Purpose and location of the vapor barrier
It is known that the roofing cake consists of several layers (that's why it is called that). It can include a different number of interlayers, but hydro, heat and vapor insulation remain unchanged. And if the waterproofing is designed to prevent moisture from above to penetrate inside the house, then the vapor barrier does not allow vapors from the inside to get into the roofing cake.
It is extremely important to place the vapor barrier below the thermal insulation material, as otherwise it will absorb the vapor coming from the bottom, swell and damp. However, we all know that there are non-insulated roofs, can they really be done without vapor barrier? Unfortunately, no - the vapor barrier not only preserves the insulation, but also maintains a comfortable indoor microclimate. If it is not there, the house will be very stuffy and humid, and the cozy home will turn into an ordinary greenhouse.
To fully appreciate and understand the roof vapor barrier, you should study the structure of the roofing cake:
- The roof covering can be continuous or consist of segments (tiles, slate). It is laid on a wooden crate or a monolithic base.
- Waterproofing layer - protects subsequent layers from moisture penetration from the outside. It is a waterproof non-woven fabric that is attached to the batten, leaving a small gap between the next layer.
- Insulation - roofing insulation materials are slabs with minimal thermal conductivity. They can be made from extruded mineral wool, rock wool, foam or polyurethane foam. Depending on the material, the water absorption is also different, which also affects the choice of vapor barrier. Polyurethane foam and foam are practically not afraid of moisture, but mineral and stone wool require the installation of high-quality vapor barrier.
- Vapor barrier layer - films or membranes are installed on the crate immediately after the insulation and a gap is left between the cladding ceiling material to ensure natural ventilation. When water vapor from the bottom enters the membrane, condensation will form, which will drain down and dry out due to the ventilation of the under-roof part.
Even the highest quality and most modern vapor barrier will not "work" if you do not take care of roof ventilation. Ventilation is important at any time of the year - in winter it will help keep warm and prevent the roof from icing up, and in summer it will give you more coolness.
If a vapor barrier is absent or improperly installed in the roof of the house, this will inevitably lead to the formation of non-ventilated condensation, dampness, mold and mildew. Ultimately, timber structures and roof elements will rot and collapse.
Vapor barrier materials
Today on the construction market you can find a lot of roofing materials. Most of them are films based on polyethylene. They are waterproof, vapor barrier and antioxidant. The latter are special in that they are covered on the inside with an absorbent fleecy fabric layer that actively collects condensate, preventing it from getting onto the next layer of the roofing cake.
Previously, the main material for the roof vapor barrier was glassine. Today it is used only by overly economical builders, but if you look at the performance characteristics of glassine and compare them with the qualities of modern materials, the profitability of the latter will be obvious.
Depending on the physical and technical parameters, there are three types of vapor barrier films:
All film materials used for vapor barrier must have good elasticity, be tear-resistant and maximally comfortable to work with. It is imperative that the vapor barrier film does not tear during fixing, but wraps around the fastener. Even in case of accidental mechanical damage to the roof, for example, due to a tree branch falling during a hurricane, the vapor barrier must maintain its integrity, minimizing losses. Ideally, the thickness of the roof vapor barrier should be such that the material can withstand the load of thermal and waterproofing if the battens and rafters cannot withstand.
Isospanum vapor barrier
One of the most popular materials on the domestic market is izospan roof vapor barrier. It is relatively inexpensive, has excellent performance characteristics, durability and ease of installation. Izospan can be used for waterproofing and as a vapor barrier at the same time.
The manufacturer offers several different modifications of Izospan, each of which is designed for a specific purpose, however, there are also universal films. Therefore, it is very important to clarify the characteristics of the selected material before purchasing, so as not to accidentally buy the wrong Izospan variation.
Izospan B is widely used among professional builders and self-taught owners. It can be combined with any kind of roof covering. In addition to protecting the insulation from moisture, it does not allow the microfibers from the pie to crumble inside the room, as is often the case with other materials.
Installation of vapor barrier
It doesn't matter if you are making a vapor barrier for a flat roof or working with a gable roof - the film or membrane should be installed only after the insulation has been laid.
Features of installation of vapor barrier:
- The canvases can be installed both vertically and horizontally.
- If you prefer horizontal mounting, start from the top.
- Lay the canvases with an overlap of at least 10 cm. Be sure to glue the seams with single-sided or double-sided tape.
- Choose a wide tape of at least 10 cm.
