It is possible not to use a vapor barrier when constructing housing only if the object of construction is a hut in the forest. When it is necessary to build a permanent house, then one of critical operations will be the installation of a vapor barrier layer. In addition to protecting walls from moisture penetration in Russia, the construction of private houses is carried out using insulating materials.
And vapor barriers allow you to obtain a high-quality barrier to the penetration of cold air into the room, but only under the condition correct placement materials relative to each other. Therefore, a private developer may have many questions, the answers to which cannot always be obtained even from sales consultants, and when using modern materials and from professional builders.
For example, which side should the vapor barrier be placed against the insulation?
Although the likelihood of acceptance the right decision is 50/50, the cost of losing will be too high.
To completely eliminate the possibility of error, you should carefully study the characteristics of the insulation and vapor barrier material. Only with understanding physical properties and mechanical qualities, you can become an expert in the use of insulation and vapor barriers, but to achieve a high professional level, you always need to start from the basics.
Why do you need a vapor barrier?
Water is the most powerful solvent, which has a high specific heat capacity. This liquid is also an essential compound for all life on planet Earth. For a traveler lost in a hot desert, discovering a source of cool liquid will certainly cause a feeling of intense euphoria, but a completely opposite reaction can be expected if high humidity causes the walls in a living room to become covered with a thick layer of mold.
The ability of water, when heated within 100 degrees, to transform from one state of aggregation to another is widely used by man for the production of electricity, steam cleaning of fabric, and up to the 20th century inclusive steam traction used in power plants in transport. Unfortunately, this property of water also has a negative side.
Suspended water particles in the form of steam easily penetrate into any openings less than 1000 nanometers in size. If the insulation of walls, ceilings or floors does not have an additional layer of vapor barrier, then when steam condenses, the moistened material begins to deteriorate over time and lose its thermal insulation qualities.
The negative impact of high humidity is especially strong on hygroscopic materials, such as glass wool. To prevent the destruction of the heat insulator, as well as to prevent the proliferation of pathogenic microflora, behind the layer finishing material lay down vapor barrier material.
It is used not only to protect insulation in residential premises, but is also used in the same capacity when constructing a roof, as well as to prevent the penetration of soil moisture at the stage of laying the foundation.
It is difficult to overestimate the importance of vapor barrier materials in the construction of modern housing, but in order to figure out which side to lay the vapor barrier against the insulation, you need to know about the main types of this material.
Types of vapor barrier materials
In the 20th century, only glassine and roofing felt were used as the main materials used as vapor barriers. Currently, there is no need for such vapor barriers due to the availability of worthy alternatives.
Modern materials have greater strength, less weight, and the cost of many of them does not greatly affect the budget allocated for thermal insulation work.
The main vapor barrier materials include:
- Polyethylene film.
- Polypropylene film.
- Membranes.
- Foil materials.
1. Polyethylene film is the most inexpensive material, which can be used as a vapor barrier. Typically, a material with a thickness of at least 150 microns is used for these purposes.
The disadvantage is low strength and short service life, especially when used indoors where the air temperature is quite high.
The main question that a private builder may have is which side to lay this material The solution to the insulation is very simple: the polyethylene film can be facing the insulation on absolutely any side.
2. Polypropylene film - resistant to low and high temperatures, tear resistant. Usually it has two layers, the outer one is covered with cellulose or viscose (rough structure).
You need to lay polypropylene with the smooth side facing the insulation.
3. Membranes are more durable, but at the same time the most expensive vapor barrier material. The main quality of membranes is their ability to “breathe”, that is, to allow steam to pass in only one direction.
When implementing installation work When using diffuse membranes, it is necessary to correctly attach the material to the insulation. The membrane type of vapor barrier materials must be laid with the smooth side facing the insulation, otherwise the effectiveness of the heat insulator will significantly decrease.
4. The use of a foil vapor barrier is also carried out taking into account a thin layer of aluminum applied to its surface.
The material is always laid with the side free from the metal layer facing the insulation, and the aluminum layer should be directed into the room.
Ceiling vapor barrier
When conducting finishing works a private developer is often interested in the question of correct placement of vapor barrier on the ceiling. The vapor barrier for the ceiling, which side is installed towards the insulation, must be determined before starting practical work.
If you make mistakes at this stage with the placement of the vapor barrier layer and insulation, then over time the insulation will begin to rot. Destruction of the heat insulator will not only negatively affect the effectiveness of the heat-insulating layer, but can also lead to streaks on the ceiling when using plaster for finishing.
It is permissible not to use a vapor barrier on the ceiling only if the house has a heated attic; otherwise, it is recommended that the vapor barrier be laid on the side of the living room.
If a breathable membrane film is used, it is also important to lay this material correctly. Regardless of the location of the insulated plane, such material is always laid with the rough side out. And when laying foil insulation, the metallized layer should be facing down.
Polyethylene film can be used as the main vapor barrier, but care should be taken when handling this material. Polyethylene or propylene film can be accidentally damaged during installation work by any sharp object, which will lead to a complete loss of vapor barrier properties.
It is not recommended to use thin film vapor barrier when insulating the ceiling in the kitchen. In this room, high temperatures can lead to the destruction of a thin barrier and the insulation will become unusable within a short period of operation.
Roof vapor barrier
When arranging a residential attic, you cannot do without high-quality roof insulation, so the issue of correct placement of the vapor barrier layer will also be relevant.
The most suitable material for protecting the heat insulator from moisture penetration is a membrane film. This material also lays on the smoother side of the insulating material. To prevent steam from penetrating through mounting holes, it is recommended to attach the membrane film to wooden beams construction stapler. Only in this way can a high-quality fit of the vapor barrier material be ensured.
