How to choose the right vapor barrier for your roof What is a roof vapor barrier and how to choose the right one. Types of pasting vapor barrier materials

Wet insulation loses its thermal insulation properties and, in contact with the rafter system, creates conditions for its decay. Therefore, waterproofing is necessarily present in the composition of the roofing pie of the mansard roof.

The choice of waterproofing materials and the technology of their installation depend on the type of roofing.

Waterproofing films

As a waterproofing of the mansard roof, two-layer films with an anti-condensation surface can be used. The same applies to cold roofing.

Advantages:

• high tensile strength;
• the possibility of using as a temporary roof for 1-3 months;
• the presence of an anti-condensate layer capable of retaining moisture until conditions for its weathering are created;
• lower price (3-4 times less compared to membranes).

Main disadvantage- limited vapor permeability, therefore, two ventilation gaps are required:

• the first, between the roof and the film - for the removal and evaporation of condensate;
• the second, between the insulation and the film, is for weathering water vapor from mineral wool.

Both gaps are made using two counter-lattice bars:

1. The first block of the counter-lattice with a section of 4-5 cm is stuffed onto the rafters. It is necessary for the lower ventilation gap, and provides a slight sagging of the film (up to 2 cm), necessary for the condensate to drain to the drip.
2. Waterproofing is attached to this bar (anti-condensate layer up).
3. Through the sealing tape, another rail with a section of 4-5 cm is stuffed, to which the crate for the roof is attached.
4. The film under the ridge is laid with a “gap” of 5-10 cm. To prevent the blowing of fibers from mineral wool, the mats should be laminated with fiberglass.

membranes

Superdiffusion waterproofing membranes are laid on top of the insulation without a gap. The structure of the material is similar to a sandwich: a microporous membrane in the middle, a reinforcing fabric on both sides.

Weathering of moisture from mineral wool occurs due to high vapor permeability, and only one ventilation circuit of the under-roof space is needed.

Despite reinforcement, all membranes inferior in tensile strength waterproofing films. And when choosing a particular brand, you need to pay attention to this indicator. It is measured in Newtons, which are "applied" to a sample 50 mm wide.

Membrane name	Strength*, N/50mm	Steam permeability, Sd	Weight, g/sq.m	Note
DELTA®-VENT N	220/165	0,02	130	The best choice from the German manufacturer DORKEN
Tyvek Soft	165/140	0,02	58	Very light and durable membrane from DuPont
UTAVEK 115	260/170	0,02	115	Czech membrane, many good reviews
Izospan AQ proff	330/180	0,03	-	Reinforced membrane, with good lightfastness
Izospan AM	160/100	0,03	-	Budget membrane, medium strength
Ondutis A120	160/100	0,01	110	Wind and moisture protection for attics with a slope angle of at least 35 degrees
Ondutis SA115	160/90	0,02	100	For a country house of temporary residence
Ondutis SA130	250/120	0,02	140	An excellent choice for a mansard roof from Ondulin

Mounting Features

The installation process of the membrane is similar to a conventional film, but without a “break” in the ridge area:

1. The membrane is attached to the rafters with a stapler. Laying is carried out in stripes from the bottom up from the eaves to the ridge.
2. For hip and complex roofs on slopes along the axis of the valleys and ribs, the membrane is mounted in a separate strip even before the main layer of waterproofing is laid.
3. With a connecting tape, the lower edge of the canvas is attached to the dropper, as well as the joints of the canvases between themselves. The overlap of adjacent strips must be at least 15 cm.
4. The upper strip on the ridge is laid with an overlap over the waterproofing of both slopes.
5. Vertical joints are performed with an overlap on the rafter legs.
6. After laying the waterproofing on the rafters, the slats of the counter-lattice are stuffed. For Izospan membranes, the recommended thickness of the rail is 4-5 cm. For Ondutis membranes, the thickness of the bar must be at least 3 cm for profiled roofing and 5 cm for non-profiled. A sealing tape is laid between the rail and the membrane.
7. A roofing crate is attached over the bar.

Waterproofing of a mansard roof made of bituminous tiles

Bitumen shingles differ from other types of pitched roofing in both laying technology and waterproofing.

There are two waterproofing layers:

• between solid flooring and shingles.
• Superdiffusion membrane over insulation.

Underlayment over the entire roof area is only required at a pitch angle of up to 18° (minimum 12°). On a roof with a slope of 18° (1:3), underlayment is required only on valleys, ribs, eaves and front overhangs, at junctions (around skylights, chimneys, ventilation pipes).

Waterproofing film or membrane: which is better to choose?

At the mansard roof, the main heat loss occurs due to its “blowing” from the insulation. This will happen if you use conventional waterproofing films and two ventilation gaps.

The membrane, laid on top of the insulation, serves as a windscreen and reduces heat loss by preventing it from “blowing” out of the insulation. The material is more technologically advanced, but it costs more than conventional films.

The vapor barrier for the mansard roof protects the insulation and load-bearing wooden structures of the roof from saturation with wet vapors that appear as a result of human activity.

This reduces the risk of fungus and mold in the under-roof space.

Single layer films

What vapor barrier to choose for the attic?

Multilayer films

Reflective films

1. 
   
2. AirGuard Sd5 - suitable for houses with non-permanent residence.

   It has limited vapor permeability to remove residual moisture from the room.

3. Yutafol are Czech films from the Juta company.

   A lot of good reviews from builders, an excellent choice in terms of price-quality ratio.

The vapor barrier film is laid on top of the insulation from the side of the attic and fixed with a construction stapler.

The joints of the canvases are glued with mounting tape to ensure tightness.

The minimum overlap of one sheet to another should be 10 cm.

Joints and junctions must be carefully glued.

After fixing the vapor barrier, a wooden crate is made with 25 mm slats.

It is needed for fastening the rough skin and the device for the ventilation gap. When finishing the ceiling and walls of the attic with drywall, a special metal profile is used instead of bars.

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Benefits of this option
What a cold roof
Installation steps
Roof construction for metals including waterproofing
Cold loft tools and accessories

Currently, specialists use all types of roof structures in the construction of a private house, but most often they build a cold roof.

This is ideal when the attic is not intended to be used as a residential building. Below we will talk about how to properly install a cold metal roof.

Which steam bari to choose for the attic?

Benefits of this option

The construction of such a roof is quite simple - you need to build a building, apply a layer of waterproofing, a box and a control panel, a roof. The main thing when installing a cold roof is to provide an air gap to allow the removal of condensed moisture. This is necessary to ensure that the supporting structure and roofing material are not exposed to moisture.

In itself, the installation of such a roof should not be accompanied by complications in the process of work, it is only necessary to correctly fix the roofing so as not to leave precipitation through the connection in the underground space. Before creating a mug on the roof of a cool attic, you need to perform a full list of calculations, determine the slope of the skateboard, rotate the basket and choose the appropriate method of fastening the sheet metal.

What a cold roof

The cold roof technology of metal roofs takes over the initial installation of the roofing system, after which a membrane and polyethylene film will be placed on it, which will provide waterproofing.

They fill the control box, assemble and lay the roof in the form of metal.

Characteristic of such a roof is that there is no need to install insulation - all that is needed is to equip ventilation holes under the ridge and on the slopes to remove moisture. Make sure all pre-calculations are accurately defined.

The roof installation has the following characteristics:

1. If you are planning to build a hot roof over time, then protecting the moisture barrier membrane must be thorough.

   If you plan to build an attic, a PVC membrane must be present.

2. If the roof does not need to be insulated in the future, it will be necessary to install micro-perforated waterproofing, which is used for cold roofs. It is impossible to install insulation with such a film, and in case of further insulation, you will need to buy a new membrane.

   Otherwise, the roof will be deprived of moisture protection in the future, the heaters will not have enough time to dry, and the roofing material will be brown in time.

Installation steps

When installing the moisture protection membrane, it should be noted that it must remain a small bead of at least 20 mm. In this way, condensation moisture can be achieved, thereby protecting the rafters and other roof elements from decay.

To ensure that the water does not evaporate in time, without stagnation and thereby creating an unfavorable environment, care should be taken to include in the project a fan steam, which is installed between the repellents to protect the film and the roof of the ridge.

Such a clearance will allow a simple circulation of the air flow in the room under the roof and the removal of all condensate. The built-in membrane must not be damaged or otherwise damaged. The best way to fix this is to use a structural stapler.

The membrane layers are laid with a slight overlap and the edges are laid with adhesive tape.

The design of the cold attic roof is such that it can be used in regions with any climatic characteristics. Many believe that this type of roof does not apply to the northern regions, although in fact this is not the case. Often in such regions, cold attic rooms are often installed.

The attic is insulated, and the cold roof does not affect the internal microclimate of the upper floors. The attic cannot be used because the installation of an insulating layer between the upper floor and the space under the roof eliminates all the nuances that affect heat loss.

When installing a cold metal roof, measures must be taken to isolate vents, chimneys, and exits in the attic.

In this case, you do not have to worry about the accumulation of condensate, icing, heat loss or rain and water melting.

A cold roof can be covered with almost all roof tiles, and due to the ease of installation, a metal roof is used much more often.

Some other types of roofing materials, especially soft tops, also work well in this situation, but they require a lot of time and money to install.

Roof construction for metals including waterproofing

To block a cold attic with a metal roof, the most convenient and easy way to install a roof.

In this case, the roofing cake consists of a waterproofing material that is attached to the raft frame, battens and roofing (metal tiles). In fact, the application of such a coating is very fast. The insulating film is fixed with staples or nails, and then additionally pressed with a thread, self-tapping screws are screwed on. Laying rail guides is carried out taking into account the dimensions of the metal plate.

The cabinet plate is made from gauges from 25 to 100 mm, and sometimes plywood or chipboard is used if hard floors are needed.

Laying a film or membrane for attic waterproofing is loose, with some stretch.

