Vapor barrier is common name a whole package of methods for protecting thermal insulation or building materials from the appearance of steam inside them and the release of condensate. This type of insulation allows you to withstand absolutely any temperature conditions, and therefore vapor barrier is considered an important link in preserving heat inside a building during the winter season. A well-designed vapor barrier prevents destruction insulation materials and thus contributes to the durability of the entire structure. So, vapor barrier - how to install it correctly.
Vapor barrier materials
Vapor barrier, as a method of heat conservation, is needed in order to wet steam, created indoors, did not cause the appearance of fungus or mold, did not have a destructive effect on the ceiling structures, roof, walls, floor and easily penetrated outside. There are many materials that provide stable vapor barrier: film, penofol, membranes and others. Let's take a closer look at each of them.
Still the most common material is film. It must be tensioned well during installation, and also remember to make gaps for ventilation.
Membranes represent a modern construction material, which can be used not only as a vapor barrier, but also for waterproofing premises. There are several types of membranes: single-sided and double-sided, single-layer and multi-layer. Double-sided membranes are perhaps the most economical option, they are often used for roof vapor barrier. 
Another type that needs to be mentioned is reflective vapor barrier. Often such insulators are used in baths and saunas. Penofol is one of the materials in this group, which is foamed polyethylene. Can also be used as a lightweight thermal insulator. The next common reflective vapor barrier is foil on kraft paper. It can be used in almost any room, even at elevated temperatures. 
Which side should the vapor barrier be laid against the insulation?
This is probably the most frequently asked question - which side to lay the vapor barrier against the insulation, so it was highlighted as a separate item.
The vapor barrier film has a two-layer structure. One side is smooth, the other has a rough surface to retain drops of condensation and its subsequent evaporation. This film is laid with the smooth side outward (adjacent to the insulation), and the rough side into the room.
Reflective (foil) vapor barrier is created not only to protect the insulation, walls or roof, but also to return heat to the room thanks to the reflective surface. Therefore, to perform this function, it must be placed with the reflective side in the room.
An air-permeable vapor barrier membrane protects walls and roofs from moisture, but at the same time allows the structure to “breathe”. The membrane can be either double-sided, with the same characteristics on both sides, so it can be laid on either side, or one-sided, in this case, manufacturers indicate the reverse side on the surface of the material. When purchasing, you must read the installation rules.
How to properly install a vapor barrier
Once we have decided which side to lay the vapor barrier against the insulation, we can proceed directly to work. Let's describe the process using film as an example:
- First we lay thermal insulation and sound insulation, after which we can lay the film;
- the film should not be sagging, so stretch it well during installation;
- The film is secured with double-sided adhesive tape or tape. For fastening, you can also use nails with a wide head, driven in increments of 30 cm, or a furniture stapler, which can make the work much easier. You can also use wooden slats, which are screwed with the same frequency of 30 cm;
- The sheets of material must be laid with an overlap (10–15 cm), while specifically for the film (as it does not allow air to pass through), do not forget to make gaps for ventilation from time to time, about 5 cm wide.
Now you can find others, more modern options. For example, membranes with an adhesive side provided. You just need to remove the protective layer and stick it on.
We have reviewed general rules How to properly install a vapor barrier, now let's describe the nuances for the roof and floor.
Roof vapor barrier
Protecting the walls of your home from moisture and steam is only half the battle. After all, the main part of the evaporation flows tends upward, and condensation cannot be avoided after heavy snow and rain, and it is the roof of the house that takes the first blow.
Among other things, poor roof vapor barrier leads to a decrease in indoor temperatures, unpleasant smell and dampness in the house, fungus, rust and other troubles. To protect your home from problems, you need a vapor barrier and it is very important to do it correctly.
Experts recommend using membrane materials for roofing that allow air to pass through, but do not allow moisture to pass through, thereby removing excess moisture from the roof insulation. Double-sided membranes can work on both the internal and external surfaces of the roof.
The sequence of laying the material is very important, you can see it in the photo below.
Floor vapor barrier
Floor vapor barrier plays no less important role. Wet cleaning, showering, cooking and even normal breathing can affect the release of condensation. And the main flow of it settles on the floor.