In addition to membrane vapor barrier, it is possible to use material with a foil layer. As with ceiling insulation, this material is laid with the heat-reflecting side inside the room. Fastening the material is possible using nails with wide heads. Also, to increase the reliability of the vapor barrier layer at the joints, the seams are additionally sealed using tape.
External vapor barrier of house walls
When insulating walls from the outside, the insulation must also be protected with a vapor barrier. Vapor barrier is necessary primarily to protect the heat insulator from atmospheric moisture, which can also destroy the insulation layer. For external insulation, a double layer of vapor barrier is usually used.
With a properly installed vapor barrier, when installing the outer layer of insulation, the material will be completely protected from the negative effects of moisture.
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 is skipped, the building's structural elements 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?
A special film that protects the heat-insulating material from moisture is necessarily included in the “pie” of the walls or roof. 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 damage to the structural elements of the building.
Depending on the variety, the cost of the material may vary. For example, a conventional 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 of country houses are often 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 make all the 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 of the vapor barrier film and the required overlaps.
How to distinguish the inside from the outside
If the manufacturer’s instructions are missing or do not contain the necessary information about which side of the film is considered internal, then you should independently determine this based on 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
. The outer side 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.
Installation of a vapor barrier is mandatory during the construction of residential buildings: the membrane protects the insulation from vapors emanating from the premises into the under-roof space; on the other hand, the vapor barrier film prevents condensation from draining into the room. Incorrect installation membranes (on the wrong side) are fraught with the accumulation of excessive amounts of vapors inside the room, as well as uncontrolled access of moisture directly under the roof. The insulation will gradually become saturated with water and will cease to perform its functions, and the material of the sheathing and roofing will undergo intensive destruction.
Installing a vapor barrier under the roof
Which side to attach the vapor barrier
Special materials for vapor insulation are available in the form of single-layer films, foamed polyethylene with a metallized coating and two-layer membranes. Their installation has some differences, which is why it can be difficult to figure out which side to attach the vapor barrier to:
- The polypropylene film is installed with a rough surface to the under-roof space. This insulation texture will collect moisture, which will evaporate through the ventilation gap. However, its size must be at least 20 mm. If the film is the most common (polyethylene), its sides will be identical.
- The two-layer membrane is laid with the smooth side facing the thermal insulation. For ease of use, manufacturers often apply special markings to the underside of the fabric.
- One-sided laminated polypropylene is also directed with a smooth surface towards the insulation.
- The foil side of the special films is turned towards the insulation.
Considering the variety of vapor barrier materials on construction market, difficult to compose comprehensive guide according to their installation. detailed information usually contained in the instructions provided by the manufacturers. But still, there are two more general rules:
- If the instructions are unclear and the film is colored different colors, the lightest tone should be turned towards the insulation.
- Many materials are rolled up so that the side that ends up at the bottom when it is rolled out can be immediately placed on the thermal insulation.
Main stages of installation
For pitched roof There is a certain sequence according to which a high-quality vapor barrier is installed. It is installed after laying the insulation, the surface of which should be free of defects. The beams for the sheathing are treated with antifungal compounds, after which a pre-calculated amount of film is prepared (covered area + 15%) and the following:
- construction stapler;
- special double-sided tape for insulating and fastening fabrics;
- construction/stationery knife;
- self-tapping screws;
- roulette;
- single-sided adhesive tape for joints, defects and crevices (from the same manufacturer);
- screwdriver;
- pencil;
- scissors.
On the rafters, between which the thermal insulation boards are laid, fill the lower part of the sheathing with two boards. Apply a strip of special tape with two adhesive sides. Cut the roll into sheets of appropriate length. Then, starting from the bottom of the sheathing, lay the membrane horizontally with the markings up on the insulation, slightly stretching the panel.
- Attach the edges of the canvases to the rafters using a stapler.
- Release the top layer of the tape and carefully glue the bottom of the film to the sheathing.
- Stepping back 15 cm from the top, stick the next piece of tape without removing the top protective layer yet.
- Having secured the edges of the membrane with staples, glue the overlap, gradually removing the protective layer from the film. In this case, the film must be straightened.
- Lay the required number of rows in a similar manner. Cover the ridge with a solid sheet, making a sufficient overlap, avoiding the joint at the corner. Cover the other side of the roof in the same way.
- The laid membrane is additionally secured along the edges of the roof using beams with a section of 3x5 cm. This is important, because the specified parameters are necessary to create an optimal ventilation gap. Condensation will escape through it.
- Mount the sheathing, securing the beams with self-tapping screws.
- Install roof covering, paying special attention to ventilation in the area of the ridge and cornice.
When laying the membrane, it is necessary to ensure the integrity of its surface. If defects are found in the fixed area, the damaged blade should be replaced or (if the damage is minor) sealed with mounting tape.
Features of installing a vapor barrier for wall insulation
It is necessary to install a vapor barrier on the walls only if mineral insulation is used and/or their outer surface is located on the street. It is especially important how to properly install the vapor barrier film on the walls. To do this, using the above accessories, do the following:
- position it with the appropriate side and carefully secure it to the sheathing, being careful not to damage the surface;
- carefully glue puncture sites, overlaps and possible cracks;
- install the sheathing using beams with the cross-section indicated above to create ventilation;
- cover the structure with wall panels, plasterboard or other finishing material.
A vapor barrier is a layer that protects insulation or building structures from the penetration of wet steam, which in turn leads to the accumulation of condensation on them, loss of beneficial properties and rotting under the influence of moisture. To create a vapor barrier, completely impenetrable double-sided or having one correct work surface films and canvases. It is extremely important to determine exactly which side to place the vapor barrier on the insulation; a mistake at this stage provokes accelerated destruction of building materials and significant financial costs. The main guideline is the manufacturer's instructions, but often this document is not available upon purchase; the choice is made taking into account the type of vapor barrier film and installation conditions.