However, it makes sense to ensure that the integrity of the coating is not interrupted, i.e. any holes or cracks are excluded. As a rule, the film can be stretched by 15-25 mm. In this way, ventilation of the inside of the waterproofing membrane is achieved, condensed moisture is removed at the handle and further into the drain. Ignoring such a simple rule will eventually lead to premature deformation of the roof frame and the entire roof.

The peculiarity of metal tile roof is that the cold roof film cannot reduce the noise that occurs when the metal falls in heavy rains.

Therefore, living spaces with such a coating provide a layer of thermal insulation that absorbs a lot of noise. Without this layer, as a rule, only rooms for autonomous attics are equipped.

Thus, a cold roof will include the following layers:

• A vapor barrier for the cold roof is installed inside, which only emits moisture and prevents penetration into the living room.
• Then install the roof raft frame.
• The next layer is a waterproofing material.

  The film is laid with a recess for condensate drainage.

• A control grid is then attached, which compresses the waterproofing, fixes it and provides ventilation holes.
• The rack is then filled to repair the roof.

  It is made of 50 x 50 mm blades and laid along the ramps, divided into 35-45 cm. Depending on the type and degree of the roof beam, the pitch and thickness of the panel can be changed.

• The back floors are made of metal.

Cold loft tools and accessories

It is worth noting that you do not need too complicated professional construction tools for laying metal tiles.

You can use the basic set that every housewife has in the house.

In addition to the carcass frame, frames, slats and counterflow flasks require membrane or foil insulation for steam and waterproofing, as well as a sufficient number of metal tile sheets purchased from the same series.

Fastening of all elements is carried out using clamps, self-tapping screws, galvanized nails and even anchor bolts.

However, it should be remembered that they must be of high quality so that the roof does not deteriorate ahead of time.

As for the roofing roof, the evaluation lists are pasted, the necessary roof valley (internal and external), wreaths, wind and snow stations and watercourses.

The main difference between a cold roof and a warm one is the presence of thermal insulation material in the back layer, located between the water layer and the vapor barrier.

The main functions of the attic vapor barrier
Types of vapor barrier materials - which one is better to choose
Polyethylene films
Polypropylene films
Vapor barrier reflective membranes
Vapor barrier installation rules

Thermal insulation of the attic is a very important process, since a large amount of heat escapes through the roof and walls.

To reduce the loss of thermal resources, it is necessary to carefully consider the structure of the roofing pie and ensure the efficient functioning of each layer.

An important role in this process is given to the attic vapor barrier, since this layer does not allow moisture to penetrate into the insulation and to the wooden elements of the truss frame, thereby extending their service life without loss of performance.

The main functions of the attic vapor barrier

To answer the question of which vapor barrier to choose for the attic, you need to know its purpose.

When connecting streams of warm and cold air, steam and condensate are always formed, the accumulation of which will certainly lead to a decrease in the performance of any, even the most reliable building material.

Rotting wood reduces the strength of the entire structure, which causes the repair or complete replacement of the main parts of the structure. In addition, high humidity promotes the formation of mold and fungi, which release toxic substances.

As a result, a person may experience malaise and headache, and even allergies.

The joint work of insulation and vapor barrier not only prevents the penetration of steam, but also retains heat as much as possible in the attic room.

Types of vapor barrier materials - which one is better to choose

Various materials can be used as a vapor barrier layer, including roofing material, glassine and various films.

The most popular today are polyethylene and polypropylene films, as well as vapor barrier membranes. To understand which vapor barrier is best for the attic, you should get acquainted with the basic materials.

Polyethylene films

Such material is laid during the installation of the roof, a prerequisite for use is the creation of gaps for ventilation.

This will prevent condensation from forming, since polyethylene is not able to pass air. Laying with the rough side facing out helps the vapor particles to evaporate.

Polyethylene film can be used for vapor barrier and waterproofing due to its versatility. Reinforcement with a special metal mesh helps to increase the strength of the material.

Polypropylene films

High durability and strength are the main characteristics of this material, but at the same time it has one significant drawback.

How to choose a vapor barrier for a mansard roof

The upper side of the reinforced film is covered with drops of condensate. If the choice of vapor barrier for the attic is made in favor of this material, then laying an additional layer of viscose or cellulose, which absorb fumes, will help solve the problem.

Vapor barrier reflective membranes

For this insulation, ventilation gaps are not needed, since the structure of the material is able to pass air and retain moisture.

In addition, the membrane is characterized by high quality and reliability. Installation of the attic vapor barrier should be carried out on top of the insulation.

In addition, the vapor barrier is equipped with isospan or penoplex.

These are high quality materials, characterized by low thermal conductivity, excellent waterproofing and vapor blocking properties. One of the advantages of using them is high temperature operation.

Vapor barrier installation rules

The reflective vapor barrier for the attic, installed in accordance with all the rules, can protect the insulation from moisture penetration and maintain its performance.

Firstly, it is necessary to first seal and insulate the main structural elements and all protruding parts of the structure.

Secondly, the method of attaching the vapor barrier material depends on the type of surface. The material is attached to concrete, bricks or blocks with double-sided adhesive tape. On wooden surfaces, the vapor barrier is fixed with nails or a construction stapler.

Thirdly, when using a foil vapor barrier for the attic, the reflective layer must be turned inside the room.

Fourth, for maximum efficiency, you should use a vapor barrier without damage. And during the installation process, the material should be stretched to avoid sagging.

The attic in the house has its advantages and disadvantages. Which? About it read here. As shown by the voting results ( see results here) a house with an attic attracts about 50% of readers.

Attic insulation work is carried out either from above before roofing installation either from below after the house is protected from rain.

The first option - from above, is more convenient in installation, and allows you to work faster and better.

In the second option - from below, you can postpone the work and expenses for arranging the attic for later.

The designs of the insulated roof in both cases are somewhat different.

Attic insulation from above

In this article, we will consider the use of steam-wind-moisture protective membranes in the design of the insulated roof of the attic floor using the Izospan brand protective materials system as an example. You can read about the materials of this system in the article. "Films and membranes steam-wind-hydroprotective".

The device of the warmed roof of the attic

1. Roofing
2. Windproof film Izospan AS, AM
3. Counter rail
4. Insulation
5. Vapor barrier Izospan B
6. Rafter
7. Interior decoration
8. Lathing

Scheme of protecting the attic insulation from wind, moisture and condensate in Fig. 2

Wind-moisture protection of the attic insulation

Fig.2. To protect the attic insulation from wind, moisture and condensate, a ventilated gap is arranged, and films and Izospan membranes are laid from below and above.

Why protect the insulation from the wind?

Mineral wool insulation, which is usually used for roof insulation, has an open porous structure.

The air moving in the ventilated gap easily penetrates the insulation, blowing heat out of it. The effectiveness of thermal insulation due to air infiltration can be almost halved.

In addition, the air moving under the action of the wind in the gap tears off and carries away the particles of insulation. The weathering of the insulation occurs - over time, its density and thickness decrease, the insulation becomes a source of dust that can penetrate the house.

To prevent these processes, the insulation from above, from the side of the ventilated gap, is covered with a windproof vapor-permeable material.

In addition, the wind-moisture protective membrane (item 2 in Fig. 1) protects the insulation and load-bearing structural elements from under-roof condensate, snow and atmospheric moisture, which can be blown into the gaps of the roofing or penetrate at the joints of the roof sheets due to capillary suction.

The wind and hydroprotective membrane should not prevent the release of steam from the insulation (vapor permeability is not less than 750 g/m2 per day).

It is recommended to use vapor-permeable roofing membranes Isospan AM or Isospan AS in the construction of insulated roofs as waterproofing and wind protection. Materials Izospan AM and Izospan AS placed directly on the insulation without ventilation gap between them.

Izospan AM and Izospan AS are not intended for use as the main or temporary, for the period of installation, roofing.
Izospan AM and Izospan AS are laid with the white side to the insulation.
When installing an insulated roof, Izospan AM (Izospan AS) is rolled out and cut directly over the insulation. Installation is carried out by overlapping horizontal panels, starting from the bottom of the roof. Overlapping of panels along horizontal and vertical joints - at least 15 cm.

The stretched material can be additionally fixed to the rafters with staples using a construction stapler.

On top of the material, wooden antiseptic counter-rails 4x5 cm are fastened vertically along the rafters on nails or self-tapping screws. The place of vertical overlap or junction of two horizontal panels should be pressed against the rafters with a counter rail.

A crate or a solid plank flooring is mounted along the counter-rails, depending on the type of roofing.

For weathering water vapor and under-roof condensate ventilation gap must be provided between the outer side of the material Izospan AM (Izospan AS) and the roof covering for a counter-rail thickness of 4-5 cm.

In addition, to ensure ventilation of the under-roof space ventilation holes are provided in the lower part of the roof and in the ridge area for air circulation.

The material Izospan AM (Izospan AS) is fastened in a taut position so that water can freely slide over its surface. The bottom edge should provide natural drainage of moisture from the surface of the membrane into the gutter.

Attic insulation vapor barrier

The vapor barrier film (item 5 in Fig. 1) performs several functions at once:

1. Protects the insulation from the penetration of water vapor into it from the attic room. From the article "Dew Point, Vapor Barrier and Air Gap" you can find out why, without a vapor barrier, the insulation will accumulate moisture and collapse.
2. In addition, vapor barrier performs another function - it reduces the air permeability of the attic enclosing structures, thereby reducing heat loss.
3. The material protects the living space from the penetration of microfibers (dust) of the insulation.

Izospan V used as a vapor barrier in insulated roofs of mansards operated with various types of roofing.
When installing an insulated roof, the Izospan V vapor barrier is mounted on the inside of the insulation on the rafters or on the rough sheathing using a construction stapler or galvanized nails. Installation is carried out from the bottom up with overlapping horizontal panels with an overlap along the horizontal and vertical joints of at least 15 cm.

