How to properly install roof insulation. Installing a Roof Vapor Barrier - Detailed Technology for Installing a Vapor Barrier Membrane Roof Vapor Barrier Installation

20.06.2020

An innovative way to protect your home from moisture is a vapor barrier for the roof. Special materials laid under the roofing increase the quality of heat preservation in the house, prevent the influence of internal moisture on the structure.

Lack of vapor barrier - consequences

Laying a vapor barrier on the roof prevents the destruction of the thermal insulation layer and the roof structure. Steam generated from cooking, cleaning, bathing and other household chores rises under the roof. When exposed to low temperatures, condensate forms, which, without a vapor barrier layer, penetrates into the fibers of the warm material and violates its integrity.
As a result of constant wetting, wooden floors begin to rot, and major repairs may soon be needed. To extend the life of the roof, do not neglect preventive maintenance.

Is there a difference between vapor barrier and waterproofing?

When creating a waterproofing protection for a roof, it is important to take into account its difference from waterproofing. The main point is the vapor permeability of the materials used:

Waterproofing is mounted in places where moisture drips, and condensate flows off the roof along the envelope edges.
The elimination of steam formation is needed to block the ingress of steam into the inner layers of the insulation.
Waterproofing is placed under the main coating material, and vapor barrier - from the side of the attic.

Waterproofing layers protect against the spread of water, but do not prevent steam, so it is important to choose the right material to eliminate vapors.

The choice of vapor barrier material

The simplest option is roofing material, but its flooring requires a significant amount of time. Progressive owners of private houses prefer high-quality building materials. Which vapor barrier to choose from the modern materials on the market? Each of them has a number of advantages and disadvantages, so it is advisable to pay attention to the technical characteristics.

Polyethylene vapor barrier

The polyethylene film serves as a membrane that prevents dampness from penetrating into the insulation. Due to its ability to block moisture, it is used as a waterproofing.
To prevent the appearance of evaporation, the perforated film is laid in 2 layers - on top (moisture does not enter from the outside) and below (steam generated in the house does not penetrate) of the insulation. When planning which side to lay the vapor barrier, consider the texture of the material. The smooth side is attached to the insulation, and the rough side is visible from the outside.
An incorrectly fixed layer, without releasing steam upward, will accumulate condensate. To avoid leaking or rotting of the new roof, follow the installation technique:

film laying starts from above, always with an overlap of 10 cm;
joints are fixed with stationery tape;
the film is attached to the rafters with the help of building brackets.

When buying a polyethylene vapor barrier material, pay attention to its quality - a cheap one will quickly become unusable and will not provide adequate protection.

Polypropylene vapor barriers

Polypropylene vapor barriers are an economical product with smooth and rough sides. It is necessary to lay the vapor barrier according to the previous technique - with the smooth side to the heat-insulating surface. The self-laying polypropylene layer requires compliance with the work algorithm:

installation is overlapped by 10 cm.
it is necessary to carefully fix the barrier to the rafters. Use an adhesive based on synthetic rubber, a mixture of polyurethane and acrylic. The adhesive tape is not able to hold the weight of the material.
gluing points are reinforced with clamping beams.

After laying the propylene, be sure to apply an antioxidant compound to the surface - this will prevent condensation from forming.

Vapor barrier with foam

The material consists of two layers - foamed polyethylene and a thin aluminum part glued to the base. The foil layer is fixed with a reflective surface inside the room. The laid penofol also copes with the task of thermal insulation, because. capable of reflecting infrared rays.
When carrying out construction tasks, be guided by the following technique:

insulation is attached to the rafters with a construction stapler or wide-head nails.
To ensure the tightness of the joints, adhesive tape is used.
in places where the material adjoins the wall, a layer of sealant is applied and the film is ironed.

The optimal foam thickness for high-quality steam insulation is 10 mm.