- Double-sided tape is glued inside the overlap - first stick it on the bottom layer, then remove the protective cover and secure the top with an overlap.
- If you are laying the vapor barrier along the rafters without a rough lining of the insulation, overlap and fix the canvases directly on the rafters.
- The vapor barrier is attached to a wooden crate or rafters with a construction stapler or galvanized nails (do not rust).
- It is recommended to reinforce the gluing points with clamping strips. This advice is especially relevant for roofs with a slope of up to 30 degrees and with loose thermal insulation.
- At the points of abutment to aisles, hatches or dormer windows, a so-called dormer apron should be arranged through the roof, which is usually included in their package. If not, glue 2-sided butyl tape around the perimeter of the window frame or opening.
- In places where water pipes pass through the roof, wrap the vapor barrier material down, wrap the pipe with it and seal it with electrical tape.
When the vapor barrier is installed, attach the antiseptic treated bars on top of it at a distance of 50 cm from each other. This will create an air passage where condensation will quickly evaporate and the foil will not touch the ceiling sheathing. If you are using a vapor barrier membrane, the bars are optional. But they will come in handy to occupy this space with various communications. If you are planning to decorate the interior of the house with plasterboard, use a galvanized metal profile instead of wooden blocks.
Errors in the installation of the vapor barrier
Very often, when arranging a roofing pie, builders make mistakes that lead to fatal consequences. If you confuse the location of the insulation layers, the roof may become unusable after a year of operation.
We have prepared a list of the most common mistakes when installing a vapor barrier:
- The joints of the film are not sealed tightly, as a result of which the effectiveness of the vapor barrier is reduced to a minimum, the insulation becomes damp, the rafter structures begin to rot.
- Using a narrow adhesive tape to seal the seams - during operation, tape 5 cm wide or less will simply come off. The recommended tape width is 10 cm or more.
- There is no deformation margin when working with window openings - any house shrinks, therefore it is required to leave a margin in the form of a fold of 20-30 mm.
- The film around the skylights is not protected by finishing from the inside - if this is not done, after several months of operation, the vapor barrier will completely deteriorate and collapse under the influence of sunlight.
- The film envelops the rafters - if the vapor barrier material bends around the rafter legs, moisture will penetrate to the wooden elements, as a result of which they will begin to rot.
- Where the vapor barrier is adjacent to the inner walls of the house, shafts or chimney, it is necessary to take into account the specifics of the irregularities to which the material will be attached in order to ensure the tightness of the fixation.
- If you are attaching the film to a rough brick wall or rough wood surface, you can only do this with polyurethane, acrylic or synthetic rubber.
- Do not use polyurethane adhesive tapes or butyl rubber tapes, as they do not adhere well and may soon come loose from the surface.
The penetrating ability of water vapor is extremely high, so you should take a very responsible approach to the vapor barrier. In addition to the popular Izospan, Technonikol roof vapor barrier is widely used today. The most important thing is to correctly select the materials and install them in the desired sequence, then the roofing cake will last for more than a dozen years without repair.
In the process of washing, cooking, cleaning, steam is generated in the premises, which rises up in accordance with the laws of convection. Having passed through all layers of roofing materials, it cools down and turns into condensate, which settles on the thermal insulation, as a result of which it gets wet and loses its effectiveness, as well as the rafter system, contributing to its early decay. In order to prevent this from happening, the roof vapor barrier is being installed.
What is a roof vapor barrier for? This question is asked by many owners before building a roof. Often people simply do not understand the purpose of this material and want to save money by completely abandoning vapor barrier, but in vain. It ensures effective ventilation of the roof both in summer and winter, while protecting the roof from excess moisture coming out of the room.
In the summer, the correct design will save you from the heat, because hot air, when going up, will freely come out through the ventilated hole, taking with it the moisture in the insulation, as well as the heat from the hot roof. This is especially important if your home has any of them. Therefore, when a question arises whether to install a vapor barrier or not, it is worth knowing that in its absence there is a risk of mold, moisture accumulation in the rafters, freezing of the roof due to moisture ingress from the inside of the house, as well as damage to the ceiling finish.
There are several types of vapor barrier films:
- Foil. Such a film is used in buildings with increased temperature requirements.
- Reinforced vapor barrier membrane.
- Polyethylene. The advantage is the low price, but the durability and strength leave much to be desired.
- Universal vapor barrier film. The most commonly used material, perfectly compatible with all types of insulation.
- Unreinforced vapor barrier membranes with a reflective aluminum layer.