When finishing the room with clapboard (plywood, decorative panels, etc.), the vapor barrier is fixed along the frame with vertical antiseptic wooden slats 4x5 cm, and when finishing with drywall - with galvanized profiles.

The installation of the material is carried out with a snug fit with the smooth side to the insulation, the rough side down. The interior decoration of the room is attached to the rack frame or galvanized profiles with a ventilation gap of 4-5 cm.

To ensure the tightness of the vapor barrier, it is recommended to fasten the sheets of the Izospan B material together with the Izospan KL or SL connecting tape. Adjacent points of Izospan materials to wooden, concrete and other surfaces are glued with Izospan ML proff adhesive tape.

Instead of Izospan B, Izospan RS, Izospan C or Izospan DM can be used as a vapor barrier when installing an insulated roof. The installation scheme is similar.

Heat-reflecting vapor barrier of attic insulation

Can be used as a vapor barrier heat reflective vapor barrier: Izospan FS; Izospan FD and Izospan FX. The material is mounted on the inside of the insulation (on the rafters or on the rough sheathing using a construction stapler or galvanized nails) with a metallized surface towards the room.

There must be an air gap of 4-5 cm in front of the metallized surface of the membrane. Only in this case does reflection of heat flow, which increases the thermal resistance of the coating. Installation is carried out by overlapping horizontal panels, starting from the bottom of the roof. The overlap of the material along the horizontal and vertical joints is at least 15 cm (Izospan FX - butt).

Vapor barrier sealing

The vapor barrier prevents the insulation from getting wet. In places with vapor barrier defects, the insulation is saturated with moisture in winter. These places begin to freeze, fungus and mold appear on the walls, and the insulation itself is gradually destroyed.

Careful sealing of the vapor barrier layer is a necessary condition for a long and reliable service of thermal insulation and wooden roof parts. The same thing happens if water enters the insulation from above. But developers, due to a misunderstanding, often neglect the threat of wetting the insulation from below, from inside the room.

The vapor barrier film is attached to wooden parts using staples with a stapler. It is glued to the metal profiles of the crate with double-sided tape. The vapor barrier film is laid with a 10 cm overlap. The film should not be stretched too much, as the film changes its dimensions when the temperature changes.

The joints of the film are glued with adhesive tape made of a material with a similar coefficient of thermal expansion. Adjacencies of the film to the walls are more reliable press the strips with applying a sealant under them on the wall because adhesive tapes do not stick well on rough surfaces.

It is more reliable to make the joints of the films over a solid surface, where, in addition to gluing, the joints can be pressed with spacers, battens, fastened with brackets, etc. Passages through the vapor barrier of chimney and ventilation pipes are also carefully sealed. Don't neglect sealing plumbing piping and electrical wiring.

Choosing a heater for the attic

To insulate the attic, it is recommended to choose a fireproof mineral wool insulation. In summer, the roof can heat up to 60 degrees C, and in winter, up to 25% of heat can escape through a thin layer of damp insulation. Therefore, it is so important to lay a sufficient layer of insulation and prevent it from getting wet.

Modern energy saving standards recommend providing a heat transfer resistance of 4-5 m2 * K / W for the attic roof. In order to obtain the economically justified resistance to heat transfer required by the standards, it is necessary to lay a layer of mineral wool insulation with a thickness of 20 - 25 cm.
How to calculate the thickness of the attic insulation find out here.

The height of the roof rafters, as a rule, does not exceed 15-18 cm. Additional layers of thermal insulation are placed between the bars of the inner crate, or bars of the required height are nailed to the rafters from below.

Soundproofing attic

In addition to good thermal protection, the outer fencing of the attic should provide sufficient sound insulation of the attic rooms from airborne noise. People sleeping in the attic should not wake up from the impact of raindrops or hail on the metal roofing.

Therefore, rather stringent requirements for sound insulation are imposed on the outer fence of the attic.

In accordance with current regulations, the airborne sound insulation index of the outer attic fence - Rw, must be at least 45 dB. As sound insulation from airborne noise, the same mineral wool insulation is used as for thermal insulation.

To achieve this indicator in the outer fences of the attic the thickness of mineral wool sound insulation must be at least 250 mm. If the thickness is less, then the sound insulation will not meet the standards. Thus, the thickness of the mineral wool thermal and sound insulation of the attic is selected based on two conditions: thermal insulation and sound insulation. The thickness of the larger of the two indicated is accepted.

Insulation of the attic when performing work from the inside

The design features of the attic insulation when performing work from the inside, under the mounted roofing, are clearly visible in the figure below (to zoom in, press the keys: Ctrl and + at the same time):

If the ceiling of the upper floor in the house is made on wooden beams, then the floors and partitions in the attic should be light in weight and provide the necessary sound insulation. It is best in this case to make a floating floor with a dry screed of gypsum fiber sheets (GVLV) or other plates, as well as install soundproof frame partitions. Just such an option is shown in the figure.

Please note that the frame partition should cut through the attic sheathing as far as possible, and the base of the partition should be supported on the subfloor. Such a design will exclude the transmission of sound to the adjacent room bypassing the partition, through the finishing floor covering and attic sheathing.

If no special measures are taken, then soundproofing of attic rooms with framed outer walls, partitions, floors and ceilings will be insufficient.

If the floor of the upper floor in a house with an attic is made of reinforced concrete slabs or precast-monolithic of light blocks, then on such a floor it is more profitable to lay partitions made of bricks, as well as light gypsum or concrete building blocks.

Watch the video material, which clearly shows the thermophysical processes in the insulated roof and the basic installation rules. Watching the film, remember the need for wind protection of mineral wool insulation.

Next article:

Bituminous tiles. Mogtage, laying a soft roof

Previous article:

Heating scheme with a solid fuel boiler and a heat accumulator.

When building a mansard insulated roof, a vapor barrier is required. The absence of this layer in the roofing cake leads to wetting of the insulation and premature destruction of the truss system.

The vapor barrier for the mansard roof protects the insulation and load-bearing wooden structures of the roof from saturation with wet vapors that appear as a result of human activity. This reduces the risk of fungus and mold in the under-roof space.

Do not confuse vapor barrier with superdiffusion membranes. The latter are laid on top of the insulation and play the role of waterproofing, but at the same time retain the ability to "breathe" and remove moisture from the surface of the insulation.

Roof vapor barrier materials are represented by several types of films:

Single layer films made of polyethylene or polypropylene. They are characterized by low strength, with careless handling the film is easy to tear.

Multilayer films- have higher strength and service life, can be additionally reinforced with a reinforcing layer.

Reflective films with a reflective foil layer - allows you to keep warm in the room and will be an excellent solution when installing a roof over a sauna, swimming pool or bathroom.

See also: how to properly insulate the roof of the house.

1. If financial possibilities allow, choose Delta Reflex or AirGuard Reflective films.
   Delta DAWI GP is a little simpler and cheaper.
2. AirGuard Sd5 - suitable for houses with non-permanent residence. It has limited vapor permeability to remove residual moisture from the room.
3. Yutafol are Czech films from the Juta company. A lot of good reviews from builders, an excellent choice in terms of price-quality ratio.
4. Ondutis and Izospan are an economy option.

Rules for installing a vapor barrier film

The vapor barrier film is laid on top of the insulation from the side of the attic and fixed with a construction stapler. The joints of the canvases are glued with mounting tape to ensure tightness.

When working with the material, the following tips should be considered:

Cloths can be laid in any direction in the presence of a rough filing of insulation. When mounting directly on the rafters, it is better to place the sheets horizontally.

The minimum overlap of one sheet to another should be 10 cm. Joints and junctions must be carefully glued.

When working with window openings, it is necessary to provide for a deformation margin (fold). Next to windows, it is important to pay special attention to sealing the junctions and protecting the material from sunlight.

After fixing the vapor barrier, a wooden crate is made with 25 mm slats. It is needed for fastening the rough skin and the device for the ventilation gap. When finishing the ceiling and walls of the attic with drywall, a special metal profile is used instead of bars.

Competent and high-quality work on the attic vapor barrier will extend the life of the roof and save the owner of the house from costly repairs.

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

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

The standard composition of a roofing pie includes:

• Inner finishing layer;
• The design of the crate;
• vapor barrier material;
• Counter-breech;
• Thermal insulation (not applicable for a cold attic);
• Waterproofing layer (read about chimney waterproofing here);
• ventilation shafts or gaps;
• Roof covering.

Why do you need roof insulation?

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. When in contact with a colder environment, the vapor turns into condensate, which lingers in voids.

This can lead to a violation of the functionality of the heat-insulating material, as well as the occurrence of decomposition and decay processes in the summer. In winter, freezing water expands, thereby breaking bonds between cellular elements.

The main characteristic of a 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.

Release form of vapor barrier films - roll. Vapor barrier can be made of various materials. Some of them have additional positive properties that increase the efficiency of the operation of the interior of the building. Installing a vapor barrier on the roof is not as difficult as it seems at first glance, but it requires a careful approach and accuracy.

Types of vapor barrier

Single layer polyethylene films

They are made of low-density polyethylene, which provides an increased degree of steam penetration. This material often has defects associated with the ingress of foreign particles during manufacture. The cheapest type of insulating material.

Reinforced polyethylene films

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

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

Anti-condensation film

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

Polymers with a foil layer

They are made of penofol or foamed polypropylene, covered with a thin layer of metal. Due to the reflective properties of metal surfaces, such a vapor barrier performs an additional function protection against heat loss.