- How is vapor barrier installed?
- Technology violations
- Tips and tricks
For ordinary or double-sided reinforced polyethylene, this problem is not relevant; in other cases, the working surface is a vapor-impermeable surface. Most often, the vapor barrier is laid with the smooth side facing the insulation, and the protected side facing the source of steam penetration. Depending on the type of materials it is:
- Laminate on cardboard (it is not recommended to place it on critical objects).
- Reflective side of foil and aluminum roll coverings.
- A fleecy or rough surface of antioxidant films coated with viscose or cellulose.
- The vapor-tight side of the membranes is usually brighter.
1. Laying a vapor barrier on the floor.
Protection from steam and moisture is required when insulating floors or horizontal planes, or assembling timber structures. Reflective films that return heat to the house are considered optimal for flooring. When constructing or repairing the first floors, the insulation is protected with a layer of waterproofing, and on top - with rolled vapor barrier materials, laid overlapping (from 10 cm and above) with sizing with metallized tape. The situation is slightly different when arranging attic floors and interfloor ceilings: the films are turned with the impenetrable side down to protect against steam penetrating through logs or slabs.
2. Vapor barrier of ceiling structures.
Most often, the need to close the ceiling arises in baths, saunas, kitchens, showers and other structures with high humidity. The greater the volume of vapors released and the higher their temperature, the more reliable vapor barrier is required from them. To protect steam room ceilings, dense aluminum, lavsan and antioxidant vapor barrier materials are well suited for living rooms- the same, plus regular penofol. Required condition There is an overlap of at least 10-15 cm and sealing of the joints; for reliability, the vapor barrier is fixed to the ceiling with gratings or staples. IN in this case the reflective or vapor-tight side is directed exclusively into the room.
3. Vertical structures.
Installation of a vapor barrier when insulating walls is necessary when: using fibrous and cotton wool insulation, erecting frame wall panels, arranging ventilated facades; in the latter case, it also performs the functions of wind protection. In all the points mentioned, it is not recommended to choose completely impermeable films; the insulation must breathe, the best option Diffusion and superdiffusion membranes are considered to be permeable to air, but not to moisture or steam. For exterior work, the vapor barrier is laid with the smooth side facing the mineral wool or other insulation on the walls, and the rough side facing the street. The film or canvas should not sag, but excessive tension is also unacceptable. On internal vertical walls they are held in place by staples or upholstery with thin strips, the vapor-tight side facing the room.
4. Roof vapor barrier.
A vapor barrier is a mandatory layer when laying a roofing pie. It prevents the accumulation of condensation in the inner insulating layer and protects the rafters from fungus. The vapor barrier requires the greatest possible tightness, preference is given to antioxidant and reflective types, the side impenetrable to vapor is directed inward attic space. Overlap - from 15 cm, as well as gluing joints and seams. An important condition is the need to seal vapor barrier materials adjacent to vertical structures.
5. Other applications.
A vapor barrier is also needed for insulation basements and balconies (areas in contact with cold external surfaces. For basement and underground areas, membrane films are considered the best; the walls and ceiling of the basement must breathe, the floors are insulated on the ground side. For the installation of vapor barriers when insulating balconies and loggias, preference is given to foamed polyethylene with a reflective side, directed into the apartment. This is almost the only case when materials are placed end-to-end and not overlapping, but sealing adjacent areas is still required.
Possible mistakes
In addition to choosing the wrong side, violations of technology include:
1. Lack of overlaps or insufficient insulation of joints.
2. Pulling thin films, especially on structures exposed to temperature changes, leads to their rupture. But excessive sagging is also not required.
3. Lack of ventilation gaps for evaporation of condensate from the vapor-tight side of the film ( shining example mistakes - installation of internal cladding directly on the bottom layer of the roofing pie).
Before laying a vapor barrier, you should calculate it required quantity. Usage different types undesirable, although there are no clear standards in this case. A common mistake is to buy rolls strictly according to the area of the working surfaces without a 15% margin for overlaps and trivial damage.
There is only one option when it is not necessary to install a vapor barrier - when building a house from wooden beams, but this exception does not apply to absorbent insulating materials and floors; they always need protection. The work is carried out in the warm and, if possible, dry season, the films are protected in every possible way from getting wet. An important condition is that the vapor barrier is tightly connected to the insulation (ventilation gaps remain on the outer, reflective and impenetrable side), voids and sagging are unacceptable. All surfaces must be clean, grease-free and dry.
If you are in doubt about the correctness of the decision regarding which side to lay the vapor barrier against the insulation, you should read the instructions again. Reflective and rough planes are easy to determine, with membranes it is more difficult. Typically, the side facing down when unrolling the roll is considered to be the inside side. Experts advise paying attention to the coloring: lighter shades are observed on the sides adjacent to the insulation. But there is a variety in which it is the matte (usually fabric) surface that is vapor-tight. If this is not enough to identify the desired properties, then the canvas or film is rolled out a little on the floor, the tight-fitting side of the material will be the inner one.
During construction country house or private bath An important step is thermal insulation various surfaces. In addition, the insulation itself needs high-quality and reliable vapor barrier protection. To prevent the negative impact of external factors and the formation of condensation on the thermal insulator, any homeowner should have a general understanding of how to properly install a vapor barrier to ensure the long life of the entire structure.
Membrane structure and operating principle
The most popular for their performance characteristics are breathable multilayer membranes, which are designed to create reliable vapor barrier protection.