Features of installation of vapor barrier
Before you start laying, you should pay attention to which side to lay the vapor barrier for the roof, since it has a one-sided orientation, namely, it passes steam in only one direction, like a membrane. The fastening of the film should ensure its maximum safety, for which the use of double-sided tape would be most suitable. Fastening to wooden surfaces is possible with construction brackets or self-tapping screws with large heads.
Basic rules for installing a vapor barrier film:
- The vapor barrier should be installed on the roof with the smooth side in relation to the insulation. If condensation forms, then it will fall on the vapor barrier film from the rough side, which will not allow it to roll, but will retain it on its surface until it dries completely.
- The vapor barrier should be laid with an overlap, while the joints must be pasted over with special adhesive tape.
- Due to the fact that the steam has a high penetrating ability, increased attention during the installation of the roof should be paid to the places where the film adheres to pipes, rafters, walls.
- Diffusion of steam is much more intense with a sharp temperature drop, because steam moves from a heated room to a cold one, so when asked "Do you need a vapor barrier under a cold roof?", The answer is obvious - it is definitely needed.
Roof vapor barrier installation instructions
The device for vapor barrier of the roof is carried out quite simply, therefore, experience is not required to carry out such work. If you do not know how to properly make a vapor barrier, or if you are not confident in your own abilities, you can always turn to specialists for help. Below is a step-by-step sequence of performing work on your own:
- The vapor barrier film can be mounted both horizontally and vertically. If horizontal installation is chosen, it should be started from the bottom, gradually rising to the top of the roof.
- Each subsequent strip is neatly superimposed on the previous one with an overlap of at least 10 cm. At the same time, the seams must be carefully glued to avoid the appearance of gaps in the insulation, allowing the steam to penetrate through it. When using double-sided tape, it will be convenient to first apply it to the bottom layer, then remove the protective coating and fix it with the top layer.
- It is most comfortable to fasten the film to the rafters using a construction stapler. In the case of nailing, use galvanized, which does not rust. If the roof slope is less than 30 degrees, then it will not be superfluous to additionally strengthen the junction of the canvases with strips.
- If there are pipes in the roof, they should be wrapped with foil, having previously wrapped it down, and then carefully glue it with adhesive tape.
Before laying the vapor barrier on the roof, it is necessary to prepare and apply an antiseptic coating on the bars, which, at the end of the installation, will need to fix the film, keeping a distance of 0.5 m.This is necessary to form a ventilation corridor that will facilitate the rapid evaporation of the condensate that appears.
Vapor barrier is not the material that is worth saving, because it is it that ensures the safety and long service life of the roof, thereby guaranteeing the residents a pleasant and comfortable life.
Almost every owner of a private house or country cottage knows that the main "enemy" of the roof is the steam emitted by a person during breathing, formed during cooking, which is converted into condensation and settles in the roof carpet. This can lead to a deterioration in the functioning of the thermal insulation layer and, ultimately, to the destruction of the roof covering.
To avoid such situations, it is necessary to use a vapor barrier when laying the roofing. For this, special building materials with a vapor permeability coefficient are used, which will reduce the risk of damage to the insulation.
Laying a vapor barrier has its own characteristics and subtleties that you need to know about if you are going to carry out the installation yourself.
It is important to note that if chimneys or chimneys are placed on the roof, then a double layer of vapor barrier is required next to them, since one can be damaged by the heat emanating from them.
Leave a gap between the vapor barrier and the insulation for additional heat retention. The choice of film is best done taking into account the climatic conditions of your region, the area where the house is built and the type of roofing used.
Note to owners of houses from a bar When building a house from a bar, you can refuse vapor barrier, since this natural material has the ability to absorb moisture, thereby preventing the formation of condensation.
Installation instructions for roof vapor barrier
- before arranging the vapor barrier, install the insulation and waterproofing; carefully stretch the vapor barrier film, otherwise it will not function in a sagging state; you can mount the film with adhesive tape or double-sided tape on a metal, brick or concrete surface. When installing in a wooden house, you can use a nail with a wide head, hammer in at intervals of 30 centimeters; fasten the film with an overlap in several layers, leaving gaps for ventilation, 5 cm in size.
Important To maintain the integrity of the vapor barrier of the entire home, it is necessary to ensure that the film is covered with a continuous carpet without tears, scratches or holes.
In general, the arrangement of the roofing carpet should look like this:
- installation of a vapor barrier film from the side of the interior; laying of insulation; installation of a windproof membrane; roof lathing; installation of roofing.