Membranes (film for roof vapor barrier)

Membrane vapor barrier materials are divided into five main classes:

• Type A. It has increased resistance to moisture and wind. It is laid between the roof covering and the heat-insulating layer. Manufacturing technology - spunbond. Such a vapor barrier does not allow moisture flowing through the cracks of the roofing material, as well as from the resulting condensate. The absence of a laminating layer allows the use of such membranes in roof structures with a slope. over 35 degrees. To remove excess moisture, it is necessary to arrange ventilation holes from a double crate located between the membrane and the insulation.
• Type AM. Unlike Type A has a multilayer structure. It is located between the insulation and the roof, to provide adequate protection from negative atmospheric influences. The most common is a three-layer construction, consisting of two layers of spunbond with a diffuse film located between them. It acts as a waterproofing, as it allows steam to pass through, but retains water. Laying is carried out directly on the heat-insulating layer, which reduces labor costs for the device of the ventilation gap.
• Type B. Double layer material. It consists of a layer of vapor barrier film and spunbond. It is used to protect the insulation from the internal vapors of the building. Applies only in insulated roof structures.
• Type C. It is made similarly to type B membranes. It has a stronger and thicker spunbond layer, which provides better protection of the insulation from moisture. Used in insulated and non-insulated, pitched and flat roofs.
• Type D. Consists of a polypropylene fabric protected on one side with a laminating polymer coating. The structure of the material allows it withstand significant mechanical stress. This causes it to be laid between the insulation and the attic floor screed, as well as in non-insulated roof structures.

Which side is the vapor barrier for the roof?

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

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

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

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

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

CAREFULLY!

When joining elements, a mandatory seam sealing, which provides optimal protection against moisture ingress into the gap between them. Most often, gluing is done with one- or two-sided adhesive tape or adhesive tape. In roofs with a slope of up to 3o degrees, additional fixation with wooden planks.

1. The vapor barrier is attached to the wooden truss elements with the help of galvanized nails or a construction stapler.
2. When installing films and membranes near roof hatches, you need to use a special vapor barrier apron which is included as standard.
3. At the joints with ventilation pipes, film and membrane structures are wrapped down, wrapped around the pipe and tightly fixed with construction tape.
4. After laying the vapor barrier layer, it is necessary to nail wooden blocks. The rules for laying vapor barrier on the roof dictate the following rule - the step between the bars of the crate should be 500 mm. In this case, a ventilation gap is formed, and additional fastening of the vapor barrier layer is carried out. Now you know how to lay a vapor barrier on the roof, you can move on to the issue of waterproofing.
5. If the vapor barrier for the roof was damaged, then small cuts or holes can be stick with special tape for vapor barrier membranes.

Roofing pie scheme

Gluing joints with adhesive tape

The final version of the vapor barrier

NOTE!

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

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

Waterproofing materials also perform the function of protecting structural elements from moisture. However, unlike vapor barriers, they are not resistant to moisture-saturated air masses. That is, the steam leaving the premises will freely penetrate through the insulating layer. Therefore, when buying vapor barrier films and membranes, make sure that they are used correctly. Learn more about roof waterproofing here.

Useful video

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

Conclusion

Vapor barrier is the lightest and thinnest layer of the roof. But neglecting its device can nullify all material and physical efforts to create a high-quality roof. Therefore, do not neglect this important element, it will significantly increase the life of the entire building.

One of the most important tasks in the construction of the attic is to protect it from the formation of condensate, which can lead to damage to the roof system and thermal insulation material, as well as to increased costs for heating the house. Proper attic vapor barrier should be laid at the design stage. But if mistakes were made during the construction of the structure, then the volume of subsequent repair work, as well as measures for the rehabilitation of the attic, will only be commensurate with the new stage of construction.

Condensation mechanism

Before deciding which vapor barrier to choose for a mansard roof, it is necessary to understand the mechanism of formation and movement of water vapor. There are two principles of transfer and formation of condensate:

1. Diffusion is the movement of vapor from an area of ​​high pressure to a place of low pressure. In winter, such a transfer is carried out from a warm, heated room to a cold outside, where a low partial pressure is observed. In summer, the direction of the flow changes, and the steam from the warmer and more humid outdoor air is directed to the drier and cooler attic space. Mansard roof structures (waterproofing, insulation, vapor barrier, finishing) are on the way of the diffusion flow. It is the diffusion permeability of these materials that determines the amount of vapor that can penetrate due to diffusion. Since the layers of waterproofing and insulation practically do not resist the passage of steam, they can be ignored. In such a design, only the qualities of the vapor barrier material are important. That is why it is so important to choose a high-quality vapor barrier for the attic.

Important! The diffusion flow is the stronger, the greater the difference in temperature and humidity between indoors and outdoors.

1. Convective is the movement of air and steam flows through loose layers of coatings and heat-insulating materials. The intensity of this transfer is directly related to the strength of the wind and the dimensions of the cracks. In modern roof systems, the function of air protection is performed by layers of hydro- and vapor barrier. They can completely eliminate the possibility of convective moisture transfer.

In actual roof operation conditions, both mechanisms of moisture penetration are present. At the same time, the intensity of the diffusion process is directly related to the choice of a good vapor barrier and pressure drop. In turn, the convective process depends entirely on the quality of the insulation work and the use of sealing tapes and mastics.

Attention! When comparing the degree of wetting of roof structures during a diffuse and convective process, it can be said that the latter of them is much more dangerous, since more water vapor penetrates into the structures.

Consequences of wetting structures

The vapor barrier of the mansard roof is an important component of the design of the roofing pie. If we choose low-quality vapor barrier material or install it in violation of technology, then homeowners may face the following negative consequences of waterlogging the thermal insulation material:

• The entire structure reduces the resistance to heat transfer. This leads to higher operating costs.
• Mold and moisture can damage roof structures (both metal and wood).
• Due to the increased air permeability of structures and the ingress of dust, the air quality in the house is reduced. The favorable microclimate and the comfort of living in attic rooms suffer significantly.

That is why, when arranging the roof structure and the roof itself, it is important not only to know which vapor barrier film is better, but also to properly install the material. Of particular danger from the point of view of poor-quality vapor barrier are loose overlaps of vapor barrier material, poor-quality junctions with walls and other structural components of the roof.

Important! The main task in the arrangement of the roof is to exclude or minimize the uncontrolled movement of air containing water vapor through the roof structures.

Varieties of materials

Today, we can choose not only high-quality vapor barrier materials, but also entire vapor barrier systems, which include special films, adhesive tapes and mastics, as well as ready-made technical solutions for roofing. The choice of characteristics and type of vapor barrier material is directly related to the design features of the attic room and its temperature and humidity conditions.

Below we provide a list of the most common vapor barrier systems with their pros and cons:

1. Single layer polyethylene films. The advantages include high vapor diffusion resistance (more than 100 m) with a small material thickness (200 microns), the ability to control the quality of insulation due to the transparency of the material, as well as good elongation at break. Among the minuses, it is worth mentioning the low strength of the material in the places of fixation with staples.
2. Polyethylene multilayer films with reinforcement. Pros: high strength and transparency. Cons: low resistance to vapor diffusion due to the thinness at the point of interweaving of the fibers of the reinforcing mesh. It should be noted that films weighing at least 200 g / m² are more often used.
3. Polymer films on a woven basis with lamination in one layer. The advantages include high strength. The disadvantage is the lack of transparency, low diffusion resistance due to the presence of a continuous thin polymer layer, as well as a small elongation at break.
4. Multilayer foil polyethylene film. The advantages include the high density of the material and a relatively good vapor diffusion resistance coefficient, as well as additional heat preservation in the room due to the reflex layer. Self-adhesive tapes go along the edge of the material for a more hermetic laying. The only downside is the lack of transparency.
5. Polymer-bitumen rolled self-adhesive vapor barriers. They are quickly mounted, as they are simply glued to a solid base of concrete or OSB on a primer layer. Such products can be used on a sheer surface without additional gluing of overlaps.
6. OSB can be used as a vapor barrier, but this material is only suitable for places with normal humidity in buildings where wet finishing work is not used. Their sphere of use is prefabricated and frame structures. The junctions and overlaps must be additionally glued with tapes. OSBs are only suitable for roofs with simple geometries. Above wet rooms, it is required to lay a layer of film vapor barrier. This material is not suitable for use in timber and log houses due to high shrinkage.
7. The adaptive polyamide vapor barrier has a variable vapor permeability and is only suitable for repairing areas with normal humidity. It is not used in new construction.

As you can see, the abundance of vapor barrier systems allows you to reliably protect roof structures from condensate. However, the effectiveness of any material is directly related to the correct choice of it, taking into account the temperature and humidity conditions of the room and the roof structure, the use of accessories for better layer tightness, as well as the use of the right technical solutions.

Why, with a properly composed roofing “pie”: vapor barrier + insulation + membrane, it often becomes necessary to rebuild attics.

The mass construction of insulated attics is due to the appearance on the free market of modern lightweight insulation, which are laid in the truss supporting structure without causing its overload and without requiring major changes. Additional, living space appears easily and simply, without serious costs.

However, the name of the material - "insulation" does not mean that it will uniquely insulate the structure. Without the creation of certain conditions, a material with high air permeability can be a source of dampness and rotting of the structural wooden elements of the structure.

Due to their low thermal conductivity, insulation allows you to separate the warm air of the interior from the cold external atmosphere. However, due to their high air permeability, mineral wool insulation does not prevent the passage of warm, moist internal air, which, upon contact with cold outer areas of the insulation, condenses with a constant accumulation of moisture.

In order for mineral fiber wool to work successfully as a heater in the cold season, it is necessary to use special building films:

• a vapor barrier is installed on the inner (warm) side of the insulation, which prevents the penetration of moist air from the room.
• on the outer (cold) side of the insulation, a wind-waterproof diffusion membrane is installed to protect against external leaks, wind blowing, heat leakage, mineral fiber carryover. In addition, the membrane must ensure the constant removal of moisture from the thickness of the thermal insulation and constantly maintain its dry state, due to high vapor permeability.

Such a system of two films with opposite properties in terms of vapor permeability, a vapor barrier and a membrane (abbreviated as “P + M”), creates conditions for the operation of mineral wool and other highly permeable materials as a full-fledged, effective insulation.

