The table shows the vapor permeability resistance values of materials and thin layers of vapor barrier for common ones. Resistance to vapor permeation of materials Rп can be defined as the quotient of the thickness of the material divided by its vapor permeability coefficient μ.
It should be noted that vapor permeation resistance can only be specified for a material of a given thickness, in contrast to , which is not tied to the thickness of the material and is determined only by the structure of the material. For multilayer sheet materials the total resistance to vapor permeation will be equal to the sum of the resistances of the material of the layers.
What is the resistance to vapor permeation? For example, consider the value of vapor permeation resistance of an ordinary 1.3 mm thick. According to the table, this value is 0.016 m 2 h Pa/mg. What does this value mean? It means the following: through square meter The area of such cardboard will pass 1 mg in 1 hour with a difference in its partial pressures at opposite sides of the cardboard equal to 0.016 Pa (at the same temperature and air pressure on both sides of the material).
Thus, vapor permeation resistance shows the required difference in partial pressure of water vapor, sufficient for the passage of 1 mg of water vapor through 1 m 2 of sheet material of the specified thickness in 1 hour. According to GOST 25898-83, vapor permeation resistance is determined for sheet materials and thin layers of vapor barrier having a thickness of no more than 10 mm. It should be noted that the vapor barrier with the highest resistance to vapor permeation in the table is.
| Material | Layer thickness, mm |
Resistance Rп, m 2 h Pa/mg |
|---|---|---|
| Ordinary cardboard | 1,3 | 0,016 |
| Asbestos cement sheets | 6 | 0,3 |
| Gypsum cladding sheets (dry plaster) | 10 | 0,12 |
| Hard wood fiber sheets | 10 | 0,11 |
| Soft wood fiber sheets | 12,5 | 0,05 |
| Hot bitumen painting in one go | 2 | 0,3 |
| Painting with hot bitumen in two times | 4 | 0,48 |
| Oil painting in two times with preliminary putty and primer | — | 0,64 |
| Painting with enamel paint | — | 0,48 |
| Coating with insulating mastic at one time | 2 | 0,6 |
| Coating with bitumen-kukersol mastic at one time | 1 | 0,64 |
| Coating with bitumen-kukersol mastic in two times | 2 | 1,1 |
| Roofing glassine | 0,4 | 0,33 |
| Polyethylene film | 0,16 | 7,3 |
| Ruberoid | 1,5 | 1,1 |
| Roofing felt | 1,9 | 0,4 |
| Three-layer plywood | 3 | 0,15 |
Sources:
1. Building codes and rules. Construction heating engineering. SNiP II-3-79. Ministry of Construction of Russia - Moscow 1995.
2. GOST 25898-83 Construction materials and products. Methods for determining vapor permeation resistance.
To create favorable microclimate indoors, it is necessary to take into account the properties building materials. Today we will look at one property - vapor permeability of materials.
Vapor permeability is the ability of a material to allow vapors contained in the air to pass through. Water vapor penetrates the material due to pressure.
Tables that cover almost all materials used for construction will help you understand the issue. After studying this material, you will know how to build a warm and reliable home.
Equipment
If we are talking about Prof. construction, it uses special equipment to determine vapor permeability. This is how the table that appears in this article appeared.
The following equipment is used today:
- Scales with minimal error - analytical type model.
- Vessels or bowls for conducting experiments.
- Tools with high level accuracy for determining the thickness of layers of building materials.
Understanding the property
There is an opinion that “breathing walls” are beneficial for the house and its inhabitants. But all builders think about this concept. “Breathable” is a material that, in addition to air, also allows steam to pass through - this is the water permeability of building materials. Foam concrete and expanded clay wood have a high rate of vapor permeability. Walls made of brick or concrete also have this property, but the indicator is much less than that of expanded clay or wood materials. 
Steam is released when taking a hot shower or cooking. Because of this, increased humidity is created in the house - a hood can correct the situation. You can find out that the vapors are not escaping anywhere by looking at the condensation on the pipes and sometimes on the windows. Some builders believe that if a house is built of brick or concrete, then it is “hard” to breathe in the house.
