Correct vapor barrier of the walls of a frame house. How to vapor barrier walls from inside a frame house

When using mineral wool as insulation, regardless of its type and manufacturer, you need to use vapor barrier films and membranes. The task of vapor barrier of a frame house is to prevent moist air from the room from entering the insulation, since even a slight increase in the humidity of the insulation sharply reduces its thermal insulation properties, and when it reaches the cold external wall, such moist air becomes the cause of condensation and the actual wetting of the insulation.

What does SP 31-105-2002 prescribe?

Paragraph 9.3.1.3 says

It is recommended to use materials for air insulation in frame structures that simultaneously have low vapor permeability (for example, polyethylene film with a thickness of at least 0.15 mm). In this case, one layer of such material provides vapor barrier and protection against internal air leaks.

In other words, according to SNiP, the vapor barrier of a frame house is performed with plastic film. By the way, in Canadian technology, polyethylene film is a mandatory design element, however, in Canada, a house must be equipped with a forced ventilation system.

What then are all the numerous membranes for? Is it worth paying extra for them?

To say out loud that the membrane is a waste of money somehow makes no sense, they have become too widely used. For those who want to understand what a vapor barrier membrane is, we advise you to conduct a simple experiment. Call any manufacturer and report that the builders installed the membrane on the wrong side and you are afraid of serious consequences due to their mistake. The answer will be that the membrane is vapor-tight on both sides and there is no big difference between how it is laid, just like for polyethylene film. In general, stories that vapor barriers “breathe”, unlike polyethylene, are exaggerated, to put it mildly.

Wind-waterproof films are another matter. These are the ones that protect the insulation from the outside. It is not indicated which side they should be installed; this information can be taken from the instructions for the specific membrane. When installing them, it is really important not to confuse the sides. A correctly installed membrane removes water vapor from the insulation and prevents moist air from outside from penetrating into the insulation. If you are not confident in the builders and their ability not to mix up the sides, then you can buy a three-layer membrane that can be installed on either side. They are a little more expensive, but they guarantee results.

Gross mistake when installing membranes

A truly serious mistake can be considered when builders confuse the films themselves. They install hydro-wind protection from the inside, on the side of the room, and a vapor barrier on the outside. This does lead to serious problems. Water vapor from the room freely passes into the insulation from the side of the room and accumulates there, unable to escape outside, since a vapor barrier is installed there. As a result, after a year or two of use, the insulation in the floor literally floats in a puddle of water, which means everything needs to be disassembled and redone.

Ventilation gap between the membrane and the insulation.

On the outside, where the wind-waterproof membrane is installed, a ventilation gap is required. It is needed there so that the steam from the insulation does not “rest” against the facade material, but freely goes out into the street through the ventilation gap. On the inside, between the sheets of internal finishing cladding, for example plasterboard, and the vapor barrier, SNiP requires a ventilation gap to be made, and we also always do this in our homes. However, for the sake of objectivity, we give an excerpt from the official forum of the manufacturer Izospan (respected and serious people).

Wind protection for the walls of a frame house and rafter roof is a mandatory element of the building design. The “pie” of frame walls and roof consists of several layers, each of which performs a strictly assigned function. Failure to comply with the rules for constructing external fences, in particular the lack of wind insulation, significantly worsens the characteristics of a frame house. And its illiterate use, and even worse, can lead to a significant reduction in the service life of the building. Let's talk about how to choose and install windproofing correctly.

Why do you need wind protection?

From the name it is clear that wind protection is designed to protect the building from the wind. But not in the sense that the frame house will not be blown away by the wind. And the point is that the wind does not blow through the frame walls and roof, does not take away heat with it, so that cold does not seep through the cracks. However, fighting drafts is by no means the only purpose of wind protection. However, the exact technical term is wind insulation, not wind protection, and we will mainly use it.

