How to properly install a vapor barrier on a roof. Instructions for laying roof vapor barrier Correct installation of vapor barrier on the roof

It seems to people ignorant of construction that installing a vapor barrier on the roof of a residential building is excessive caution and reinsurance, which only results in additional expenses. However, every experienced roofing specialist will confirm that a correctly selected waterproofing film significantly increases service life roofing, and also improves the microclimate in the attic or attic. In this article we will tell you how to choose your own hydro-vapor barrier for the roof, as well as how the process of laying the material on the rafter frame occurs.

Vapor barrier film – special material, which is necessarily included in the composition roofing pie roofs, which has a pronounced vapor-blocking effect. According to the well-known law of convection, warmer and wet air, abundantly released during human activity, rises up into the under-roof space, then it settles in the form of condensation on the roof rafter frame, leading to dampening of the insulation and rotting wooden elements designs. The vapor barrier film as part of the roof performs the following functions:

Preservation of the performance qualities of the insulation. Installing a vapor barrier prevents condensation from accumulating inside thermal insulation material, which significantly reduces the efficiency of insulation.
Extending the service life of roofing coverings. Roofing materials are much better protected from moisture and corrosion with outside. Installing a vapor barrier solves the problem of condensation affecting the lower surface of the roof covering.
Protection of the wooden roof frame from rotting. A properly installed vapor barrier film prevents the roof rafters from getting wet due to condensation, which results in wood rotting.

Note! Vapor blocking film “works” effectively only if it is correctly selected for climatic conditions, roof structure, type roofing material. An unsuitable vapor barrier will not only be of no benefit, but will also intensify the process of condensation.

Material requirements

The most primitive and cheap material for roof vapor barrier is glassine. But in modern realities installation of this outdated canvas is practically not carried out, since there are more effective and durable analogues. Current vapor barriers are made from high-strength polymers with improved performance characteristics. A properly selected vapor blocking film has the following qualities:

Wide temperature range. To do possible installation in any climatic conditions, the film must withstand high, low temperatures and even sudden changes. The optimal temperature range for products of this type is considered to be between -70 and +100 degrees.
High degree of vapor permeability. The lower this indicator is for the vapor barrier, the better. Previously, polyethylene films with a vapor permeability of 13-20 g/m2 were laid, but now they are used for roofing polypropylene analogues, transmitting no more than 0.4 g/m2.
Long service life. Installing a vapor barrier whose service life does not exceed 10 years is impractical, since modern roofing materials last more than 20-25 years, and it is almost impossible to replace the film without disassembling the structure.
Elasticity. Vapor blocking film based on resistant polymers is highly elastic, which simplifies the installation of the material and also reduces the amount of damage during installation.

Important! Experienced craftsmen think that main indicator vapor barrier qualities – high strength qualities of the material. A properly installed vapor blocking sheet can even withstand the weight of snow, rain or melt water in the event of extensive damage to the roof.

Types of materials

Vapor-blocking film is a special material; it does not allow moisture-saturated, heated air to pass through, which leads to the formation of condensation, wetting of the insulation, and destruction of the roof frame. It is a thin, lightweight, but very durable and UV-resistant fabric based on thermoplastic polymers. Distinguish the following types materials for vapor barrier:

Polyethylene. Polyethylene is a fairly thin, lightweight and at the same time cheap polymer that is used to make vapor-blocking membranes. However, the strength qualities of such a film are low, so it is reinforced with a special mesh or fabric. Installation of laminated polyethylene vapor barrier is carried out in saunas, baths and other rooms where it is necessary to retain heat.
Propylene. Vapor blocking membranes based on propylene are characterized by increased strength, resistance to ultraviolet radiation, and low vapor permeability. They are a woven material with an anti-condensation layer.

Please note that the use of perforated materials to organize a vapor barrier for the roof is not allowed. It is important to choose the right vapor blocking membrane to protect roofs from the negative effects of condensation.

Technology of use

Laying vapor barrier material- an important technological operation performed during the construction of a roof, the quality of which determines its reliability, service life and strength. Installation of vapor barrier is carried out from the inside attic room after ready rafter frame roofs in accordance with the following rules:

Vapor blocking fabric can be laid lengthwise or crosswise rafter legs frame.
Be sure to start installation from the roof ridge, placing strips of material overlapping with an overlap of 10-15 cm.
The material will be fixed using staples construction stapler or galvanized nails.
The joints between the strips are hermetically connected using special adhesive strips located along the edges of the canvas.
After installing the waterproofing, a glazing bead treated with an antiseptic is nailed along the rafters so that the sheathing does not touch the membrane.