Diffuse membranes

Perforated nonwoven fabric with small holes is produced in the form of a film. Small cells allow steam to pass through and retain water. Diffuse membranes are laid, excluding the ventilation gap, close to the insulation layer.
Features of the installation of products are as follows:

the membrane is fastened with brackets to the rafters.
during installation, the material is slightly stretched, sagging by 1-2 cm is allowed.
joints are glued with a special adhesive tape.

The total cost of work will depend on the density of the film, but you cannot save on the quality of the vapor barrier.

Antioxidant films

The main advantage of antioxidant films lies in their texture. Inner surface It consists of a fluffy non-woven material that absorbs moisture. The fleecy side prevents moisture from entering the insulation, and the moisture in it dries out due to air movements in the gap. Installation is similar to other diffuse membranes or penofol.
The owners of private houses prefer one-sided and two-sided materials. The former can conduct steam in one direction, while the latter can be placed on the insulation on either side. Give preference to multilayer membranes that accumulate vapors and remove them gradually.

Ways to protect the roof from evaporation

Before starting construction work, identify areas of greatest risk - the boundaries of contact between cold and heat on the roof. Depending on the complexity of the event, you need to choose an acceptable method of vapor barrier.

Laying roll steam protection

Penofol, diffuse membranes or polyethylene can provide high-quality vapor blocking. Rolls need to be rolled out and measured to the required length. Then the canvas is fixed with wooden slats or aluminum profiles horizontally. A ventilation gap of 4 cm should be arranged between interior decoration and a vapor barrier layer. The fastening strength is controlled by the tension of the material.

Formation of the leaf system

To fix the sheet vapor barrier, a profile frame is installed. The material is inserted into the structure, fixed with self-tapping screws, and the joints are sealed with PVC or isospan. When fastening, it is important to take into account the features of laying the material.

How to choose the right side for the placement of the vapor barrier?

The vapor barrier film consists of two layers. The rough side holds the condensing droplets and gradually evaporates them. A smooth layer is needed for a high-quality connection with the insulation and return of heat to the dwelling, so the material should be fixed on it.

General algorithm for installing vapor barrier materials

All vapor barrier materials differ only in structure, but are mounted in the same way. Following the instructions below, even a novice builder will figure out how to properly lay the vapor barrier on the roof.

Installation takes place on the inside of the roof in a horizontal or vertical way.
With a horizontal technique, the canvas should be rolled out from above, segment by segment.
The rolls are stacked with an overlap of 10 cm and glued with stationery tape 10 cm wide.
A double-sided tape is glued on the inside of the overlap to the bottom layer, then the protection is removed and the top layer is glued onto the adhesive tape.
Using vapor protection for wooden buildings, the material is laid along the rafters, securing it with a stapler or galvanized nails.
Working on a roof with a loose heat-insulating coating, they press the vapor barrier with special strips.
At the junction of the rolls to the hatch, attic windows or entrance groups make an apron or glue window openings with butyl tape.
If there are communications, the pipes are wrapped with vapor barrier material and sealed with electrical tape.
The vapor barrier is laid in layers - behind the roofing and behind the insulation. A gap is necessarily maintained, which creates the effect of ventilation and contributes to the high-quality drying of fumes.

Installation of vapor barrier should be carried out simultaneously with roofing work, since prolonged exposure to the sun reduces the film's insulating properties.

Common Mounting Mistakes

How to lay vapor barrier without mistakes? Pay attention to the shortcomings that can be made in a hurry or with insufficient awareness of the installation process:

Adjacent defects to the roof elements occur without sealing the material with glue and adhesive tape. The more complex the roof structure, the more expensive the vapor barrier process.
narrow adhesive tape (up to 50 mm) should not be used. Work with stationery tape that is at least 10 cm wide.
do not forget to leave a deformation stock of material for window openings.
if the vapor barrier material around the windows is not protected by interior decoration, it will quickly lose its properties.
the vapor barrier film should not go around the rafters. Moisture will get into the formed space and lead to the decomposition of wood.
the film at the junction must be hermetically fixed. Consider the characteristics of the material, because adhesive tape is not compatible with everyone. Use an adhesive based on acrylic or polyurethane mixtures or synthetic rubber.
loosely sealed joints between the canvases lead to a loss of vapor barrier properties. Carefully glue the places where the material is applied to each other.
the use of polyurethane adhesive tapes based on butyl rubber contributes to the depressurization of the vapor barrier, due to their insufficient adhesive properties.