In reality, the situation is better - in a modern home, about 95% of the steam escapes through the window and hood. And if the walls are made of “breathing” building materials, then 5% of the steam escapes through them. So residents of houses made of concrete or brick do not suffer much from this parameter. Also, the walls, regardless of the material, will not allow moisture to pass through due to vinyl wallpaper. “Breathing” walls also have a significant drawback - in windy weather, heat leaves the home.
The table will help you compare materials and find out their vapor permeability indicator:
The higher the vapor permeability index, the more moisture the wall can absorb, which means that the material has low frost resistance. If you are going to build walls from foam concrete or aerated block, then you should know that manufacturers are often cunning in the description where vapor permeability is indicated. The property is indicated for dry material - in this state it actually has high thermal conductivity, but if the gas block gets wet, the indicator will increase 5 times. But we are interested in another parameter: the liquid tends to expand when it freezes, and as a result, the walls collapse.
Vapor permeability in multilayer construction
The sequence of layers and the type of insulation are what primarily affect vapor permeability. In the diagram below you can see that if the insulation material is located on the facade side, then the indicator of pressure on moisture saturation is lower. 
If the insulation is located on the inside of the house, then between load-bearing structure and this construction will cause condensation. It negatively affects the entire microclimate in the house, while the destruction of building materials occurs much faster.
Understanding the coefficient
The coefficient in this indicator determines the amount of vapor, measured in grams, that passes through materials 1 meter thick and a layer of 1 m² within one hour. The ability to transmit or retain moisture characterizes the resistance to vapor permeability, which is indicated in the table by the symbol “µ”.
In simple words, coefficient is the resistance of building materials, comparable to the permeability of air. Let's look at a simple example: mineral wool has the following vapor permeability coefficient: µ=1. This means that the material does not allow moisture to pass through. worse than air. And if you take aerated concrete, then its µ will be equal to 10, that is, its vapor conductivity is ten times worse than that of air.
Peculiarities
On the one hand, vapor permeability has a good effect on the microclimate, and on the other hand, it destroys the materials from which the house is built. For example, “cotton wool” perfectly allows moisture to pass through, but in the end, due to excess steam on windows and pipes, cold water Condensation may form, as indicated in the table. Because of this, the insulation loses its quality. Professionals recommend installing a vapor barrier layer with outside Houses. After this, the insulation will not allow steam to pass through. 
If the material has a low vapor permeability rate, then this is only a plus, because the owners do not have to spend money on insulating layers. And get rid of the steam generated from cooking and hot water, a hood and a window will help - this is enough to maintain a normal microclimate in the house. When a house is built from wood, it is impossible to do without additional insulation, and special varnish is required for wood materials.
The table, graph and diagram will help you understand the principle of operation of this property, after which you can already make your choice suitable material. Also, do not forget about climatic conditions outside the window, because if you live in an area with high humidity, then you should completely forget about materials with a high vapor permeability rate.
1. Only insulation with the lowest thermal conductivity coefficient can minimize the extraction of internal space
2. Unfortunately, the accumulating heat capacity of the array outer wall we lose forever. But there is a benefit here:
A) there is no need to waste energy resources on heating these walls
B) when you turn on even the smallest heater, the room will almost immediately become warm.
3. At the junction of the wall and the ceiling, “cold bridges” can be removed if the insulation is partially applied to the floor slabs and then decorated with these junctions.
4. If you still believe in the “breathing of walls,” then please read THIS article. If not, then the obvious conclusion is: thermal insulation material should be pressed very tightly against the wall. It’s even better if the insulation becomes one with the wall. Those. there will be no gaps or cracks between the insulation and the wall. This way, moisture from the room will not be able to enter the dew point area. The wall will always remain dry. Seasonal temperature fluctuations without access to moisture will not have an impact negative influence on the walls, which will increase their durability.
All these problems can be solved only by sprayed polyurethane foam.
Having the lowest thermal conductivity coefficient of all existing thermal insulation materials, polyurethane foam will occupy a minimum of internal space.
The ability of polyurethane foam to reliably adhere to any surface makes it easy to apply it to the ceiling to reduce “cold bridges.”
When applied to walls, polyurethane foam, being in a liquid state for some time, fills all cracks and microcavities. Foaming and polymerizing directly at the point of application, polyurethane foam becomes one with the wall, blocking access to destructive moisture.