Important! The vapor blocking film has two sides, which differ in the nature of the surface and properties. When installing, you need to place the canvas with the rough anti-condensation side down.

Video instruction

Purpose and location of vapor barrier

It is known that the roofing pie consists of several layers (that’s why it is called that). It may include different quantity interlayers, but hydro-, heat- and vapor barrier remain unchanged. And if waterproofing is designed to prevent moisture from above from penetrating into the house, then vapor barrier prevents vapors from inside from entering the roofing pie.

It is extremely important to place the vapor barrier below the thermal insulation material, since otherwise it will absorb steam coming from below, swell and become damp. However, we all know that there are also roofs that are not insulated; is it really possible to make them without a vapor barrier? Unfortunately, no - 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 structure of a roof vapor barrier, you should study the structure of the roofing pie:

The roof covering can be continuous or consist of segments (tiles, slate). It is laid on a wooden sheathing or monolithic base.
Waterproofing layer – protects subsequent layers from moisture penetration from the outside. Is waterproof non-woven material, which is attached to the sheathing, leaving a small gap between the next layer.
Insulation – roofing thermal insulation materials are slabs with minimal thermal conductivity. They can be made from compressed mineral or stone wool, polystyrene foam or polyurethane foam. Depending on the material, water absorption also differs, which also affects the choice of vapor barrier. Polyurethane foam and polystyrene 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 sheathing immediately after the insulation and leave a gap between the sheathing ceiling material to ensure natural ventilation. When water vapor coming from below hits the membrane, condensation will form, which will flow down and dry due to 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 retain heat and prevent icing of the roof, and in summer it will provide more coolness.

If a vapor barrier is missing or incorrectly installed in the roof of a house, this will inevitably lead to the formation of unaired condensation, dampness, mold and fungi. Eventually, wood structures and roof elements will rot and collapse.

Vapor barrier materials

Today you can find a lot of roofing materials on the construction market. Most of these are polyethylene-based films. They are waterproofing, vapor barrier and antioxidant. The latter are special in that with inside covered with an absorbent fleecy fabric layer that actively collects condensation, preventing it from getting onto the next layer of roofing cake.

Previously, the main material for roof vapor barrier was glassine. Today it is used only by extremely economical builders, but if you look at the performance characteristics of glassine and compare them with the qualities of modern materials, the benefits of the latter will be obvious.

Depending on the physical and technical parameters, three types of vapor barrier films can be distinguished:

All film materials used for vapor barriers must have good elasticity, be tear-resistant and as comfortable as possible to use. It is extremely important that the vapor barrier film does not tear during fixation, but grips fastener. Even if there is accidental mechanical damage to the roof, for example, due to a tree branch falling during a hurricane, the vapor barrier should 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 sheathing and rafters fail.

Vapor barrier with isospan

One of the most popular materials on the domestic market is isospan roof vapor barrier. It is relatively inexpensive, has impeccable 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 intended for a specific purpose, but 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 variation of Izospan.

Izospan B is widely used among professional builders and self-taught owners. It can be combined with any type of roofing. In addition to protecting the insulation from moisture, it does not allow microfibers from the cake to fall off inside the room, as is often the case with other materials.

Installation of vapor barrier

It doesn't matter if you do a vapor barrier for flat roof or work with gable roof– the film or membrane should be installed only after laying the insulation.

Features of vapor barrier installation:

The canvases can be installed both vertically and horizontally.
If you preferred horizontal installation, start installation from the top.
Lay the pieces of canvas with an overlap of at least 10 cm. Be sure to seal the seams with single-sided or double-sided adhesive tape.
Choose a wide ribbon of at least 10 cm.
Double-sided tape is glued inside the overlap - first stick it to the bottom layer, then peel it off protective covering and fix the top one with an overlap.
If you are laying a vapor barrier along the rafters without rough filing the insulation, overlap and fix the sheets directly on the rafters.
TO wooden sheathing or the vapor barrier is secured to the rafters with a construction stapler or galvanized nails (they do not rust).
It is recommended to strengthen the places where the canvases are glued with pressure 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 contact with passages, hatches or roof windows, a so-called attic apron should be installed through the roof, which is usually included in their package. If it is not there, glue it around the perimeter window frame or opening 2-sided butyl tape.
Where it passes through the roof water pipes roll the vapor barrier material down, wrap it around the pipe and seal it tightly with electrical tape.

