Which side to lay the vapor barrier installation tips

An adequate insulation system is essential for maintaining a warm and cozy home. Vapor barriers are a crucial part of any good insulation system. This small layer can go a long way toward preventing moisture buildup in your home’s walls, which over time can result in mold, mildew, and even structural damage.

Installing a vapor barrier isn’t as simple as it sounds, though. One of the most frequent queries from homeowners is, "Which side should the vapor barrier face?" It’s a legitimate worry because doing it incorrectly can reduce its efficacy. The type of insulation you’re using and the climate where you live will determine where to put the vapor barrier.

We’ll go over some helpful advice in this post to assist you in choosing the appropriate side to lay the vapor barrier. We’ll go over various scenarios according to climate zones and insulation types so you can decide what kind of insulation best fits the needs of your home. Whether you’re renovating your old insulation or building a new one, knowing these tips will help you maximize the comfort and energy efficiency of your house.

  1. Purpose of vapor barrier
  2. Features
  3. Which side should be laid vapor barrier film correct installation
  4. Features of insulation of the attic
  5. Types of vapor barrier films, properties
  6. Varieties for roofing ↑
  7. Features of installation of vapor barrier
  8. Preparatory work
  9. Technology of laying vapor barrier on the ceiling
  10. Technology of laying vapor barrier on the floor
  11. Types of vapor barrier materials A, B, C and D
  12. Type A insulation: only for vapor escape on the other side
  13. Vapor barrier B: classical double-sided laying
  14. Type C membrane: for increased protection against water vapor
  15. Which side to put the vapor barrier on the insulation material
  16. How to distinguish the inner side from the outer side
  17. Rules of laying vapor barrier on mineral wool
  18. Vapor barrier and its functions
  19. Basic rules of vapor barrier laying
  20. Which side to lay Izospan on the insulation?
  21. How to distinguish the inner side from the outer side?
  22. Which side to put the vapor barrier to the floor insulation?
  23. What vapor barrier is needed for
  24. The need for vapor barrier
  25. Recommendations for proper laying of vapor barrier materials
  26. Why do you need a vapor barrier insulation
  27. Varieties of materials
  28. Purpose of vapor barrier
  29. The right side of the vapor barrier myth or reality
  30. Laying vapor barrier with your own hands
  31. The main nuances of installing a vapor barrier
  32. Correct laying of the vapor barrier
  33. The main types of vapor barrier
  34. What is the difference between anti-condensation film and anti-condensation side
  35. Cut off the attic and the basement
  36. Peculiarities of installation works
  37. Correct positioning and installation
  38. Video on the topic
  39. Mansard roof vapor barrier. Mistakes of vapor barrier installation. Döcke Pie BR vapor barrier film+.
  40. 🟢 Roof vapor barrier and insulation of a complex mauerlate assembly!
  41. Mistakes when laying the vapor barrier. The result after 3 years.
  42. Installation of vapor barrier roofing, which side to lay the vapor barrier to the insulation, thickness, laying
  43. How to install the vapor barrier. All nuances. Which side to lay the vapor barrier and how to fix it!!
  44. How to properly lay a vapor barrier / What vapor barrier is needed for roofing
  45. Installation of vapor barrier. Nuances of installation.

Purpose of vapor barrier

Steam and condensation have a major influence on the state of the roof, walls, and floor’s structural components. Overwetness encourages the growth of mold and fungus, corrodes metal, and rots wooden components. The insulating qualities of wet insulation, particularly mineral wool, are significantly diminished, permitting the cold to seep through. Wet vapor cannot enter the "pie" due to the protective layer provided by the vapor barrier fabric, but it can still escape out of it.

The temperature differential between the heated room and the cold street is caused by the formation of condensate. Seeking to escape the structure, the steam cools and condenses into droplets of water. Moisture cannot reach the insulation material because the vapor barrier film is correctly installed on one side. Condensate either dries on the fabric’s surface or runs down it without touching the structural components. Certain vapor-retardant products don’t require you to select which side of the insulation material to turn them toward. These all-purpose films are particularly useful for novice builders.


It’s important to carefully follow the right steps and use the best materials when insulating a house.

Regretfully, homeowners who decide to insulate their houses frequently overlook the vapor barrier, which is a crucial component. They just install insulation, not even considering that it will soon start to form condensation in the form of water droplets because it is in contact with either too warm or too cold air inside the room.

Furthermore, this not only degrades the insulation but also ruins the material itself by moistening it. If the vapor is not allowed to evaporate, mold develops and the insulation’s structural integrity is compromised. Furthermore, because of our climate, this scenario arises at least four times a year. The insulator is the battlefield, and the temperature inside the room and outside its boundaries "conflict" as a result of the changing seasons.

This is why installing a "vapor barrier" is a crucial step in the insulation process. The vapor barrier "closes" the room, making it impossible for steam to pass through and preventing it from turning into water. It also keeps steam from coming into contact with air that is either too hot or too cold.

Which side should be laid vapor barrier film correct installation

Today, a large variety of film vapor barriers from both domestic and foreign manufacturers are available on the domestic building materials market. Its various varieties may also have surfaces with varying textures, so before installing, carefully read the manufacturer’s instructions.

While it is easy to ascertain that, when film with a one-sided coating of aluminum foil is used to insulate rooms with high humidity (baths, steam rooms, bathrooms, and so forth), the metallized surface should be directed into the room, it is not as evident, for instance, for the material "Izospan B." The two layers of this film’s structure are its smooth and rough surfaces. According to the manufacturer’s instructions, the smooth, tightly adhered insulation material should be directed into the room and should have a rough surface designed to retain condensate drops and their subsequent evaporation.

There won’t be any condensation inside if the vapor barrier was installed correctly.

Features of insulation of the attic

  • the film is fixed to the rafters from inside the attic with galvanized nails or construction stapler, covering the insulation;
  • Strips of material are laid horizontally, from bottom to top, with an overlap of one strip on the other at least 15 cm;
  • in rooms with high humidity strips are fastened together with a special connecting tape;
  • fixation is made by fixing to the rafters of the frame, designed to fix decorative panels or sheets of gypsum plasterboard.