Windproofing installation process for a frame house

The purpose of windproofing is not only to prevent the walls and roof from blowing through, but also to ensure the maintenance of normal humidity in the enclosing structures of a frame house. Let's take a closer look at the functions of wind insulation in a frame house:

Wind insulation of a frame house can perform several functions simultaneously:

• Actually wind protection.

• Protection against leaks through the sheathing or roofing of rain and melted snow. Protection against condensation forming on the casing or coating.

• Ensuring ventilation of wooden elements and fiber insulation in order to remove excess moisture from them and maintain them in a state of normal humidity.

These three functions are not always combined in one type of windproofing. The choice of windproofing material is dictated by the design of the wall or roof. To understand how to choose the right wind insulation for the walls of a frame house and its roof, we need to consider the tasks facing wind protection in more detail.

Preventing blowing of enclosing structures

The wall frame or roof truss system can be blown out at the locations of double elements (posts, rafters, lintels) if there are gaps between them. Many types of thermal insulation are very susceptible to blowing. Insulating the walls of a frame house with mineral wool, ecowool or other fibrous insulation makes the external fences very sensitive to blowing. Through the fibrous material with an open structure, the wind penetrates easily and to the entire depth of the layer. But closed-cell insulation material is airtight. Therefore, insulating a frame house with polystyrene foam (whether regular polystyrene foam or EPS), coupled with filling the gaps between the double frame elements with construction foam or sealant, will make the walls not blown through.

Mineral wool is an easily blown fibrous material. If you do not protect it from the wind, the air flow will literally blow all the heat out of the house.

Protection of the frame and insulation from precipitation and condensation

Through cracks in the wall sheathing or roofing, slanting rain can get inside the frame wall or rafter roof, snow can blow in, and melt water from snow accumulated on the roof can penetrate. Also, under certain conditions, condensation forms on the inside of external coatings. Dew falls in very large quantities on steel roofing or metal siding for walls, less on asbestos-cement sheets and natural tiles, cement-bonded particle boards, and Euro-slate. Condensation almost never occurs on oriented strand boards (OSB), plywood, and wood sheathing.

A noticeable amount of water may get inside the roof, and heavy drops may occasionally fall from the condensation-producing roof covering. There are fewer problems with walls: if there is a ventilation gap under the sheathing, most of the drops will fall down without hitting the wind barrier.

In order to prevent the frame and insulation from getting wet, wind insulation must have, albeit not complete, but still waterproofing properties: the requirements for water drainage are higher for the roof, lower for the walls.

During the off-season, condensation may form on the back side of the roofing. In the photo there is abundant dew that has fallen on a steel sheet

Ventilation and maintaining normal humidity levels of the wooden frame and insulation

Fiber insulation and wooden frame elements require constant ventilation. This is necessary to remove excess moisture that penetrates hygroscopic building materials from the air in the form of water vapor.

To prevent moisture from accumulating in the insulation and wooden elements of a frame house, the internal structure of the walls and roof requires constant ventilation. It is provided by ventilation gaps through which a weak air flow moves from bottom to top.

In the off-season, during rains and fogs, the humidity of the outside air can be high, water vapor penetrates the fibrous wood and insulation and settles in their structure. In winter, noticeable amounts of water vapor condense into liquid form inside the building envelope at the “dew point.” If the tree gets wet, it will be affected by fungi and the process of destruction will begin. Wet mineral fiber insulation loses its heat-saving properties, and thermal insulation made from organic materials (for example, ecowool) will also begin to rot.

It is extremely important to keep the timber frame and insulation dry, otherwise the frame house will be cold and will not last long. To prevent waterlogging of wood and insulation, it is necessary to ensure constant removal of excess moisture. This is achieved by a ventilation device inside the enclosing structures. There are two possible options for ventilation of frame walls and rafter roofs:

Location of the ventilation gap under the windbreak

A ventilated air layer is placed between the windproofing and the insulated frame. Under the wind barrier, viewed from the outside. Air from the street enters the ventilation gap through the cracks.