They consist of three layers, each of which performs an important function. The first layer prevents the penetration of steam into the insulation, the second provides the necessary strength of the base, and the third protects against moisture from the outside.
Each individual layer has the necessary perforation for good air exchange. The first layer removes excess moisture, allowing dried air to penetrate. The reinforcing layer retains warm air masses inside thanks to a special weaving of threads. The third layer provides a sufficient level of traction inside the structure.
Some types of membranes have an additional anti-condensation layer based on viscose or cellulose. She holds excess moisture, deposited on paper fibers. For natural removal of moisture from the membrane, it is provided technological gap 2.5 cm between the vapor barrier and finishing surfaces.
Features of vapor barrier installation
An important stage in protecting insulating materials is laying a reliable vapor barrier layer. All work is carried out during the repair or reconstruction of a finished building or during the construction of a new building. To correctly install a vapor barrier, you need to understand how to connect membrane sheets and which side to fix them to the insulating base.
Preparatory work
At this stage, work is carried out to select the appropriate type of vapor barrier, taking into account the features of the installation process, operational characteristics and material requirements.
Before laying a vapor barrier, careful surface preparation will be required. It is important to consider the type of material used in the construction of floors, walls, ceilings and roofing structures.
- During the construction of a log house, everything structural elements are being processed protective antiseptics and fire retardants.
- When carrying out repair and reconstruction work, complete dismantling is carried out finishing, cleaning and preparation of surfaces:
Wooden elements are treated with compounds against aging, rotting and burning. Concrete, block and brick surfaces are treated with antiseptic compounds deep penetration.
Proper preparation of surfaces will ensure a long service life of the insulating material and the entire structure.
Technology for laying vapor barrier on the ceiling
If the roof structure and interfloor ceiling are made of wood, then the installation of a membrane for waterproofing is carried out on a prepared base.
Roll or block insulation is installed in the space between the rafters and joists; the best option is mineral or basalt wool. Next, you can lay vapor barrier protection on the ceiling surface.
When the thickness of the insulation is equal to the height of the logs, an additional slatted counter-lattice is installed to maintain natural ventilation.
It is necessary to install a vapor barrier on the ceiling with a slight overlap on the walls around the perimeter, and special attention should be paid to the corners. It is better to place the joints on the joists and glue them on both sides with tape on a reinforced base.
Important! When installing a vapor barrier, sagging and deformation of the panels should be avoided.
For thermal insulation flat roof or a concrete ceiling, a waterproofing film is mounted from the inside on a self-adhesive tape, then a lathing made of wood or metal is installed.
The height of the sheathing is determined based on the thickness thermal insulation material and minimum technological clearance for ventilation. The installation step is 3 cm narrower than the width of the heat insulator, which allows for high-quality installation of the insulator into the prepared sheathing cells.
Technology for laying vapor barrier on the floor
The installation scheme for vapor barrier protection on the floor is similar to how the material is laid on wall and ceiling surfaces.
The wooden floor is insulated using joists, on which a waterproofing layer is laid. Next, insulation is placed in the space between them - wool on a mineral or basalt basis. After this, vapor barrier material is laid.
The rolled material must be laid with an overlap of 12 cm, with the joints carefully sealed with metallized tape on both sides. A properly laid vapor barrier should completely cover the floor surface with an overlap of up to 10 cm on the walls.
To install a vapor barrier on a concrete base, you will need to install a sheathing, in the cells of which a waterproofing layer and a heat insulator will be laid.
Choosing a side for installing a vapor barrier
Once the material for the vapor barrier has been selected, an important question to consider is which side to attach the vapor barrier to the insulation. Such materials can be fixed as follows:
- Polyethylene films (reinforced and plain) are laid on any side, which does not impair the protective properties of the material.
- Foil films are installed with the reflective side facing the inside of the room to effectively reflect heat.
- Anti-condensation films are mounted with a fabric surface inside the room, treated - to a heat-insulating base.
- Membranes of any type are attached with a smooth surface to the heat insulator, and with a rough surface - inside the room.
- Foam-based insulators are laid similarly to membrane materials.
Important! Before laying the vapor barrier to the insulation, it is recommended to lay out the prepared material on a flat surface to correctly determine the inner and outer sides.
The face or the back of a vapor barrier?
If a breathable membrane is used to create a protective barrier, the main thing is to determine which side to lay the vapor barrier on - face or back.
The vapor barrier cake must be placed so that the protection is directed towards the heat insulator on both sides with the smooth back side, and with the rough front side facing the inside of the room.
The rough surface provides protection against moisture penetration into the insulation, and smooth surface promotes maximum heat accumulation.
Determining the width of the overlap when installing the membrane
There are special markings along the edge of the insulating membrane to determine the width of the overlap of the sheets, which ranges from 8 to 20 cm.
The vapor barrier strips on the roof should be laid in a horizontal plane from bottom to top, overlapping each other with a width of 15 cm. At the ridge the overlap is 18 cm, at the valley - 25 cm.
On walls, ceilings and floors, the canvases are mounted with an overlap of 10-15 cm.
Is a layer required for ventilation?
At the bottom of the membrane vapor barrier there is a 5-centimeter ventilation gap, which helps prevent the formation of condensation on surfaces and the heat insulator.
Diffusion membranes can be attached to insulation, plywood sheets or OSB. In a membrane with an anti-condensation layer, gaps up to 6 cm wide are located on both sides.
To create a gap for ventilation when insulating the roof structure, a counter-lattice is used. In the process of fastening a ventilated facade, a technological gap is created when installing racks located perpendicular to the vapor barrier.