Using a vapor barrier also helps prevent mold and mildew growth. Using this layer, you, first of all, take care of the health of your loved ones.
The roof structure is a complex system. It consists of several layers of dissimilar materials, each of which performs its own unique function.
To ensure the comprehensive protection of the building from the influence of the environment, it is necessary to perform all installation work of high quality, as well as the correct choice of basic and insulating materials. This whole process is briefly called roof insulation.
The standard composition of a roofing cake includes:
What is a roof vapor barrier for?
Why do you need a roof vapor barrier?
The vapor barrier layer protects the roof from the penetration of water vapor into the thermal insulation. The fact is that insulating materials for the most part have a porous structure, since the air contained in them acts as a heat insulator. When in contact with a colder medium, steam turns into condensate, which is retained in the voids.
This can lead to a violation of the functionality of the heat-insulating material, as well as the occurrence of decomposition and decay processes in summer. In winter, the freezing water expands, thereby destroying the bonds between the cellular elements.
The form of release of vapor barrier films is a roll.
Vapor barrier can be made of various materials. Some of them have additional positive properties that increase the efficiency of the interior of the building. Installing a vapor barrier on the roof is not as difficult as it seems at first glance, but it requires a careful approach and accuracy.
Types of vapor barrier
Single layer polyethylene films
Manufactured from low-density polyethylene for increased steam penetration. This material often has defects associated with the ingress of foreign particles during manufacture. The cheapest kind of insulating material.
Reinforced polyethylene films
In comparison with single-layer polyethylene, the reinforced vapor barrier is slightly thicker, since it includes a reinforcing frame. It consists of polymer twisted threads, located in mutually perpendicular directions. The mesh is fastened to the polyethylene base by warm pressing.
This technique does not affect the waterproofing and mechanical properties of the material, but it can reduce the degree of vapor barrier.
Anti-condensation film
It is made of two layers: smooth and fleecy. The smooth layer is attached to the insulated surface.
The fleecy layer is created from cellulose fibers. Steam, falling on such a surface, clings to the fibrous structure, thereby preventing moisture from draining onto the underlying structures of pitched roofs. Excess water is removed along with the air through the ventilated space.
Foil-coated polymers
They are made of foam or expanded polypropylene coated with a thin layer of metal. Due to the reflective properties of metal surfaces, such a vapor barrier provides an additional function of protection against heat loss.
Membranes (film for roof vapor barrier)
Membrane vapor barrier materials are divided into five main classes:
Has increased resistance to moisture and wind. It is laid between the roofing and the heat-insulating layer. Manufacturing technology - spunbond.
Such a vapor barrier prevents moisture from flowing through the cracks of the roofing material, as well as from the resulting condensation. The absence of a laminating layer allows the use of such membranes in roof structures with a slope of more than 35 degrees. To remove excess moisture, it is necessary to arrange ventilation openings from a double lathing located between the membrane and the insulation. Type AM.
Unlike Type A, it has a multi-layer structure. It is placed between the insulation and the roof to provide adequate protection against negative weather conditions. The most common is a three-layer construction, consisting of two layers of spunbond with a diffuse film located between them.
It acts as a waterproofing agent, as it allows steam to pass through, but retains water. Laying is performed directly on the heat-insulating layer, which reduces labor costs for the ventilation gap. Type B. Two-layer material.
Consists of a layer of vapor barrier film and spunbond. It is used to shield the insulation from the internal vapors of the building. It is used only in insulated roof structures. Type C.
It is made similarly to type B membranes. It has a stronger and thicker layer of spunbond, which provides better protection of the insulation from moisture. It is used in insulated and non-insulated, pitched and flat roofs. Type D.
Consists of polypropylene fabric protected on one side with a laminated polymer coating. The structure of the material allows it to withstand significant mechanical stress. This leads to its installation between the insulation and the screed of the attic floor, as well as in non-insulated roof structures.
Which side is the vapor barrier for the roof?
The principle of installation of vapor barrier materials depends on which side the layer responsible for repelling water vapor is on:
- ordinary and reinforced polyethylene films, as well as type A and AM membranes can be laid on the insulation of either side. Anti-condensate vapor barriers are laid with the smooth side to the insulation, and the fleecy side towards the vaporization. Foil elements are laid with a metal layer inside the room, since it is there that should be reflected from the building heat. Type B membranes are laid with the film side to the thermal insulation layer. Type C and D membranes must adjoin the insulation with their rough side.