VAPIROPER PERMEABILITY OF WALLS
Supporters of the false concept of “healthy breathing of walls”, in addition to sinning against the truth of physical laws and deliberately misleading designers, builders and consumers, based on a mercantile motive to sell their goods by any means, slander and slander thermal insulation materials with low vapor permeability (polyurethane foam) or The thermal insulation material is completely vapor-tight (foam glass).
The essence of this malicious insinuation boils down to the following. It seems like if there is no notorious “healthy breathing of the walls,” then in this case the interior will definitely become damp, and the walls will ooze moisture. In order to debunk this fiction, let's take a closer look at the physical processes that will occur in the case of cladding under a plaster layer or using inside a masonry, for example, a material such as foam glass, the vapor permeability of which is zero.
So, due to the inherent thermal insulation and sealing properties of foam glass, the outer layer of plaster or masonry will come to an equilibrium temperature and humidity state with the outside atmosphere. Also, the inner layer of masonry will enter into a certain balance with the microclimate interior spaces. Processes of water diffusion, both in the outer layer of the wall and in the inner; will have the character of a harmonic function. This function will be determined, for the outer layer, by daily changes in temperature and humidity, as well as seasonal changes.
Particularly interesting in this regard is the behavior of the inner layer of the wall. In fact, the inside of the wall will act as an inertial buffer, whose role will be to smooth out sudden changes in humidity in the room. In the event of sudden humidification of the room, the inside of the wall will adsorb excess moisture contained in the air, preventing air humidity from reaching the maximum value. At the same time, in the absence of moisture release into the air in the room, the inside of the wall begins to dry out, preventing the air from “drying out” and becoming desert-like.
As a favorable result of such an insulation system using polyurethane foam, the harmonic fluctuations in air humidity in the room are smoothed out and thereby guarantee a stable value (with minor fluctuations) of humidity acceptable for a healthy microclimate. Physics this process has been studied quite well by developed construction and architectural schools of the world and to achieve a similar effect when using inorganic fiber materials as insulation in closed systems for insulation, it is strongly recommended to have a reliable vapor-permeable layer on inside insulation systems. So much for “healthy breathing of the walls”!
Table of vapor permeability of building materials
I collected information on vapor permeability by combining several sources. The same sign with the same materials is circulating around the sites, but I expanded it and added modern meanings vapor permeability from the websites of building materials manufacturers. I also checked the values with data from the document “Code of Rules SP 50.13330.2012” (Appendix T), and added those that were not there. So this is the most complete table at the moment.
| Material | Vapor permeability coefficient, mg/(m*h*Pa) |
| Reinforced concrete | 0,03 |
| Concrete | 0,03 |
| Cement-sand mortar (or plaster) | 0,09 |
| Cement-sand-lime mortar (or plaster) | 0,098 |
| Lime-sand mortar with lime (or plaster) | 0,12 |
| Expanded clay concrete, density 1800 kg/m3 | 0,09 |
| Expanded clay concrete, density 1000 kg/m3 | 0,14 |
| Expanded clay concrete, density 800 kg/m3 | 0,19 |