Elements for fastening vapor barrier
To securely fasten membrane or film vapor barriers, wide-headed nails or metal construction staples are used. Most practical option fasteners - counter rails.
To increase the tightness of the structure, individual vapor barrier elements are additionally glued with double-sided adhesive tape or wide metallized tape.
To ensure long service life modern insulation materials, you will need high-quality vapor barrier protection. Otherwise, it will be difficult to obtain the optimal ratio of temperature and humidity indicators in the premises. The main thing in this matter is to choose the right material and know how and which side to lay to the heat insulator.
A fairly common problem after insulating a house is the lack of the expected effect from the work performed. It would seem that a traditional material has been chosen, e.g. mineral wool, everything is done according to building laws and canons, but it’s still cold inside the room. The reason for this may be the ignorance of “specialists” about basic standards, including which side of the insulation to lay the vapor barrier. Let's look at this issue in more detail.
Vapor barrier is divided into two types according to the method of application:
- liquid paint vapor barrier;
- vapor barrier membranes (film).
Painting vapor barrier is applied using brushes and rollers in places where roll vapor barrier is difficult to use, for example, on ventilation and chimneys. This family of vapor barriers is represented by materials such as bitumen, tar and tar.
Vapor barrier membranes
First of all, let's define the types of vapor barrier films according to their purpose. According to their specificity, membranes used in construction are offered in the following versions:
- membranes with vapor barrier properties;
- membranes are vapor permeable.
To protect the mineral wool from exposure to moisture from the inside, it is necessary to additionally lay a layer of vapor barrier. When insulating a roof, floor or internal space house located directly below it, it is recommended to use an appropriate film. Note that the insulating layer is laid from below, under the laid mineral wool (from the side of the room).
In cases where external protection of walls is carried out, the corresponding components must not have perforations or pores.
Always pay attention to the value of the vapor permeability coefficient; the lower it is, the better for you. An excellent option is regular plastic film. The ideal choice would be a material with additional reinforcement. Availability of foil aluminum coating only considered a plus.
Do not forget that the presence of a vapor barrier finish leads to a multiple increase in humidity in the insulated space, so you should take care of a good ventilation system in advance.
Polyethylene reinforced film
Existing special vapor barrier films are made with an antioxidant coating. Due to this, moisture does not accumulate. As a rule, they are attached under components that are sensitive to rust formation. It's about about metal tiles, corrugated sheets, galvanization, etc. The rough fabric layer on the back of the film guarantees effective moisture removal. It is laid with the treated side facing the insulation, and the fabric side facing out, so that there is a distance of 20-60 mm to the mineral wool.
https://youtu.be/xTWpLwH8-QI
Video No. 1. IZOSPAN vapor barrier laying technology
When insulating the walls of a house from the outside, a building membrane is used that can carry out evaporation and protect the material from strong wind gusts. In addition, it is suitable for protecting pitched roofs and facades with a leaky base from moisture. Often, the vapor barrier film has very small pores and surface perforations, due to which water is effectively removed from the insulation into the ventilation ducts. The more actively the vapor removal occurs, the better the process. This will allow the insulation to dry quickly and efficiently.
The following types of vapor-permeable films are distinguished:
- Pseudo-diffusion membranes that transmit no more than 300 grams/m2 of evaporation over 24 hours.
- Diffusion membranes, with a vapor permeability coefficient in the range of 300-1000 grams/m2.
- Superdiffusion membranes, with an evaporation rate of more than 1000 grams/m2.
Since the first type of insulation is considered good protection against moisture, it is often located under the roof surface as an outer layer. Additionally, it will be necessary to provide an air gap between the insulating layer and the film. At the same time, this component is not suitable for facade processing, since it conducts steam quite poorly. This is explained by the penetration of dust and other debris into the pores of the membrane during dry times, the “breathing” effect disappears and condensation begins to accumulate on the surface of the insulating material.
Superdiffusion membrane IZODACH 115
The two remaining types of membranes have large pores, this eliminates the possibility of their clogging, which is why there is no need to leave an air ventilation layer in the lower part. As a result, there is no need to install sheathing and counter battens.
Three-dimensional diffusion films are available for sale. A ventilation layer is already provided inside the membranes, due to which moisture will not be able to reach metal surfaces. The specifics of the film structure are similar to the antioxidant version. The only difference is the removal of moisture from the insulation. This is beneficial because when the roof is tilted, even at a slight angle of 3-15 degrees, the possibility of condensate draining through the bottom is eliminated. Therefore, corrosion of the galvanized coating will gradually occur, followed by its final destruction.
Which side should the vapor barrier be attached to the insulation?
First you need to figure out in which places you may need to lay a vapor barrier membrane, and then decide on the side of the vapor barrier.
- If insulation is installed from the front part of the wall, then the vapor barrier film is fixed from the outside, this will be waterproofing.
- Treatment of the ceiling and roof requires the use of an antioxidant vapor barrier. Volume and diffusion coatings are often used. They are laid on top of the mineral wool according to the principle of organizing a ventilation facade.
- With absence additional insulation roof and ceiling vapor barrier film is attached to the underside of the rafters.
- Thermal insulation of the upper part of the ceiling of rooms, ceilings located under attic space, requires laying a vapor barrier membrane on the underside of the insulation.
- When insulating walls and floors from the inside, it is recommended to additionally lay a vapor barrier film on the outside of the mineral wool.
Many “experienced” builders have no idea how the vapor barrier membrane should be attached to the walls: front side or back side.
The best solution would be to use a material with the same back and front sides.
What to do in the case of a one-sided option, in particular with antioxidant insulator? You need to know that the wrong side is the fabric surface located during installation in the inside of the room.