Foam insulation does not have high air permeability and, at first glance, does not require the use of protective films, but the same phenomena occur at the joints of the plates and at the junctions to the frame, caused by the passage of air. Therefore, foam insulation also needs protection from external leaks, the penetration of wind and internal steam.

In reality, despite the presence of a vapor barrier, a certain amount of water vapor is constantly supplied to the insulation, which is formed in the process of life. Moisture in the form of H 2 O gas penetrates through each square meter of the polymer film surface, which has a certain vapor permeability, as well as through defects and film joints. This moisture must be removed to the external space through a vapor-permeable hydro-windproof film (diffusion membrane) installed on the cold side of the insulation and thus preventing the accumulation of condensate.

Violations and shortcomings in the film insulation system heaters “P + M” are most pronounced in insulated attics. The fact is that the vapor barrier of attic floors experiences maximum steam pressure, since the pressure of a column of rising warm air, 6-10 m high (2-3 floors), is added to the partial steam pressure. In addition, the accumulation of condensate in the insulation of inclined attic surfaces inevitably leads to the formation of visible leaks, which are usually invisible on vertical walls, where an increase in the humidity of the insulation can only be judged by the cold and dampness in the room.

As practice shows, about 30% of domestic attics, even those built by well-known serious construction organizations, are reworked after the first winter. A study of the condition of the warm attics of five cottages on Rublevskoye Highway, on the ceilings of which condensate leaks appeared, carried out in the winter of 2003, showed that at T = -30 ° C, frost and ice fouling of vapor-permeable vegro-waterproofing membranes covering the roof insulation is observed.

Reworking the replacement of the film system requires the removal of roofing and interior decoration, drying the insulation. At the same time, some of the materials go to marriage. Even if the builders install the “P+M” insulating film system, there is no guarantee that the system will perform its functions if its design does not take into account the peculiarities of the Russian climate, which (unlike Western Europe) is characterized by stable negative round-the-clock temperatures.

As the outside temperature decreases, the volume of steam penetrating through the vapor barrier increases due to an increase in its partial pressure drop. At the same time, the processes of moisture migration through the cold membrane and the outer layers of the insulation slow down, but do not completely stop: at sub-zero temperatures, the mechanisms of sublimation (dry sublimation of a solid) and desublimation of moisture frozen inside the insulation are activated. Accurate calculations that reliably describe these processes do not yet exist, so let's pay attention to the empirical aspects of the operation of vapor-permeable membranes and vapor barrier, which are necessary to avoid errors in practical work on insulation.

membranes

The main criteria for choosing a roofing membrane are high mechanical strength, high vapor permeability and high water resistance.

Roof insulation leaks can be caused by minor damage. It is almost impossible to detect defects in the roofing membrane, since damages usually occur during the installation of roofing elements and are hidden by the roof. Therefore, the use of a thin, fragile membrane often results in subsequent repairs associated with the removal of the entire roof and the replacement of the film.

For full-fledged work on removing moisture from diffusion membranes from insulation at low temperatures, it is necessary to ensure the following conditions:

• Diffusion (wind-waterproofing) membrane should fit snugly (without gaps) to the outer surface of the insulation. The presence of even a small gap leads to cooling of the membrane material to a temperature lower than the temperature of the vapor migrating from the insulation, which causes it to condense in the form of ice on the membrane and, as a result, the vapor permeability is lost.
• The ventilation gap above the roofing membrane must ensure the removal of water vapor even at sub-zero temperatures. Despite the assurances of European manufacturers about the sufficiency of a gap width of 40 - 50 mm, in Russian conditions it is recommended to increase this size to 100 mm; First of all, this applies to roofs of a large area (more than 300-500 m 2), where ventilation of the gap is difficult. The design of ventilation air inlets and outlets should exclude the possibility of their overlapping with snow accumulating on the ridge and in drains. The best solution is not to use ventilation ridges that get clogged with snow, but to install exhaust ventilation pipes along the roof ridge.
• The amount of steam coming from the room through the vapor barrier should be minimal. Even superdiffusion membranes (with a vapor permeability of 1000 g/m 2 per day) at significant negative temperatures, when moisture transfer processes slow down, may not be able to cope with the removal of an excessive amount of moisture. So in Russian climatic conditions, the quality of the vapor barrier is of particular importance.

vapor barrier

An effective vapor barrier device is possible only when using special building vapor barrier materials with minimal vapor permeability.

In Western Europe, with its mild winters, there is no need for high quality vapor barriers, so cheap packaging and agricultural films are sometimes used there, which are mainly imported to Russia. Such films with low vapor barrier properties include the following rolled materials:

• single-layer tubular films made of LDPE (low density polyethylene) always have microdefects and uneven thickness, vapor permeability of more than 10 g/m 2 per day. Designed for commercial packaging.
• reinforced rolled LDPE materials produced by hot pressing of polyethylene films to a polymer mesh made of twisted thread. When performing this operation, the films are injured at the points of contact with the grid nodes. The presence of such microdefects does not affect the high mechanical and waterproofing properties of the material, but its vapor barrier properties deteriorate. Designed for use in agriculture;
• bag fabrics made of film PP (polypropylene) threads 3-5 mm wide, laminated with LDPE melt. The polyethylene melt cannot physically form a uniform, continuous film on an uneven basis. The applied film has a large defect and vapor permeability. The material has high mechanical strength and is used for the manufacture of polypropylene bags and containers;
• spunbonds (non-woven polypropylene fiber) melt-laminated with LDPE or PP. The vapor permeability of such materials reaches 15-25 g / m 2 per day, which is completely unacceptable for vapor barrier;
• Metal (aluminum) foil has the best vapor barrier properties, which makes it indispensable for vapor barrier devices in steam rooms, where the volume and pressure of water vapor are the highest. Combined film-foil materials are suitable for vapor barrier of shower rooms, swimming pools, bathrooms and other non-residential premises with high vapor emission, but with low temperature.

However, a solid metal foil screen located around residential premises significantly distorts the natural electromagnetic field of the Earth, which is completely unacceptable in recreational (cottage, country) construction.

The choice of vapor barrier, which is installed inside the living space and has a huge emitting surface, must be approached with caution. The environmental cleanliness of the premises depends on the possibility of the release of harmful substances from the vapor barrier. For example, MPCs (maximum allowable concentrations of hazardous substances) for materials intended for use in open spaces can be harmful when used indoors due to low air exchange and the possible accumulation of harmful substances. Films can be made from cheap grades of polyethylene or low-purity polypropylene, which can be identified by the smell of a rolled film roll. The use of glassine as a vapor barrier is currently avoided, precisely because of the release of harmful substances.

Execution of work

The final result depends not only on the materials used, but also on the quality of the work, which is difficult to control after installing the interior finish. To obtain a high-quality vapor barrier, it is necessary to ensure its complete tightness (the absence of the slightest holes) both during installation and during operation. For this:

• Sealing the joints of the vapor barrier sheets is carried out using double-sided adhesive tape or butyl rubber tape. But this is not enough. The adhesion of the sticky layer decreases over time, and at the slightest load, the sheets may peel off. Therefore, the glued joint should not be in a free state: it must be clamped with a rail on a rigid edge of the frame. These strips, 2-3 cm thick, create a gap under the inner lining for laying electrical wires without damaging the vapor barrier.
• The places where the vapor barrier adjoins brick walls or passing pipes are carefully sealed with tapes or sealants and must be clamped with rails screwed to the wall or pipe.

Consideration should be given to the possibility of changes in the size of roof structures caused by wood drying and wind loads. In order to avoid the formation of gaps under the cladding and roofing when the frame moves, film materials should be laid without tension - with a margin, which is easily done for vapor barrier. However, this requirement contradicts the condition of tight contact between the diffusion waterproofing membrane and the insulation. To fulfill this requirement, you can do the following. The roof insulation must rest on a rigid base formed by an internal crate and vapor barrier, and protrude 1.5 - 2 cm above the level of the rafters. The membrane is attached with tension to the rafters with bars. In the ventilation gap, parallel to the rafters, antiseptic slats or boards (1-2 pieces) are installed on the edge, pressing the waterproofing membrane into the insulation to a depth of 1.5-2 cm. This ensures a snug fit of the membrane to the insulation, but retains a margin for stretching along the length canvases. When choosing mineral wool insulation for attics it is necessary to proceed from maximum elasticity and minimum shrinkage during operation.

Scheme of installation of subroofing waterproofing

Frequent causes of leaks and attic reconstructions are the widespread scheme for installing European underlaying films, which is not always suitable for Russian winters. In particular, this is a scheme for installing cheap perforated films and vapor barrier films with an anti-condensate layer for waterproofing insulated roofs, which provides for two ventilation gaps. Reinforced polyethylene films with perforated needle holes have a vapor permeability of 20-40 g / m 2 per day, which is completely insufficient to remove moisture from the insulation. Therefore, they are installed in the same way as vapor barrier films - with two ventilation gaps. The lower ventilation gap - between the waterproofing film and the insulation serves to remove moisture from the insulation.

In the conditions of the Russian winter, this scheme has a serious drawback - the roof insulation remains open in the ventilation gap, what causes:

1. High heat loss - the insulation is exposed to wind blowing, and warm air easily leaves the highly permeable, horizontally located insulation. The thickness of the insulation must be recalculated and increased by 20-30%.
2. At round-the-clock, negative temperatures, the wet steam coming out of the insulation immediately condenses into ice on the underside of the film, which constantly accumulates. The anti-condensation layer also accumulates ice and does not work.

As a result, in the spring, melted ice enters the unprotected insulation and forms leaks in the attic ceiling.