There must always be a 4–5 cm ventilation gap between the vapor barrier and the cladding!

Method for installing a vapor barrier and insulation

Types of vapor barrier films, properties

Building regulations specify the requirement for waterproofing and this type of insulation. Vapor barrier film should have the following indications, per GOST:

  • Weight. Its value and the value of density, an indicator of the strength of the insulation, are directly proportional. Strong material is not only easy to work with, but better resists the effects of gravity.
  • Vapor permeability. Its performance properties improve with the reduction of this indicator. For residential premises in Russian conditions are suitable brands, the vapor permeability of which is much less than 1 g / sq. cm. м.

Selecting a vapor barrier is an important decision. Remember that the composition of technical polymers may include different additives, such as UV stabilizers or plasticizers, which can lead to the build-up of hazardous materials in the small area. The possibility that the product is composed of simple, poorly purified raw materials cannot be ruled out either.

We advise It is very easy to determine whether vapor barrier material is harmful. The low-quality film will begin to release an odor when you roll it out in a closed, warm room, and it will be impossible to ignore it when you visit the room later.

Varieties for roofing ↑

  • Polyethylene vapor barrier film. One of the most popular insulation options. While it is cheaper than others, this option is quite effective. As a rule, the material is reinforced by using a special reinforcement mesh or cloth.
  • perforated, equipped with micro-holes, which provide vapor permeability. However, its level does not meet the normative, so the presence of a ventilation gap in the roof cake is mandatory;
  • smooth (non-perforated) – when installing them use a special tape for vapor barrier film, using which connect the individual cloths;
  • foil vapor barrier films. They have a fairly high performance and also reflect heat back to the surface.

Take note! For a vapor barrier in a room with a typical microclimate, laminated insulation is not appropriate. They are frequently utilized when designing spaces with high humidity, like saunas and swimming pools.

Table of Vapor Barrier Film Comparisons

Table of Vapor Barrier Film Comparisons

  • Polypropylene. They are characterized by a very high level of durability and UV resistance. Materials with an anti-condensation layer made of viscose with cellulose, which absorbs and retains moisture, are in particular demand. The advantages of such a layer are obvious: it not only fully absorbs moisture, but also instantly dries naturally as soon as the causes causing condensation disappear.
  • Diffusion membranes. This is a synthetic nonwoven material. It is much more effective than polyethylene or polypropylene products. True, their cost is much higher.
  • . This is a cold emulsion of polymers, which is sprayed on the surface, using special equipment. An undoubted advantage of this option can be considered the ability to apply this type of vapor barrier in the roof structure, which has even the most intricate shape.

When it comes to installing a vapor barrier in your home for heating and insulation, choosing the right side to face can make a big difference. Generally, you"ll want to place the vapor barrier on the warm side of the insulation to prevent moisture from getting trapped inside the walls, which can lead to mold and other problems. In colder climates, this means the vapor barrier should face towards the interior of the house. However, in warmer climates, it should face towards the exterior. Always remember to seal any seams and overlaps tightly to ensure a continuous barrier. Following these simple tips can help you maximize the efficiency of your home"s heating and insulation, keeping it comfortable and energy-efficient all year round.

Features of installation of vapor barrier

Ensuring a vapor barrier layer is a crucial step in protecting insulation materials. All of the work is done while constructing a new structure or when repairing or reconstructing an already completed building. Knowing which side to attach the membrane cloths to the insulation base and how to connect them is essential for correctly installing vapor barrier.

Preparatory work

At this point, efforts are made to choose the right kind of vapor barrier, taking into consideration the material requirements, operational characteristics, and installation-specific details.

Surface preparation is a prerequisite for applying the vapor barrier.

Here, it’s critical to consider the kind of material that was used to build the roofing structure, walls, floors, and ceilings.

  1. When building a log cabin, all structural elements are treated with protective antiseptics and fire retardants.
  2. When carrying out repair and reconstruction work, a complete dismantling of the finish, cleaning and preparation of surfaces is carried out:

Compositions are applied to wooden elements to prevent aging, rotting, and combustion. Deep penetration antiseptic compounds are used to treat the surfaces of concrete, blocks, and bricks.

The building as a whole and the insulation material will have a long service life if surfaces are prepared properly.

Technology of laying vapor barrier on the ceiling

Installing the waterproof membrane follows a planned procedure if the interfloor ceiling and roof structure are composed of wood.

The best option is to install roll or block insulation—basalt or mineral wool—in the space between the rafters and lags. After that, you can cover the ceiling surface with a vapor barrier.

To maintain natural ventilation, a slatted counter batten is installed in addition if the thickness of the insulation matches the height of the battens.

Installing the vapor barrier on the ceiling with a slight overlap on the outer walls is recommended, with particular focus on the corners. Locating the joints on the lags and using reinforced tape to glue them on both sides is preferable.

Crucial! It’s important to prevent the fabrics from sagging and deforming when installing the vapor barrier.

A waterproofing film is put on self-adhesive tape and a metal or wood batten is inserted to insulate a concrete ceiling slab or flat roof from the interior.

The minimum technological gap for ventilation and the thickness of the insulation material determine the height of the purlins. The installation step is 3 cm narrower than the heat insulator’s width, allowing for proper insulator laying in the purlins’ prepared cells.

Technology of laying vapor barrier on the floor

The process for installing vapor barrier on a floor is comparable to that of installing the material on walls and ceilings.

The waterproofing is laid on the rafters of the wooden floor, which is insulated. The insulation, which is either basalt or mineral wool, is then placed in the void created by them. The material for the vapor barrier is then laid down.

The rolled material should be 12 centimeters overlapped, and the joints should be carefully glued with metallized tape on both sides. A properly installed vapor barrier should cover the entire floor, with a maximum 10-cm overlap on the walls.