Carrying out vapor barrier works will help to achieve the optimal ratio of humidity and temperature conditions in the house, increase the life of the roofing flooring. Following simple rules, you can perform the vapor barrier yourself.

Purpose and location of the vapor barrier

It is known that the roofing cake consists of several layers (that's why it is called so). It may include a different number of layers, but hydro, heat and vapor barriers remain unchanged. And if the waterproofing is designed to prevent moisture from penetrating inside the house from above, then the vapor barrier does not allow evaporation from the inside to enter the roofing pie.

It is extremely important to position the vapor barrier below thermal insulation material, because otherwise it will absorb steam coming from below, swell and become damp. However, we all know that there are non-insulated roofs, can they really be made without vapor barrier? Unfortunately, no - the vapor barrier not only preserves the insulation, but also maintains a comfortable indoor climate. If it is not there, the house will be very stuffy and humid, and cozy housing will turn into an ordinary greenhouse.

In order to fully appreciate and understand the roof vapor barrier device, you should study the structure of the roofing pie:

Roof covering can be continuous or consist of segments (tile, slate). It is laid on a wooden crate or a monolithic base.
Waterproofing layer - protects subsequent layers from the penetration of moisture from the outside. It is a waterproof non-woven material that is attached to the crate, leaving a small gap between the next layer.
Insulation - roofing heat-insulating materials are plates with minimal thermal conductivity. They can be made from pressed mineral or rock wool, styrofoam or polyurethane foam. Depending on the material, water absorption is also different, 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 crate 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, condensate will form, which will flow 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 to keep warm and prevent ice on the roof, and in summer it will give more coolness.

If the roof of the house is missing or incorrectly installed vapor barrier, this will inevitably lead to the formation of non-weathered condensate, dampness, mold and fungi. Eventually the wood structures and roof elements will rot and collapse.

Vapor barrier materials

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

Previously, parchment was the main material for roof vapor barrier. Today it is used only by overly economical builders, but if you look at performance characteristics glassine and compare them with the qualities of modern materials, then the advantage 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 barrier must have good elasticity, be tear-resistant and be as comfortable to use as possible. It is extremely important that the vapor barrier film does not tear during fixing, but wraps around the fastener. Even with accidental mechanical damage roofs, for example, due to a tree branch that fell during a hurricane, the vapor barrier must maintain 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 fail.

Vapor barrier isospan

One of the most popular materials in the domestic market is isospan roof vapor barrier. It is relatively inexpensive, has excellent performance, 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, 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 V 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 the microfibers from the cake to crumble into the room, as is often the case with other materials.

Vapor barrier installation

It does not matter whether 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:

Cloths can be installed both vertically and horizontally.
If you prefer horizontal installation, start installation from above.
Lay the pieces of cloth with an overlap of at least 10 cm. Be sure to glue 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 on the bottom layer, then remove the protective coating and fix the top one with an overlap.
If you are laying a vapor barrier along the rafters without a rough filing of insulation, overlap and fix the sheets directly on the rafters.
A vapor barrier is attached to a wooden crate or rafters construction stapler or galvanized nails (do not rust).
It is recommended to strengthen the places where the sheets are glued 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 junction points to the aisles, hatches or dormer windows, a so-called dormer apron should be organized through the roof, which is usually included in their package. If it is not available, glue 2-sided butyl tape around the perimeter of the window frame or opening.
At the points of passage through the roof water pipes wrap the vapor barrier material down, wrap it around the pipe and seal it tightly with electrical tape.