We figured out which side to put the vapor barrier on the roof, now we will analyze in detail how to properly put the vapor barrier on the roof.
Vapor barrier for the roof: how to properly lay using a special technology
The roof vapor barrier is installed as follows:
Laying can be done vertically or horizontally. In the second version, the installation of the roof vapor barrier is carried out starting from the low-lying part of the roof. Each subsequent strip is superimposed on the previous layer with an overlap, the size of which should not be more than 10 cm.
The vapor barrier is attached to wooden rafters with galvanized nails or a construction stapler. When installing films and membranes near mansard hatches, you need to use a special vapor barrier apron, which is included in the standard package. At the joints with ventilation pipes, film and membrane structures are wrapped down, wrapped around pipes and tightly fixed with construction tape. After laying the vapor barrier layer, it is necessary to nail in wooden blocks.
The rules for laying the vapor barrier on the roof dictate the following rule - the step between the lathing bars should be 500 mm. In this case, a ventilation gap is formed, and additional fastening of the vapor barrier layer is carried out. Now you know how to lay a vapor barrier on the roof, you can move on to the issue of waterproofing. If the vapor barrier for the roof has been damaged, then small cuts or holes can be sealed with special tape for vapor barrier membranes.
Roofing cake scheme
Gluing joints with tape
The final version of the vapor barrier
Roof waterproofing and vapor barrier - what's the difference?
Waterproofing materials also serve to protect structural elements from moisture. However, unlike vapor barrier, they are not resistant to moisture-saturated air masses.
That is, the steam coming out of the premises will freely penetrate the insulating layer. Therefore, when buying vapor barrier films and membranes, make sure that they are correctly used. Read more about roof waterproofing here.
Useful video
And now we suggest that you familiarize yourself with the video instruction on the vapor barrier of the roof:
Conclusion
Vapor barrier is the lightest and thinnest roof layer. But neglect of its device can negate all the material and physical efforts to create a high-quality roof. Therefore, do not neglect this important element, it will significantly increase the life of the entire building.
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Modern film vapor barrier is designed to increase the effective service life of heat-insulating materials, wood and metal structures. Indeed, during the operation of a residential building, residents use many sources of intense evaporation - hot baths or showers, aquariums.
If the roof is equipped with a hydro-barrier, water vapor will condense on it from the inside, constantly moistening the insulation and building structures. At the same time, wooden elements are exposed to mold fungi, and metal elements are exposed to intensive corrosion processes.
Application area
Today, modern SNiP norms regulate the use of vapor barrier in the following cases:
- When arranging a heat-insulating layer of roofing in warm attics and attics.
- In the case of production of insulation of walls of structures from the inside. This is especially true of metal structures - garages, change houses, insulated containers and others. This event will significantly increase the service life of mineral wool or expanded polystyrene used as insulation.
For vapor barrier of first floor wooden floors.
Often, in our conditions, the floors of the first floor are also equipped with an insulating layer to prevent heat from escaping from the premises in winter. And with a significant difference between the internal temperature and the external temperature, it will be natural for drops of condensed moisture to appear on cold floor surfaces. As a result - again, the impregnation of the insulation with water, which leads to a significant deterioration in its thermal insulation qualities and premature destruction of the wooden floor structures.
Do-it-yourself vapor barrier installation technology
When laying a vapor barrier with your own hands, you should adhere to simple rules:
- The film must be mounted with the smooth side to the vapor-insulated surface - the insulation of the roof, walls or floor. In the case of using a foil modification of the film, it should be laid with the polyethylene side to the insulated surface, and with a reflective screen - inside the room. It will be especially effective when equipping internal hot rooms - baths and saunas.
- Stacked exclusively with an overlap with an overlap of at least one hundred millimeters. Pre-fastening to wooden structures is carried out using a construction stapler with staples, a hammer with galvanized nails or a screwdriver with anodized screws.
- A prerequisite is the tightness of its performance. In practice, this means the need for careful gluing of all sheets in the overlap areas and around the perimeter. For these purposes, it is recommended to use high-quality double-sided tape, and its width should not be less than 100 millimeters.
Features of laying a vapor barrier film on various structural elements of buildings
Direct installation of the vapor barrier is carried out as follows:
- In the case of organizing the vapor barrier of the floor covering, the film is spread and fixed on the surface of the subfloor. Once all overlaps and perimeters have been glued, the final floor and floor covering can be laid.
- For walls and pitched roofs, it is possible to lay a vapor barrier film with vertical or horizontal canvases.