Installing a batten, in whose cells the waterproofing layer and the heat insulator will be placed, is required in order to install a vapor barrier on a concrete base.

Types of vapor barrier materials A, B, C and D

You must first identify the type of vapor barrier in order to comprehend which side should be laid and why, for example, it suddenly turned out to have both sides smooth. Not every type has two distinct personalities!

Type A insulation: only for vapor escape on the other side

For instance, type A vapor barrier roofs are unsuitable for use since the vapors will eventually seep into the insulation. Ultimately, the primary function of this kind of insulation is to guarantee their unhindered passage, rather than allowing rainwater to enter from the exterior.

In order to allow water droplets to easily roll down and evaporate (and thereby help the ventilation gap between such insulation and insulation), this type of insulation is used on roofs with slope angles of 35 ° or more.

Vapor barrier B: classical double-sided laying

However, B really is a vapor barrier. With its two-layer construction, vapor barrier B prevents condensation by allowing moisture to be absorbed into its lint in the morning and evaporated during the day.

That’s why the smooth side of a type B vapor barrier is always placed against the insulation (film side), and the rough side is placed outward. Type B vapor barrier is not used for insulation; rather, it is only utilized in roofs that are insulated. к. It is not strong enough for one that is not insulated.

Type C membrane: for increased protection against water vapor

A type C vapor barrier is a more densely packed two-layer membrane. The vapor barrier film layer thickness is notably different from type B. While it is more durable on its own, it is utilized in the same applications as type B vapor barriers.

This vapor barrier is also used on flat roofs to improve the protection of thermal insulation and on uninsulated roofs to safeguard the wooden components of the attic floor. Additionally, vapor barrier C needs to be installed inside the space, rough side facing inward.

The ultra-sturdy type D vapor barrier is made of a strong polypropylene cloth with a laminating coating on one side. These are capable of withstanding heavy mechanical loads. It is utilized in insulated roofing to prevent leaks in addition to serving as a waterproofing layer to insulate the attic floor. Additionally, type D vapor barriers are essential in rooms with extremely high humidity levels.

Here are the situations and locations where each of these insulation types is necessary:

Which side to put the vapor barrier on the insulation material

At first glance, it seems very easy to lay the film on the walls and the floor; just place the film on the stapler on top of the insulation, and you’re good to go. As with everything, there are crucial things to remember, though. For instance, what kind of film is used, what kind of structure is insulated—the floor, ceiling, or walls—what kind of operating conditions are anticipated, etc.

But figuring out which side will hold moisture is the most crucial step.

How to distinguish the inner side from the outer side

The direction of the film towards the mineral wool should always be indicated in the manufacturer’s instructions. However, if the package doesn’t include instructions, you can use outside factors to independently determine the vapor condensate film’s working surface.

To do this, you must carefully read the content and focus on the following points:

1. The side of the film that will be facing the floor when the roll is being rolled out is regarded as the inner side and should be facing the insulation;

2. In the event that the film is colored differently on both sides, the heated room should be on the darker side and the insulation on the lighter side;

3. The film is placed smooth side up against the insulation because the hairy side is made to hold onto moisture while the smooth side allows it to flow through.

Vapor barrier application in roofing

Rules of laying vapor barrier on mineral wool

Polyethylene film is laid on all sides on the floor and ceiling. The smooth side of the diffusion membrane is placed on the insulation, and it should face the heated room. In order for the metallized layer to reflect the heat radiation back towards the warm room, foil vapor barriers, also known as foam foil, are fixed with the reflective side facing outward and a ventilation gap.

Keep in mind that vapor-proof materials can only be laid if a ventilation gap is made between the film and the finishing material. The film’s surface will not weather well if the wall cladding is installed next to the film. Keep an eye on the film’s integrity when laying, and use scotch tape to seal the joints between rolls that are at least 200 mm apart. View the manufacturer’s instructions video for more information.

Vapor barrier and its functions

In addition to ventilated facades and roof insulation, street air is also used to dry mineral wool. The primary issue with this approach is that the rapid evaporation and strong flow of moisture accelerates its penetration from the inside of the building. Special materials are used to limit the saturation of the insulation vapor, ensuring that the inflow of moisture does not surpass its evaporation potential.

Roof insulation comprises the following elements: underlay, vapor barrier, rafters, insulation, windproof membrane, counter-batten, purlins, and roof covering.

This case also has a number of subtleties. For instance, there is an increased air saturation with moisture on the opposite side of the insulation contour, which needs to be considered in the new recalculation of the dew point route. However, in order to allow the wall to "breathe," the barrier’s capacity must be carefully chosen. It should not be too small, as this would prevent the insulation from evaporating outside.

A home’s ventilated exterior composed of expanded clay concrete: 1 – expanded clay block wall; 2 – ventilated facade subsystem; 3 – moisture from the room; 4 – membrane distance laths; 5 – vapor-permeable membrane; Sixth: insulation against heat

A vapor barrier should not be positioned in a location where moisture condensation is likely to occur, as this increases the likelihood that the moisture will condense inside the barrier. They can occasionally take advantage of this behavior: if the vapor barrier has a vent on the side of the room, the responsible structures won’t get wet, and the membrane’s vapor permeability is naturally controlled.

Pie insulation of the home’s frame wall: Siding or other exterior cladding; 2 purlins; 3 windproofing; 4 insulation; 6 – vapor barrier; 5 – wall frame; 7-purlins; 8. Decorative interiors

Basic rules of vapor barrier laying

Anyone who knows how to hold a hammer and a ruler in his hands can lay a vapor barrier.

To install the necessary vapor barrier material:

  1. Preliminarily clean the surface from dust and dirt.
  2. Fix cracks or fill them with assembly foam.
  3. Then primed and dried.
  4. Check the condition of the insulation.
  5. Eliminate gaps at the joints.
  6. Treat with antiseptic.