The advantage of this solution is good ventilation of the insulation. Another advantage: if the wall cladding is not blown, it can simultaneously serve as a wind insulator. For example, cladding a frame house with OSB, DSP or plywood on the outside replaces wind insulation. Oriented strand boards do not form condensation, are not blown by the wind, and the wall structure is ventilated through a ventilation gap located under the OSB. For ventilated sheathing (for example, siding) or roofing (for example, euro slate), a vapor barrier film or any other non-blown material (for example, roofing felt) can serve as a wind barrier.

Disadvantage: when the ventilation layer is located under the windbreak, the insulation will be blown out to some extent in strong winds. Another disadvantage, although insignificant, is the relative complexity and increased thickness of the structure. Condensation-forming coverings (roofing and wall cladding) must also be ventilated from the inside. Accordingly, there should also be a ventilation gap between the outer skin and the windproofing. That is, with this solution there are two ventilation gaps, on both sides of the wind barrier.

The truss roof structure has two ventilation gaps. The lower one is located under the wind insulation; it is into it that air enters directly from the street and the insulation is ventilated.

The upper ventilation gap serves only to remove condensation from the roof covering

Location of the ventilation gap in front of the windbreak

The ventilation gap can be located between the outer sheathing (for walls), the roof covering (for roofs) and the wind barrier. In this case, there is no gap between the wind insulation and the insulation, or there is one, but air from the street does not enter directly into the gap, and air flows do not carry away heat.

The release of excess moisture from the insulation and wood to the outside occurs through the windproofing material. With this solution, additional requirements are imposed on wind insulation: while maintaining windproof properties, it must be gas permeable and sufficiently allow water vapor to pass through. This type of wind barrier is called vapor-permeable membranes or diffusion membranes.

The structure of a frame wall with a ventilation gap located between the sheathing and the windproofing membrane. The insulation is completely protected from blowing, the gap is provided by a counter-rail stuffed on top of the membrane

The advantage of using membranes and placing the ventilation gap in front of the windbreak is the complete absence of blowing and maximum safety of the structure of the frame wall and roof. If there is one gap, the structure of the frame is simplified and its thickness is reduced.

Disadvantage: diffusion membranes are more expensive than conventional vapor-proof films. However, the difference in cost is relatively small.

The ventilation gap in the truss roof structure, into which openings are open from the street and through which the insulation and wooden frame are ventilated, is located above the wind insulation. With this solution, the windproofing film must be vapor permeable and waterproof. Condensation rolls down the membrane

Types of windproofing materials

From the above it follows that the wind insulation of a frame house and rafter roof, depending on the design of the external fence, is divided into two types: vapor-tight and vapor-permeable.

Vapor-tight insulation

Let us remind you that a vapor-tight wind barrier is impenetrable to water vapor and protects the frame and insulation of a wall or roof only from wind, condensation or roof leaks. In this case, the removal of excess moisture from the insulation and wood must be organized through a ventilated gap located between the windproofing layer and the insulation.

Vapor-tight insulation is also called vapor barrier, vapor-waterproofing, vapor barrier. As a rule, vapor barrier films made of polyethylene, polypropylene and reinforced with synthetic mesh are used for frame houses. You can use fiberboard or other sheet material.

The construction vapor barrier film is airtight; it does not allow either liquid water or water vapor to pass through.

The external enclosing structures of a frame house, where fiber insulation is used, must be insulated from water vapor also from inside the premises. The air inside the house most of the year has higher humidity compared to outside. If you do not install a vapor barrier, mineral wool or its equivalent will constantly absorb moisture coming from inside.

In the absence of internal vapor barrier, the hygroscopic materials used in the frame structure will become damp. In the diagram on the left is the interior, on the right is the street

Some readers ask whether it is possible to sheathe OSB walls from the inside of a frame house and whether this will be enough. Answer: sheathing is possible, but this is not enough, since OSB is partially vapor permeable. A vapor barrier film should be placed between the frame and the particle boards.

