Which vapor barrier membrane to choose for the roof? Which vapor barrier to choose for the roof
Roof vapor barrier is only needed when insulating with mineral wool. This is due to the properties of the insulation itself. Usually two reasons for the arrangement of this layer are indicated: loss thermal insulation properties and wetting of wooden structural elements with which the cotton wool comes into contact. Although there is also a third function - protecting the living space from penetration of insulation fibers. But quite often in reviews, when listing species, authors paro insulating materials make one fundamental mistake. Which one exactly is described in this article.
Roof vapor barrier - view from inside the attic Source bohoworld.ru
Types of modern vapor barrier materials
Modern vapor barrier film for the roof - this multilayer material with limited or practically zero diffusion properties.
Note! Of course, you can use regular high-density polyethylene film. But given the low resistance to mechanical damage, it is not even recommended to use it when installing a vapor barrier for the floor. And the roof has the degree of “responsibility” of this layer roofing pie higher.
The simplest version of the film contains two layers, one of which has an anti-condensation surface.
The anti-condensation surface has a “rough” appearance and is turned into the attic Source kristan.com.ua
Reinforced films also have a reinforcing layer in their structure - a mesh of durable polypropylene threads. This type of vapor barrier belongs to the Standard category. For example, the Utah company offers a special type of vapor barrier, Yutafol Special, with improved fireproof properties, which, as a third layer, does not contain a reinforcing mesh, but a self-extinguishing reagent.
And the last option is three- and four-layer films with a heat-reflecting surface. In this case, the vapor barrier receives another additional function– energy saving.
About misconceptions. Differences between vapor barrier and waterproofing
The most common misconception is the use of the term “vapor barrier membrane for roofing.” An even bigger mistake is when superdiffusion membranes are classified as vapor barrier materials.
Important! Both “regular” and “superdiffusion” membranes are classified as waterproofing materials. But not to vapor barrier.
This is what the insulation structure looks like and relative positions insulation materials throughout the house Source guru220v.ru
The very concept of “membrane” for woven and nonwovens means breathability. If a vapor barrier should prevent steam from penetrating into the insulation from the room, then waterproofing should only protect it from the penetration of water from the roof, and remove water vapor outside.
Although there are waterproofing materials with limited ability for vapor diffusion - vapor permeability.
Remember! To put it briefly, any vapor barrier does not allow water and steam to pass through, and a waterproofing membrane cannot serve as a vapor barrier for a roof.
This difference in properties determines the position in the composition of the roofing pie:
Waterproofing is “on top” of the insulation– on the rafters or counter-lattice (distance strip) under the roof. It protects mineral wool from condensation and leaks through leaky roof joints or its attachment points to the sheathing.
The vapor barrier is located “bottom” of the insulation. It is attached to the inside of the rafter legs.
There is only one case when a vapor barrier film is used as waterproofing - metal roofing.
Important! The peculiarity of metal tiles or corrugated sheets is that with daily temperature fluctuations, quite a large number of condensate
An example is the Izospan C or Izospan DM films, which the Hexa company positions as a vapor barrier - they are laid instead waterproofing membrane. And the Utah company produces for this case a special vapor-proof waterproofing Yutakon - a four-layer material with reinforcement and an anti-condensation coating.
And at the end of the section. If we talk about the differences between waterproofing and vapor barrier, then they can most clearly be seen using the example of Utah materials. The labeling of the main products of this company in the “Waterproofing” and “Vapor Barrier” sections differs only in one letter. And the structural difference comes down to the presence or absence of a layer with microperforation.
On our website you can get acquainted with the most . In the filters you can set the desired direction, the presence of gas, water, electricity and other communications.
Features of roof vapor barrier depending on the device and the nature of its operation
There are three types of roofs:
uninsulated;
insulated;
combined.
The first type does not require roof vapor barrier. Only the ceiling is insulated, so the vapor barrier is laid on the surface of the “rough” ceiling of the upper floor on the side of the heated room.
If the cold roof is not covered with a metal roof, then in some cases you can even do without waterproofing. For example, when using slate or ondulin, which has a rough (fibrous) texture - a kind of anti-condensation surface.
Insulated roofs, the internal volume of which is completely occupied by attics or occupied attics with engineering equipment, have a “continuous” roof vapor barrier device. That is, a vapor-proof film is mounted below the insulation along rafter legs a continuous and continuous layer over the entire inner surface of the roof.