Here’s where laying comes in:

  1. Rolled. At the same time:
  • Roll out the material.
  • Cut off so much that the overlap on the next strip is 100-200 mm.
  • Fixing with wooden laths.
  • Joints, together with the overlap, are connected with tape.
  • It is obligatory to check the strength of connections.
  1. Sheet. This method requires the creation of a frame. The vapor barrier is placed in it, fixing it with a stapler.

Which side to lay Izospan on the insulation?

This material is multilayered and composed of polymer film with various additives. It provides dependable defense for the house’s framework and insulation. It will ensure that they are completely protected from any vapor that may come from the room’s interior. It consistently keeps dangerous particles found in the insulation material out of the house. These substances pose a serious risk to human health. Inside the house, place the vapor barrier between the finishing material and the insulation by laying it on the supporting frame’s elements.

The material is divided into the proper length of strips. and then firmly placed over the insulation, overlapping it horizontally from bottom to top by at least 15 centimeters. Izospan XL tape is used to join the horizontal strips together. The smooth side of the insulation material should be laid upon. Using a stapler, secure.

The finishing material and the vapor barrier should have a ventilation gap. Isospan is fastened with 4 cm laths on top.

There are various varieties of Izospan, and as such, their uses will vary:

  1. Two-layer. It has a smooth surface on one side and a rough surface on the other. It is used to cover interior partitions, basement and floor.
  2. Isospan, the basis of which is a woven polypropylene fabric. They are used in rooms with high humidity, when the floor is made with a cement screed.
  3. Izospan, which has a layer of polyethylene foam, It is used for thermal insulation of roofs. It is covered on one side with lavsan metallized film.

A few unique aspects of installing a vapor barrier:

  • In unheated attic rooms, the vapor barrier material is attached to the floor between the floors. It is obligatory to make a ventilation gap and lay a rough ceiling.
  • When laying a vapor barrier on the insulated exterior walls of the house, it is attached to the frame.
  • Vapor barrier material with its smooth surface is directed towards the wall, and rough – to the outside.

How to distinguish the inner side from the outer side?

The smooth-coated inner side of the vapor barrier material is thought to be the one that is positioned underneath the insulation material. A moisture barrier is provided by the outer pile portion. The side that is next to the roll when it is rolled out on the floor will be its inner side, and it must be laid in the direction of the thermal insulation.

Which side to put the vapor barrier to the floor insulation?

The floor is a complicated structure, particularly in a home made of wood. A vapor barrier is required to preserve the insulation (there is no way to do this without it), boards, and joists for many years to come. Washing, cooking, and steaming are done in every living area, and the steam needs to be let out. If this isn’t done, moisture starts to show.

For maintaining the floor, reinforced non-perforated film is a wise option. Not even very fine vapor can get through it. Aluminum-laminated polyethylene film has shown excellent results. It effectively manages its dual roles as a vapor barrier and an infrared reflector, maintaining the room’s temperature. It is most frequently used as a floor vapor barrier in bathrooms and kitchens.

Installing a floor vapor barrier requires careful thought and adherence to rigorous technological guidelines.

Following these guidelines is essential when using a vapor barrier:

  • The side that has a rough surface must be in contact with the insulation material;
  • aluminum surface should face inward.

One strip of material is laid over the other so that there is an overlap.

Tape or double-sided tape is used to glue the joints together. The vapor barrier is fastened to the frame using construction staplers.

What vapor barrier is needed for

Vapor barrier materials are used to ensure that moisture in a room circulates normally. Ignoring the vapor barrier exposes the insulation to airborne moisture, which progressively erodes the material.

The vapor barrier will act as a barrier to prevent dangerous materials from entering the room if buildings are constructed from the material, which is already an insulator.

Material used for insulation that blocks heat. Based on where the raw material came from, it is separated into:

Which kind of vapor barrier is required?

  • organic thermal insulation – the basis is wood, plants, animal hair;
  • Inorganic thermal insulation – mineral wool, fiberglass, concrete.

You cannot use insulation—which is excellent at absorbing moisture—without vapor barrier. When it isn’t present, moisture seeps into the insulation’s structure and condenses into water. The insulation material’s capacity to provide thermal insulation will deteriorate with time. It will be feasible to see the growth of mold and fungus after a specific amount of time. By using a vapor barrier, the insulation and the apartment’s interior air are effectively shielded from one another.

The insulation will function well and for a long time if the vapor barrier is installed correctly.

The need for vapor barrier

Vapor barrier is a kind of special film (or various materials like rubyroid), which, along with other parts of the building structure, prevents the penetration of steam into the room and does not allow condensation to form.Before starting vapor barrier works it is necessary to determine the most critical areas. It is necessary to protect the areas that are in direct contact with warm and moist air.Vapor barrier helps to increase the service life of insulation, so it does not allow moisture to penetrate into the insulation layer. Especially relevant properties of vapor barrier, in the period when the temperature in the house and outside the window is different, i.e. in winter. For this reason it is possible to form vapor in the premises, which should easily leave the building.Vapor barrier layer is mandatory for laying on the ceiling, rooms assigned to the basement, attic rooms and, of course, on the first floors of buildings. It should be noted that vapor barrier walls are not mandatory if they are insulated from the outside. This is because the vapor barrier in this type of construction will run along the outside of the building. When using a technology in which the walls are insulated inside, it is necessary to lay a vapor barrier layer on top of the insulating material.Installation of the vapor barrier layer should be carried out depending on which part of the dwelling is insulated. Accordingly, the order of work will be different.

Recommendations for proper laying of vapor barrier materials

The first step in the planning of vapor barrier installation is identifying the most important areas that need special attention. Where the surface becomes the boundary where warm and cold air meet, moisture-resistant material must be laid down.