When the vapor barrier is laid, attach antiseptic-treated bars on top of it at a distance of 50 cm from each other. Thus, you will create an air corridor where condensate will quickly evaporate, and the film 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 finish the interior of the house with drywall, use a galvanized metal profile instead of wooden bars.

Errors when installing vapor barrier

Very often, when arranging a roofing pie, builders make mistakes that lead to fatal consequences. If you confuse the location of the insulating 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 hermetically sealed, as a result of which the effectiveness of the vapor barrier is reduced to a minimum, the insulation becomes damp, and the truss structures begin to rot.
Using a narrow adhesive tape to seal the seams - during operation, adhesive tape 5 cm wide or less will simply peel off. The recommended tape width is 10 cm or more.
There is no deformation margin when working with window openings - any house shrinks, so it is required to leave a margin in the form of a fold of 20-30 mm.
film around skylights not protected by interior decoration - 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 wraps around 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 interior walls houses, mines 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 attach the film to a rough brick wall or unplaned wood surfaces, this can only be done with polyurethane, acrylic glue or synthetic rubber.
Do not use polyurethane adhesive tapes and butyl rubber tapes, as they do not adhere well and may soon peel off the surface.

The penetrating power of water vapor is extremely high, so you should approach the vapor barrier device very responsibly. 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 right sequence, then the roofing cake will last for decades without repair.

Humid air in residential premises tends to go outside, including through the roof. Laying a vapor barrier on the roof helps to avoid the accumulation of moisture in the roof structure. The article talks about the varieties, properties and functions of vapor barrier films offered on the construction market. You will get acquainted with the intricacies of laying technology and the main stages of roof vapor barrier work.

Vapor barrier on mansard roof Source oooarsenal.ru

Vapor barrier functions

One of the conditions for long-term operation of the roof is a ventilated roofing device. Air gaps in a properly constructed roof help regulate the temperature in your home, keeping you warm in winter and cool in summer. The air rising from the living quarters is warm and humid; once in the under-roof space, it cools down. At the same time, water vapor collects in condensate and tends to settle in the roofing pie. Over time, if the roof is unprotected, the insulation becomes damp, and the wood of the truss frame becomes a prey for mold.

The solution to this problem is the use of special protective layers in the roofing cake. For the normal functioning of the roof, waterproofing is laid on the outside of the insulation (under the roofing); under the insulation - a vapor barrier sheet, which has the following functions:

Insulation protection. The vapor barrier, which was installed in accordance with the technology, blocks the penetration of condensate into the heat-shielding layer. This preserves the performance characteristics of the material and the effectiveness of the insulation of the building.

The place of the vapor barrier film in the roofing cake Source stroyfora.ru

Rafter frame protection. A vapor barrier installed according to the rules will protect the wooden rafters from getting wet and rotting.

Extending the life of the finish coat. The lower surface of the coating is protected from moisture much worse than the front. The vapor barrier film protects the inside from harmful condensate.

material requirements

The main property of all vapor barrier materials is their ability to resist the penetration of steam. The lower the vapor permeability, the less water vapor is able to pass through the material layer, and the better the protective properties it has. Three classes of materials are on sale; they differ in two interrelated parameters: vapor permeability resistance and mechanical strength:

1 class. Rigid foil-based materials with the highest vapor permeability resistance.

Grade 2. Materials based on polyethylene or polypropylene.

3rd grade. soft materials with low (50-100 times lower than the 1st grade) indicators.

Vapor barrier and steam diffusion in the roof Source krovlyakrishi.ru

Film materials are also subject to Additional requirements, important for the durability of the roof:

Lifetime. Installation of a roof vapor barrier with a service life of 10-15 years is inappropriate for modern roof structures designed for 20-25 years. After 10-15 years have passed, the vapor barrier layer will no longer cope with its duties, which will begin to affect the condition of the entire roof. Replacing the film in this case is an extremely troublesome (and costly) matter, often associated with the analysis of the structure.