Along with external wind insulation, internal vapor barrier is a mandatory element of the design of the external walls and roof of a frame house.

Theoretically, any vapor- and waterproof material can be used as a vapor barrier. For example, roofing felt, old linoleum, greenhouse film, sheets of tin. Another question is how long the alternative material will last and how long it will take to install it.

Vapor-permeable (membrane) windproofing

Vapor-permeable wind insulation ensures the effective removal of water vapor from the enclosing structures of a frame house, while it is impermeable to liquid water to a certain extent. Membrane insulation, as a rule, is a multilayer polymer film, often polypropylene. The diffusion membrane has tiny pores through which gases and water vapor freely penetrate. In this case, the size of the pores is such that liquid water is not able to penetrate through them due to the influence of surface tension forces.

Drops of water falling on the diffusion membrane are not absorbed into it, but roll down

Of course, the waterproofing properties of the membrane are limited; it is waterproof to individual droplets, and not to the flow of water.

Diffusion vapor-permeable films are divided depending on the scope of application into roofing films and those intended for walls:

• Under-roof membrane windproofing must have a fairly high level of water resistance (from 1000 mm of water column and above), especially when used with condensation-forming types of roofing.

• Windproofing the walls of a frame house does not require high water resistance (300 mm of water column is sufficient), since a large amount of liquid water does not fall on it.

The structure and principle of operation of a diffusion membrane: steam passes through, water repels

The industry produces many types of diffusion membranes, among them there are special models with increased strength, non-flammable, insulated. The membrane is secured with a stapler, and the joints of the panels are sealed with special tapes.

Is windproofing of a frame house always required?

We have already mentioned that building materials and insulation, depending on the structure, are divided into ventilated and non-ventilated. Some materials are hydrophobic (absorb moisture), others are not. Organic materials are quickly destroyed by water, mineral materials are not.

The very common mineral wool and ecowool (fluff cellulose) absolutely require windproofing. Polystyrene foam, extruded polystyrene foam - no. The wooden frame of the house must be ventilated to avoid dampness. But, provided that the double elements are insulated from blowing (with foam, sealant, tape), there is no need to additionally protect them from the wind.

The situation is approximately the same with a metal frame (LSTK). That is, with some reservations, we can say that insulating a frame house with polystyrene foam makes the use of special windproofing materials unnecessary. True, this statement applies only to walls; a roof with a condensation-forming coating still needs to be protected from condensation drops.

A frame house insulated with foam plastic practically does not need wind protection if the double frame elements are not blown through

In a warm, dry climate, the walls of a frame house can only be protected by external cladding, provided that it is solid. For example, OSB. No film or membrane is needed under the slabs. This solution is common in the USA and Southern Europe, but is not very suitable for us. Even in the Krasnodar region it can be cold and damp in winter. What can we say about central Russia? The thickness of the insulation for the walls of a frame house in the Moscow region should be at least 15 cm, the recommended value is 25 cm.

Which windproofing to choose

The use of diffusion membranes ensures the best operating conditions for the frame house structure and rafter roof. The complete absence of blowing and timely removal of water vapor from fiber insulation and wood improves the thermal efficiency of the building and extends its service life.

The relatively small costs associated with the purchase and installation of the membrane are fully justified. However, you need to understand that a prerequisite is a competent design of frame walls with insulation, the correct location of the ventilation gap, and its sufficient thickness (4-5 cm). It is necessary to ensure the free passage of air through the ventilation gap; in the lower and upper parts of the walls and roof there should be holes of sufficient cross-section protected from the penetration of rodents and insects.

Construction: assembling the walls of a frame house, installing a rafter system, external and internal cladding, insulating frame walls, installing a roof - a difficult and responsible process. Installing a vapor barrier and wind barrier, at first glance, is a simple task. However, even here, numerous pitfalls can await the “teapot”. For example, the production line of the well-known domestic company GEXA includes 5 vapor-permeable windproof membranes, 6 vapor barrier waterproof films, 4 energy-saving vapor-waterproofing materials, 7 types of connecting tapes. Even deciding on the optimal choice of material without going deeply into construction technology is not easy.