The most typical places are walls, attics, ceilings, roofs, and basements. In order to properly address vapor barrier works, wooden structures are needed:

  • Layer protecting against moisture should be laid smooth side to the insulation materials, in this case there will be no inflow of steam, will not begin to form rot or fungus, heat will not be lost. This is especially important for buildings made of wood.
  • If the walls are insulated from the outside, then the vapor barrier is placed outside the room. When installing thermomaterials internally, the layer of film, shielding from moisture, should also be on this side.
  • The most common mistake is loose adhesion of the film to the insulation.
  • When gluing the seams of the vapor barrier webs, it is necessary to use a wide tape of at least 10 cm.
  • When work is carried out in the areas of window openings, it is often forgotten to leave a small reserve of film, which is needed in case of deformation or shrinkage. It should be a fold of 2-3 cm.
  • The film must be protected from the effects of sunlight, in just one season, the exposed surface can fall into disrepair.
  • To connect the joints of the foil with the foil surface, you need to use metallized scotch tape.

While working with vapor barriers doesn’t require a lot of skill, there are still a lot of subtleties to consider. The primary requirement for proper foil installation is that the right side of the foil must face the insulation. Finding a material’s face and flip side is typically not too difficult. As demonstrated in the video, lay Izospan:

Why do you need a vapor barrier insulation

In order to stay warm and save money, people are now insulating the walls, floors, and ceilings of residential buildings due to the rise in gas and light prices. However, a new issue has emerged at the same time: vapor and moisture buildup on the insulating boards.

Some requirements for the vapor barrier:

  1. To prevent this from happening, it is necessary to lay a vapor barrier on the side of the room. Especially this issue is of concern in winter, when the difference between the air temperature outside and indoors is much different. In this case, moisture is formed at the boundary between cold and heat, which needs somewhere to go out. The room becomes damp, which affects the health of households.
  2. Another reason for laying a vapor barrier is to keep the structural parts of the building free from moisture, This can result in mold, rot, corrosion and fungus that spreads very quickly. The service life of such a building is shortened. Both wooden and metal structures can not withstand the effects of moisture. Metal is subject to corrosion and wood to rot.
  3. It will save the roof from bloating when vapor enters from the room.
  4. You do not need a vapor barrier for the walls if the house is insulated from the outside. But on the floor, ceiling or attic to lay a vapor barrier is necessary.
  5. When insulating the walls inside the room vapor barrier is laid on the insulation material. Insulation will fulfill its functional duties for a long time.
  6. The vapor barrier of a building can be laid outside or inside. The thermal and vapor barrier is a comprehensive protection of the house. And, if ignored, there will be a constant leakage of heat from the house, moisture and vapor on the cold walls in the winter time. When it is cold outside and the house is warm, condensation forms on walls, ceilings and floors. The structure of the house becomes susceptible to moisture absorption. All this leads to serious and expensive repairs.

Varieties of materials

Understanding the various vapor barrier types and technologies is made simpler by closely examining what is currently available in the pertinent market segment. The Axton brand’s products will be taken into consideration after that in order to give the study credibility. This producer offers a sizable selection of materials.

The type "B" vapor barrier membrane is the most economical. It is composed of two layers, each having a distinct surface quality. The more abrasive side holds condensation on itself until it evaporates organically. It is the vapor barrier facing the exterior of the home.

This device keeps moisture from penetrating other parts of the building structure and stops droplets from moving freely. Up to 15 m² can be covered by one standard package, which weighs approximately one kilogram. Utilizing this high-quality content doesn’t present any major challenges.

A vapor barrier that provides waterproofing is designated with the letter "C." It has both indoor and outdoor applications. This kind of film is especially frequently utilized when installing ventilated facade structures. Compared to the previous version, it is stronger but roughly 30% heavier.

Modern vapor-permeable membrane "D" for waterproofing is strengthened with unique structural inserts. These products are employed in the process of adding an insulation layer beneath the roof. Even if there are major infractions in the tile or other finish coating layer, they won’t allow water through if the proper installation technology is used.

The following groups can be conditionally applied to all products in this category:

  • The simplest inexpensive materials for vapor barrier of 1-2 layers. They are able to perform only basic functions.
  • Vapor barrier membranes with modified surface roughness. A typical example of such products – the above-mentioned film "B" brand "Axton".
  • "Active". This group includes products with microscopic holes. Such vapor barrier films are air permeable, so they are often used in combination with wooden structures of houses.
  • Infrared reflecting vapor barrier was discussed above. Quality products of this category can significantly increase the efficiency of heating devices. They are more expensive, but their installation helps to save money in the process of operation.
  • An interesting variety of foil materials is a layer of several millimeters of foamed polymer. Not bad thermal insulation properties of this type of vapor barrier film are used for solving various practical tasks.
  • Vapor permeable waterproofing ("Axton" "C") is more expensive. But it is stronger than other options, has good resistance to loads and mechanical effects of different nature.

Film material with reinforcement for vapor barrier

Purpose of vapor barrier

It is important to think about the vapor barrier’s features and purpose before deciding which side to install it on. Owners of homes and apartments insulate the walls, ceilings, roofing, etc. when building or remodeling. But if the vapor barrier isn’t put in during the installation process, all the expenses for buying insulation and other finishing supplies will be pointless.

It’s possible that inside the building, the humidity will rise. This occurs, for instance, when washing clothes, watering plants, and cooking. Moisture permeates the building materials used to construct the structure, to varying degrees. Only metal and glass lack this quality.

Condensation forms as a result of temperature variations between the inside and outside of the building. The dew point is the level at which it evaporates. It is usually found inside the roof or wall structure. The temperature front moves through this area. Condensation can cause moisture to build up inside the thermal insulation. It may freeze during the winter, which would destroy the building material. The ice will melt and seep through the ceiling or walls when the weather warms. Additionally, moisture buildup within the insulation may cause the material’s thermal insulation qualities to decline.

By installing a vapor barrier, damp air from the room cannot enter the external insulation materials. It will be possible to prevent wetting the insulation in this situation. The point of dew will change. Not only will installing a vapor barrier keep the insulation dry, but it will also stop fungus and mold from growing. These microbes are responsible for the room’s unhealthful microclimate and the deterioration of the wood.