Operating parameters. Materials are valued that can properly perform their functions in a wide temperature range. Most film products are designed for operation in the range from -70 to +100°C.

Elasticity. A parameter that is important both for ease of installation and during operation, when a layer of insulation puts pressure on the film.

Flexibility is one of important properties Source iobogrev.ru

Types of films

The construction market is represented by rolled vapor barrier, created using several technologies and having a different set of properties and service life. Certified products are supplied with instructions with a detailed indication of the parameters of the material and its purpose - familiarity with this information will help you make the right choice. Roofing films offered on the market can be classified in two ways:

By material. Modern vapor barrier sheets are made of polyethylene or polypropylene.

By functionality. There are vapor barrier, waterproof and anti-condensate materials. The purpose determines which side to put the vapor barrier on the roof.

Polyethylene films

A single-layer underlay film with a low density, which, however, can provide sufficient tightness and protect the insulation from moisture. The main advantage of this insulating material is its budget cost. The main danger is low quality: manufacturing defects are not uncommon on the surface of the thinnest films, and the service life is not long.

Reinforced polyethylene film Source donnews.ru

roof repair service

Reinforced polyethylene

In terms of vapor transmission capacity, polyethylene films with reinforcement are comparable to the previous variety. The thin canvas is reinforced with a pressed-in frame made of polymer threads, which increases its strength and durability. The material has a minus - during thermal lamination (gluing layers), the junctions of polyethylene with a reinforcing mesh become thinner, forming microscopic cracks. Western European manufacturers have practically abandoned the production of reinforced film made of polyethylene, since it is not able to provide a stable vapor barrier.

Polypropylene films (vapor barriers)

Reinforced propylene films compare favorably with polyethylene materials by longer service life, increased strength and a higher degree of vapor barrier. Polypropylene protection is resistant to ultraviolet and low temperatures, elastic enough under tension and does not tear on bends; the combination of qualities allows for the installation of waterproofing on the roof in winter.

Anti-condensation films Source info-krovlya.ru

bag fabrics

The vapor barrier fabric looks like burlap; It is made of polypropylene threads laminated with a polyethylene melt. Vapor barrier is characterized by high mechanical strength, but weak vapor protection, which makes it mainly used in the arrangement of cold roofs.

On our site you can find contacts of construction companies that offer the service of completing unfinished houses. You can directly communicate with representatives by visiting the exhibition of houses "Low-Rise Country".

Anti-condensation membranes

The material is suitable for both steam and hydroinsulation. One side has a rough surface that makes it difficult for condensation to form. During installation, this side is placed inside the building; moisture is removed through the ventilation gaps. The second, smooth side of the material is on top and protects against possible infiltration of atmospheric water.

foil films

An aluminum foil vapor barrier is the most effective vapor barrier; it is widely used to isolate wet rooms (kitchens, baths, saunas). The use of foil materials is most appropriate for the construction of a mansard roof. The foil surface is able to accumulate heat, reflecting it inside the housing.

Vapor barrier foil film Source mokivezi.lt

Diffusion non-woven membranes

Technological material produced from specially perforated polyethylene or polypropylene. The smallest, diffusion openings of the membrane allow air with water vapor to pass through, but retain water (droplets or condensate). Regardless of what technology and what material the membrane is made of, it will still exhibit “breathing” properties, providing diffusion (penetration at the molecular level) of water vapor with parallel protection against condensate. There are the following types of nonwoven membranes:

Diffusion. Such materials are characterized by a lower throughput, which requires the mandatory arrangement of ventilation gaps (they are not laid directly on the insulation). The diffusion membrane is spread out from the outside with respect to the insulation; only in this case will the vapors be removed from the roof structure, keeping the thermal insulation dry.