Determining the side of installation of vapor barrier
The metal plane faces in the same direction foil membrane– shiny side towards the inside of the room.
For any film vapor barrier materials The following rule applies: the smooth side is laid against the insulation, while the rough side must face the room.
The same rule applies foam-propylene vapor barriers, which are placed with the smooth side to the insulation.
The vapor barrier is laid with the dark side facing the insulation
It must be borne in mind that when rolling out a roll, for example, on the floor, the inner side should be on the floor.
In addition, most often the darker side is the outer side.
Is there a need for an air gap at the membrane?
You should always leave it on. A special gap up to 50 mm wide is arranged on the bottom side of the films. This will prevent condensation from appearing on the walls, floors and insulation. It is important to avoid contact of surface cladding with the membrane. By using diffusion film for floors, walls or ceilings, you save yourself from many problems, since it can be fixed directly to thermal insulation, OSB or moisture-resistant plywood. A ventilation layer will be required on the outside of the membrane. In the version with an antioxidant component, the air gap should be within 40-60 mm on both sides.
Organization of a ventilation gap when laying vapor barrier
If everything is clear with the walls and floor, then with the roof and ceiling the situation is different. When creating a ventilation gap, additional installation of a counter-lattice based on wooden blocks will be required. When organizing a ventilated facade, a gap is left during the construction of horizontal profiles and racks located perpendicular to the wall and film.
Video No. 2. ONDUTIS vapor barrier laying technology
How is the vapor barrier attached?
The membrane can be fixed to the walls, floor or ceiling using nails with a wide head or a construction stapler. However best choice will be the use of counter rails.
The vapor barrier is laid in an overlap with an overlap of at least 10 cm. After the vapor barrier is secured, the joints are taped with special tape or vapor barrier tape.
Conclusion
In conclusion, let's say that membranes will allow any building structure serve to the utmost long term. Unfortunately, it is impossible to achieve a positive ratio of moisture and temperature in other ways. In addition, do not forget about the rules for installing vapor barriers. Most manufacturers also distribute installation instructions along with the product. This is especially true for diffusion and superdiffusion membranes. Therefore, do not be lazy before purchasing to clarify with the sales consultant all the questions that interest you.
Insulation is a very important stage in the construction or renovation of a house, which determines whether you will be comfortable staying in it. Improper implementation of this “procedure” can lead to unpleasant consequences, for example, the release of condensation, increased humidity in the air. But this will not happen if you take care of the vapor barrier and install it right side to the insulation.
Peculiarities
When insulating a house, you should carefully follow the correct sequence of actions and use only the most best materials. Unfortunately, often owners who undertake to insulate their home themselves forget about one very important thing: important aspect– about the vapor barrier. They install only insulation and don’t even think about the fact that it comes into contact with too warm or too cold air inside the room, and that condensation in the form of water droplets will soon begin to form on it.
And this not only does not contribute to insulation, but also spoils the material itself - it moisturizes it, and if the steam does not yet have time to evaporate, mold appears and the insulation structure deteriorates. Moreover, taking into account our climatic conditions, a similar situation occurs at least four times a year - when the seasons change and, accordingly, the temperatures in the room and outside “conflict”, and the insulation becomes the battlefield.
That is why an important stage of insulation is the installation of a “vapor barrier”. The vapor barrier becomes an impenetrable obstacle to steam, preventing it from turning into water, as it “closes” it inside the room and prevents it from coming into contact with excessively warm or excessively cold air.
Materials
Vapor barrier can be made using several materials. From this set, three main types should be distinguished.
- Film. A solid vapor barrier that does not allow water vapor to pass through. One of the main advantages is low price. As a rule, it is made from polyethylene or butylene, their derivatives. Vapor-condensate films are two-layer with a smooth inner and rough outer surface. Lingering on the outside, drops of condensate do not flow down, but evaporate over time. In the case of a solid vapor barrier, you also need to take care of the air gap in order to avoid the greenhouse effect, but more on that later.
- Diffusion membrane. The main difference from film is that the membrane allows some of the vapor to pass through itself - but only the optimal amount that does not linger inside and evaporates instantly. Therefore, the vapor permeability of membranes is usually considered limited. The diffusion membrane is made of polymer film and polypropylene and has two sides.
- Reflective or energy-saving film. The outer layer of this film is metalized, which allows it to withstand high temperatures. Therefore, it is most often used in baths or saunas, reflecting part of the infrared radiation.
As is known, to insulate houses in modern conditions materials such as mineral wool, polystyrene foam, and ecowool are used. Vapor barrier is also needed in the case of mineral wool insulation.
In fact, vapor barrier is always needed, no matter how expensive or high-quality insulation material you use. Mineral wool or mineral wool is otherwise the cheapest material, but its level of thermal conductivity is low, which reduces the likelihood of heat loss in the room. Rodents, mold, and mildew do not like mineral wool; it has high sound insulation and is easy to install. But it still requires a vapor barrier.
The most commonly used is a vapor-permeable limited diffusion membrane. It is laid against the walls, after which you need to lay mineral wool, and in symbiosis they allow the walls of the house to “breathe”.
The question of vapor barrier also arises when insulating a house with ecowool. In general, ecowool is loose cellulose fibers that have the ability to absorb warm moisture and still remain dry. Fungus and mold do not grow on it, the air in it simply does not get wet (if changes in humidity do not exceed 25% percent). From all of the above it follows that in the case of ecowool, the vapor barrier need not be attached.
