Vapor permeability is a typical misconception. Vapor permeability of materials and thin layers of vapor barrier High vapor permeability criterion such ability

To create a climate favorable for living in a house, it is necessary to take into account the properties of the materials used. Particular attention should be paid to vapor permeability. This term refers to the ability of materials to pass vapor. Thanks to knowledge of vapor permeability, you can choose the right materials to create a house.

Equipment for determining the degree of permeability

Professional builders have specialized equipment that allows you to accurately determine the vapor permeability of a particular building material. The following equipment is used to calculate the described parameter:

• scales, the error of which is minimal;
• vessels and bowls necessary for conducting experiments;
• tools that allow you to accurately determine the thickness of the layers of building materials.

Thanks to such tools, the described characteristic is precisely determined. But the data on the results of the experiments are listed in the tables, so when creating a project at home, it is not necessary to determine the vapor permeability of materials.

What you need to know

Many are familiar with the opinion that "breathing" walls are beneficial for those living in the house. The following materials have high rates of vapor permeability:

• wood;
• expanded clay;
• cellular concrete.

It is worth noting that walls made of brick or concrete also have vapor permeability, but this figure is lower. During the accumulation of steam in the house, it is removed not only through the hood and windows, but also through the walls. That is why many believe that it is “hard” to breathe in buildings made of concrete and brick.

But it is worth noting that in modern homes, most of the steam leaves through the windows and the hood. At the same time, only about 5 percent of the steam escapes through the walls. It is important to know that in windy weather, heat leaves the building made of breathable building materials faster. That is why during the construction of a house, other factors that affect the preservation of the microclimate in the room should be taken into account.

It is worth remembering that the higher the vapor permeability coefficient, the more moisture the walls contain. The frost resistance of a building material with a high degree of permeability is low. When different building materials get wet, the vapor permeability index can increase up to 5 times. That is why it is necessary to competently fix the vapor barrier materials.

Influence of vapor permeability on other characteristics

It is worth noting that if no insulation was installed during construction, in severe frost in windy weather, heat from the rooms will leave quickly enough. That is why it is necessary to properly insulate the walls.

At the same time, the durability of walls with high permeability is lower. This is due to the fact that when steam enters the building material, moisture begins to solidify under the influence of low temperature. This leads to the gradual destruction of the walls. That is why, when choosing a building material with a high degree of permeability, it is necessary to correctly install a vapor barrier and heat-insulating layer. To find out the vapor permeability of materials, it is worth using a table in which all values ​​\u200b\u200bare indicated.

Vapor permeability and wall insulation

During the insulation of the house, it is necessary to follow the rule according to which the vapor transparency of the layers should increase outward. Thanks to this, in winter there will be no accumulation of water in the layers if condensate begins to accumulate at the dew point.

It is worth insulating from the inside, although many builders recommend fixing heat and vapor barrier from the outside. This is due to the fact that steam penetrates from the room and when the walls are insulated from the inside, moisture will not enter the building material. Extruded polystyrene foam is often used for internal insulation of a house. The vapor permeability coefficient of such a building material is low.

Another way to insulate is to separate the layers with a vapor barrier. You can also use a material that does not let steam through. An example is the insulation of walls with foam glass. Despite the fact that the brick is able to absorb moisture, foam glass prevents the penetration of steam. In this case, the brick wall will serve as a moisture accumulator and, during fluctuations in the level of humidity, will become a regulator of the internal climate of the premises.

It is worth remembering that if the walls are not properly insulated, building materials may lose their properties after a short period of time. That is why it is important to know not only about the qualities of the components used, but also about the technology for fixing them on the walls of the house.

What determines the choice of insulation

Often homeowners use mineral wool for insulation. This material has a high degree of permeability. According to international standards, the vapor permeability resistance is 1. This means that mineral wool practically does not differ from air in this respect.

This is what many manufacturers of mineral wool mention quite often. You can often find a mention that when a brick wall is insulated with mineral wool, its permeability will not decrease. It really is. But it is worth noting that not a single material from which the walls are made is capable of removing such an amount of steam so that a normal level of humidity is maintained in the premises. It is also important to consider that many of the finishing materials that are used in the design of the walls in the rooms can completely isolate the space, without letting the steam out. Because of this, the vapor permeability of the wall is significantly reduced. That is why mineral wool has little effect on steam exchange.