If you are just building a house and not renovating, there will be less hassle. The first thing to do is process everything wooden elements gender special composition against rotting, insects and fungus. If you are making repairs, you must remove the old coating and thermal insulation. Check for sagging or rotten boards, if necessary, replace them completely or partially, and then also treat them with protective agents.
All previously listed materials can be used for vapor barrier of the floor. For the film, you should also make gaps for ventilation; other materials do not require this.
The most popular material is isospan. It should be noted that there is a difference between the ground floor floor and the interfloor ceiling. On the ground floor, waterproofing must be laid on the subfloor, followed by insulation and vapor barrier. On the second and subsequent floors we replace the waterproofing with a vapor barrier layer. You can see all this in the photo below. 
Let's briefly describe the process for interfloor slabs. We lay a vapor barrier on the load-bearing frame of the floor; the sheets should overlap with a width of about 15 cm. We fasten using any of the previously described methods, but most often it is recommended to use a special duct tape. Next, the insulation is laid, after which another layer of vapor barrier is laid overlapping in the same way.
Vapor barrier along with waterproofing for the home - necessary thing. Protecting walls, roofs and floors leads to the preservation of the material, its original appearance and properties, protects against the appearance of fungus, mold, drying out and rust, and also ensures the home optimal temperature. And that’s all, we hope that this article was useful to you.
Last time we dealt with species and , which is made from stone wool. Despite its ability to repel moisture, even this material needs protection. For this purpose, vapor barrier is used. Today we will tell you how to properly install vapor barriers in thermal insulation pies of walls, roofs and floors. For interfloor ceilings where both floors are heated, such films are not needed.
How to lay a vapor barrier when insulating walls
Both sides of the vapor barrier are equally impervious to moisture and steam.
Let's figure out how to properly install vapor barrier on walls. There are two insulation options:
- internal;
- external
Of course, it is preferable to install thermal insulation outside the room, but in this case a vapor barrier film is not required. The material used for insulation also matters. Film is needed only when it is necessary to protect thermal insulation from moisture and steam. To figure out how to properly lay a vapor barrier film, you need to understand the principle by which air circulates. He always moves from the zone high pressure(where the temperature is higher) to the zone low pressure(where the temperature is lower). It turns out that the air, along with moisture, tries to leave the warm room and end up outside.
Which side to lay the vapor barrier to the insulation does not matter, since it does not allow moisture to pass in any form in both directions. Those who ask such questions most likely confuse a vapor barrier film with waterproofing (diffusion membrane).
Scheme of laying vapor barrier on the wall from the inside.
Therefore, on numerous forums, when asked which side to attach the vapor barrier to the insulation, supposedly experts answer that it is rough. Where is the rough surface of the vapor barrier? It is a completely smooth material on both sides. As it turns out, even the builders themselves confuse these concepts. In our previous article we clearly explained .
Another frequently asked question regarding how to properly install a vapor barrier is the need for a ventilated gap. Some film manufacturers write that a ventilation gap is not needed at all, but it’s still not worth making hasty conclusions. When installing an insulation pie for walls from the inside, a ventilation gap is needed between the film and the finish, but is not necessary (although it won’t hurt) between the film and the insulation. Here we are somewhat replacing the concept of a ventilation gap, since in the space between the film and the finishing (even more so the insulation) it is not always possible to achieve the necessary air circulation.
Let's leave these subtleties aside for now and call the buffer air zone between materials a ventilation gap. Layers of insulation cake for walls, starting from the inside:
- finishing;
- ventilation gap;
- vapor barrier;
- insulation;
- wall.
The ventilation gap will keep the finish dry, as a result there will be no mold on it and it will last as long as it should.
Laying a vapor barrier film on the roof
Layout of vapor barrier for roof insulation.
The question of how to properly lay a vapor barrier is especially relevant for roof insulation, since this is where the most mistakes are made, which subsequently bring many problems. Before explaining the layer diagram, remember what we said about the direction of movement air flow and the main function of the vapor barrier. Our main goal is to protect the insulation from steam, so the film should be laid on the side of the warm room. There is no need to think about which side to attach the vapor barrier; absolutely all construction films are wound into a roll so that when unrolled they lay correctly.