Another popular insulation material, polystyrene foam, actually has another more common name: polystyrene foam. It applies to both external and internal surfaces, and in the case of external insulation of loggias, balconies or attic floors, it does not require a vapor barrier - it itself copes well with this if the insulation technology is maintained. But if you insulate with foam plastic interior spaces, vapor barrier and waterproofing are required to avoid the formation of fungus, mold and wetting of the walls.
Device
Purchasing a set of quality materials is only a third of success. In fact, these materials need to be installed correctly and arranged in the correct sequence. It is for this purpose that you should find out which side the vapor barrier is laid, how it is fixed, in what order, and what to nail first - a vapor barrier or insulation.
First you need to carry out preparatory work. At this stage, the type of coating that you will insulate is determined, it performance characteristics and requirements for insulation and vapor barrier materials.
So, the surface needs to be carefully prepared. This takes into account the type of material from which it is made. Wooden elements must be treated with compounds against aging, rotting and burning. In the case of concrete and brick, it is possible to use antiseptic compounds of deep penetration. Half the success in its operation depends on proper surface treatment.
If you are carrying out repairs or reconstruction, then pay attention to the fact that before insulation, all traces of the previous finishing must be removed and a complete cleaning must be carried out. And if we are talking about a log house, then all elements must be treated with fire retardants and antiseptics.
Vapor barrier on the ceiling
In the case of roofing structures and interfloor covering The installation of a vapor barrier is supposed to be on an already prepared and properly treated surface. It is best to use a diffusion membrane here.
The main difference between laying a vapor barrier on the ceiling and laying it on other surfaces is that in this case the insulation is laid first, and only then the membrane. This can be mineral or basalt wool in blocks or rolls. It is mounted between the joists and rafters. If the thickness of the insulation is equal to the height of the logs, you will need to additionally install a slatted counter-lattice so that the ceiling is ventilated. After all this, you can work on the vapor barrier.
It should fall slightly onto the walls around the perimeter, the joints should be fastened to the joists - to ensure that moisture does not get into the space between the membrane and the insulation. Pay special attention to the corners - this problem areas, it is better to seal them additionally. Use reinforced tape or a construction stapler as a fastener.
In the case of flat roof insulation or concrete ceiling You can also use a regular vapor barrier film from the inside. It is attached to self-adhesive tape also after the insulation, and then the sheathing is installed - metal or wood.
Vapor barrier on the floor
In the case of laying a vapor barrier on a wooden floor, additional waterproofing must be installed. The floor is also insulated along the joists. Mineral wool or basalt-based wool is installed in the space between the logs. Further without any additional work vapor barrier flooring is being installed.
If we are talking about a rolled vapor barrier, it is laid with an overlap of 12-15 cm with the joints, gaps and cracks glued on both sides with metallized tape as thoroughly as possible. As in the case of ceiling insulation, the overlap on the walls should be within 10 cm.
For a concrete floor you will need sheathing. You will need to lay a waterproofing layer in the cells of the sheathing, a heat insulator on top, and after the mineral wool, the third layer is a vapor barrier.
Vapor barrier on walls
The process of insulation and vapor barrier of walls is a little more complicated than performing the same work on the ceiling or floor and involves a slightly larger number of stages. Let's look at the installation process vapor barrier film on the walls.
First of all, a frame is mounted from small cross-section bars. The size of the sheathing is determined by the width of the heat insulator block - the distance between the cells is equal to the width of one slab. Classically, mineral wool is used.
At this stage, you should pay special attention to possible gaps that arise due to the difference in the width of the insulation, frame and vapor barrier. The cracks are sealed with reinforced tape, and the sheets of film are glued horizontally with a 15 cm overlap.
Installation subtleties
When installing a vapor barrier, special attention should be paid to important issues.
Which side should the vapor barrier be laid?
Very often masters find it difficult to answer this question, but everything is not so complicated. Ordinary film has the same front and back sides - and then it doesn’t matter which side it is laid on. But in the case of single-sided films, the situation is a little more complicated.
For example, antioxidant films have a fabric backing, and according to installation requirements, it must face the inside of the room. Vapor condensate films must be laid with the smooth side facing the insulation, and the rough side facing outwards. But with diffusion films, you should look directly at the instructions, since such films can be either one-sided or double-sided. Energy-saving films are laid with the foil side, on the contrary, outward - after all, they should reflect and not absorb heat. The same applies to metal coatings.
How to distinguish outside from internal?
This information should be indicated in the instructions or on the manufacturer’s website; you can ask a consultant or technician about this. However, if none of the above suits you, you will have to learn to determine the sides of the vapor barrier yourself.
So, remember: if the vapor barrier has two-color sides, then the light side will always fit against the insulation.
But also pay attention to how the vapor barrier roll is rolled out - the side facing the floor will be the inner side, and it should be placed against the insulation. In the case of a vapor barrier with different surface the smooth layer will always be internal, and the fleecy or rough layer will always be external.
What kind of fastener should I use?
This can be either a regular construction stapler or nails with a wide head, but counter-battens are considered to be the best option.
Is an air gap necessary near the membrane?
It is believed that this is a mandatory point - it is absolutely forbidden for the wall to come into close contact with the membrane; a gap of about five centimeters should be left for ventilation. Condensation will not accumulate this way. In the case of a diffusion vapor barrier, the air layer is made with outer side, and the film itself is laid directly on the insulation.
Do I need to tape the joints?
This is also mandatory - the individual parts of the vapor barrier should be hermetically connected to each other without forming gaps, the same applies to the places where the vapor barrier is attached to windows or doors. For this, self-adhesive tapes are used - double-sided or single-sided - usually made of polyethylene or butylene, propylene. These tapes not only perfectly hold membranes together, but are also used in their repair - they can be used to seal holes and cracks.