When the vapor barrier is laid, attach bars treated with antiseptics on top of it at a distance of 50 cm from each other. This way, you will create an air corridor where condensation will quickly evaporate, and the film will not touch the ceiling cladding. If you are using vapor barrier membrane, it is not necessary to install bars. But they will come in handy to occupy this space with various communications. If you plan to decorate the interior of the house with plasterboard, use a galvanized metal profile instead of wooden blocks.

Errors when installing vapor barriers

Very often, when arranging a roofing pie, builders make mistakes that lead to fatal consequences. If the location of the insulating layers is mixed up, the roof may become unusable after just a year of operation.

We have prepared a list of the most common mistakes when installing vapor barriers:

The junction areas 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, truss structures begin to rot.
Using narrow adhesive tape to seal seams - during use, 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, so you need to leave a margin in the form of a fold of 20-30 mm.
Film around skylights is not protected by finishing from the inside - if this is not done, after a few months of operation the vapor barrier will completely become unusable and collapse under the influence of sunlight.
The film envelops the rafters - if the vapor barrier material goes 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 internal 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 tightness of the fixation.
If you attach the film to a rough brick wall or surfaces made of unplaned wood, this can only be done using polyurethane, acrylic glue or synthetic rubber.
Do not use polyurethane adhesive tapes or butyl rubber tapes as they do not adhere well and may soon peel off from the surface.

The penetrating ability of water vapor is extremely high, so you should approach the vapor barrier device extremely responsibly. In addition to the popular Izospan, TechnoNIKOL roof vapor barrier is widely used today. The most important thing is to choose the materials correctly and install them in the right sequence, then the roofing pie will last for decades without repair.

The roof structure is a complex system. It consists of several layers of dissimilar materials, each of which performs its own unique function.

To provide comprehensive protection buildings from influence environment it is necessary to carry out all installation work with high quality, as well as correct choice basic and insulating materials. This whole process is briefly called.

The standard composition of the roofing cake includes:

Internal finishing layer;
Lathing design;
Counter-breach;
(does not apply to a cold attic);
(about);
Ventilation shafts or gaps;
Roofing covering.

Why do you need a roof vapor barrier? 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 porous structure, since the air contained in them performs the function heat insulator. On contact with a colder environment, steam turns into condensate, which lingers in the voids.

This may result in loss of functionality heat-insulating material, as well as the occurrence of decomposition and decay processes in summer. In winter, freezing water expands, thereby destroying the connections between cellular elements.

The main characteristic of vapor barrier material is vapor permeability, depending on the density of the material. The values of this indicator can be found in the passport of the packaged building material.

Form of release of vapor barrier films - roll. Vapor barrier can be made from various materials. Some of them have additional positive properties, increasing operational efficiency interior spaces building. Installing a vapor barrier on a 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

Made from low-density polyethylene, which provides an increased degree of steam penetration. This material often has defects due to the ingress of foreign particles during manufacturing. The cheapest type of insulating material.

Polyethylene films with reinforcement

Compared to single-layer polyethylene, reinforced vapor barrier has little greater thickness, since it includes a reinforcing frame. It consists of polymer twisted threads located in mutually perpendicular directions. The mesh is attached to the polyethylene base by warm pressing.

This technique does not affect waterproofing and mechanical properties material, but maybe reduce the degree of vapor barrier.

Anti-condensation film

Made from two layers: smooth and fleecy. The smooth layer is attached to the insulated surface. The fleecy layer is created from cellulose fibers. Steam hitting such a surface clings to fibrous structure, thereby preventing moisture from draining onto underlying structures pitched roofs. Excess water is removed along with the air through the ventilated space.

Polymers with foil layer

They are made of penofol or foamed polypropylene, coated with a thin layer of metal. Thanks to its reflective properties metal surfaces such a vapor barrier carries out additional function heat loss protection.