That is, you take a roll, apply it to the work surface, gradually unwind it and staple the film, everything is as simple as shelling pears. In the process of installing the film with a stapler, installing the counter-lattice and stuffing the trim, holes will appear in the vapor barrier in any case. Through these holes, steam will penetrate into the insulation, and the film itself does not protect 100%. Therefore, you cannot cover the thermal insulation with a vapor barrier on both sides; you need to give moisture the opportunity to escape. A membrane should be placed between the insulation and the low temperature zone, which releases steam but does not allow the material to get wet.
Now we’ll tell you how to properly attach a vapor barrier using an example. Let's consider roof insulation with mineral wool, layers from the inside:
- vapor barrier;
- mineral wool;
- diffusion membrane;
- counter-lattice, thanks to which a ventilation gap appears;
- roof finishing.
In addition to the ventilation gap between the membrane and the roof trim, it would also help to have a gap between the same membrane and the insulation (optional, but preferable).
The vapor barrier is laid stretched; it should not sag. At the joints there is an overlap of about 10 cm, the joints are taped.
Need either construction tape with aluminum coating, or specialized double-sided tape for films, the second is preferable. Correct styling vapor barriers:
- First, one tape is laid;
- double-sided tape is glued along the edge;
- the protective paper tape is removed - sometimes the paper tears, small pieces may remain that must be removed;
- The next tape of film is laid on top.
Double-sided tape connects the films very tightly, so that later you can’t tear them apart from each other.
How to properly install a vapor barrier on the floor
Scheme for laying vapor barrier when insulating the floor along the joists in wooden house.
Insulating a floor is not much different from a roof, the only thing is that there is no finishing of the subfloor. Thermal insulation is laid between the joists wooden house. A subfloor is first laid underneath, which should not be solid, that is, between the narrow boards there should be indentations no less than their width. Thanks to these indentations, steam will have the opportunity to leave the insulation. Moisture enters the thermal insulation along with the air from the room, so the layers of floor insulation in a wooden house should be laid as follows:
- finishing floor;
- vapor barrier;
- insulation;
- wind protection or waterproofing.
A gap between the insulation and the vapor barrier is not required, but whether it is needed between the finished floor and the film is a controversial issue. Let's return to the moment when we talked about replacing the concept of a buffer air zone with a ventilated gap. Essentially, a ventilation gap is a space where constant air circulation occurs; if this does not exist, then it is just a buffer zone.
A ventilation gap in the classic design can be observed in the roof structure and When insulating walls from the inside, it is still possible to achieve circulation in the buffer air zone, but with the floor it is increasingly more difficult. We need to make holes in the floor, but there is no guarantee that air will circulate there the way we need and whether it will at all.
Therefore, many craftsmen refuse a ventilation gap between the finished floor and the vapor barrier, and the same applies to walls. But if you look from the other side, a gap is still needed. Even if moisture condenses on the film, it will not be absorbed into the material in contact with it, and accordingly, it will not mold.
Correct installation of vapor barrier: results
To figure out how to properly install a vapor barrier, you need to know why it is needed and the principle of air circulation. The film is needed to protect the thermal insulation from moisture that is in the warm air. The circulation of air flows occurs in the direction from a warm room to a cold street. Accordingly, the vapor barrier must be laid from the side of the room, preferably leaving a gap between the film and the finish. How to determine the sides of a vapor barrier? It has two sides: this and that, and both are the same. The film does not allow vapor to pass through in both directions. Such questions are asked by those who do not understand the difference between a vapor barrier and a diffusion membrane (waterproofing).
Preface. When building a private house Special attention attention should be paid to vapor barrier of the ceiling, floor, walls and roof. If this important step will be missed, the structural elements of the building will not last long. We’ll talk further about why it is important to install a vapor barrier in a private home and how to do it correctly.
Why do you need a vapor barrier for insulation?
Special film that protects thermal insulation material from moisture, it is necessarily included in the “pie” of walls or roofs. The fact is that due to the temperature difference, especially in winter period Over time, condensation settles on the walls and ceiling outside and in the house, indoors. As a result, the heat insulator gets wet and stops performing its functions. The house is getting cold. In addition, moisture leads to spoilage structural elements building.