If the “height” of the rafter section is not sufficient to accommodate mineral wool calculated thickness, a counter-lattice is installed from the inside, between which an additional layer of insulation is laid. In this case, the vapor barrier is attached to the counter-lattice.
Combined roofs have a dedicated “warm” contour. It can take different forms:
Cut off any part of the attic By vertical level from the side of the slope or pediment. In this case, the walls are attic space insulate according to the principle frame house. And the vapor-proof film of the walls is overlapped and hermetically sealed with tape to the vapor barrier of the roof in its insulated part.
Cut off part of the attic along the horizon. In this case, the attic has “its own” cold attic, which is insulated along its ceiling. And the vapor barrier is sewn from below to its ceiling (or false ceiling) and connected with tape to the vapor-proof film of the insulated part of the slope.
The gables of houses with a gable or multi-gable roof are insulated in the same way as the facade.
Installation features
After installing the rafter system, the waterproofing is attached, then the roof sheathing and the roof itself. Insulation is placed between the rafters, and laying a vapor barrier on the roof is the penultimate stage of its arrangement. Next comes the interior lining (finishing) of the attic space.
To create a continuous sealed vapor-tight layer, the film is installed from the bottom up with an overlap of adjacent panels by at least 15 cm. The same principle is followed if it is necessary to increase the length of the panel. Attach the film to the rafters (or sheathing) with a stapler or wide-headed nails.
Joints and interfaces with adjacent surfaces are additionally sealed with sealed vapor barrier tape. To do this, use a tape 10-25 mm wide with a butyl rubber or acrylate double-sided self-adhesive layer.
The Ondulin company produces a vapor barrier film that already has a self-adhesive layer located from the edge of the panel at an overlap distance Source stroymaterialy52.ru
First, remove the anti-adhesive paper from one side and apply it to the bottom vapor barrier strip. Then, overlap the bottom strip with the top strip of vapor-proof film, remove the anti-adhesive paper from the other side of the tape and press the strips together. When gluing the roof vapor barrier to adjacent fences and structures (made of concrete, brick, metal or plastic), their surfaces must be cleaned of dust and dirt.
Final fixation of the vapor barrier to the rafters or to the sheathing internal lining carried out using wooden slats or metal profile.
For " proper operation» anti-condensation or reflective surface between the vapor barrier film and finishing cladding clearance is required. If finishing is carried out wall panels, then for the sheathing use a lath with a section height of 4-5 cm.
A batten or board over a vapor barrier also serves as sheathing for the interior lining of a residential attic. Source stroimkryshy.ru
When covering an insulated attic with plasterboard, the gap size is set using a direct suspension (the height of the side ceiling profile CD is insufficient - only 28 mm).
Video description
From the video you can learn about installing a vapor barrier:
Conclusion
The durability of the entire structure depends on the vapor barrier of the roof. pitched roof. Incorrectly selected materials or the absence of a vapor-proof layer create the preconditions for rotting wooden knots rafter system. Therefore, the design and installation of the roof should be carried out by professionals.
Vapor barrier film for roofing is a material that, due to its characteristics, protects wooden structures from the destructive effects of steam, and also does not release heat outside the house. We will tell you in this article what types of vapor barrier films for roofing there are.
Why do you need a vapor barrier film?
The task of the vapor barrier film is to prevent steam from penetrating into the thermal insulation and bearing structures roofs. In the absence of vapor barrier films, the service life of the roof is reduced and the need for repairs arises.
The indoor air contains a large amount of moisture, since people cook food, take a shower, etc. in the premises. If a vapor barrier is not installed in the structures, the moisture settles in the insulation. Excessive humidity leads to a decrease in the properties of the heat insulator. Corrosion processes also begin, which lead to disastrous results: wooden elements become infected with fungus, and metal elements are corroded by rust.
Vapor barrier film eliminates the following problems:
- the appearance of condensation on wooden elements And building structures; destruction interior decoration ceilings and walls due to excessive indoor air humidity; freezing of the insulation layer;
What roofs is it suitable for?
Vapor barrier film is used for all types of houses and roofs. It doesn't matter the complexity roofing structure. The flexibility, lightness and strength of the material allows it to be used on any roof, regardless of their level of curvature. Roof vapor barrier films are indispensable for:
- Roofs of frame houses. For heated cottages and country houses. For heated verandas and attics. To protect the roof of a bathhouse and/or sauna.