Video description

About the types and choice of vapor barrier in the following video:

Superdiffusion. They are characterized by high vapor permeability, which allows the membrane to be laid directly on the thermal insulation layer. Distinguish between one- and two-sided membranes. In the first case, it is important that the vapor barrier is laid in a strictly defined way - with the correct side inward. In the second case, the material is spread out in an arbitrary way (it does not matter which side is on top or bottom).

Subtleties of vapor barrier installation

The main question that arises when installing a vapor barrier for a roof is which side to lay the material, and in which part of the roofing pie. The location depends on the type of roof structure being constructed:

Insulated attic and mansard roof. In this case, it is important to protect the heat-insulating layer from vapors penetrating from the lower rooms. Therefore, the film is spread under the insulation (on the inside), on the truss structure or rough sheathing. cloths roll material laid horizontally and overlapped, fastened with nails or staples.

Ceiling vapor barrier Source pedkolledj.ru

cold roof. If the roof remains uninsulated, but further insulation is planned, the best solution would be to use reinforced vapor and waterproofing. The film is fixed on rafters or boardwalk (if the roof has a slight angle of inclination, sagging of the material can be avoided). The method is also suitable for a roof with a complex (broken) structure.

Any certified vapor barrier material is supplied with an instruction manual. It provides all the necessary information on laying vapor barrier on the roof; which side this or that material is located depends on the layer responsible for blocking water vapor. General rule can be formulated in the following terms:

Bilateral (superdiffusion) membranes, ordinary and reinforced polyethylene films have the same properties of both surfaces. Such materials can be laid on the heat-insulating layer on either side.

Video description

About diffuse vapor and waterproofing in the following video:

Double layer anti-condensation film spreads with a smooth side to the insulation, and the rough side - to the source of warm moist air, living quarters.

foil film it is laid with a metal layer to the living quarters - so it can return some of the heat inside, increasing the thermal efficiency of the building.

Diffusion double-sided membranes give the roofing cake the opportunity to "breathe". If both surfaces of the membrane are the same, it is laid on either side. If you have chosen a one-sided type membrane, it is better to check with the manufacturer for data on the front and back surfaces (in most cases, the membrane is adjacent to the thermal insulation with a rough surface).

Laying a vapor barrier in a roof with steep slopes Source bostonglobe.com

Stages of installation of a vapor barrier layer

Installation instructions must be followed manufacturer-defined; at the same time, the rules allow the laying of film materials both before and after the arrangement of the roofing pie. The progress of the installation of the vapor barrier is as follows:

Before installation it is necessary read the instruction from the manufacturer, determine the side of the material, the function of which is contact with steam.

Choice of spreading method, horizontal or vertical. Most manufacturers allow both schemes; in the instructions you can find out about the acceptable options and details of the layout. The direction of the layout is affected by the slope of the slopes. On a sloping roof, the roll is rolled out horizontally, perpendicular to the rafters. On a steep roof, the film is laid along the rafter legs.

For any mounting method material is laid with an overlap, the value of which is often indicated along the edge of the film. The instructions also indicate other values \u200b\u200b(depending on the steepness of the structure).

Video description

About the membrane installation technology in the following video:

The main condition for laying - the film is fixed without tension, with a sag of about 2 cm. The reserve is created due to the ability of the wooden frame to change its dimensions with the change of seasons (with changes in humidity); otherwise there is a risk of tearing the film.

For horizontal mounting laying is carried out from above (from the ridge). The strips are laid with a reverse overlap (the lower strip overlaps the upper one), for additional protection of the insulation; connect them with adhesive tape, and fix them on the structure with galvanized nails or a stapler.

If the thermal insulation layer is loose, the roll web fixed with rails, which must be antiseptic.

Particular attention is paid to junctions(mansard, windows, hatches, pipes, ventilation ducts); they are carefully isolated.