The construction industry offers a wide range of diffusion membranes and hydro-vapor barrier films. It is important to choose the right material suitable for a specific wall or roof structure

Video instructions: thermal insulation of a frame house with mineral wool

A useful video from the Technonikol company, which shows the technology and scheme for insulating a frame house with mineral wool, tells how to sheathe the walls inside a house with OSB, correctly install a windproofing membrane and a vapor barrier:

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

Choosing a material for vapor barrier

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

Reinforced polyethylene

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

Advantages:

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

Flaws:

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

Various types of mastic

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

Advantages:

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

Flaws:

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

Ruberoid

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

Advantages:

• Relatively low cost.
• Availability of material.

Flaws:

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

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

Vapor barrier films

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

Flaws:

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

Advantages:

Long service life.

Easy to install.

Reliability.

High functionality.

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

Installation of vapor barrier from outside

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

Stages of vapor barrier outside

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

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

Installation of vapor barrier from the inside

Stages of vapor barrier from the inside

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

The most important stage in the insulation of any structure is the vapor barrier of the walls. Why is it needed, what functions does it perform, and why is it impossible to do without it in most cases? An amazing fact: in the course of normal life, a family of three releases about 150 liters of water into the environment in the form of water vapor. This volume is enough for a large, nice bay of neighbors! Meanwhile, all this moisture does not go down, but rises up and to the sides and tries to naturally leave the room through the walls and ceiling.

Wood is a very porous material that allows air to pass through and absorbs moisture. Imagine that it is now about -15° “overboard”. The house is warm. You breathe, cook borscht for lunch, do laundry, and take a hot bath in the evening. All this leads to the formation of water vapor. Moisture is absorbed into the walls and tries to come out. Somewhere in the thickness of the wall - closer to the outer or inner surface (this depends on the thickness of the walls and the quality of the insulation) - there is a “dew point”: the boundary at which water vapor turns into water.

This water freezes (it’s cold outside!), as a result of which several very undesirable processes occur at once:

• Dampness of the wall and/or insulation.
• Freezing of walls due to moisture trapped inside turning into ice.
• Gradual destruction of the wall structure.
• The appearance of fungus and mold.

Vapor barrier of the walls of a wooden house helps to avoid all this.

In extreme weather conditions, some water may get under the cover. Therefore, when building a house, ventilation gaps are made and a vapor barrier film is installed.

Installation of external and internal vapor barrier

In our climatic conditions, insulating the walls of houses is a necessity: in order to ensure a comfortable indoor temperature in winter, without spending astronomical amounts on heating, we have to use the benefits of civilization in the form of insulating materials. In order for them to work efficiently, it is necessary to vapor barrier the walls of a wooden house from the outside or from the inside - it depends on where the insulation is located. If moisture gets into the heat-insulating layer, it will significantly increase its thermal conductivity, which means heat loss and reduce the service life of the insulation - vapor barrier allows you to avoid this.

Vapor barrier films are made using the weaving method. Consists of a polypropylene base coated with laminite on one or both sides

How to insulate wooden walls from the outside

Insulated walls are a multi-layer structure. Its base is the walls of the house. A lathing made of wooden blocks is attached to them, between which insulation slabs are laid - stone wool, basalt wool. Then a vapor barrier film is attached on top of them, which is pressed against the sheathing with slats. Facing material is mounted on them - lining, siding, etc. As a result, an air gap is formed between the vapor barrier and the cladding. It is necessary so that moisture, condensing on the vapor barrier, gradually evaporates without getting inside the structure and without moistening the lining.

Another version of the same design provides an additional layer of wind-waterproofing, which is located immediately on the wall of the house, between it and the insulation. This prevents the insulation from getting wet vapors into the insulation from inside the house.