Pitched metal roofs especially need protection from steam, since increased moisture provokes destructive processes in them, corrosion, the appearance of microcracks and loss of basic functional abilities. To extend the service life of metal tiles or seam roofing coverings, it is important to use reliable vapor barrier films, the types of which will be discussed below .
What types of vapor barrier films are there?
On the market building materials A large number of films for roof vapor barrier are presented. The following types are distinguished:Polyethylene films
Polyethylene films are materials whose key feature is fabric reinforcement or reinforcement mesh. This is done to give strength.
There are two types of films:
Perforated - they have micro holes that provide vapor permeability. However, this indicator does not correspond to the standard, therefore, when arranging an insulating pie, a ventilation gap must be made;
Non-perforated - materials used directly for vapor barrier. When installing them, tapes are used that are designed to connect individual panels.
There is another type of polyethylene films - laminated with aluminum foil. Their main advantage is good vapor barrier properties. Films are not suitable for rooms with a normal microclimate. But when arranging saunas or baths, they are widely used.
Polypropylene films
Polypropylene films are materials that have been used for many years. At first they were brought from Finland, and then they began to be produced in Russia. The main advantage of such films is their excellent strength characteristics and resistance to impact. sun rays. The material has another significant advantage: the presence anti-condensation layer, absorbent and retains moisture. This layer has excellent performance because even in critical conditions it absorbs all the moisture, eliminating the formation of drops. And when the causes of condensation disappear, polypropylene films dry naturally.
Vapor barrier films Ondutis
There are several types of Ondutis films that are suitable for creating a vapor barrier layer under the roof: Ondutis B (R70) are three-layer polymer vapor barrier membranes that are used for insulated roofs and attic roofs. Ondutis D (RV) are anti-condensation films with a special inner layer made of non-woven fleecy textiles in which moisture is concentrated. Used for metal roofs. In addition, this type of Ondutis films can serve as a temporary roof covering for 2 months.
How to choose a roofing film
When choosing a vapor barrier film for your roof, pay attention to: - Purpose of the film. For the roof, use only roofing film. Vapor permeability of the film. The lower the better. For high-quality insulation In a residential area, the vapor permeability indicator is 1 g/m2 per day. Film weight. How more weight film, the higher the density of the material and, accordingly, its strength. No foreign odors – important indicator. The film used in the home must be safe for humans and the environment.
When planning your home design, you always want it to be warm and cozy.
To do this, you should follow the instructions when carrying out construction work.
It is also necessary to pay enough attention, in particular, to the competent provision of all types of insulation.
How to choose a vapor barrier for a roof and not make a mistake? First, let's get acquainted with the types of vapor barrier materials.
In residential premises there is always water vapor that circulates inside it. And according to the laws of physics, it rises with warm air. Over time, it will penetrate into the under-roof space, where it will begin to absorb insulation.
With the onset of cold weather, all the moisture that has undergone condensation forms an ice crust. And when spring comes, all the ice melts, and the resulting moisture washes away the internal filling of the roof structure. This will lead to its destruction and loss of basic properties: When the insulation is slightly moistened, heat loss increases significantly.
To avoid these consequences, it is necessary which should be present in any roofing pie. Some people believe that finishing the attic with cladding, which prevents moisture from entering, eliminates Negative consequences. But it is recommended to always use a special coating that is placed between the ceiling and the insulation.
Which vapor barrier to choose for the roof?
Exist the following types vapor barriers for the roof:
- painting;
- pasting.
Painting room
Used more often for high-rise buildings, soft roofs from roofing felt, iron roofing sheets, where insulation is not used. This vapor barrier is well suited for flat roof. The main difficulty in using mixtures of this kind is preparing the surface before application. For this type of insulation, the following compositions are used: 
How:
- hot bitumen;
- bitumen-kukersol mastic;
- varnish based on chlorinated rubber or polyvinyl chloride.
Pasting (membrane)
This type more popular, especially in individual construction. Materials for this type of insulation are produced in rolls and this provides some advantages:
- simplification of installation;
- ensuring a tight connection when overlapping;
- reduction in the number of seams.
NOTE!
The adhesive insulation is laid in one layer, if the room humidity is below 75%, otherwise add one more extra.