Membranes (film for roof vapor barrier)

Membrane vapor barrier materials are divided into five main classes:

Type A. Has increased resistance to moisture and wind. It is laid between the roofing covering and the heat-insulating layer. Manufacturing technology: spunbond. This vapor barrier does not allow moisture to flow through the cracks of the roofing material, as well as from the condensation that forms. The absence of a laminating layer allows the use of such membranes in roof structures with a slope more than 35 degrees. To remove excess moisture, it is necessary to arrange ventilation holes made of double lathing located between the membrane and insulation.
Type AM. Unlike Type A has a multilayer structure. It is placed between the insulation and the roof to provide adequate protection from negative atmospheric influences. The most common is 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 done directly on the heat-insulating layer, which reduces labor costs for creating a ventilation gap.
Type B. Double layer material. Consists of a layer of vapor barrier film and spunbond. It is used to protect insulation from internal building vapors. Applicable only in insulated roof structures.
Type C. Manufactured similarly to type B membranes. It is more durable and thick layer spunbond, providing more high-quality protection insulation against moisture. Used in insulated and non-insulated, pitched and flat roofs.
Type D. Consists of polypropylene fabric, protected on one side by a laminating polymer coating. The structure of the material allows it withstand significant mechanical stress. This dictates its installation between the insulation and the attic floor screed, as well as in non-insulated roofing structures.

Which side is the vapor barrier for the roof laid on?

The principle of installation of vapor barrier materials depends on which side the layer responsible for repelling water vapor is located:

We have figured out which side to lay the vapor barrier on the roof, now we will look in detail at how to properly lay the vapor barrier on the roof.

Vapor barrier for the roof: how to install it correctly using special technology

Laying a vapor barrier on the roof is carried out as follows:

Laying can be done vertically and horizontally. In the second option, installation of roof vapor barrier is carried out starting from ridge part roofs. Each subsequent stripe is superimposed on the previous layer with an overlap, the size of which should not be more than 10 cm.

CAREFULLY!

When joining elements, mandatory seam sealing, providing optimal protection against moisture ingress into the gap between them. Most often, sizing is done with single- or double-sided adhesive tape or tape. On roofs with a slope of up to 3 degrees additional fixation using wooden planks.

To wooden ones rafter elements vapor barrier is attached using galvanized nails or a construction stapler.
When installing films and membranes near roof hatches, you need to use a special vapor barrier apron, which is included as standard.
At the junctions with ventilation pipes, film and membrane structures are folded down, wrapped around the pipe and tightly fixed with construction tape.
After laying the vapor barrier layer, it is necessary to nail wooden blocks. The rules for laying vapor barrier on the roof dictate next rule — the pitch between the sheathing 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 a roof, you can move on to the issue of waterproofing.
If the vapor barrier for the roof was damaged, then small cuts or holes can be seal with special tape for vapor barrier membranes.

Roofing pie diagram

Sealing joints with tape

Final vapor barrier option

NOTE!

A tightly stretched film is the key to a good vapor barrier.

Hydro and vapor barrier of the roof - what is the difference?

Useful video

And now we invite you to familiarize yourself with the video instructions on roof vapor barrier:

Conclusion

Vapor barrier is the easiest and thin layer roofs. But neglect of its structure can nullify all material and physical efforts to create quality roof. So don't neglect it important element, it will significantly increase the service life of the entire building.

In contact with

A properly installed roof vapor barrier effectively retains heat in a residential building and ensures a normal microclimate in it.

Any of us wants to live in a warm and cozy home. Your home will be such only if you build it according to good project, not forgetting the need for proper installation of the roof and its reliable protection from getting inside premises external moisture. In addition, you should also remember negative impact onto the roof of steam formed in living and other rooms.

Physical laws say that warm air the house is saturated with water vapor. This mixture rises to ceiling surface and accumulates there, trying to find a way out of the home. The air tends under the roof, where the temperature and humidity are low.

If on its way it encounters a heat-insulating layer that is not additionally protected by anything, a mixture of steam and heated air will begin to penetrate into the insulation, leading to its destruction.

Mixture of steam and heated air

When it gets cold outside, the steam on the outside of the insulator will become frost and then turn into a crust of ice. The formation of the latter will lead to freezing of the heat-insulating material. All its cracks will be filled with ice. With the arrival of the warm season, frozen steam will begin to melt and spread over the interior roofing. As you yourself understand, this will cause the insulation to lose its heat-insulating characteristics.

If you insulated the roof with polystyrene foam, it will last a couple of winters, after which it will become completely unusable. Often used for thermal insulation mineral wool will stop fulfilling his protective functions already in a year. Avoid this serious problems allows vapor barrier of the roof. You can easily create an additional barrier with your own hands that will prevent condensation from entering the insulation. This protection:

guarantees non-rotting of wood structures;
eliminates the risk of heat leakage from the home;
prevents the appearance of mold under the roof.