Depending on the variety, the cost of the material may vary. For example, a regular vapor barrier polyethylene film costs about 500 rubles per roll. The foil version will cost about 1400-1800 rubles. A three-layer diffusion membrane will cost about 4000-5000 rubles. The popular vapor barrier “Izospan” will cost about 800-1000 rubles. per roll.
Types of vapor barrier materials
Vapor barrier in frame wall. PhotoThere are only three main types of films designed to protect mineral wool or expanded polystyrene from moisture:
Standard. The cheapest and not particularly durable type of vapor barrier. In most cases, this is ordinary thick polyethylene film.
Foil. It is more expensive than polyethylene, but at the same time, in addition to the vapor barrier itself, it performs another function - it reflects heat back into the room. Owners country houses Very often people are interested in which side to lay the vapor barrier on the walls and ceiling. This question usually arises in relation to this variety. Let's look at how such a film is actually mounted below.
Membrane. Features limited vapor barrier. This allows you to control the removal of moisture from the room.
Basic rules for laying vapor barrier
Of course, before you go to the store to buy film, you need to do everything necessary calculations. This procedure is completely easy to perform. All you need to do is calculate the area of all structural elements of the house that require protection. The calculation is made taking into account the width vapor barrier film and necessary overlaps.
How to distinguish the inside from the outside
If the manufacturer's instructions are missing or do not contain necessary information about which side of the film is considered internal, you should independently determine this by external factors. Please note the following:
1 . If the waterproofing film has a different color on both sides, then the light side of the isospan is placed next to the insulation.
2 . The side of the waterproofing that faces the floor when rolled out is considered internal and should face the insulation.
3
. External side it is made fleecy so as not to allow moisture to pass through, and inner side smooth and fits towards the insulation.
Which side should the vapor barrier be placed on the insulation?
Which side to lay the vapor barrier on the floor
Of course, it’s also worth knowing how to install this type of vapor barrier. In this case, as in all others, the sheathing is initially installed. The sheets are mounted on it and secured with self-tapping screws. The joints are taped with tape.
When installing stone wool insulation, it is necessary to use vapor barrier and waterproofing (windproof) films to protect the insulation from vapors and moisture. If this is not done, the insulation will quickly pick up moisture, which will lead to significant loss of it. thermal insulation properties and to rapid spoilage.
There are many manufacturers of such films (Nanoizol, Izospan, Rockwool, etc.), but they are all produced according to similar principles. Vapor barrier is marked “B” in the name, wind protection is marked “A”. These films are attached on different sides to the insulation. Let's consider them separately.
Which side to attach the vapor barrier
The vapor barrier film has one smooth side and the other has a rough structure. This is done so that water vapor absorbed on the film does not collect in drops and flow down, but is evenly retained on the surface of the film and then evaporates again into the air. Otherwise, at the bottom of the wall or pitched roof Accumulations of water could form, causing processes of rotting of finishing materials.
This means that the vapor barrier needs to be installed with the smooth side facing the insulation, and the rough side inside the room.
Which side to attach the windproof film
Windproof film, unlike vapor barrier, has two functions: protecting the insulation from atmospheric moisture, and removing water vapor from the insulation to the outside. Waterproofing (also called windproof) film also has smooth and rough sides. The rough side is designed to absorb water vapor from the thermal insulation and remove it outside. The smooth side should collect moisture and, without allowing it to be absorbed, quickly remove it from the insulation.
Thus, the wind protection is attached with the smooth side outward and the rough side to the insulation.
Don't forget to use tape to hold the pieces together protective films between each other during installation so that moisture does not penetrate to the insulation through the joints.
The installation of any insulation includes the installation of a vapor barrier. It is necessary for all types of materials and is used in any part of the structure.
The need for steam insulation
The main function of a vapor barrier is to prevent the formation of condensation. As a result of human activity, the air in the room is humidified, and the resulting steam penetrates through interior decoration and insulation.
The thermal insulation layer is capable of not only accumulating, but also retaining moisture in its structure. During the cold season, warm steam comes into contact with cold walls or environment, which causes condensation to form. Moistened material loses its insulating qualities.