Types of adhesive vapor barrier materials
- Waterproofing. Prevents steam from penetrating into the insulation. Have special perforation, which allows steam to penetrate outside. Mounted with some clearance from roofing, What promotes air circulation between the outer and under-roof space. Has unidirectional vapor permeability, keeps the insulation dry. You can talk about waterproofing materials.
- Anti-condensation. Equipped with special fleecy layer, which is located on their inner surface. It retains moisture and prevents contact with thermal insulation. Moisture quickly disappears due to air circulation in the gap. This type of insulation must be laid with an adsorbent layer to the inside of the room. Attached using a counter-lattice.
- Vapor tight. Provide impenetrable protection inner side roof insulation. Sometimes they have a layer aluminum foil , which is capable of reflecting part of the radiant energy back inside. It is laid with a ventilation gap to the insulation. Provides good protection from moisture, while maintaining heat.
- Membranes. They are modern vapor barrier materials that can prevent moisture from escaping, while allowing air to pass through. When using membranes, ensure air gap often not necessary. This material for roof vapor barrier has gained great popularity these days.
Do you need a vapor barrier for a cold roof?
The special design of such roofs does not require laying two layers: thermal insulation and vapor barrier. This saves money and construction resources. Water vapor that passes through the film ends up between the waterproofing and the corrugated sheet, from where it is removed by an air flow.
Therefore, the main task when installing cold roof is ensuring good ventilation, which is ensured by creating a gap using a counter-lattice.
Cold roof installation
Do you need a vapor barrier under the corrugated roof of a cold roof? No, it’s not necessary, the main thing is to take care of good ventilation.
Vapor barrier for attic roof
The most commonly used materials are glassine, roofing felt and foil insulation. Modern membranes are also quite effective, which have proven themselves in this sector and are excellent for vapor barriers of soft roofs.
First of all, it is necessary to seal and insulate the various structural elements. The vapor barrier is laid on and secured using a method that matches the surface material. About insulation mansard roof can be read.
Fastening to concrete, brick and metal surfaces performed using double-sided adhesive tape, laid with a 10 cm overlap. And it is attached to the tree with nails or staples.
CAREFULLY!
The vapor barrier film must be installed without sagging, with slight interference.
The foil film is installed with a reflective layer inside the room so that thermal energy remained inside the building. A gap is provided between the thermal insulation and vapor barrier parts for ventilation, as well as to create a warm air barrier.
Detailed diagram of the roofing pie of the attic roof
The joints of the film are taped with tape made of a material with a similar coefficient of thermal expansion. It is better to press the junctions of the foil to the wall with strips with sealant applied under them.
Vapor barrier under corrugated sheets or metal tiles
Metal tiles are a thermally conductive coating, so with the onset of cold weather, condensation causes irreparable damage to them. To solve this problem, it is necessary to provide the roof with proper vapor barrier and. Before choosing, you should decide what is more important: price or efficiency? Let's look at which vapor barrier is better for metal roofing:
Cheap option - glassine and polyethylene
Glassine can last a long time, while it has sufficient flexibility and low cost. However, a large mass bad smell heat and installation difficulties make it not the best option.
Polyethylene retains steam well and protects the thermal insulation layer from moisture. It is cheap, but polyethylene is very easy to damage. It is difficult to install it yourself. Due to the significant mass, install the film standard method It’s hard to handle corrugated sheets. Therefore, installation occurs to the inside of the cladding using a stapler. The film is mounted in two layers.
Reinforced film, foil, membranes
In terms of price, it is also an acceptable option. Reinforced film consists of several layers with a reinforcing fabric mesh that adds strength. Light weight and rigidity allow you to install such insulation yourself. Attached with self-adhesive tapes. Significant disadvantage- this is the absence of an anti-condensation layer, which can negatively affect the insulation.
Diagram of a metal tile roof
Which vapor barrier to choose for a roof under metal tiles? One of best options is foil. It has low thermal permeability, which allows you to retain heat in the room, is lightweight and has sufficient strength. The big disadvantage of this material is its tendency to corrosion.
Useful video
We invite you to watch a video about the properties of vapor barriers:
Conclusion
The penetrating ability of steam is sometimes underestimated, which leads to rapid failure of thermal insulation. Therefore, it is necessary to take a responsible approach to the issue of vapor barrier and take into account all the nuances when choosing materials and carrying out work. This will ensure long term services for future construction.