Film Fixing Source pro-uteplenie.ru

Conclusion

The use of unsuitable vapor barrier, as well as errors in its installation, lead to a sad result - the insulation is saturated with moisture and loses its heat-shielding properties, and condensate begins to destroy the wooden truss system. In advanced cases, the roof freezes through, finishing the ceiling loses its appearance, and the owners face an unplanned overhaul to their full height. A competent choice of a vapor barrier sheet and compliance with technological rules during its installation will help to avoid unnecessary trouble and money costs.

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During the operation of the roof, it is affected by several negative factors, among which the most significant is the effect of moisture, since it damages the truss system and reduces the practicality of the heat-insulating layer. To avoid such a situation, you should seriously approach the waterproofing and vapor barrier of the roofing pie.

To prevent excessive moisture in roofing materials, to protect the roof from precipitation and wind with sufficient ventilation, you can use vapor-tight waterproofing under-roofing films.

A vapor barrier of a flat roof is made of film roll material, which is offered on the modern construction market in a wide range. It will be quite difficult for inexperienced developers to distinguish films with different levels of vapor permeability from each other.

Creation of highly vapor permeable insulation

To create a highly permeable vapor barrier, materials with a vapor permeability level of 700 g/m3 for 1 day are selected, with a maximum of 3000 g/m3. In this case, Sd is inversely proportional to these values and reaches about 30 cm.

Such superdiffusion membrane or, as they are also called, diffusion, films easily pass water vapor, thereby eliminating the condensation process that negatively affects mineral insulation. Such a design guarantees the laying of the membrane and roof insulation without a ventilation gap between them. In structure, this styling resembles a layer of fabric or paper.

It is important to know that for a high-quality roofing pie, a vapor barrier material can be attached in 2-3 layers, where the main components will be vapor and moisture-proof polyethylene or polypropylene films, as well as a laminated protective fiber.

The four-layer one has the highest efficiency, where a reinforcing mesh made of polyethylene or polypropylene is used to reinforce the material.

The production of roofing vapor barrier is carried out with the addition of various color shades:

black;
white;
yellow;
blue
gray
bright green.

The difference between low-vapor-permeable films and the above-described material lies in the structure and the raw materials used, the transmission capacity of which is much lower - about 25-40 g / m3 per 1 day.

Vapor barrier: basic materials for work

A vapor barrier is being constructed - instructions for its installation, as a rule, are offered by the manufacturer, depending on the purpose of the room and the conditions for its maintenance.

The described method is quite effective, but due to the increase in wood prices, it requires large material investments. It will be much more economical to build a film vapor barrier that does not need additional flooring. So, do-it-yourself roof vapor barrier for a flat roof can be equipped. If the roof has complex structure or it is planned to install various lucarnes, skylights, kinks and other similar elements, then the use of ventilation gaps will be quite difficult. The best option is the laying of low-vapor-permeable materials on simple roofs, for example, gable roofs.

It is important to take into account the negative impact of UV radiation on the film - it becomes less waterproof, loses elasticity and, ultimately, may break.

The most dangerous in this case is the transitional stage of completion on the roof without subsequent installation. roofing when the film is exposed to direct sunlight. To avoid this phenomenon, it is recommended to install the vapor barrier film and waterproofing before directly attaching the coating sheets.

Appointment of a special vapor barrier

Along with low and high vapor permeable films, a special vapor barrier is offered on the market, designed for certain types of material, or for roofs with a special design:

Organization of a roofing pie, detailed instructions on video:

How to fix the vapor barrier film

Traditional vapor barrier films are easily mounted to any surface, subject to certain rules:

they are fastened to a wooden base with galvanized nails with wide hats, or construction brackets;
when using a metal, brick or concrete base, you will need double-sided adhesive tape or adhesive tape.

Before starting the installation of the film, a thorough isolation and sealing of the surface is carried out, where there are many relief roofing elements, for example, chimneys, ventilation ducts, antennas. Chimneys and chimneys are covered with an additional insulating layer in order to prevent the film from thermal damage.