| Expanded clay concrete, density 500 kg/m3 | 0,30 |
| Clay brick, masonry | 0,11 |
| Brick, silicate, masonry | 0,11 |
| Hollow ceramic brick (1400 kg/m3 gross) | 0,14 |
| Hollow ceramic brick (1000 kg/m3 gross) | 0,17 |
| Large format ceramic block(warm ceramics) | 0,14 |
| Foam concrete and aerated concrete, density 1000 kg/m3 | 0,11 |
| Foam concrete and aerated concrete, density 800 kg/m3 | 0,14 |
| Foam concrete and aerated concrete, density 600 kg/m3 | 0,17 |
| Foam concrete and aerated concrete, density 400 kg/m3 | 0,23 |
| Fiberboard and wood concrete slabs, 500-450 kg/m3 | 0.11 (SP) |
| Fiberboard and wood concrete slabs, 400 kg/m3 | 0.26 (SP) |
| Arbolit, 800 kg/m3 | 0,11 |
| Arbolit, 600 kg/m3 | 0,18 |
| Arbolit, 300 kg/m3 | 0,30 |
| Granite, gneiss, basalt | 0,008 |
| Marble | 0,008 |
| Limestone, 2000 kg/m3 | 0,06 |
| Limestone, 1800 kg/m3 | 0,075 |
| Limestone, 1600 kg/m3 | 0,09 |
| Limestone, 1400 kg/m3 | 0,11 |
| Pine, spruce across the grain | 0,06 |
| Pine, spruce along the grain | 0,32 |
| Oak across the grain | 0,05 |
| Oak along the grain | 0,30 |
| Plywood | 0,02 |
| Chipboard and fibreboard, 1000-800 kg/m3 | 0,12 |
| Chipboard and fibreboard, 600 kg/m3 | 0,13 |
| Chipboard and fibreboard, 400 kg/m3 | 0,19 |
| Chipboard and fibreboard, 200 kg/m3 | 0,24 |
| Tow | 0,49 |
| Drywall | 0,075 |
| Gypsum slabs (gypsum slabs), 1350 kg/m3 | 0,098 |
| Gypsum slabs (gypsum slabs), 1100 kg/m3 | 0,11 |
| Mineral wool, stone, 180 kg/m3 | 0,3 |
| Mineral wool, stone, 140-175 kg/m3 | 0,32 |
| Mineral wool, stone, 40-60 kg/m3 | 0,35 |
| Mineral wool, stone, 25-50 kg/m3 | 0,37 |
| Mineral wool, glass, 85-75 kg/m3 | 0,5 |
| Mineral wool, glass, 60-45 kg/m3 | 0,51 |
| Mineral wool, glass, 35-30 kg/m3 | 0,52 |
| Mineral wool, glass, 20 kg/m3 | 0,53 |
| Mineral wool, glass, 17-15 kg/m3 | 0,54 |
| Extruded polystyrene foam (EPS, XPS) | 0.005 (SP); 0.013; 0.004 (???) |
| Expanded polystyrene (foam), plate, density from 10 to 38 kg/m3 | 0.05 (SP) |
| Expanded polystyrene, plate | 0,023 (???) |
| Cellulose ecowool | 0,30; 0,67 |
| Polyurethane foam, density 80 kg/m3 | 0,05 |
| Polyurethane foam, density 60 kg/m3 | 0,05 |
| Polyurethane foam, density 40 kg/m3 | 0,05 |
| Polyurethane foam, density 32 kg/m3 | 0,05 |
| Expanded clay (bulk, i.e. gravel), 800 kg/m3 | 0,21 |
| Expanded clay (bulk, i.e. gravel), 600 kg/m3 | 0,23 |
| Expanded clay (bulk, i.e. gravel), 500 kg/m3 | 0,23 |
| Expanded clay (bulk, i.e. gravel), 450 kg/m3 | 0,235 |
| Expanded clay (bulk, i.e. gravel), 400 kg/m3 | 0,24 |
| Expanded clay (bulk, i.e. gravel), 350 kg/m3 | 0,245 |
| Expanded clay (bulk, i.e. gravel), 300 kg/m3 | 0,25 |
| Expanded clay (bulk, i.e. gravel), 250 kg/m3 | 0,26 |
| Expanded clay (bulk, i.e. gravel), 200 kg/m3 | 0.26; 0.27 (SP) |
| Sand | 0,17 |
| Bitumen | 0,008 |
| Polyurethane mastic | 0,00023 |
| Polyurea | 0,00023 |
| Foamed synthetic rubber | 0,003 |
| Ruberoid, glassine | 0 - 0,001 |
| Polyethylene | 0,00002 |
| Asphalt concrete | 0,008 |
| Linoleum (PVC, i.e. unnatural) | 0,002 |
| Steel | 0 |
| Aluminum | 0 |
| Copper | 0 |
| Glass | 0 |
| Block foam glass | 0 (rarely 0.02) |
| Bulk foam glass, density 400 kg/m3 | 0,02 |
| Bulk foam glass, density 200 kg/m3 | 0,03 |
| Glazed ceramic tiles | ≈ 0 (???) |
| Clinker tiles | low (???); 0.018 (???) |
| Porcelain tiles | low (???) |
| OSB (OSB-3, OSB-4) | 0,0033-0,0040 (???) |
It is difficult to find out and indicate in this table the vapor permeability of all types of materials; manufacturers have created a huge number of different plasters, finishing materials. And, unfortunately, many manufacturers do not indicate this on their products. important characteristic like vapor permeability.