- When arranging a vapor barrier for a flat insulated roof, after laying it, it is necessary to fill a frame made of wooden slats 10-20 millimeters thick over the film. These slats serve as additional fasteners for the film material and provide ventilation between the vapor barrier and the final finish of the flat roof.
Using double-sided tape
Tyvek double-sided adhesive tape for sealing vapor barrier
When organizing a vapor barrier layer, the following types of double-sided tape are used:
- paper-based; polypropylene-based.
The second option is of better quality in terms of durability and ability to withstand external destructive factors - the effects of moisture and high temperatures.
The use of double-sided polypropylene tape is especially justified when arranging a vapor barrier in excessively hot and humid rooms, for example, in Russian baths.
Double-sided tape is applied as follows:
- First, the material is unwound and glued to the edge of the lower abutting fabric with release paper upward.
- Then the next sheet of vapor barrier tape is laid out and unfastened with the required amount of overlap.
- After that, a layer of anti-adhesive paper is removed from the upper side of the adhesive tape and by light pressing and smoothing, both layers of the vapor barrier film are securely fastened together.
If you follow all the technological nuances of installing vapor barrier materials, using only high-quality products, you can significantly extend the effective life of the structural elements of the building - floors, walls, ceilings, roofs and buildings in general.
Remember that your costs for arranging a high-quality vapor barrier layer in a residential building will be incomparably less than the cost of repair work due to prematurely lost insulation, load-bearing wooden structures and interior finishing materials. Therefore, insignificant savings on vapor barrier during construction of a building can result in significant losses in the future.
For more information on the technology of laying and attaching a vapor barrier for a warm roof with your own hands, see the video.
Currently, vapor barrier is one of the components of any construction. First of all, we are talking about the roof vapor barrier.
The fact is that moisture is present in any room. The water itself is not so scary. The most detrimental effect on the roofing materials is the condensation that forms on the inner surface of the roof in hot weather.
The scheme of the vapor barrier of the walls from the inside.
Laying a vapor barrier on the roof means protecting all building and finishing materials from the harmful effects of moisture. This is especially true of private houses and cottages, where, in most cases, mineral wool is used as insulation.
Condensation can penetrate into its structure, destroying it and significantly reducing its service life. Below you will find instructions on how to install the roof vapor barrier. This is where it is worth fighting condensation.
Materials used for roof vapor barrier
Currently, a huge variety of materials are used that are used for vapor barrier. As for the roof, the choice is simply huge. More recently, roofing material was the main material used for the roof.
Recently, people began to refuse him, since he has a limited service life. Under the most favorable conditions, roofing material will last no more than five years. In addition, now there are many materials similar in composition and properties.
Glassine is a material that is very often confused with roofing material. They are similar in appearance, but the production technology is somewhat different.
In the production of glassine, cardboard is also the main substance. This material lasts much longer than roofing felt. For roof vapor barrier, it fits just fine.
Properties and scope of vapor barrier materials.
Films are also widely used for roof vapor barrier. They are mainly placed in private houses, where a residential attic is equipped, that is, an attic. There are several types of polyethylene films used for vapor barrier.
For example, reinforced materials are widely used in this direction. Don't forget about polypropylene films. They are now becoming more and more popular, as they have a fairly long service life.
Today, the most widely used breathable films are also called membranes. They differ among themselves in the way of installation.
Modern membranes can be single-sided or double-sided. Many experts unanimously argue that membranes allow several times to reduce the cost of air conditioning and heating a room. This is a fairly profitable option for roof vapor barrier.
It is the membranes that are currently used most often for these purposes. Moreover, it is not necessary to be a specialist in the field of construction in order to lay such material on your roof. It is worth noting the fact that membranes are installed in our country using a variety of technologies.
This is due to the fact that in Russia there is no strict rule according to which this should be done. Each specialist and firm does the work as it suits them. Basically, there is nothing to worry about.
Now it's worth touching on the topic of vapor barrier instructions. It is worth considering the main aspects associated with arranging this layer on your roof.
Installation and roofing is a necessary thing. Its main goal is to prevent the formation and accumulation of moisture inside the roof.
If this happens, your roof will begin to rot and deteriorate from the inside, as a result of which its technical properties will quickly disappear. Below we will describe how to properly lay a vapor barrier with your own hands.
A roofing cake is made up of specific layers of different materials. It includes a different number of layers, but vapor barrier, thermal insulation, etc., are always key.