The table shows the values ​​​​of vapor permeability of materials and thin layers of vapor barrier for common ones. Resistance to vapor permeability of materials Rp can be defined as the quotient of the material thickness 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 vapor permeability resistance? For example, consider the value of resistance to vapor permeability of an ordinary thickness of 1.3 mm. According to the table, this value is 0.016 m 2 ·h·Pa/mg. What does this value mean? It means the following: 1 mg will pass through a square meter of such cardboard in 1 hour with a difference in its partial pressures on opposite sides of the cardboard equal to 0.016 Pa (at the same temperature and air pressure on both sides of the material).

In this way, vapor permeation resistance indicates the required difference in partial pressures of water vapor, sufficient for the passage of 1 mg of water vapor through 1 m 2 of the area of ​​the sheet material of the specified thickness in 1 hour. According to GOST 25898-83, vapor permeability resistance is determined for sheet materials and thin layers of vapor barrier having a thickness of not more than 10 mm. It should be noted that the vapor barrier with the highest vapor permeability in the table is.

Vapor resistance table

Material	layer thickness, mm	Rp resistance, m 2 h Pa / mg
Cardboard ordinary	1,3	0,016
Asbestos-cement sheets	6	0,3
Gypsum sheathing sheets (dry plaster)	10	0,12
Rigid wood fiber sheets	10	0,11
Soft wood fiber sheets	12,5	0,05
Painting with hot bitumen in one go	2	0,3
Painting with hot bitumen for two times	4	0,48
Oil painting for two times with preliminary putty and primer	—	0,64
Enamel paint	—	0,48
Coating with insulating mastic in one go	2	0,6
Coating with bitumen-cookersalt mastic at a time	1	0,64
Coating with bitumen-cookersalt mastic for two times	2	1,1
Roofing glassine	0,4	0,33
Polyethylene film	0,16	7,3
Ruberoid	1,5	1,1
Tol roofing	1,9	0,4
Three-layer plywood	3	0,15

Sources:
1. Building codes and regulations. Construction heat engineering. SNiP II-3-79. Ministry of Construction of Russia - Moscow 1995.
2. GOST 25898-83 Construction materials and products. Methods for determining the resistance to vapor permeation.

Table of vapor permeability of building materials

I collected information on vapor permeability by linking several sources. The same plate with the same materials walks around the sites, but I expanded it, added modern vapor permeability values ​​from the sites of building materials manufacturers. I also checked the values ​​with the data from the document "Code of Rules SP 50.13330.2012" (Appendix T), added those that were not there. So at the moment this is the most complete table.

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 ceramic)	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 fiberboard, 1000-800 kg/m3	0,12
Chipboard and fiberboard, 600 kg/m3	0,13
Chipboard and fiberboard, 400 kg/m3	0,19
Chipboard and fiberboard, 200 kg/m3	0,24
Tow	0,49
Drywall	0,075
Gypsum slabs (gypsum boards), 1350 kg/m3	0,098
Gypsum slabs (gypsum boards), 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
Expanded polystyrene extruded (EPPS, XPS)	0.005 (SP); 0.013; 0.004 (???)
Expanded polystyrene (foam plastic), plate, density from 10 to 38 kg/m3	0.05 (SP)
Styrofoam, plate	0,023 (???)
Ecowool cellulose	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. not natural)	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 tile (tile)	≈ 0 (???)
Clinker tiles	low (???); 0.018 (???)
Porcelain stoneware	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 variety of plasters and finishing materials. And, unfortunately, many manufacturers do not indicate such an important characteristic as vapor permeability on their products.

For example, when determining the 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 had vapor permeability indicated in the characteristics of the stone.

Also, different manufacturers have different vapor permeability values. For example, for most foam glass blocks it is zero, but for some manufacturers the value is "0 - 0.02".

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Vapor permeability table- this is a complete summary table with data on the vapor permeability of all possible materials used in construction. The word "vapor permeability" itself means the ability of layers of a building material to either pass or retain water vapor due to different pressures on both sides of the material at the same atmospheric pressure. This ability is also called the resistance coefficient and is determined by special values.