Thus, the vapor barrier ensures that water vapor that is dangerous for the heat-insulating layer is removed to the outside. It is considered by construction professionals to be an essential element of a roof ventilation system.

Previously, the vapor barrier for the roof was made with roofing felt. This material has proven itself well. Roofing felt is attached to the roof on rafters made of OSB boards, or on rigid wood flooring, under which they must leave small gap for high-quality ventilation of the structure.

This vapor barrier is effective. But its cost is quite high due to the need to build a deck. In addition, installing insulation using roofing felt significantly increases labor and time costs. Therefore, modern experts call such vapor barrier on the roof a thing of the past.

Currently, higher quality and environmentally friendly film materials are used much more often. Their installation does not require the installation of wood flooring or slabs. And most importantly, their installation can be easily done by anyone with their own hands, even those who are not very strong in construction science.

Eco-friendly film materials for vapor barrier

Vapor barrier films have high tensile strength, as they are made of elastic components. Due to this, installing them yourself does not bring surprises - the films do not tear when fixed with dowels. Also film products:

maintain integrity when the roofing structure receives any mechanical damage;
are able to withstand serious loads that occur when the heat-insulating material loses its initial elasticity and slides onto the elements.

Vapor barrier films are made from polypropylene and polyethylene. Polypropylene products are made from woven material, which is laminated on both sides using a special technology. Due to this, the film becomes resistant to ultraviolet radiation.

Sometimes another layer is applied to polypropylene products - an antioxidant one. It is necessary to prevent condensation. This layer absorbs moisture coming from inside the house and holds it until the condensation conditions completely disappear. Installation of films with antioxidant coating is carried out smooth surface up, and the rough one (on which the additional layer is located) down.

Antioxidant Coated Film

Film products made of polyethylene are less durable. They need to be additionally reinforced with mesh (reinforcement) or special fabric. Polyethylene films are non-perforated and perforated. The vapor barrier on the roof should be made from non-perforated products. Their perforated counterparts are designed for roofing waterproofing.

If you plan to install an insulating coating yourself on the roof of a swimming pool or home bath, it is better to use films laminated with reflective aluminum foil. They have proven themselves excellent as protectors against steam in humid and very hot rooms.

As you can see, there is no clear answer to the question of which insulation is best suited for roofing. For some objects you can use inexpensive polyethylene films. But other rooms need higher quality and, naturally, more expensive vapor barrier material with special properties.

In any case, you should remember that the vapor insulation you purchase must meet all the basic requirements for such products. If you install low-quality material, it will quickly fail, which will require its replacement. But this will not be easy to do, because the vapor barrier is installed in hard to reach place. Getting under the roof structure is very difficult.

You should install films to protect the roof from steam yourself, taking into account the following recommendations:

Protective sheets can be mounted horizontally and vertically.
The vapor barrier layer is laid from the inside of the object after completion of the installation of insulation.
To elements roofing structure The vapor barrier made of wood is fixed with nails with a galvanized surface or special staples.
In areas where ventilation pipes are laid through the roof, the film vapor barrier material is folded down and carefully wrapped around the pipe. After this, you need to seal the film with adhesive one-sided tape.
If you are laying material horizontally, the process starts from the top. The overlap of the canvases should be 10–12 cm. In this case, you will need to do a high-quality sealing of the resulting seams with your own hands. Double or single sided adhesive tape is suitable for these purposes. If a double-sided product is used, it is attached inside the overlap. When single-sided tape is used, it is installed from the outside.
Without exception, all joints should be glued, ensuring their complete tightness. The joint areas can be reinforced with strips (they are called clamping strips), which must be used when the density of the heat insulator is low, as well as on roofs with a large (about 30°) slope.
Installation of the vapor barrier is carried out with a slight interference fit; even slight sagging of the material is not allowed.

Installation of roof vapor barrier

In those areas where the vapor barrier is adjacent to various passages and openings (pipes, hatches, attic window openings, etc.), you need to install a special apron. You can use butyl double-sided tape instead. It should be placed around the perimeter of the frame of the structure that interferes with you.

Another one important recommendation for home craftsmen who love to do everything with their own hands. After installation of film vapor barrier products you need to lay between the thermal insulation and the ceiling internal lining small pieces of wood that have previously been antiseptic treatment.

These elements create air gap between the steam barrier and the casing and securely fixed thermal insulation coating. Their installation, among other things, makes it possible to install any engineering communications in the resulting space. Note! When covering a room with plasterboard, it is better to use galvanized profiles instead of wooden blocks.