Since the flow of warm air in the house rises, the roof vapor barrier must also be installed so that the foil surface is located closer to the interior - then the heat will be reflected from it without dissipating to the outside (more: ""). The film is attached to the heat-insulating material with a small gap, due to which the heat will be reliably stored in the roofing pie.

It is impossible to imagine the arrangement of the roof without hydro and vapor barrier, which help to maintain the effectiveness of the heat-insulating material, inside which, as a rule, moisture and water vapor accumulate. For right choice vapor barrier material among the products offered on the market, it is enough to have an idea about the climatic conditions where the building is being built, as well as its roof structure.

For people who are far from the topic of construction, it may seem that the installation of a roof vapor barrier is not important process. However, any master who is intimately familiar with roofing can say that this is not an extra waste of money or a precaution. Qualitatively performed works on roof waterproofing prolong the service life of the roofing and contribute to the creation of a favorable microclimate in the attic or attic space. But for this you need to know the rules for choosing vapor barrier and waterproofing materials and how to lay it on the truss system.

Definition and purpose of a vapor barrier for a roof

Vapor barrier film is called special material as part of a roofing cake, capable of blocking steam as much as possible.

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

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

Maintaining the quality characteristics of the thermal insulation material. Laying a vapor barrier prevents the formation of condensate, which negatively affects the quality of insulation.
Extension of the operating period roofing material. The vapor barrier protects the roofing material from the negative effects of moisture and the formation of corrosion from the inside.
Protection wooden elements truss system from the appearance of rot. Thanks to the protection of the vapor barrier film, the resulting condensate does not affect wooden frame, therefore, the wood remains dry and does not rot.

When deciding how to properly make a roof vapor barrier, it is necessary to select the appropriate material. This takes into account several factors: climatic conditions, roof construction, type of roofing material. Incorrect selection can cause increased condensation.

Qualitative 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 of this type, characterized by greater efficiency and durability. High-quality vapor barrier gasket for the roof is made of high-strength polymers, which are characterized by improved properties.

Vapor blocking can be effective provided that the material meets the following requirements:

Possibility of operation in a wide temperature range. Optimal performance should correspond to temperatures from -70 to +100 degrees.
Proper vapor permeability. Modern materials they pass no more than 0.4 g / m 2, but outdated options could “boast” of vapor permeability up to 20 g / m 2.
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 spoils less during the laying process.

In addition, high-quality vapor barrier must have high strength characteristics. At correct installation the laid durable canvas is able to retain snow, melt and rain water 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 condensation, wetting of thermal insulation and destruction of wooden roof structures. Modern vapor barrier is a thin and light material made of thermoplastic polymers, which is durable and resistant 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 slight thickness. Based on it, vapor-blocking membranes are produced. To improve strength polyethylene film perform reinforcement with a special mesh or fabric. Laminated options are widely used in places where heat retention is important, for example, in a sauna or bath.
Propylene. The propylene-based membrane is characterized by high strength, resistance to ultraviolet rays, the minimum vapor permeability. This material is a woven base with an anti-condensation layer.

According to experts, the use of perforated materials does not give the desired effect. For right decision tasks, how to make a roof vapor barrier, and for reliable protection roofs from condensate, it is better to choose a vapor-blocking membrane.

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

The installation of a vapor barrier material is considered a very important step in the entire roof construction process, since the service life, strength and reliability of the structure being built depends on it.

The technology of laying the roof vapor barrier involves working from the inside of the truss frame in accordance with the following rules:

Laying vapor barrier material can be done across the rafters or along them.
Work should start from the ridge, while the strips should be mounted with an overlap of 10-15 cm.
The canvases are fixed with construction brackets or galvanized nails.
For hermetic connection of the strips on the edges of the material there is a special adhesive composition.
At the end of the laying along the rafter legs, a counter-lattice treated with an antiseptic solution is stuffed.

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