The right side of the vapor barrier myth or reality

Let’s examine the notion of condensation; it’s crucial. The problem is that, for whatever reason, most people are certain that condensation won’t occur at all if a high-quality vapor barrier is installed.

Conversely, it will quickly vanish on its own. As a matter of fact, vaporized moisture ascends upward and condenses from it.

The term "temperature boundary" (t.е.) refers to a specific condition wherein the air temperature and humidity are high enough for vapor to form droplets. For instance, condensation will start to form at 15°C and an approximate air humidity of 65%. On the other hand, condensation will form at 17 °C if the air humidity hits 80%.

In other words, the whole process of water vapor formation appears as a result of the difference in the so-called "partial pressure". All water vapors that are contained in the air, trying to go outside – to the colder street through the enclosing structures of the roof, but meet on their way a barrier in the form of vapor barriers. If the air in the house has warmed up faster than the surface of the vapor barrier, then moisture from the air will precipitate on it in the form of condensation. Here you can clearly see the difference between the insulated roof and uninsulated: any vapor barrier, which is laid on the insulation, will warm up much faster than the one that is in direct contact with the cold elements of the roof.

In the event that there is insufficient or no vapor barrier layer, water vapor will enter the roofing pie and meet the "cold front" there, turning the vapor into condensate and, in certain cases, ice. And inside the roof, it all transpires! You won’t notice this ice until spring arrives and the street temperature rises, warming the roof’s components. After that, the ice buildup will melt and create complete drips on the interior slopes of the house.

However, condensation shouldn’t occur at all on a properly installed roof, so in this regard, the distinction between the smooth and rough sides is actually negligible.

Laying vapor barrier with your own hands

It’s important to realize that installing a vapor barrier requires working from inside the attic space before learning how to install one on the roof. The video below illustrates how the vapor barrier layer should be laid correctly:

Installation of the vapor barrier film can be carried out both horizontally and vertically, but such work should be started only after the thermal insulation is installed. When installing horizontally, it is necessary to start laying the material from the highest point of the roof. All strips of vapor barrier material are placed with an overlap of at least 80 millimeters. Do not skimp on the vapor barrier, if possible, you should increase the overlap to 100-150 millimeters. The joints of strips of vapor barrier material are securely fastened to each other with the help of construction tape. It can be either one-sided or two-sided, it all depends on the chosen type of gluing, inside or outside.

The overlap of the film sheets should line up with the location of the wooden beams if the vapor barrier material is installed vertically. Because of this, it is far more practical to position the vapor barrier such that it is perpendicular to the support rungs that hold up the roof.

As previously mentioned, dowels or staples should be used to secure the vapor barrier material to the roof’s wooden components. The spacing between the rafters determines the spacing between the fasteners.

Verify that the seams are firmly joined and sealed after the vapor barrier material is installed. Clamping strips can be used to further secure the glued parts. Their application is particularly crucial if the roof has a slope angle of more than thirty degrees or if the thermal insulation layer is not very thick.

The most challenging areas to install the vapor barrier material are those with roof openings, such as chimneys and windows. In these locations, a vapor barrier apron needs to be installed.

Generally speaking, all standard sets of materials for the configuration of vapor barriers include vapor-containing factors. If they are not available, double-sided butyl tape should be used with caution to cover the roof’s openings.

It is essential to secure the vapor barrier material with pre-cut wooden bars after it has been placed. They ought to be positioned 50–60 centimeters apart from one another. These extra fasteners are necessary because they keep the foil from coming into contact with the ceiling sheathing. Additionally, the use of bars strengthens the thermal insulation layer by ensuring that air space forms between the vapor barrier and the exterior of the ceiling slab.

This completes the vapor barrier layer installation. It will last for many years if done properly. It is evident from everything above that installing a roofing pie should be done responsibly for all other work as well as for insulation and waterproofing.

The main nuances of installing a vapor barrier

There are several aspects of vapor barrier film installations that a non-professional builder should be aware of. Inexperienced builders frequently make seemingly insignificant errors, which prevents the vapor barrier material from functioning as intended.

The primary characteristics and subtleties of installing the roof pie’s vapor barrier layer should be as follows:

  • tightness of fixing the vapor barrier film. It is not necessary to save fastening elements. The material should tightly adhere to the wooden layers of the roof. Otherwise, the installation of the vapor barrier will not be performed successfully;
  • If the vapor barrier is arranged around the roof passages, the material used should have a reserve of 2-3 centimeters. This is necessary in case of precipitation of the film;
  • Do not allow the vapor barrier material to be twisted on the rafters. Otherwise, moisture will accumulate in such places;
  • and finally the most important nuance. The vapor barrier film has one side that is rough and one side that is smooth. It is the smooth side of the membrane that the vapor barrier should be placed against the thermal insulation material.

By following all of the previously mentioned guidelines and accounting for the subtleties and peculiarities of installation, you can arrange the vapor barrier layer of the roofing pie with great success even without hiring workers.

Correct laying of the vapor barrier

Due to the fact that today on the market is presented a wide variety of vapor barrier materials, the question arises as to which side should be laid vapor barrier, so that the insulation will serve for a long time and most importantly reliably.Before proceeding to the vapor barrier work is required to make a number of mandatory calculations. This is not a complicated procedure, as it may seem at first glance. It is only necessary to calculate the area of each of the elements that make up the house structure and require special protection. When calculating it is necessary to take into account the width of the vapor barrier material, plus specify the size of overlaps.You should also carefully prepare for the installation of the vapor barrier. And for this purpose, a number of preparatory procedures should be carried out:

  • Preliminary surface should be cleaned of any debris and dust;
  • Gaps are sealed with special means, for example, you can use primer;
  • Thorough drying. From how well the surface is dried depends on how the vapor barrier material will manifest its properties.

It is crucial to make sure the material is laid on the correct side when installing the vapor barrier. To begin with, it is important to identify its interior and exterior components.