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The building materials market is expanding more and more every year, not only quantitatively, but also qualitatively. The same applies to the construction industry - instead of traditional developments, today they use modern technologies and materials to achieve best result. In particular, we are talking about vapor barrier of roofing structures.
One of biggest problems for any roof is the effect of moisture on its internal elements. A particular danger is posed by condensation, which leads to the destruction of the roof even if it was made hermetically. To protect against steam and the condensation that goes hand in hand with it, vapor barrier materials are used. This article will discuss which vapor barrier is best for roofing.
Purpose of vapor barrier
A vapor barrier layer is an essential component of any roof, which can increase the service life of the entire structure and prevent its premature destruction. Vapor barrier is a thin material or film that allows air masses to pass through, but prevents the passage of moisture. As a rule, vapor barrier is installed in warm roofs, since it is in them that condensation constantly forms.
Before installation, the roofing vapor barrier material is cut into strips so that they can be attached to the rafters with a stapler or glue. The strips need to be laid with a slight overlap, and the joints are subsequently covered with sealant to ensure the tightness of the structure. When laying, you need to carefully monitor how the vapor barrier material is positioned - they all have one-sided passage, and an incorrectly installed vapor barrier simply will not work.
Roof vapor barrier film performs several important functions:
- Protection of insulation from moisture ingress. Air mixed with moisture enters the insulation, which as a result loses its thermal insulation qualities and cannot fully perform its functions. Naturally, practically no water comes out of thermal insulation material, therefore, when cold weather sets in, it freezes, and the ice violates the integrity of the insulation. After a few years of such exposure, the thermal insulation will have to be completely replaced.
- Protection of the rafter system from rotting. Moisture that gets into the under-roof space always leads to rotting of the wood. To prevent the roof frame from collapsing from moisture entering from the outside, waterproofing is used, and a vapor barrier layer is necessary to protect the roof from condensation entering inside.
- Increasing the service life of roofing coverings. Almost all roofing coatings are well protected from moisture with outside, but few materials can boast of reliable internal protection. Those who suffer the most metal coatings, subject to corrosion. Good vapor barrier for the roof protects it from rust, thereby allowing it to last longer.
Today, not a single roof can do without a vapor barrier layer. All roofing coverings are, to one degree or another, susceptible to moisture, so a vapor barrier is necessary so that the roof can serve its intended life.
Requirements for roof vapor barrier
The following series of requirements are imposed on vapor barrier materials aimed at their effective operation:
- Complete waterproofness, which protects the inside of the roof from the harmful effects of steam and moisture;
- High strength, allowing the vapor barrier layer to be installed without problems and ensuring its normal performance in the future;
- Durability - the service life of the vapor barrier must be no less than the service life of the roofing;
- Non-combustibility, which is especially important if the building has a high risk of fire.
Which vapor barrier to choose - which material is better
Before choosing a vapor barrier for a roof, you need to consider a whole range of parameters, which include:
- Climate in the region where construction is taking place. In order for the vapor barrier to be sufficiently effective, it is necessary to know the average temperatures in summer and winter.
- Purpose of the under-roof space. If a residential attic is to be built under the roof, high-quality vapor barrier is much more important than in the case of a non-residential attic, where the roof will be well ventilated naturally.
- Characteristics of roofing material. Different roof coverings require appropriate vapor barriers so that the properties of the materials do not ultimately conflict.
Roofing felt, roofing felt and waterproofing cannot be used as vapor barrier materials - these materials not only do not allow air to pass through, but also create favorable conditions for condensation to form.
Types of vapor barrier films and membranes
Currently used as a vapor barrier polymer membranes various configurations. This material due to the multilayer structure, it prevents the passage of moisture, but provides good ventilation of the roof frame.
There are the following types of vapor barrier materials:
- Vapor barrier films. This material is made in the form of thin polyethylene films, are lightweight and have a very reasonable cost. If necessary, you can purchase reinforced film, which has greater strength.
- Diffuse membranes. Such membranes consist of several polyethylene and propylene layers. Weight and thickness of vapor barrier of this type minimal.
- Anti-condensation films. This vapor barrier film for roofing is a special fabric that has vapor barrier properties. There is a pile on the inner surface of anti-condensation films that prevents condensation from settling.