For example, defining a value for warm ceramics(position “Large-format ceramic block”), I studied almost all the websites of manufacturers of this type of brick, and only some of them listed vapor permeability in the characteristics of the stone.
Also different manufacturers different meanings vapor permeability. For example, for most foam glass blocks it is zero, but some manufacturers have the value “0 - 0.02”.
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There is a legend about a “breathing wall,” and tales about “the healthy breathing of a cinder block, which creates a unique atmosphere in the house.” In fact, the vapor permeability of the wall is not large, the amount of steam passing through it is insignificant, and much less than the amount of steam carried by air when it is exchanged in the room.
Vapor permeability is one of the most important parameters, used in calculating insulation. We can say that the vapor permeability of materials determines the entire insulation design.
What is vapor permeability
The movement of steam through the wall occurs when there is a difference in partial pressure on the sides of the wall (different humidity). In this case, there may not be a difference in atmospheric pressure.
Vapor permeability is the ability of a material to pass steam through itself. According to the domestic classification, it is determined by the vapor permeability coefficient m, mg/(m*hour*Pa).
The resistance of a layer of material will depend on its thickness.
Determined by dividing the thickness by the vapor permeability coefficient. Measured in (m sq.*hour*Pa)/mg.
For example, the vapor permeability coefficient brickwork accepted as 0.11 mg/(m*hour*Pa). With a brick wall thickness of 0.36 m, its resistance to steam movement will be 0.36/0.11=3.3 (m sq.*hour*Pa)/mg.
What is the vapor permeability of building materials?
Below are the values of the vapor permeability coefficient for several building materials (according to the regulatory document), which are most widely used, mg/(m*hour*Pa).
Bitumen 0.008
Heavy concrete 0.03
Autoclaved aerated concrete 0.12
Expanded clay concrete 0.075 - 0.09
Slag concrete 0.075 - 0.14
Burnt clay (brick) 0.11 - 0.15 (in the form of masonry on cement mortar)
Mortar 0,12
Drywall, gypsum 0.075
Cement-sand plaster 0.09
Limestone (depending on density) 0.06 - 0.11
Metals 0
Chipboard 0.12 0.24
Linoleum 0.002
Polystyrene foam 0.05-0.23
Polyurethane solid, polyurethane foam
0,05
Mineral wool 0.3-0.6
Foam glass 0.02 -0.03
Vermiculite 0.23 - 0.3
Expanded clay 0.21-0.26
Wood across the grain 0.06
Wood along the grain 0.32
Brickwork made of sand-lime brick on cement mortar 0.11
Data on the vapor permeability of layers must be taken into account when designing any insulation.
How to design insulation - based on vapor barrier qualities
The basic rule of insulation is that the vapor transparency of layers should increase towards the outside. Then, during the cold season, it is more likely that water will not accumulate in the layers when condensation occurs at the dew point.
The basic principle helps to make a decision in any case. Even when everything is “turned upside down,” they insulate from the inside, despite persistent recommendations to do insulation only from the outside.
To avoid a catastrophe with the walls getting wet, it is enough to remember that the inner layer should most stubbornly resist steam, and based on this, for internal insulation apply extruded polystyrene foam in a thick layer - a material with very low vapor permeability.
Or don’t forget to use even more “airy” mineral wool on the outside for very “breathable” aerated concrete.
Separation of layers with a vapor barrier
Another option for applying the principle of vapor transparency of materials in multilayer construction— separation of the most significant layers with a vapor barrier. Or the use of a significant layer, which is an absolute vapor barrier.
For example, insulating a brick wall with foam glass. It would seem that this contradicts the above principle, since it is possible for moisture to accumulate in the brick?
But this does not happen, due to the fact that the directional movement of steam is completely interrupted (when sub-zero temperatures from the room to the outside). After all, foam glass is a complete vapor barrier or close to it.
Therefore, in this case the brick will enter an equilibrium state with internal atmosphere at home, and will serve as an accumulator of humidity during sudden fluctuations indoors, making the indoor climate more pleasant.