These days, a lot of manufacturers provide information about which side is internal; in the absence of such information, external data should be used to make the determination. For this reason, it’s important to focus on specifics like:

  • If the film for waterproofing has different coloring of the sides, then the side that is light should be laid to the insulation;
  • When rolling out the waterproofing film, it is easy to identify the inner part of the material, just follow which side is facing the floor.
  • The inner part of the material for vapor barrier is smooth, it is laid in the direction of the insulation, as for the outer side, it is covered with a pile, which is necessary in order not to let moisture through.

The material is typically laid with the smooth side facing the insulation and the rough side facing outwards in any area of the room with a two-layer structure.The shiny side of an aluminum layer applied to the vapor barrier should face inward; the rough side should face the insulation material.Every material used to create a vapor barrier is laid in layers; it’s crucial that the layers overlap by at least 15 cm. Once the joints are formed, tape should be used to glue them together.

Fix the vapor barrier on the surfaces using a construction stapler.There are a few peculiarities when equipping the vapor barrier. So, if the room is unheated, the layer of vapor barrier is attached directly to the floor, located between the floors of the building, it is necessary to do this in such a way that a gap is formed. After the work is done, the so-called rough ceiling is laid on.When it is necessary to insulate the outer walls of the house, the vapor barrier is attached to the frame, with the smooth side of the material is located in the direction of the wall, and the rough surface remains looking toward the street.

The main types of vapor barrier

The manufacturer’s installation instructions for vapor barrier film typically take into account the features of the room, including its intended use and conditions. Differentiate between low- and high-permeable films as well as special purpose films using these parameters.

They can have varying thicknesses or an aluminum foil coating applied to them.

Knowing how to properly lay the vapor barrier film, say, foil mounted reflective layer outward, is important because there are a lot of options.

  • Highly permeable vapor barrier is provided by materials with a vapor permeability level of at least 700 g per cube. м. in one day. Since diffusion foils allow vapor to pass freely, there is no need for ventilation gaps between the layers of vapor and thermal insulation.

Side note: Four-layer membranes reinforced with a polyethylene or polypropylene reinforcing mesh are the most effective membranes.

  • low-vapor-permeable differ in their structure, the permeability of this type of material is much less – about 25-40 g per cube. м. in one day. Such material is optimal, for example, for the device vapor barrier flat roof;
  • under metal roofing. Insulation should have increased resistance to high, because, as is known, the metal surface heats up quite quickly under the sun;
  • Special vapor barrier with aluminum spraying is in high demand. Its main difference is its ability to reflect excessive heat. Such a vapor barrier device is especially in demand in private countryside construction, as it maximally reduces the probability of overheating of rooms that are located directly under the roof;
  • For roofs with rigid decking, special materials are recommended that are closer in function to the roofing made of roofing felt. These materials are mainly characterized by high vapor permeability with a small thickness. When laying OSB boards, a small ventilation gap should be left when laying the insulation. In the case of building a deck of boards that are tightly connected to each other vapor barrier can not be laid;
  • for high-quality and reliable joints of insulation strips can be used special tape for vapor barrier film. Particularly relevant question, what to glue the vapor barrier film, when installing a soft roof, which requires absolute tightness. Scotch tape is also recommended for use in the construction or repair of objects located in areas with heavy precipitation accompanied by strong winds, for example, in mountainous, coastal, etc., where the vapor barrier itself is used. д.

They range in price depending on the type. For instance, the cost of the foiled polyethylene vapor barrier is approximately 1400–1800 rubles, whereas the simple one costs roughly 500 rubles. Three-layer diffusion membranes are far more expensive, costing 4000-5000 rubles.

What is the difference between anti-condensation film and anti-condensation side

As previously mentioned, the majority of contemporary producers stress that their vapor barrier films feature a "anti-condensate side":

The presence of a hairy layer on the "anti-condensation" side sets it apart from other "anti-condensation" sides. This layer absorbs a small amount of condensation and holds it until it evaporates.

This increases the likelihood that the film surface won’t get wet and extends the life of the interior roof pie finish. Because of this, the smooth side should always be leaned against the insulation material and the rough side should always face the interior of the living room or attic. But is that really the case?

Experience has shown that the pile side of the film cannot assist with condensation that forms inside the roofing pie, and it makes no difference if the drops are held on the film or flow downward. It’s terrible enough that they exist at all. The anti-condensation waterproofing film on the other side of the insulation and the anti-condensation side of the vapor barrier are two entirely different things!

To sum up, the "right" side of the vapor barrier does not have the same qualities as the anti-condensation film; that is, it is unable to eliminate moisture droplets, eliminate water vapor, or resolve the condensation issue.

However, if you are still building a roof, follow the manufacturer’s instructions in the instructions that came with the product for peace of mind. Forget it and stop worrying if you have already installed the vapor barrier and are unsure if it is the right decision. However, do not hold your breath if you think that the "correct" side of the vapor barrier will absorb all of the device’s future flaws.

Skilled roofers frequently claim that they treat the entire debate over which side of the vapor barrier to fix as a sort of shamanic divination. It is purported that increasing the product’s complexity will improve its market positioning. In fact, as we’ve already mentioned, if the vapor barrier is placed correctly, there shouldn’t be any drops on the walls; if there are, even the wall wagon will swell and the wallpaper will come off because everything is so serious.

After all, only grave errors in the roof’s construction can cause this. Furthermore, there is no purpose in addressing the vapor barrier at all if it is to be situated between the mineral wool and plasterboard due to its intricate structure. The vapor will essentially not be able to reach the inner vapor barrier because the plasterboard itself absorbs moisture well. Even a basic pergamin is quite acceptable in this design!

For instance, some inquisitive roofers even carry out their own vapor barrier tests to ascertain whether or not the "wrong" side functions:

Moreover, astute observers point out that a polyethylene vapor barrier with a rough side can be produced easily in a factory setting when polyethylene is mixed with nonwoven material. The film is adhered to the rough layer, giving the final product a true dual-sided appearance. Furthermore, refining the second side to make it smoother by joining it to another polyethylene layer is pointless because the manufacturing process will cost more and the vapor barrier properties won’t change.