Conclusion
Vapor barrier is integral element any modern roofing, ensuring its safety and durability. There are many vapor barrier materials, so the decision about which vapor barrier to choose for the roof must be extremely balanced and thoughtful.
Modern roofing technologies are very different from the methods of covering residential and commercial buildings a century ago. More advanced and durable roofing materials retain heat better, protect more reliably from moisture penetration and make housing more comfortable to live in. However, complete tightness also has back side – « Greenhouse effect» and the resulting condensation that settles inside the roof structure. To protect the frame and insulation from destruction as a result of getting wet, a vapor barrier is performed on the roof. In this article we will tell you what vapor barrier materials exist, how they differ and how they are used in roofing pie.
Roof vapor barrier is an essential component of the roofing pie, on which the service life and safety of the finishing coating depend. It is a thin fabric or film, the structure of which allows air to pass through, but blocks larger water molecules. Vapor barrier materials are used as part of a “warm” roof, since it is more prone to condensation due to heating of the under-roof space. Vapor barrier performs the following tasks:
- Prevents the thermal insulation material from getting wet. Warm, moist air that rises to the top penetrates the insulation, increasing the thermal conductivity of the material, which leads to a decrease in its efficiency. And when it freezes, the water absorbed by the fibers of the thermal insulation crystallizes, which leads to the destruction of the insulating layer after several freeze-thaw cycles.
- Protects the roof frame from rotting. Waterproofing protects rafter system roofs from the penetration of moisture from the outside, and vapor barrier materials reduce the formation of condensation, due to which microorganisms actively multiply, leading to wood rotting.
- Increases the service life of the roofing covering. Most topcoats are well protected from contact with moisture only with outside, while the lower surface often suffers from corrosion, which is formed as a result of the condensation process. A vapor barrier prevents rust from affecting the roofing material, extending its service life.
Note! Most modern roofing coatings require the installation of a vapor barrier, which provides protection against condensation and wetting. Only if this condition is met will the waterproofing material last the service life declared by the manufacturer.
Quality requirements
Vapor barrier materials are an essential component of the roofing pie of a “warm” roof; they are attached to the inner surface of the rafters with a construction stapler or adhesive. The material is cut into strips, which are overlapped so that condensation cannot penetrate through the joints. For efficient work vapor barrier required:
- Pronounced water resistance. Water vapor barrier must contain not only steam, but also water in order to reliably protect the “insides” of the roof from contact with water.
- Strength. High strength properties ensure resistance to mechanical damage during installation and operation.
- Long service life. Roof coverings last at least 15 years, since the vapor barrier cannot be replaced without dismantling the structure, it must have a service life no less.
- Non-flammability. To increase the safety of living in buildings with a high risk of fire, it is recommended to use non-combustible vapor barrier.
Important! Water vapor barrier is a material that combines the properties of waterproofing and vapor barrier coatings, that is, it does not allow water or steam to pass through, while remaining breathable.
Criterias of choice
During construction own home non-professionals often wonder which hydro-vapor barrier is better, and how to choose the right one for specific design material. Experienced craftsmen It is recommended to follow the recommendations of the roofing manufacturer, and also take into account the following criteria:
- Climatic conditions of the region in which construction is taking place. For the right choice vapor barrier material, it is necessary to know the average annual temperature in winter and summer period to determine the difference between indoor and outdoor temperatures.
- The nature of the use of the under-roof space. A heated attic can be located under the roof of the house, from which a large amount of heated, humid air, or non-residential attic, which is a natural air insulation for the roof surface.
- Properties of roofing material. Finish roof coverings have different composition, shape and installation method, therefore they require installation of a type of vapor barrier suitable for its properties.
Please note that the use of roofing felt, roofing felt or waterproofing material as a vapor barrier in combination with modern roofing materials not allowed, as they do not allow air to pass through. Despite affordable price And high strength, they do not protect the frame structure from condensation, but rather stimulate its active formation.
Kinds
Modern vapor barriers for roofs are high-tech polymer membranes, the multilayer structure of which effectively protects against the penetration of water and steam, but at the same time allows air to pass through, which is necessary for ventilating the rafter frame. IN roofing works The following vapor barrier materials are used:
Important! Vapor barrier materials have 2 sides, one of which allows steam or water to pass through, and the other does not. Therefore, during installation it is important to properly fasten the sheet, otherwise the operation of the roofing pie will be disrupted.
Video instruction