Waterproofing layer gives protection to subsequent layers from moisture penetration and dampness from the outside. This layer is a waterproof special material that is attached to, leaving a gap between the subsequent layer.
Insulation layer - these are, as a rule, heat-insulating materials, which are plates with low thermal conductivity. They come in pressed, polyurethane foam or.
Water absorption also depends on the material chosen, and this also significantly affects the choice of a vapor barrier layer.
Several years ago, glassine was the main material for the vapor barrier layer. Currently, it is used only by very economical builders. And if we compare the performance indicators of glassine with high-quality modern materials, then the latter option is clearly more profitable.
Types of films
There are three types of vapor barrier films. They are classified depending on the physical and technical indicators.
- Polyethylene films.
- Polypropylene films.
- Diffuse film.
Polyethylene used not only for vapor barrier, but also actively used for a waterproofing layer. 
These films are divided into:
- perforated,
- non-perforated.
But in any case, during installation, they must be reinforced with a light fabric or mesh.
For the waterproofing layer, perforated films are mainly chosen, and non-perforated films are suitable for the vapor barrier layer.
Modern manufacturers offer several different modifications of isospan. Each specific version of this material is designed for a specific purpose, but there are also universal films.
This material is often used by professional builders and self-taught owners. Izospan is combined with any type of roofing. And besides protecting the insulation layer from dampness and moisture, it does not allow the cake to crumble inside the house, as is often the case with various building materials.
When buying Izospan, be sure to clarify the characteristics and properties of the material you have chosen so as not to accidentally acquire the wrong modification.
Vapor barrier for a flat roof Technonikol
When buying a vapor barrier for your roof, pay attention to material properties such as water repellency and strength. These characteristics have a vapor barrier for a flat roof Technonikol. It is a plastic wrap that protects the roofing cake from indoor condensation.
Roof vapor barrier film is used, as a rule, in warm roof vapor barrier systems. Thus, it is installed under an insulation layer on concrete floors.
Advantages of Technonikol roof vapor barrier:
- high strength and elasticity;
- excellent steam and water resistance;
- withstanding mechanical loads;
- favorable price for vapor barrier for.
The flat roof vapor barrier film measures 3x30 m and is packaged in rolls.
Installation of roof vapor barrier
Below we give a list of errors during the installation and installation of the vapor barrier of the roof.
- The joints of the vapor barrier film are not sealed tightly. As a result, the insulation becomes damp and the rafter systems begin to rot.
- Application of narrow adhesive tape to seal the film seams. In the process of using a tape with a width of 5 cm or less, it will simply come off.
- There is no deformation margin when working with windows. The new house gives a certain shrinkage, so it is necessary to leave a margin of 20-30 mm.
- The vapor barrier film around the windows is not protected from the inside. After a few months of use, the vapor barrier will completely collapse under the influence of sunlight.
- A vapor barrier film wraps around the wooden rafters. In this case, the rafter legs will begin to rot over time.
- In places where the vapor barrier is adjacent to the walls of the house or the chimney, you need to take into account the specifics of the irregularities to which the material will join.
- Installation of the film to a rough wall should be done using polyurethane glue or synthetic rubber.
- Do not use polyurethane adhesive tapes, as they may peel off the surface after a while.
The penetrating power of water vapor is very high, which is why it is necessary to take a responsible approach to the installation of a vapor barrier layer. In addition to the popular isospan, today a vapor barrier is used for Technonikol.
The basic rule when installing a vapor barrier for the roof - correctly select building materials and install them in a strictly defined sequence, then your roofing cake will serve you for more than a dozen years.
The introduction of each new technology in the construction industry provides an opportunity for a person to improve his own home, which as a result becomes even more reliable, safe and comfortable. But for this it is also necessary in the process of building a house to strictly adhere to the established standards and construction norms.
One of the main structural elements of the house, ensuring the comfort of living in it, is the roof. Therefore, it is imperative to know the technology of laying a vapor barrier layer on the roof.
In this article
The need to equip a vapor barrier
The steam generated inside the room is mixed with warm air and, according to the laws of physics, rises up. But, since the roof of the house prevents its further advancement, it penetrates into the layer of thermal insulation, starting its destructive effect.
In winter, due to the sharp drop in internal and external temperatures, steam will be contained in the insulation material. As a result of subzero temperatures, the steam will first turn into frost, then into ice, respectively, the layer of thermal insulation will freeze and will remain in this state until the onset of heat, then it will thaw. As a rule, the consequences of such a process are the complete loss of protective properties by the insulation material, that is, unsuitability for its further operation.