Properly installed thermal insulation will ensure you a pleasant and carefree life in your home!

For people far from the topic of construction, it may seem that installing a roof vapor barrier is not an important process. However, any master closely familiar with roofing work can say that it's not extra waste money or precaution. High-quality roof waterproofing work extends the service life of the roofing and helps create a favorable microclimate in the attic or attic space. But for this you need to know the rules for choosing vapor barriers and waterproofing materials and methods of laying it on the rafter system.

Definition and purpose of vapor barrier for roofing

A vapor barrier film is a special material in the roofing pie that can block steam as much as possible.

According to the laws of physics from school course warm air, saturated with water vapor, and which is an integral part of human life, rises. In the under-roof space it turns into condensation, and, settling in this form on the rafters, becomes the cause of rotting wooden structures and damage to insulation.

The use of vapor barrier materials for roofing helps solve the following problems:

Maintaining the quality characteristics of thermal insulation material. Laying a vapor barrier prevents the formation of condensation, which negatively affects the quality of insulation.
Extending the service life of roofing materials. The vapor barrier protects the roofing material from negative impact moisture and corrosion from the inside.
Protection of wooden elements rafter system from the appearance of rot. Thanks to the protection of the vapor barrier film, the resulting condensation does not affect wooden frame Therefore, the wood remains dry and not susceptible to rotting.

When deciding how to properly make a roof vapor barrier, you need to select the appropriate material. Several factors are taken into account: climatic conditions, roof design, type of roofing material. Incorrect choice may cause increased condensation formation.

Quality characteristics of the material

With a small construction budget, private developers choose simple and cheaper materials. In particular a budget option vapor barrier involves the use of glassine. But today there is a huge variety of materials similar type, characterized by greater efficiency and durability. High-quality vapor barrier for roofing is made of high-strength polymers, which are characterized by improved properties.

Vapor locking can be effective provided the material meets the following requirements:

Possibility of operation in a wide temperature range. Optimal indicators should correspond to temperatures from -70 to +100 degrees.
Proper vapor permeability. Modern materials they allow no more than 0.4 g/m2 to pass through, but outdated versions could “boast” of vapor permeability up to 20 g/m2.
Long operational period. The recommended service life of the vapor barrier should correspond to the service life of the roofing material.
Good elasticity. A material that can bend well not only simplifies installation work, but also deteriorates less during installation.

In addition, high-quality vapor barrier must have high strength characteristics. At correct installation laid durable fabric is capable of holding snow, melted and rainwater in case of damage to the roofing material.

Types of vapor barrier materials

A high-quality roof vapor barrier film retains warm air saturated with water vapor well, thereby preventing the formation of condensation, wetting of the thermal insulation and destruction of wooden roof structures. Modern vapor barrier is thin and lightweight material, made of thermoplastic polymers, characterized by strength and resistance to ultraviolet radiation.

Today, you can solve the question of how to make a roof vapor barrier using the following materials:

Polyethylene. This is the cheapest polymer, characterized by lightness and low thickness. Vapor blocking membranes are produced on its basis. To increase strength polyethylene film They are reinforced with a special mesh or fabric. Laminated options are widely used in places where heat preservation is important, for example, in a sauna or bathhouse.
Propylene. A propylene-based membrane is characterized by high strength, resistance to impact ultraviolet rays, minimum vapor throughput. This material is a woven base with an anti-condensation layer.

According to experts, the use of perforated materials does not allow desired effect. For the right decision tasks, how to make a vapor barrier on the roof, and to reliably protect the roof from condensation, it is better to choose a vapor blocking membrane.

Rules for installing vapor barrier on the roof - how to do it correctly

Installation of vapor barrier material is considered very important stage from the entire roof construction process, since the service life, strength and reliability of the structure being built depends on this.

The technology for installing roof vapor barrier involves working on the inside of the rafter frame in accordance with the following rules:

Laying vapor barrier material can be done across the rafters or along them.
Work should begin from the ridge, and the strips should be installed with an overlap of 10-15 cm.
The panels are fixed with construction staples or galvanized nails.
For a hermetically sealed connection of the strips on the edges of the material there is a special adhesive composition.
Upon completion of installation, a counter-lattling treated with an antiseptic solution is filled along the rafter legs.

It should be noted that the sides of the roofing vapor barrier film have different properties and surface characteristics. During the installation process, it is important that the rough anti-condensation side is located at the bottom.