The higher the vapor permeability index, the more moisture the wall can contain, which means that the material has low frost resistance.

Vapor permeability table indicated by the following indicators:

1. Thermal conductivity is, in a way, an indicator of the energy transfer of heat from more heated particles to less heated particles. Therefore, equilibrium is established in temperature regimes. If the apartment has a high thermal conductivity, then this is the most comfortable conditions.
2. thermal capacity. It can be used to calculate the amount of heat supplied and the amount of heat contained in the room. It is necessary to bring it to a real volume. Thanks to this, it is possible to fix the temperature change.
3. Thermal absorption is an enclosing structural alignment during temperature fluctuations. In other words, thermal absorption is the degree of absorption of moisture by the surfaces of the walls.
4. Thermal stability is the ability to protect structures from sharp fluctuations in heat flows.

Completely all the comfort in the room will depend on these thermal conditions, which is why it is so necessary during construction vapor permeability table, as it helps to effectively compare different types of vapor permeability.

On the one hand, vapor permeability has a good effect on the microclimate, and on the other hand, it destroys the materials from which houses are built. In such cases, it is recommended to install a layer of vapor barrier on the outside of the house. After that, the insulation will not let steam through.

Vapor barrier - these are materials that are used from the negative effects of air vapor in order to protect the insulation.

There are three classes of vapor barrier. They differ in mechanical strength and vapor permeability resistance. The first class of vapor barrier is rigid materials based on foil. The second class includes materials based on polypropylene or polyethylene. And the third class is made up of soft materials.

Table of vapor permeability of materials.

Table of vapor permeability of materials- these are building standards of international and domestic standards for the vapor permeability of building materials.

Table of vapor permeability of materials.

Material	Vapor permeability coefficient, mg/(m*h*Pa)
Aluminum
Arbolit, 300 kg/m3
Arbolit, 600 kg/m3
Arbolit, 800 kg/m3
asphalt concrete
Foamed synthetic rubber
Drywall
Granite, gneiss, basalt
Chipboard and fiberboard, 1000-800 kg/m3
Chipboard and fiberboard, 200 kg/m3
Chipboard and fiberboard, 400 kg/m3
Chipboard and fiberboard, 600 kg/m3
Oak along the grain
Oak across the grain
Reinforced concrete
Limestone, 1400 kg/m3
Limestone, 1600 kg/m3
Limestone, 1800 kg/m3
Limestone, 2000 kg/m3
Expanded clay (bulk, i.e. gravel), 200 kg/m3	0.26; 0.27 (SP)
Expanded clay (bulk, i.e. gravel), 250 kg/m3
Expanded clay (bulk, i.e. gravel), 300 kg/m3
Expanded clay (bulk, i.e. gravel), 350 kg/m3
Expanded clay (bulk, i.e. gravel), 400 kg/m3
Expanded clay (bulk, i.e. gravel), 450 kg/m3
Expanded clay (bulk, i.e. gravel), 500 kg/m3
Expanded clay (bulk, i.e. gravel), 600 kg/m3
Expanded clay (bulk, i.e. gravel), 800 kg/m3
Expanded clay concrete, density 1000 kg/m3
Expanded clay concrete, density 1800 kg/m3
Expanded clay concrete, density 500 kg/m3
Expanded clay concrete, density 800 kg/m3
Porcelain stoneware
Clay brick, masonry
Hollow ceramic brick (1000 kg/m3 gross)
Hollow ceramic brick (1400 kg/m3 gross)
Brick, silicate, masonry
Large format ceramic block (warm ceramic)
Linoleum (PVC, i.e. not natural)
Mineral wool, stone, 140-175 kg/m3
Mineral wool, stone, 180 kg/m3
Mineral wool, stone, 25-50 kg/m3
Mineral wool, stone, 40-60 kg/m3
Mineral wool, glass, 17-15 kg/m3
Mineral wool, glass, 20 kg/m3
Mineral wool, glass, 35-30 kg/m3
Mineral wool, glass, 60-45 kg/m3
Mineral wool, glass, 85-75 kg/m3
OSB (OSB-3, OSB-4)
Foam concrete and aerated concrete, density 1000 kg/m3
Foam concrete and aerated concrete, density 400 kg/m3
Foam concrete and aerated concrete, density 600 kg/m3
Foam concrete and aerated concrete, density 800 kg/m3
Expanded polystyrene (foam plastic), plate, density from 10 to 38 kg/m3
Expanded polystyrene extruded (EPPS, XPS)	0.005 (SP); 0.013; 0.004
Styrofoam, plate
Polyurethane foam, density 32 kg/m3
Polyurethane foam, density 40 kg/m3
Polyurethane foam, density 60 kg/m3
Polyurethane foam, density 80 kg/m3
Block foam glass	0 (rarely 0.02)
Bulk foam glass, density 200 kg/m3
Bulk foam glass, density 400 kg/m3
Glazed ceramic tile (tile)
Clinker tiles	low; 0.018
Gypsum slabs (gypsum boards), 1100 kg/m3
Gypsum slabs (gypsum boards), 1350 kg/m3
Fiberboard and wood concrete slabs, 400 kg/m3
Fiberboard and wood concrete slabs, 500-450 kg/m3
Polyurea
Polyurethane mastic
Polyethylene
Lime-sand mortar with lime (or plaster)
Cement-sand-lime mortar (or plaster)
Cement-sand mortar (or plaster)
Ruberoid, glassine
Pine, spruce along the grain
Pine, spruce across the grain
Plywood
Ecowool cellulose