If the accumulated moisture does not evaporate, but is retained in the material, then consequences in the form of fungus and mold may occur. As a result, such exposure will lead to damage to the thermal insulation. A vapor barrier and room ventilation will help prevent such problems.
Types of materials
Depending on the insulation used, the barrier can be installed indoors up to facing finishing. External execution is also possible, but it has its own characteristics.
Vapor barrier is divided into two types according to the method of application:
- painting;
- film.
Painting products
It can be represented by the following varieties:
- tar;
- tar;
- bitumen.
This type of vapor barrier is applied by painting. It is mainly used on chimneys, ventilation pipes, metal roof slopes. In those places where the installation of other types of insulator is limited.
This is the most common type of vapor barrier. It has a complex multilayer structure that gives good protection from steam penetration. Such products are presented in three types:
- polyethylene;
- polypropylene;
- diffusion membranes.
Polyethylene film does not have sufficient strength, so it is produced in a multilayer version, or reinforced with a special fabric or mesh. The peculiarity of this type is that it completely prevents the passage of steam.
Also, polyethylene film can be produced with a reflective foil screen, which is applied to one side. Such insulation can be installed in rooms with high temperatures and high humidity.
Polypropylene product
The polypropylene product is highly durable. It is a woven base, on which a thin layer of polypropylene is applied on both sides. This film is resistant to UV rays. To improve properties and prevent the formation of condensation, polypropylene is coated with a special compound. The antioxidant layer is applied to one side, and it is able to absorb the resulting moisture and quickly evaporate it if ventilation is present.
Diffusion membranes can be of two types. Conventional vapor barrier is made from two components: polypropylene and polymer film. This type has limited vapor permeability and is also capable of quickly evaporating trapped moisture. The second option is an energy-saving membrane, it is resistant to high temperatures and is capable of reflecting UV rays. Its feature is a metallized outer layer.
Arrangement rules
First of all, it is necessary to decide which side we will lay the material on the insulating layer. To do this, you need to know the features of various vapor barrier materials.
If there are no markings on the surface and there are no instructions, then you can determine which side to lay using some signs:
- the fleecy surface indicates that it is external, in this case the second internal side is smooth;
- when rolling out the roll, the inner side of the vapor barrier will end up on the floor;
- if the insulator has a different color on the sides, then the darker surface is the outer one.
Features of materials
In the case when both surfaces are the same, it does not matter which side to lay the vapor barrier. This applies to ordinary polyethylene films. If there is a layer of foil on one side, it should be facing outwards.
Membranes and polypropylenes usually have a smooth and rough surface. The smooth side should be placed on insulation. If the membrane has a double-sided breathable surface, then it makes no difference which side it is turned inward.
Basic requirements for installation
The main rule when carrying out work is to maintain the integrity of the vapor barrier layer. The material should not have cuts or cracks. To fulfill this condition it is necessary:
- overlap the strips together;
- connect the seams with tape, the width of the tape must be at least 100 mm;
- use wooden slats as fasteners for brackets;
- ensure that the film sag by 1–2 cm.
Following these rules will protect the thermal insulation material from condensation.
Installation
It is carried out after installing the insulation. Work can be done both vertically and horizontally. Installation is carried out in this order.
When working in a vertical direction, the crossing of strips must be arranged on wooden rafters. The overlap of the strips should be 10 cm. A smaller value will lead to a poor-quality joint. All seams must be sealed - this can be done using adhesive tape. Horizontal strips begin to be laid on top.
Then the joints are secured. For wooden structures You can use galvanized nails or staples. Fixation is carried out with clamping strips at the junction of the strips. After installation, vapor barriers are filled wooden blocks. The casing will be attached to them in the future. The bars will provide a ventilated gap between the film and the finish.
Arrangement of individual places
Compound ventilation pipes and roofs. At this point it is necessary to lower the film and wrap the pipeline. Fix the film using tape.
Places of openings: for hatches, skylights a special apron is used. You can also arrange them yourself by gluing tape around the perimeter. For window openings a fold of 20–30 mm should be left. The deformation reserve is carried out in case of settlement.
Installing a vapor barrier is a responsible process. Steam is highly permeable, so it is necessary to provide good protection against its penetration. Insulation carried out according to all the rules will ensure a long service life of not only the insulation, but also the house itself.