This European scheme, aimed at the use of cheap roofing materials, needs to be changed in a more severe climate - the insulation must be additionally protected by a wind-moisture-proof membrane with high vapor transmission. The pursuit of cheaper under-roofing waterproofing (by 50 USD per 100 m 2 of roofing) turns into a complete restructuring of the attic - with the removal of the roof and the replacement of the under-roofing insulation system. The misleading names “diffusion, vapor-permeable” for perforated films are misleading to consumers who do not know the criteria for their applicability. With any scheme of under-roofing waterproofing of insulated attics, it is not possible to build a reliable system that guarantees against leaks for less than 1.2 - 1.4 USD / m 2 (at the cost of films).

Often, the insulation of the attic space of a house under construction is postponed for the future, and reinforced films or roofing material are installed as roofing waterproofing. In this case, subsequent insulation becomes impossible without removing the roof and film, installing a highly permeable membrane and installing a ventilated gap. For water, having small dimensions (2.8 A), they penetrate between the macromolecules of the filled polymer. Water in the liquid phase, consisting of bound, aggregated molecules, is not able to penetrate into the intermolecular spaces of this polymer. Unlike known porous membranes, which have diffusion properties due to the passage of water vapor together with air through the pores formed by interfiber gaps, TEKTOTEN membranes have zero air permeability (it is impossible to blow air through them). The wind insulation ability of these materials is truly one hundred percent. High water resistance (membranes are able to withstand pressure up to 4 m of water column) allows them to be used as a temporary roof. Three-layer membranes withstand significant loads that occur during the installation of roofs and ventilated facades, and damage to the outer layers does not entail loss of the waterproofing properties of the material.

The attic space needs to be protected from heat loss, since most of the heat escapes through the walls and roof, and especially through the roof. It is necessary to ensure the clear and competent functioning of all layers to protect the roof from heat loss. The vapor barrier layer plays a crucial role in this process, as it does not allow moisture to destroy and rot structural elements.

Why is vapor barrier needed?

The combination of warm air with cold air can lead to, which in turn will lead to a deterioration in the quality characteristics of the building material, no matter how reliable it is. This is can cause wood to rot, the design will become flimsy and unreliable. It will be necessary to carry out complex repair work on the rehabilitation or even replacement of structural elements.

Attic vapor barrier is essential

There may also be the formation of mold and various fungi, whose secretions are toxic to the human body, and can also cause allergies, malaise and headaches in an individual.

Also, the vapor barrier layer helps protect the room from excessive heat loss, working together with the insulation and protecting it from condensation.

Materials for vapor barrier

There are innumerable varieties of materials, the most common is glassine, roofing material, as well as any other film materials.

There are several types of vapor barrier material: polyethylene film, polypropylene film, and membranes.

The vapor barrier of the attic roof will protect and secure the roof

Polyethylene film stretched during installation, and also arrange ventilated gaps for it, since the film is impermeable, condensation may form inside. It is laid with the rough side outward so that the vapor particles evaporate. These films can serve as both waterproofing and vapor barrier. The film is reinforced with a special metal mesh to give it strength characteristics.

Polypropylene film- has high resistance and high strength, but this material has one not very good property. Condensation forms on the upper side of this reinforced tape. To protect the layer from the formation of moisture, a layer of viscose or cellulose is laid on this surface so that excess moisture is absorbed.

Breathing membranes do not need ventilation gaps, and also have high quality and reliability properties. They do not allow water to enter, but release steam from the room. This material is laid on a heat-insulating layer.

Mainly used materials such as: roofing material, glassine and foil materials. But in today's market there are more advanced in quality and reliability materials, such as: NPP LF foam, isopsan, penoplex, as well as armitex. They have high heat transfer, low thermal conductivity, reliable vapor barrier and waterproofing properties, and can also be used at high temperature conditions.

Detailed diagram of the attic vapor barrier

Rules for the construction of a vapor barrier layer

In order for the heat-insulating layer to be protected from moisture penetration, as well as from condensate, several basic rules must be observed.

It is important to remember that before laying this layer, it is necessary to seal and insulate various elements of the structural system, as well as all protruding elements. seal thoroughly. The vapor barrier film is laid on the heat-insulating layer, it is fixed on various surfaces by various methods.

Mounting of the film to concrete, brick, block, as well as to metal surfaces is carried out using double-sided adhesive tape. This film is attached to a wooden surface with nails or stapler staples.

If a foil film is used, then it is mounted so that the reflective layer was turned inside the room so that the heat is concentrated inside. A gap is left between the insulation and the vapor barrier for ventilation, as well as to create a warm air gap.

Gaps, gaps, extra gaps are excluded during installation, otherwise the film will not be able to perform its function correctly. The film is stretched so that it does not sag in relation to other layers.

Modern roofing technologies are very different from the methods of covering residential and utility buildings a hundred years ago. More advanced and durable roofing materials retain heat better, protect against moisture penetration more reliably and make housing more comfortable for living. However, there is a downside to complete tightness - the "greenhouse effect" and the resulting condensate that settles inside the roof structure. To protect the frame and insulation from destruction as a result of wetting, a roof vapor barrier is performed. In this article, we will tell you what vapor barrier materials exist, how they differ and how they are used in a roofing pie.

Roof vapor barrier is an essential component of the roofing roof pie, on which the service life and safety of the finish 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, as it is more prone to condensation due to heating of the under-roof space. The vapor barrier performs the following tasks:

1. Prevents wetting of heat-insulating material. 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 effectiveness. And during frosts, 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.
2. Protects the roof frame from rotting. Waterproofing protects the roof truss system from the penetration of moisture from the outside, and vapor barrier materials reduce the formation of condensate, due to which microorganisms actively multiply, leading to decay of the wood.
3. Extends the life of the roofing. Most finishes are well protected from contact with moisture only on the outside, while the bottom surface often suffers from corrosion, which is formed as a result of the condensation process. Vapor barrier prevents rust damage to the roofing material, extending its service life.

Note! Most modern roofing requires the installation of a vapor barrier that provides protection against condensation and moisture. Only under this condition, the waterproofing material will be able to serve the service life declared by the manufacturer.

quality requirements

Vapor barrier materials are an indispensable component of the “warm” roofing pie, 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 condensate cannot penetrate through the joints. For the effective operation of the vapor barrier, it is required:

• Outstanding water resistance. Waterproofing 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 qualities provide resistance to mechanical damage during installation and operation.
• Long service life. Roof coverings serve for at least 15 years, since the vapor barrier cannot be replaced without dismantling the structure, it must have no less service life.
• Fire resistance. To increase the safety of living in buildings with a high risk of fire, it is recommended to use a non-combustible vapor barrier.

Important! Hydro vapor barrier is a material that combines the properties of waterproofing and vapor barrier coatings, that is, it does not let water or steam through, while remaining breathable.

Criterias of choice

During the construction of their own home, non-professionals often wonder which waterproofing is better, and how to choose the material suitable for a particular design. Experienced craftsmen recommend following the recommendations of the roofing manufacturer, as well as taking into account the following criteria:

1. Climatic conditions of the region in which construction is underway. To choose the right vapor barrier material, it is necessary to know the average annual temperatures in winter and summer in order to determine the difference between indoor and outdoor temperatures.
2. The nature of the use of under-roof space. Under the roof of the house, a heated attic can be placed, from which a large amount of heated, humid air flows, or a non-residential attic, which is a natural air insulation for the roof surface.
3. Roof material properties. Roof finishes have different compositions, shapes and installation methods, so they require the installation of a suitable type of vapor barrier.

Please note that the use of roofing felt, roofing material or hydroisol as a vapor barrier complete with modern roofing materials is not allowed, as they do not allow air to pass through. Despite the affordable price and high strength, they do not protect the frame structure from condensate, but rather stimulate its active formation.

Kinds

Modern vapor barrier for the roof is a high-tech polymer membrane, the multilayer structure of which effectively protects against the penetration of water, steam, but at the same time passes the air necessary for ventilation of the truss 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 fix the canvas, otherwise the work of the roofing cake will be disrupted.

Video instruction

Vapor barrier prevents structural and heat-insulating materials from getting wet when vapors pass outside from the heated room. Previously, a dense polyethylene film was used as a vapor barrier. Now on the building materials market there is a large selection of special rolled vapor barrier, which, in addition to limiting vapor permeability, may have additional functions. In the article we make an overview of vapor barrier manufacturers known on the Russian market.

How to choose a vapor barrier film or membrane manufacturer

There are several manufacturers who not only produce vapor barrier materials, but also offer ready-made technical solutions for each type. And although they are advisory in nature, this allows you to choose the necessary vapor barrier for each case and carry out the installation correctly.

When choosing a film, they are usually guided by it:

• appointment;
• vapor permeability;
• strength;
• UV resistance (especially if the vapor barrier is used as a temporary roof).

The combination of these parameters and availability (cost) determine the place in the conditional rating.

Service life can not be specified as a separate characteristic. It is generally accepted that vapor barrier should last no less than enclosing surfaces: roofing, ceilings, flooring, wall materials.

Rating of vapor barrier manufacturers in Russia

We have ranked the most famous brands of vapor barrier films in terms of quality, availability and completeness of the range:

1. TechnoNIKOL;
2. Isospan;
3. Tyvek;
4. Ondutis;
5. Megaflex;
6. Glass master.

1. TechnoNicole

Photo: TechnoNIKOL vapor barrier film

This is one of the largest domestic manufacturers, which dominates the market of bituminous and polymer-bitumen waterproofing materials. It also produces building films: vapor barrier, waterproofing and wind protection.