As a result, it is simpler to give the product itself this meaning. Indeed, a good number of people have already ensured that nothing similar occurs, even when the vapor barrier’s sides are switched, and that the film functions flawlessly on both sides.

In any case, just make an effort to properly install roof vapor protection, consider all relevant factors, and do not compromise on quality!

Cut off the attic and the basement

How can an unheated basement or attic room be sealed off with a vapor barrier?

It is a little trickier to properly lay the basement’s vapor barrier than it is in other situations.

We have to presume that the following order of operation is optimal for completing the work:

  • provide a ventilation gap of at least 5 cm between the ground level and the intended floor level;
  • lay pre-treated lags at a distance equal to the width of the insulation;
  • On the floor joists, fix the rough floor from a board (you can use an untrimmed board) or laths;
  • Nanoisol should be laid with the rough surface downwards, wrapping around the joists;
  • lay the thermal insulator (the insulator should be placed with a slight compression to prevent sliding during operation);
  • After laying the thermal insulator, install the vapor barrier with the rough side facing upwards;
  • fix the insulation material with a counter batten at least 25 mm high;
  • install the finishing floor.

Installing the vapor barrier and attic insulation follows the same sequence as installing the interfloor ceiling. To provide heat insulation, the vapor barrier Nanoisol must be installed inside the space with a rough surface rather than a smooth one. In the event that the attic is not heated, the rough attic floor protects the upper portion of the insulation, and waterproofing is placed beneath the roofing material.

Peculiarities of installation works

The kind of material and the specifics of its installation must be considered in order to carry out the work required to protect the roof from moisture in an effective manner. When installing a vapor barrier film in a cold attic, it is necessary to heat the seams during the installation process.

Overlapping coatings don’t work well; to make a coating waterproof, a solid, seamless coating must be created. Time savings is another benefit of this installation method; the film can be laid in a few hours without sacrificing quality. The primary requirement is that the vapor barrier for roofing be installed carefully.

The material used to make the roof should be considered when laying the vapor barrier. Therefore, bitumen membranes should be used to create a vapor barrier for concrete flat roofs. They are bonded to the surface by heating and adhering to it securely.

Benefits of bitumen membrane application:

  • high elasticity of the material;
  • No areas with bends or kinks;
  • high protection against moisture and vapor.

The installation of this kind of vapor barrier material requires multiple workers due to its high weight indicators, so keep that in mind.

Correct positioning and installation

It is important to distinguish between the vapor barrier and wind barrier foils. On the other hand, the vapor barrier is always positioned on the side of the insulation that faces the inflow of warm, humid air. As a result, the best practice is to only ever place vapor-limiting materials underneath the interior finish layer.

The placement in question is not permitted by all building types, which is an obvious issue. What should be done with a brick wall that has minwool insulation on the outside? A hollow lining cannot be arranged specifically because it is too costly and unreasonable. Installing the vapor barrier next to the insulation is feasible in these circumstances, but only on the warm side of the insulation. Since the vapor barrier is often found in the computed condensation zone, it must be vented or a more exact determination of an appropriate throughput is required.

Brick wall insulation consists of five components: 1 vapor barrier; 2 windproofing; 3 insulation; 4 brick wall; 5 facade cladding (ventilated facade); 6-finishing the inside; 7. Dehumidification of the space

The vapor barrier’s proper installation presents the biggest challenge in these exceptional circumstances. Under typical circumstances, the frame insulation system is secured with staples, and the seams between the fabrics are hermetically sealed. The latter can be accomplished by using a specific mastic smearing or folding in the joint and double-sided gluing.

Which side to lay vapor barrier Installation tips
Warm side in cold climates Prevents condensation inside walls
Cool side in hot climates Reduces indoor humidity
Overlap seams by 6 inches Ensures continuous coverage
Tape seams with vapor barrier tape Seals out moisture effectively

A vital first step in maintaining the longevity and effectiveness of the insulation and heating system in your house is installing a vapor barrier. A vapor barrier’s main function is to stop moisture from seeping through your home’s walls and ceilings. Moisture can cause structural damage, mold growth, and reduced insulation effectiveness, all of which can lead to higher energy costs and less comfortable living conditions.

The location and climate of your home are important factors to take into account when choosing which side to install the vapor barrier on. The vapor barrier should be positioned on the warm side of the insulation in colder climates, usually facing the interior of the home. This arrangement lowers the possibility of moisture buildup and potential damage by preventing warm, humid air from inside the house from condensing within the walls during the colder months.

Conversely, in warmer climates, the vapor barrier should face outward and be positioned on the outside of the insulation. This arrangement lessens the possibility that warm, humid air from the outside will enter the walls and condense on the interior surfaces that are cooler. You can preserve the structural integrity of your home and create a comfortable indoor environment by managing moisture infiltration.

Remember that there isn’t a one-size-fits-all method for installing vapor barriers correctly. When installing vapor barriers in your home, it’s imperative to adhere to local building codes and the manufacturer’s instructions. Consulting with a qualified contractor or insulation specialist can guarantee the job is done correctly and offer valuable insights if you’re unclear about the best practices for your particular situation.

Video on the topic

Mansard roof vapor barrier. Mistakes of vapor barrier installation. Döcke Pie BR vapor barrier film+.

🟢 Roof vapor barrier and insulation of a complex mauerlate assembly!

Mistakes when laying the vapor barrier. The result after 3 years.

Installation of vapor barrier roofing, which side to lay the vapor barrier to the insulation, thickness, laying

How to install the vapor barrier. All nuances. Which side to lay the vapor barrier and how to fix it!!

How to properly lay a vapor barrier / What vapor barrier is needed for roofing

Installation of vapor barrier. Nuances of installation.

What type of heating you would like to have in your home?
Share to friends
Sergey Ivanov

I like to help people create comfort and comfort in their homes. I share my experience and knowledge in articles so that you can make the right choice of a heating and insulation system for your home.

Rate author
Add a comment