Scheme of vapor barrier device and insulation of the house from the outside

Vapor barrier of walls from the inside

In this case, the work is carried out in a similar way. The layers of materials are arranged in the following order:

• House wall.
• Frame bars, between which insulation boards are laid.
• Vapor barrier membrane pressed to the frame with slats.
• Wall cladding - plasterboard, lining, which are attached to slats.

The sheets are attached to each other using a stapler, then the vapor barrier is secured with pre-antiseptic 4x5 cm slats

Vapor barrier of frame house walls

Frame houses are distinguished by the fact that they do not have a rigid base - a wall - for insulation. It is located between the racks of the timber frame. In such houses, the cross-section of the walls looks like this:

• External cladding (OSB boards, siding, lining, block house).
• Hydro-wind protection is a membrane that protects the insulation from moisture from the outside. A ventilation gap is required between it and the outer cladding, due to which the moisture that gets on the membrane gradually evaporates from the surface due to natural ventilation.
• The frame of a house with insulation embedded in it.
• Vapor barrier membrane. It is necessary to install vapor barriers on walls using the rough side of the insulation film.
• Lathing.
• Interior wall decoration.

Since 70% of the volume of frame walls is insulation, its protection from moisture is very important. Otherwise, it loses its properties, crumples and moves away from the frame, cracks appear, and the house freezes.

When constructing frame houses, it is mandatory to use wind protection and vapor barriers

Features of laying vapor barrier on walls

Manufacturers offer different types of vapor barrier materials. The most modern and high-tech of them are vapor barrier membranes. They are made from polypropylene, with a fiberglass mesh base that gives the material strength. One or both sides of the film have a special coating that is rough to the touch. This is a layer of cellulose-viscose fibers that absorb moisture well. When it gets on the surface of the membrane, it lingers in the rough layer, without passing further and without getting into the insulation and the thickness of the walls. This moisture is then evaporated through natural ventilation. Vapor barrier materials with a metallized coating on one side are also produced. It serves to reflect thermal energy into the room, thereby reducing heat loss.

Important: the foil surface should be facing away from the insulation, towards the room.

Foil vapor barrier not only retains moisture, but also retains heat

Installation of the vapor barrier membrane on the wall is done in horizontal stripes, starting from the floor. At the joints of the strips, it is necessary to overlap them with each other by at least 10 cm. The joints are glued with a special connecting tape, which provides a tight connection. The junctions of the film with wooden or stone surfaces must also be carefully glued, achieving complete tightness. The membranes are attached to the wooden frame using a construction stapler or galvanized nails.

Laying vapor barrier on walls in a wooden house

Of course, vapor barrier of walls with your own hands is quite feasible. True, it is quite difficult for a non-specialist to carry out the entire complex of work on wall insulation: mistakes when using high-tech modern materials are fraught with serious troubles. To ensure that your new home does not require urgent repairs, it is much safer to turn to the services of professional builders.

Vapor barrier of a frame house is its protection against moisture penetration from the inside. It is needed not only for rooms with high humidity (kitchen, bathroom), but in some cases also for other rooms.

Frame house vapor barrier technology

The frame is a load-bearing structure; all the elements that form the planes of the walls, floor and ceiling are attached to it. The planes of enclosing structures, floors or partitions are formed on both sides of the frame elements. The depth of the walls is equal to the thickness of the supporting frame posts, and the thickness of the floors is equal to the height of the supporting logs (the width of the boards used). The space inside these planes is filled with insulation, which simply needs to be protected from interaction with water vapor.

If this is not done, then the dispersed thermal insulation material will quickly absorb moist fumes contained in the internal atmosphere of the house, its thermal conductivity will sharply increase and its thermal insulation properties will deteriorate.

The main technological technique used is stretching moisture-proofing membranes (for example, polyethylene film) before forming the outer and inner planes of the walls.