The range of TechnoNIKOL vapor barrier materials looks like this:

• Film TechnoNikol. The base is high density polyethylene. Appointment - protection of a roofing cake. Thickness 0.12 or 0.20 mm. Strength not less than 15/14 MPa in the longitudinal/transverse direction. Resistance to vapor permeability - not worse than 36 m 2 * h * Pa / mg.
• ISOBOX D- universal vapor barrier. Multilayer film based on woven polypropylene. Appointment - protection of a roof and constructions of the building from moisture and water vapors. Increased strength and UV resistance - can serve up to 6 months in between works as a temporary roof and facade protective cover. Permissible tensile loads: along the web - not less than 900 H/5 cm, across the web - not less than 750 H/5 cm. Vapor permeability - less than 18 g/m 2 *24 hours. UV stability - not less than 2 months.
• ISOBOX B- double-layer vapor barrier of high strength. Basis - non-woven polypropylene with special additives. Appointment - protection against vapors of building designs and a heater. An inward-facing structure is capable of retaining condensate until weathering conditions occur. Permissible tensile loads: lengthwise - not less than 110 H/5 cm, across - not less than 90 H/5 cm. Vapor permeability - less than 40 g/m 2 *24 hours. UV stability - not less than 2 months.
• ISOBOX C- vapor barrier. Basis - non-woven polypropylene with special additives. Purpose - protection of the structure from under-roof condensate and leaks, vapor barrier layer when laying laminate and parquet in rooms with a humid regime. Permissible tensile loads: lengthwise - not less than 125 H/5 cm, across - not less than 80 H/5 cm. Vapor permeability - less than 30 g/m 2 *24 hours. UV stability - not less than 2 months.
• ISOBOX THERMO- reflective vapor barrier. Basis non-woven polypropylene with a metallized coating. Reflects more than 80% of IR radiation. Operating temperatures from -40°C to +130°C. Permissible tensile loads: lengthwise - not less than 150 H/5 cm, across - not less than 130 H/5 cm. Vapor permeability - less than 5 g/m 2 *24 hours. UV stability - not less than 2 months.
• ALPHA Barrier 4.0- four-layer foil vapor barrier film with zero vapor permeability. Reinforced with mesh, there are self-adhesive strips along the canvas. Reflects up to 50% of IR radiation. Appointment - protection of overlappings, walls of frame houses, roofing cake of flat and pitched roofs. Operating temperature up to +80°C. Breaking load along and across - not less than 450 H/5 cm. UV stability - not less than 2 months.

2. Izospan

This trademark belongs to the Russian company GEKSA, which specializes only in the production of building films and self-adhesive tapes - materials for vapor and waterproofing of various structures.

The company characterizes all vapor barriers as "vapor-tight". But in reality, it has a slight vapor permeability in the range from 7 to 22 g/m 2 *24 hours.

Two-layer polypropylene films with anti-condensation surface:

• Isospan B. Purpose: insulated sloping roofs, walls of frame houses, all types of ceilings. Maximum breaking load: lengthwise - more than 130 H/5 cm, across - more than 107 H/5 cm.
• Isospan C. The purpose is the same as that of Izospan B, plus floors on a concrete base. Maximum tensile load: along - more than 197 H / 5 cm, across - more than 119 H / 5 cm.
• Isospan D. Purpose - flat and non-insulated pitched roofs, floors on a concrete base. Maximum breaking load: lengthwise - more than 1068 H/5 cm, across - more than 890 H/5 cm.
• Izospan DM. Purpose - insulated and non-insulated pitched roofs, walls of frame houses, all types of building floors. Maximum breaking load: lengthwise - more than 700 H/5 cm, across - more than 650 H/5 cm.

Three-layer reinforced films made of polypropylene and polyethylene:

• IzospanRM. Purpose - flat roofs and floors on a concrete base. Maximum breaking load: lengthwise - more than 399 H/5 cm, across - more than 172 H/5 cm.
• IzospanRS. Purpose - flat and insulated pitched roofs, frame exterior and interior walls, all types of ceilings, floors on a concrete base. Maximum breaking load: lengthwise - more than 413 H/5 cm, across - more than 168 H/5 cm.

Two-layer films made of polypropylene with an anti-condensation surface and self-adhesive tape integrated along the edges:

• IzospanBfix. Appointment - the warmed pitched roofs, frame external and internal walls, all types of overlappings. Maximum breaking load: lengthwise - more than 130 H/5 cm, across - more than 107 H/5 cm
• IzospanDfix. Purpose - flat and non-insulated pitched roofs, floors on a concrete base. Maximum breaking load: lengthwise - more than 1068 H/5 cm, across - more than 890 H/5 cm.

Reflective vapor barrier:

Photo: reflective steam-hydro insulation Izospan FX 3 mm

• IzospanFacebook. The base is kraft paper. Coating - metallized lavsan. Scope of application - baths and saunas. Operating range -60°C to +140°C. Maximum breaking load: lengthwise - more than 350 H/5 cm, across - more than 340 H/5 cm.
• IzospanFS. Basis - a polypropylene cloth. Coating - metallized polypropylene film. Purpose - insulated pitched roofs, walls of frame houses, all types of ceilings, "warm floors". Maximum breaking load: lengthwise - more than 300 H/5 cm, across - more than 330 H/5 cm.
• IzospanFD. Basis - a polypropylene cloth. Coating - metallized polypropylene film. Purpose - insulated pitched roofs, all types of ceilings, "warm floors". Maximum breaking load: lengthwise - more than 800 H/5 cm, across - more than 700 H/5 cm.
• IzospanFX. Basis - the made foam polyethylene. Coating - metallized lavsan film. Purpose - insulated pitched roofs, all types of ceilings, walls of frame houses, laminate and parquet floors, "warm floor" system. Maximum breaking load: lengthwise - more than 176 H/5 cm, across - more than 207 H/5 cm.
• IzospanRF. Basis - a polypropylene cloth. Coating - metallized polypropylene film. Reinforced with polymer mesh. Purpose - insulated pitched roofs, frame walls, all types of ceilings, "warm floors". Maximum breaking load: lengthwise - more than 450 H/5 cm, across - more than 300 H/5 cm.

UV stability of the entire Izospan vapor barrier is at least 3-4 months. The temperature range of all polymer films is from -60°C to +80°C.

3. Megaflex

Relatively "young" Russian company, which already controls about 20% of the Russian market of vapor barrier films. The peculiarity of the materials is that all films have an already integrated adhesive strip, which simplifies installation.

Vapor barrier is represented by two-layer films:

• Parostop. Appointment - protection against couple of roofs, overlappings and walls. Tensile load: along - more than 110 H/5 cm, across - more than 85 H/5 cm.

Vapor barrier from Megaflex "Parostop"

• VlagoStop. Reinforced vapor barrier. Appointment - protection against couple of roofs, overlappings and walls. Tensile load: along - more than 810 H / 5 cm, across - more than 610 H / 5 cm.
• Shingle Base. Appointment - protection from steam of a roof pie with a flexible tile on the basis of OSB, a heater of walls of frame houses. Tensile load: along - more than 810 H / 5 cm, across - more than 610 H / 5 cm.
• Sauna. Appointment - protection of walls, overlappings and roofs of baths (saunas). Tensile load: along - more than 810 H / 5 cm, across - more than 610 H / 5 cm.

Temperature conditions - from -50°C to +80°C. UV stability no more than 4 months.

4. Vapor barrier UTA

Vapor barrier film UTAH

The vapor barrier films of this company have the common name "Yutafol", and the numbers in the designation of the density brand are in g / m 2. There are four brands in total, which have a different structure, additional functions and density.

On its official website, UTA indicates density as an indicator of strength, but as a consultation, experts can provide information on tensile strength. Here they indicate UV stability, temperature conditions and vapor permeability.

The range of vapor-proof films Yutafol looks like this:

• H 96 Silver. Two layers, base polypropylene. Purpose - insulated pitched and flat roofs, ceilings and external walls (in case of internal insulation). Tensile strength: along - from 155 H/5 cm, across - from 145 H/5 cm.
• H 110 Standard and H 110 Special(with self-extinguishing reagent). Three layers, base polypropylene plus reinforcing polyethylene mesh. Purpose - flat roofs, pitched roofs, ceilings, external walls (in case of internal insulation). Tensile strength: along - from 210 H / 5 cm, across - from 190 H / 5 cm. Water vapor permeability 0.9 g / m 2 * 24 hours, which is equivalent to a diffusion thickness of 40 m of dry air.
• N AL 170 Special. Four layers. Structure; two layers of polypropylene, a reinforcing mesh of polyethylene, a layer of heat-reflecting aluminum foil. Purpose - a vapor barrier in insulated flat and sloping roofs, as well as in other structures where protection against leakage and heat loss is required. Vapor-tight, tensile strength equivalent to film Yutafol H 110 Standard.

Note. All UTA products have a working temperature regime of -40°C to +80°C, UV resistance - 3 months.

5. Tyvek

To be precise, under the brand name Tyvek, DuPont produces waterproofing membranes. And as a vapor barrier, the company has two types of film:

• DuPontAirGuardcontrol. Structure: a basis - polyethylene, a covering - polyolefin (polypropylene). Purpose - flat roofs, insulated and non-insulated pitched roofs, ceilings, walls (frame and with internal insulation). Limited vapor permeability. Tensile strength 240 H/5 cm.
• DuPontAirGuardreflective. Compared to the previous type, the composition additionally includes a metallized coating. Purpose - insulated pitched roofs, ceilings and walls. Complete vapor tightness.

Fifth place - high quality, but a limited range and high cost.

6. Ondutis

Vapor barrier membrane Oduntis

The range of this company includes both hydro-vapor barrier and vapor barrier films.

Note. Typical about The scope of Ondutis hydrovapor barrier is protection of the under-roof space from condensate and leaks, although to be precise, with the same vapor permeability characteristics (less than 10 g m 2 * 24 hours), the equivalent diffusion thickness of the hydrovapor barrier is even slightly higher.