Under no circumstances use tape for this; it is better to contact a sales consultant at a building materials store or go to the website of the company from which you purchased the vapor barrier - as a rule, companies produce materials for repairing their products.
The main purpose of a vapor barrier is to prevent water pores from leaving the room through the insulation and surfaces. This means that the vapors, one way or another, remain in the room, and in order to prevent the humidity from increasing and the microclimate from being disturbed, it is necessary to carry out natural or forced ventilation in a timely manner.
If you are interested in the question of what kind of overlap to make if parts of the membrane overlap each other, then we advise you to pay attention to the films themselves. There are markings along their edges - they indicate how exactly the overlap of the films should be. Depending on the type and company, the value indicated there is no less than 10 cm and no more than 20.
And also pay attention to the angle of the roof slope. If it is less than 30 degrees, the overlap cannot be more than 10 cm. If it is less than 20 degrees, the overlap cannot be less than 20 cm.
For information on installing a roof vapor barrier and which side to lay the vapor barrier against the insulation, see the following video.
If, when insulating a building, you do not use a vapor barrier, then the insulation itself will last a very short period of time.
Moisture will begin to enter its layers and will carry out the process of destruction. This procedure very often occurs when it is cold outside, then large temperature differences occur inside and outside the room.
In order for the vapor barrier to be installed on the walls correctly, you should know its features, because not every side of the film can be used.
Purpose of vapor barrier
Vapor barrier will protect the house from condensation Today, a pressing issue is saving money on paying for gas and electricity. To save money, more and more people are insulating their houses and apartments, and to protect the insulation itself from moisture and steam, vapor barrier materials should be used.
What exactly they are needed for can be found in the table:
| № | Basic moments | Description |
|---|---|---|
| 1 | Vapor barrier preserves the building and the health of residents. | Thanks to protection from moisture, metal and wooden structures will serve for a long time and will not be subject to corrosion and rotting. In addition, using the film will not cause mold or mildew to appear in the house. |
| 2 | If the house is insulated from the outside, then a vapor barrier may not be used. | In this case, a vapor barrier will need to be installed on the floor, ceiling or roof. |
| 3 | If insulation is carried out inside the building, the vapor barrier is laid on insulating materials. | In this case, the insulation can last a long time and will not collapse. |
| 4 | Vapor barrier can be installed inside and outside. | If you ignore installing a vapor barrier, then in addition to moisture, heat will escape from the house. |
Knowing the main tasks of a vapor barrier, we can safely say that its installation is a must in any home, but to carry out the work on your own, you will need to know the features, as well as carry out a number of preparatory measures.
In the case when insulation work is carried out from the street, the protective material must also be laid outside the room. If it happens inside the house, the film is also installed indoors.
Preparatory work
IN wooden houses use membrane films When preparing the protection of the house and insulation, you should start by choosing the vapor barrier itself, which will be used in the future. Today the choice is quite large, and films can be used not only for walls, but also for floors, ceilings, floors and other parts.
If the building is made of wood, then it is better to use films with membranes. If the base is brick or concrete, then other types of films are possible, among which are:
- Polyethylene. Most cheap option. Using such a vapor barrier will require constant ventilation.
- Polyethylene with aluminum. Used to reflect thermal energy.
- Reinforced polypropylene. Available in 1, 2 and 3 layers. The composition includes viscose and propylene. This material has one side smooth, the other fleecy.
- Diffuser membranes. Protect from moisture and release it outside. The film retains heat well and “breathes”.
Install insulation on walls impregnated with protective solutions Incorrect preparatory work will lead to low efficiency of the film itself. Preparation will depend on what the house is made of, namely the walls. If the house is just being built, and wood is used as the main material, then all elements must be impregnated with insecticides, mold, mildew and fire repellents. After impregnation, you can begin constructing and insulating the walls.
If the building is made of concrete, then there is no need to use impregnation. It will be enough to clean the surface from mold, mildew and dust. Next, the base will need to be checked for cracks and holes; if there are any, then putty them.
Vapor barrier films must be protected from contact with sun rays, since after 3 months under the sun the insulation will be unusable and its properties will be lost.
In general, installing a vapor barrier is simple and does not require any special skill. When the preparation is completed, you can begin to work, but you need to know that the film must be overlapped and additionally glued with tape.
This allows you to close access to air. Particular care must be taken to cover the areas adjacent to various openings. If a film with a foil layer is used, then the corresponding adhesive tape is also used.
Select adhesive tape according to the type of material After purchasing the film, you need to read the instructions, namely which side should be laid to the insulation, but in practice such information is not always available and to determine the front side you need to pay attention to the following factors:
On the wall, follow these instructions:
- The film is applied to the wall and fixed with a stapler.
- The next part is overlapped and also secured with staples. All parts of the vapor barrier should not be tensioned; the film should be laid loosely to leave room for ventilation.
- When the film is laid on the walls, all joints are covered with tape, which will provide maximum sealing.
During operation, tearing of the film is not allowed; if this happens, it is better to change the part or securely seal it with tape. The film itself must be dry before use. If you have to lay the film in winter, then the heating in the house must be on.
If the work is done correctly, then there will be no need to maintain the film, and the walls will serve for a long time without repair. The work of laying film on the floor and ceiling is somewhat different, but in general the essence remains the same. For more information on how to properly install a vapor barrier, watch this video:
During work, a certain supply of vapor barrier should be left near the openings. It is necessary if shrinkage or deformation of the house occurs. For reserve, a fold is made with dimensions of about 3 cm.
Read about the features in other articles on the site.
In order to properly carry out the work of laying a vapor barrier, you will need to study why such material is needed. Knowing the features and installation method, you can do the work yourself, in just one day.