Features and main errors

The most common insulation is mineral wool (also called stone or basalt wool). That's why:

• on the side of the outer planes and floor surfaces, a waterproofing PVC film or a moisture- and sound-insulating special polymer coating is laid. Here the effect of humidity from the “street” side is much stronger;
• On the inside of the wall, it is necessary to lay a vapor barrier membrane - a thinner film.

Inside the heat-insulating layer, the temperature decreases from its inner part to its outer part. But if it’s winter outside, then inside the insulation there will be a layer where water vapor will certainly condense. If you do not protect dispersed stone wool from “communicating” with the internal atmosphere of the house, then sooner or later such insulation will inevitably become saturated with moisture and lose its insulating properties.

The main mistake is that many limit themselves to only the waterproofing outer layer, which is unacceptable. In addition to insulation, wooden frame parts also need to be limited from interaction with moisture. They are strongly recommended to be used exclusively dried to furniture humidity (that is, up to 6-8%), but over a long period of time (10 years or more), wood is capable of absorbing moisture from the air in limited portions, which means it can become deformed. So vapor barrier of a house from the inside is a matter of not only heat preservation, but also the strength of the building.

Vapor barrier is the next process after insulating the house

When a vapor barrier is not required

There is no need to isolate anything from water vapor using a membrane in the following cases:

• if there is no temperature difference between the spaces on which the vapor barrier membrane is supposed to be installed (for example, on the ceiling plane, if the next floor is also heated);
• if the material that is supposed to be protected from water vapor is itself non-hygroscopic and even water-repellent.

Vapor barrier materials

The general meaning of a vapor barrier is to create a moisture-proof layer. The materials with which this barrier to water vapor is created can be different:

• polyethylene films. This thin, cheap material is ideal for creating a vapor barrier if no load is placed on the film;
• polypropylene films. These membranes are much thicker, denser and more expensive. They are good for preventing walls from blowing through and drafts;
• diffusion or “breathing” membranes. Such nonwoven materials allow air to pass through, but retain moisture. The greenhouse effect that forms inside the panel walls of a frame house goes away. This is a modern and very expensive material.

However, the use of membranes cannot be replaced by treating panel surfaces with liquid moisture-proof chemical compounds. Coating the surface of a fiberboard board with moisture-resistant varnish from the inside is not equivalent to using a polyethylene membrane.

Frame house vapor barrier diagram

Which surfaces in a frame house must be subjected to vapor barrier:

• all enclosing structures (walls) on the inside along the perimeter of the house. Necessarily;
• those sides of internal partitions containing frame parts that face rooms where there are sources of open water. For example, the kitchen;
• all walls, floor and ceiling surfaces in bathrooms and toilets. This is a space with high humidity. It must be vapor barriered even if the walls are not filled with insulation and do not contain frame elements;
• the inside of the rafters on the roof.

Do not confuse hydro- and vapor barrier membranes. The first one is thicker and denser. It is intended not only for protection from external atmospheric moisture, but also for protection from wind and drafts. The task of the vapor barrier film is to prevent the protected element or material from coming into contact with moisture contained in the internal atmosphere of the house.

However, for vapor barrier purposes, you can use a denser polypropylene film. It’s just more expensive and this overpayment is unlikely to ever justify itself (after all, vapor barriers do not need to withstand wind loads and drafts). The choice of material here depends solely on finances.

Vapor barrier of floor and ceiling

It is unwise to do a vapor barrier on the floor, because water will pour onto the floor if the pipes burst. Therefore, it is more practical to immediately stretch a denser waterproofing film. In addition, it is recommended to use a polymer soundproofing, waterproof coating. The seams must be taped with waterproof tape.

There is also no need to do complex waterproofing of the ceiling. To protect the insulation inside the ceilings, a thin polyethylene film will be sufficient. All impact from water that may fall on the floor of the second floor should be taken care of by the waterproofing of its floors. The ceiling needs to be vapor-insulated from the warm, humid air that rises up in each room.