In order to prevent the failure of the insulation after a year of operation, it is necessary to lay the vapor barrier on the roof. The vapor barrier material will prevent moisture from entering the insulation, and accordingly will significantly extend its operational period.
Materials used for arranging a vapor barrier layer
Previously, the only material to be laid to protect the roof from moisture was glassine. Today, a wide variety of building materials are used to equip a layer of vapor barrier on the roof.
- Plain low density polyethylene film. Due to its low density, experienced roofers do not recommend using it in private housing construction, since there are high risks of damage during installation and operation.
- Polyethylene film reinforced with a polymer mesh. It is already a denser, strong insulating material, which is most often used for arranging the roofs of agricultural enterprises. It is also not recommended as a roof vapor barrier in multi-apartment and private housing construction, since microscopic cracks form at the site of the polyethylene connection with the reinforcing elements, through which steam can penetrate.
- Sack fabrics made from polypropylene filaments that are subsequently laminated with melted low density polyethylene. The thickness of the vapor barrier material is half that of the reinforced polyethylene film. Such a vapor barrier material is used for arranging cold roofs.
- Aluminum foil, which has zero vapor permeability.
- Cardboard, laminated on one side with plastic wrap.
A vapor barrier sheet of several protective layers is used for roofs over rooms in which swimming pools, showers, laundries, etc.
Which side is the vapor barrier laying?
- A standard vapor barrier film consists of two layers. At the same time, on the one hand, it has a rough surface that holds back condensate drops, on the other, it has an absolutely smooth surface. It is the smooth side of the vapor barrier film that adheres to the insulation material, and the rough side is directed into the room.
- When used for vapor barrier foil film, which is intended not only to protect insulation, roofing, foundations, but also to return thermal energy back into the room, it is placed in the room with a reflective surface.
- A vapor barrier membrane capable of letting in air, protecting the base and roof from moisture penetration, provides the structure with the ability to "breathe". When using a double-sided vapor barrier membrane that has the same surfaces, it can be installed on either side. If a one-sided membrane is used to equip a vapor barrier, then the wrong side of the material is indicated by the manufacturer.
When purchasing any type of vapor barrier material, be sure to read the instructions for its operation provided by the manufacturer.
Basic rules for laying a vapor barrier film
After finding out which side to the room or insulation needs to lay the vapor barrier material, you can proceed directly to its installation. In this case, the following rules must be observed:
- The first - installation of heat-insulating, sound-insulating material is carried out, then a vapor barrier film.
- Second - the film should be well stretched, there should be no sagging areas.
- Third- fastening of the vapor barrier material is carried out using ordinary adhesive tape (adhesive tape). You can also use nails with a wide head (pitch - 30 cm) or a stapler for furniture as fasteners, which will greatly facilitate the work and reduce the time it takes to complete it. The film can be fastened with wooden slats, which are screwed in with screws in 30 cm increments.
- Fourth - individual canvases of the vapor barrier film are laid with an overlap of up to 15 cm.In this case, it is imperative to make ventilation gaps up to 5 cm wide.
These are the general rules for the use of vapor barrier material, but when laying it on different bases, the roof has its own characteristics.
Roof vapor barrier
Providing moisture protection to the walls of the house is only 50% of the work, since the bulk of the vapors is directed upward. Also, the formation of condensation as a result of heavy precipitation cannot be avoided. As a rule, the roof of the house takes the brunt.
It is also necessary to understand that poor-quality installation of vapor barrier, performed on the roof, will contribute to a decrease in temperature inside the house, an unfavorable smell, the formation of dampness, mold, corrosion of metal structural elements, etc. Therefore, it is quite important to use a high-quality vapor barrier material and install it correctly.
To protect the roof of the house, experienced roofers recommend using membrane-type vapor barrier materials that are breathable and moisture-proof. Membrane vapor barrier will also help remove excess moisture from the insulation material. Double-sided construction membranes will work on both surfaces of the roof covering.
Sequence of materials
When arranging the roof of a house, it is important that the materials of construction are in the following sequence:
- Roof covering
- Counter grill
- Lathing
- Waterproofing
- Rafters
- Insulation
- Vapor barrier
- Roof lining
Vapor barrier is one of the important points in the construction of a house, as it protects the elements of the main structure of the house from mold, decay, rust and other negative influences that contribute to a reduction in their service life. And also a high-quality layer of vapor barrier will provide an optimal temperature regime in the house for a comfortable stay.