The principle of layer separation is also used when using mineral wool - an insulation material that is especially dangerous due to moisture accumulation. For example, in a three-layer structure, when mineral wool is located inside a wall without ventilation, it is recommended to place a vapor barrier under the wool and thus leave it in the outside atmosphere.
International classification of vapor barrier qualities of materials
The international classification of materials based on vapor barrier properties differs from the domestic one.
According to the international standard ISO/FDIS 10456:2007(E), materials are characterized by a coefficient of resistance to vapor movement. This coefficient indicates how many times more the material resists the movement of steam compared to air. Those. for air, the coefficient of resistance to steam movement is 1, and for extruded polystyrene foam it is already 150, i.e. Expanded polystyrene is 150 times less permeable to steam than air.
It is also customary in international standards to determine vapor permeability for dry and moistened materials. The internal humidity of the material is 70% as the boundary between the concepts of “dry” and “moistened”.
Below are the values of the steam resistance coefficient for various materials according to international standards.
Steam resistance coefficient
Data are given first for dry material, and separated by commas for moistened material (more than 70% humidity).
Air 1, 1
Bitumen 50,000, 50,000
Plastics, rubber, silicone - >5,000, >5,000
Heavy concrete 130, 80
Concrete medium density 100, 60
Polystyrene concrete 120, 60
Autoclaved aerated concrete 10, 6
Lightweight concrete 15, 10
Fake diamond 150, 120
Expanded clay concrete 6-8, 4
Slag concrete 30, 20
Fired clay (brick) 16, 10
Lime mortar 20, 10
Drywall, gypsum 10, 4
Gypsum plaster 10, 6
Cement-sand plaster 10, 6
Clay, sand, gravel 50, 50
Sandstone 40, 30
Limestone (depending on density) 30-250, 20-200
Ceramic tile?, ?
Metals?, ?
OSB-2 (DIN 52612) 50, 30
OSB-3 (DIN 52612) 107, 64
OSB-4 (DIN 52612) 300, 135
Chipboard 50, 10-20
Linoleum 1000, 800
Underlay for plastic laminate 10,000, 10,000
Underlay for laminate cork 20, 10
Foam plastic 60, 60
EPPS 150, 150
Solid polyurethane, polyurethane foam 50, 50
Mineral wool 1, 1
Foam glass?, ?
Perlite panels 5, 5
Perlite 2, 2
Vermiculite 3, 2
Ecowool 2, 2
Expanded clay 2, 2
Wood across the grain 50-200, 20-50
It should be noted that the data on resistance to steam movement here and “there” are very different. For example, foam glass is standardized in our country, and the international standard says that it is an absolute vapor barrier.
Where did the legend of the breathing wall come from?
A lot of companies produce mineral wool. This is the most vapor-permeable insulation. According to international standards, its vapor permeability resistance coefficient (not to be confused with the domestic vapor permeability coefficient) is 1.0. Those. in fact, mineral wool is no different in this respect from air.
Indeed, this is a “breathable” insulation. To sell as much mineral wool as possible, you need a beautiful fairy tale. For example, if you insulate a brick wall from the outside mineral wool, then it will not lose anything in terms of vapor permeability. And this is the absolute truth!
The insidious lie is hidden in the fact that through brick walls 36 centimeters thick, with a humidity difference of 20% (on the street 50%, in the house - 70%) about a liter of water will leave the house per day. While with the exchange of air, about 10 times more should come out so that the humidity in the house does not increase.
And if the wall is insulated from the outside or inside, for example with a layer of paint, vinyl wallpaper, dense cement plaster, (which in general is “the most common thing”), then the vapor permeability of the wall will decrease by several times, and with complete insulation - by tens and hundreds of times.
Therefore always brick wall and it will be absolutely the same for household members whether the house is covered with mineral wool with “raging breath”, or with “sadly sniffling” polystyrene foam.
When making decisions on insulating houses and apartments, it is worth proceeding from the basic principle - the outer layer should be more vapor permeable, preferably by several times.
If for some reason it is not possible to withstand this, then you can separate the layers with a continuous vapor barrier (use a completely vapor-proof layer) and stop the movement of steam in the structure, which will lead to a state of dynamic equilibrium of the layers with the environment in which they will be located.
