to the rafters.
• The material should be rolled out according to the factory winding. Usually the laying side is marked.
• Each subsequent strip must overlap with the previous one.
• All joints must be taped with single- or double-sided tape.
• In places where pipes, risers and other things are bypassed, additional slats can be installed. The overlap of the material should be 10-20 cm.
• The material is attached with a counter-lattice to the rafters. It is acceptable to use nails.
• At the ridge, the overlap of the sheets should be 200 mm. It is better to lay more in the valley - 300 mm, and also on top of the material it is necessary to add an overlay along the entire width of the valley.
• The ventilation gap above the vapor barrier should be from 50 to 100 mm. Vents should be provided in the eaves area.
• It is recommended to minimize the number of holes. All holes must be sealed with tape to ensure the tightness of the entire layer.
• When adjacent to metal or other surfaces, fastening is carried out using double-sided tape.

Installation of vapor barrier on different surfaces

Vapor barriers can be installed on different surfaces.

For example, for the floor. In this case, the material is placed inside out against the floor beams.
Vice versa for the ceiling. The film is unrolled and installed rough side inside.

Can be installed on walls. In this case, the following rules apply:

• you need to unroll the film on the wall and secure it with staples,
• vapor barrier sheets must overlap 100-200 mm,
• Excessive tension should be avoided,
• it is necessary to provide space for ventilation,
• as in the roofing version, all joints must be taped with single-/double-sided tape to ensure complete sealing.

When installing a vapor barrier on wooden structures, the tree must first be treated with an antiseptic.

Important! Installation should not be carried out in wet or rainy weather. The vapor barrier material must be dry.

Most often, the manufacturer, along with the material, provides instructions for correct installation and these instructions should be used. Rolls should be stored on pallets at a distance from heating devices, indoors or under cover. No more than 25 rolls can be stored on one pallet. Rolls are also transported on pallets in closed vehicles.

Video of installation of vapor barrier materials

You can see more details about the installation of vapor barrier materials in the following video.

In conclusion, it must be said that vapor barrier is one of the most important elements for creating a roofing cake. From quality and correct installation The service life of the insulation and the entire roof as a whole depends.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

There are two ways out of this situation.

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

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

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

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

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

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

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

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

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

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

Windproof, waterproofing membrane for walls

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

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

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

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

Superdiffusion waterproofing membrane for roofing

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

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

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

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

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

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

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

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

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

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

What is the danger of the term vapor and waterproofing?

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

As a result, confusion begins. Vapor 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.

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:

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

about the author

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

The construction of a roofing structure is carried out taking into account the creation of the necessary conditions that would maximize its service life, reliably protect it from precipitation, maintain optimal temperature conditions, and much more.

Let's take a closer look at what roof and roof waterproofing is and what materials may be needed for it.

Materials used as a waterproofing layer prevent moisture from penetrating into the insulation, which negatively affects its level of functionality. The source of moisture entering the thermal insulation is not only the external environment, but also the internal premises, where condensation forms due to a large temperature difference.

Currently, roof waterproofing is made from different materials:

The market offers two- and three-layer materials that combine diffuse and anti-condensation properties (more details: " "). In addition, there are materials with an adsorption layer, where condensate is retained, and from there it gradually evaporates.

What is roofing hydro vapor barrier?

With the correct arrangement of the sheathing and selection of the appropriate insulation, even regardless of what types of roof waterproofing will be used during construction, you will get a reliable and warm roof into which moisture will not penetrate, and, at the same time, condensation will be freely eliminated from it.

The roofing system is equipped with a sufficient number of ventilation gaps and a layer of waterproofing, thanks to which external and internal moisture will be freely removed from under the covering.

With the help of properly installed ventilation, roofing and waterproofing mastics are reliably protected from overheating, so in winter, under the influence of sunlight, the snow cover will evenly melt and flow down the equipped drainage system without the formation of ice on the roof.

According to the above classification, the installation of water vapor barrier and under-roof waterproofing is carried out from diffusion membranes and waterproofing anti-condensation films installed under the roof.

Diffusion membranes make much better roof waterproofing - the materials for it, although expensive, have a large number of advantages:

• They can be laid on top of an insulation layer, as in the photo, which will significantly reduce the size of the cake and allow you to maximally supplement the insulation layer;
• Due to the high level of wind resistance, the percentage of heat blown out of the insulation is reduced to a minimum;
• The roof “breathes”, which is achieved due to increased internal vapor permeability and external waterproofness of the material.

During construction, roofing waterproofing is equipped with a vapor barrier film, which can be positioned in any direction, depending on the characteristics of the roof and the convenience of the developer - both horizontally and vertically (more details: " ").

It is important to know that:

• When fastening horizontally, the film is placed on top of the rafters, the gap between which should not exceed 1.2 m. Care must be taken to ensure sufficient tension of the material, that is, it should not touch the insulating layer, but it should not hang more than 2 cm. As soon as it is laid accordingly, they move on to the next stage: attaching the counter-battens and erecting the sheathing.
• In the case of a vertical position, the film is mounted with a mechanical stapler or galvanized nails from the inside of the thermal insulation material to wooden slats protruding from the load-bearing elements.

After the film is securely fixed, wooden slats are attached to create a small gap between the ceiling surface and the vapor barrier.

Characteristics of waterproofing and vapor barrier materials

Before you begin repairing roof waterproofing, you should select the necessary materials, for example, this could be:

The advantage of anti-condensation materials is that when moisture forms or penetrates, it does not flow onto the wooden structural elements, but is retained and gradually dries.

Waterproofing installation for metal tiles, detailed in the video:

“Breathable” membranes are divided into 2 types:

High-quality liquid waterproofing of a roof is only possible if there are materials that have:

• fire resistance;
• maximum strength;
• resistance to UV radiation;
• sound insulation of the roof, sufficient for a comfortable stay inside the house.

Thanks to high-quality vapor and waterproofing, the roof and under-roof space will be protected and, therefore, will last for many decades.