Range:

• B(R70) andB(R70) Smart. Vapor barrier of all types of enclosing surfaces and insulation. Tensile strength: lengthwise - from 110 H/5 cm, across - from 80 H/5 cm. Equivalent diffusion thickness - 5.4 m. Temperature range from -40°C to +80°C.
• RS, Waterproofing of non-insulated and insulated roofs with metal roofing. Tensile strength: lengthwise - from 250 H/5 cm, across - from 200 H/5 cm. Equivalent diffusion thickness - 7.36 m. Temperature range from -40°C to +80°C.
• RThermo. Vapor barrier with reflective layer. Appointment - baths and saunas. Tensile strength: lengthwise - from 150 H/5 cm, across - from 130 H/5 cm. Equivalent diffusion thickness - 11.54 m. Temperature range from -40°C to +120°C.

Sixth place. Advantages - low cost. Disadvantages - a limited range, "average" indicators of strength and vapor permeability.

7. Glass master

There are two types of film in the assortment of the brand:

• Glass master V. Two-layer film with anti-condensation surface. Composition - polyethylene and polypropylene. Appointment - protection against vapors of a heater and building constructions (roofs, walls, overlappings). Tensile strength: along - from 150 H/5 cm, across - from 110 H/5 cm.
• Glass master D. Two-layer film made of polypropylene with a laminated coating. Purpose - a vapor barrier in an insulated flat roof, protection against vapors and moisture of the attic floor of an uninsulated pitched roof. Tensile strength: along - from 500 H/5 cm, across - from 500 H/5 cm.

The choice of vapor barrier films is quite large. And this makes it possible to buy the necessary materials, taking into account the characteristics of the region, the operating conditions of the building and the budget. And what is especially pleasant, over the past ten years, Russian manufacturers have literally made a breakthrough in this area, seizing a leading position in the domestic market.

The vapor barrier film for the roof is a material that, due to its characteristics, protects wooden structures from the damaging effects of steam, and also does not release heat outside the house. What are the types of vapor barrier films for the roof, we will tell in this article.

What is vapor barrier film for?

The task of the vapor barrier film is to prevent the penetration of steam into the thermal insulation and the supporting structures of the roof. In the absence of vapor barrier films, the period of operation of the roof is reduced and there is a need for repairs.

The air in the room contains a large amount of moisture, since people cook food, take a shower, etc. in the premises. If the vapor barrier is not laid in the structures, moisture settles in the insulation. Excessive moisture 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 a fungus, and metal elements are corroded by rust.
Vapor barrier film eliminates the following problems:

the appearance of condensate on wooden elements and building structures; destruction of the interior decoration of the ceiling and walls due to excessive humidity in the premises; freezing of the insulation layer;

What roofs are suitable for

Vapor barrier film is used for all types of houses and roofs. At the same time, the complexity of the roof structure is unimportant. The flexibility, lightness and strength of the material allows it to be used on any roof, regardless of the level of their 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 the bath and / or sauna.

Pitched metal roofs especially need protection from steam, as increased moisture provokes destructive processes in them, corrosion, the appearance of microcracks and the loss of basic functional abilities. In order to extend the life of metal tiles or seam roofing, it is important to use reliable vapor barrier films, the types of which will be discussed below .

What are vapor barrier films

A large number of films for roof vapor barriers are presented on the building materials market. There are the following types:

Polyethylene films

Polyethylene films are materials whose key feature is reinforcement with fabric or reinforcing mesh. This is done to give strength.

Films are of two types:

Perforated - they have micro-holes that provide vapor permeability. However, this indicator does not correspond to the norm, therefore, when arranging an insulating pie, a ventilation gap must be made;

Non-perforated - materials used directly for vapor barrier. During their installation, tapes are used to connect individual canvases.

There is another kind 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 produce them in Russia. The main advantage of such films is excellent strength characteristics and resistance to sunlight. The material has another significant advantage: the presence anti-condensation layer moisture absorbing and retaining. Such a layer has excellent performance, because even in critical conditions it absorbs all moisture, excluding 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) is a three-layer polymer vapor barrier membrane that is used for insulated roofs and mansard roofs. Ondutis D (RV) are anti-condensation films with a special inner layer of non-woven fleecy textiles in which moisture is concentrated. Used for metal roofs. In addition, this type of Ondutis film can serve as a temporary roof covering for 2 months.

How to choose a roofing film

When choosing a vapor barrier film for a roof, pay attention to:

The purpose of the film. For the roof, use only roofing foil. The vapor permeability of the film. The lower the better. For high-quality insulation of a dwelling, the vapor permeability index is 1 g / m 2 per day. Film weight. The greater the weight of the film, the higher the density of the material and, accordingly, its strength. No foreign odors is an important indicator. The film used in the house must be safe for humans and the environment.

Water vapor, which is released by the human body, gradually penetrates into the roof insulation and moistens it, as a result, the thermal insulation deteriorates. Therefore, it is necessary to protect all elements of the roof from such an impact. And what kind of vapor barrier to choose for the roof? What options exist for it?

Why is this extra layer needed?

Not everyone thinks about the question of what kind of vapor barrier to choose for the roof of a house. Many "home" masters believe that such an additional layer is not needed. And they do it in vain. As mentioned at the beginning, there is always a lot of water vapor in living quarters. They are emitted by a person when breathing, they evaporate when cooking, when ironing clothes with a modern iron, and in many other everyday situations.

Vapor barrier of the roof of a residential building

By itself, water vapor is not dangerous to humans. But, as you know, moisture can quickly ruin almost any material. Gradually, the vapors seep through the ceilings and enter the insulation or elements of the truss system. From such moisture, the material begins to rot and soon the roof will require repair.

To prevent this from happening, it is necessary to lay a special protective layer. What kind of vapor barrier to choose for the roof is an important question. But first of all, it is worth understanding the difference between protection against steam and against water. And the difference is quite large and consists of the following:

1. Waterproofing is mounted on top of the insulation. Its main task is to prevent external moisture from entering the material. In addition, waterproofing is needed so that water vapor, which can form in heaters, freely goes outside.
2. The vapor barrier is mounted from the inside (from the side of the living room). This layer should provide protection against water vapor, while not hindering ventilation.

The main characteristics of the vapor barrier

To find out which vapor barrier to choose for a roof, you should get acquainted with its main characteristics. First, the weight of the material used is taken into account. The greater the mass, the stronger the film (or other material used). Modern manufacturers offer vapor barrier with a density of 60 to 300 grams per square meter.

Secondly, it is the ability to pass water vapor. It is this indicator that is the most important. Vapor permeability is measured in grams per square meter per day. If this indicator is less than one hundred units, then such material is suitable for our purposes. A film with more vapor permeability (the indicator can reach up to 3000 grams per square meter per day) is already used for waterproofing.

To protect the insulation and other elements of the roofing "pie" from water vapor, which is formed in residential premises, it is necessary to mount a special protective layer. To do this, you can use different materials. But to find out which vapor barrier to choose for a roof, you need to know its main characteristics. The first is permeability. For our purposes, a material with this indicator ranging from 0 to 90 grams per square meter per day is suitable. In addition, you need to choose a dense film so that it lasts as long as possible and does not tear during installation.

Choosing a material

What vapor barrier to choose for the roof? The answer to this question depends on many factors. First of all, you should consider your financial capabilities. Modern manufacturers offer a wide range of vapor barrier materials. They can differ greatly both in their characteristics and in cost.

Conventionally, vapor barrier materials can be divided into the following types:

• ordinary polyethylene film of sufficiently high density;
• polypropylene material;
• foil vapor barrier;
• non-woven membrane with different vapor permeability.

Polyethylene film

The most budget option is the use of plastic film. Such material is mounted without any problems. But its characteristics may not always be suitable for our purposes. Often the vapor permeability of such a film is too high.

The polyethylene version of the film is often produced in a perforated form. Microscopic holes are made over the entire surface of the film. This structure helps to provide better ventilation, while not letting moisture through. Laying the perforated film must be carefully mounted, with the smooth side to the insulation. If mixed up, then steam will freely penetrate into the roofing "pie".

Reinforced vapor barrier

Modern manufacturers offer a more "advanced" version of the vapor barrier. One of the brightest representatives of this type is TechnoNIKOL reinforced vapor barrier. A small reinforcing mesh made of polypropylene is glued to the insulation layer from below. This design is called a vapor barrier. The film has high strength and lasts a long time. But its main advantage is a high level of protection against water vapor. Having installed a vapor barrier, you can not be afraid for the safety of all elements of the roofing "pie".

foil vapor barrier

If you are wondering what kind of vapor barrier to choose for the roof, then you can pay attention to the foil material. This option is often chosen as a heater, but for our purposes it is quite suitable. The false side should look inside the room. In this case, steam will not penetrate into the insulation. In addition, heat rays will not “leave” the room, which will help maintain a comfortable temperature.

Vapor barrier membrane

The most modern vapor barrier material is considered to be a "breathing" non-woven membrane. She does an excellent job with the task assigned to her. In addition, the membrane is quite durable and can serve for many years.

There are three main types of vapor barrier membrane:

1. Perforated. Such material contains many small holes made in the form of funnels. Water vapor can freely pass outside, while moisture does not get on the insulation. It is worth remembering that a perforated membrane cannot be mounted without a heat-insulating layer. When freezing, a crust forms on its outer surface, which closes the holes, and the effectiveness of the material will drop sharply.
2. Porous. Here, instead of holes, the entire surface is covered with pores. Such material is similar to foam rubber. When installing a porous membrane, it is important to protect it from dust that can clog the pores.
3. Three-layer. This is the most modern material, which is often called super diffuse. Each layer performs its own function. The three-layer membrane is the most effective. In addition, its properties do not change from external influences (dust and ice crust).

The main disadvantage of this vapor barrier option is the high cost. But when it comes to the durability of a residential building, you should not save too much.

What vapor barrier to choose for the roof? Modern manufacturers can offer a wide range of materials. If the family is difficult with finances, then you can choose a budget option - plastic wrap. If you want to use modern materials, you can purchase a vapor barrier or membrane. The latter option is very popular. Prices for membranes (depending on the type) can be quite high, but the effectiveness of such a vapor barrier is at a height, which is why it is most often chosen for these purposes.