One of the most important indicators is vapor permeability. It characterizes the ability of cellular stones to retain or pass water vapor. GOST 12852.0-7 contains general requirements for the method for determining the vapor permeability coefficient of gas blocks.

What is vapor permeability

Temperatures are always different inside and outside buildings. Accordingly, the pressure is not the same. As a result, the moist air masses that exist both on the other side of the walls tend to move to a zone of lower pressure.

But since indoors, as a rule, is drier than outside, moisture from the street penetrates into the micro-crevices of building materials. Thus, wall structures are filled with water, which can not only worsen the microclimate in the premises, but also adversely affect the enclosing walls - they will begin to collapse over time.

The occurrence and accumulation of moisture in any walls is an extremely dangerous factor for health. So, as a result of such a process, not only does the thermal protection of the structure decrease, but fungi, mold and other biological microorganisms also appear.

Russian standards regulate that the vapor permeability index is determined by the ability of the material to resist the penetration of water vapor into it. The vapor permeability coefficient is calculated in mg / (m.h.Pa) and shows how much water will pass within 1 hour through 1m2 of a surface 1 m thick, with a pressure difference from one and the other part of the wall - 1 Pa.

Vapor permeability of aerated concrete

Cellular concretes consist of closed air pockets (up to 85% of the total volume). This significantly reduces the material's ability to absorb water molecules. Even penetrating inside, water vapor evaporates quickly enough, which has a positive effect on vapor permeability.

Thus, it can be stated that this indicator directly depends on aerated concrete density - the lower the density, the higher the vapor permeability, and vice versa. Accordingly, the higher the grade of porous concrete, the lower its density, which means that this indicator is higher.

Therefore, to reduce vapor permeability in the production of cellular artificial stones:

Such preventive measures lead to the fact that the performance of aerated concrete of various grades has different vapor permeability values, as shown in the table below:

Vapor permeability and interior finish

On the other hand, the moisture in the room must also be removed. For this for use special materials that absorb water vapor inside buildings: plaster, paper wallpaper, wood, etc.

This does not mean that it is not necessary to ennoble the walls with tiles burned in ovens, plastic or vinyl wallpaper. And reliable sealing of window and door openings is a prerequisite for high-quality construction.

When performing interior finishing work, it should be remembered that the vapor permeability of each finishing layer (putty, plaster, paint, wallpaper, etc.) must be higher than the same indicator of cellular wall material.

The most powerful barrier to the penetration of moisture into the inside of the building is the application of a primer layer on the inside of the main walls.

But do not forget that in any case, in residential and industrial buildings there must be an effective ventilation system. Only in this case can we talk about normal humidity in the room.

Aerated concrete is an excellent building material. In addition to the fact that buildings built from it perfectly accumulate and retain heat, they are not too wet or dry in them. And all thanks to good vapor permeability, which every developer should know about.