During the construction process, any material must first of all be assessed according to its operational and technical characteristics. When solving the problem of building a “breathing” house, which is most typical of buildings made of brick or wood, or vice versa, achieving maximum resistance to vapor permeability, you need to know and be able to operate tabular constants to obtain calculated vapor permeability indicators building materials.
What is vapor permeability of materials
- the ability to transmit or retain water vapor as a result of the difference in the partial pressure of water vapor on both sides of the material at the same atmospheric pressure. Vapor permeability is characterized by a vapor permeability coefficient or vapor permeability resistance and is standardized by SNiP II-3-79 (1998) “Building Heat Engineering”, namely Chapter 6 “Vapor Permeability Resistance of Enclosing Structures”
The vapor permeability table is presented in SNiP II-3-79 (1998) “Building Heat Engineering”, Appendix 3 “Thermal Indicators of Construction Materials”. The vapor permeability and thermal conductivity indicators of the most common materials used for construction and insulation of buildings are presented in the table below.
Material | Density, kg/m3 | Thermal conductivity, W/(m*S) | Vapor permeability, Mg/(m*h*Pa) |
Aluminum | |||
Asphalt concrete | |||
Drywall | |||
Chipboard, OSB | |||
Oak along the grain | |||
Oak across the grain | |||
Reinforced concrete | |||
Cardboard facing | |||
Expanded clay | |||
Expanded clay | |||
Expanded clay concrete | |||
Expanded clay concrete | |||
Ceramic hollow brick (gross 1000) | |||
Ceramic hollow brick (gross 1400) | |||
Red clay brick | |||
Brick, silicate | |||
Linoleum | |||
Minvata | |||
Minvata | |||
Foam concrete | |||
Foam concrete | |||
PVC foam | |||
Expanded polystyrene | |||
Expanded polystyrene | |||
Expanded polystyrene | |||
EXTRUDED POLYSTYRENE FOAM | |||
POLYURETHANE FOAM | |||
POLYURETHANE FOAM | |||
POLYURETHANE FOAM | |||
POLYURETHANE FOAM | |||
Foam glass | |||
Foam glass | |||
Sand | |||
POLYUREA | |||
POLYURETHANE MASTIC | |||
Polyethylene | |||
Ruberoid, glassine | |||
Pine, spruce along the grain | |||
Pine, spruce across the grain | |||
Plywood |
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, when determining the value for warm ceramics (item “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 from 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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The term “vapor permeability” itself indicates the ability of materials to pass or retain water vapor within their thickness. The table of vapor permeability of materials is conditional, since the given calculated values of humidity levels and atmospheric exposure do not always correspond to reality. The dew point can be calculated according to the average value.
Each material has its own percentage of vapor permeability
Determination of steam permeability level
In the arsenal of professional builders there are special technical means, which allow high accuracy diagnose the vapor permeability of a specific building material. To calculate the parameter, the following tools are used:
- devices that make it possible to accurately determine the thickness of a layer of building material;
- laboratory glassware for research;
- scales with the most accurate readings.
In this video you will learn about vapor permeability:
Using such tools, you can correctly determine the desired characteristic. Since experimental data is entered into tables of vapor permeability of building materials, there is no need to establish the vapor permeability of building materials when drawing up a home plan.
Creating comfortable conditions
To create a favorable microclimate in a home, it is necessary to take into account the characteristics of the building materials used. Particular emphasis should be placed on vapor permeability. Having knowledge about this ability of the material, you can correctly select the raw materials necessary for housing construction. Data is taken from building codes and regulations, for example:
- vapor permeability of concrete: 0.03 mg/(m*h*Pa);
- vapor permeability of fiberboard, chipboard: 0.12-0.24 mg/(m*h*Pa);
- vapor permeability of plywood: 0.02 mg/(m*h*Pa);
- ceramic brick: 0.14-0.17 mg/(m*h*Pa);
- silicate brick: 0.11 mg/(m*h*Pa);
- roofing felt: 0-0.001 mg/(m*h*Pa).
The formation of steam in a residential building can be caused by the breathing of humans and animals, cooking, temperature changes in the bathroom and other factors. Absence exhaust ventilation also creates high degree humidity in the room. IN winter period You can often notice condensation forming on windows and cold pipes. This is a clear example of the appearance of steam in residential buildings.
Protection of materials during wall construction
Building materials with high permeability steam cannot fully guarantee the absence of condensation inside the walls. To prevent the accumulation of water deep in the walls, you should avoid the pressure difference of one of the components mixtures of gaseous elements of water vapor on both sides of the building material.
Provide protection from appearance of liquid in reality, using oriented strand boards (OSB), insulating materials such as penoplex and a vapor barrier film or membrane that prevents steam from leaking into the thermal insulation. At the same time as the protective layer, it is necessary to organize the correct air gap for ventilation.
If the wall cake does not have sufficient steam absorption capacity, it does not risk being destroyed by the expansion of condensation from low temperatures. The main requirement is to prevent the accumulation of moisture inside the walls and allow its unhindered movement and weathering.
An important condition is the installation of a ventilation system with forced exhaust, which will prevent excess liquid and steam from accumulating in the room. By complying with the requirements, you can protect the walls from the formation of cracks and increase the wear resistance of the home as a whole.
Arrangement of thermal insulating layers
To ensure the best performance characteristics of a multilayer structure, the following rule is used: the side with a higher temperature is provided with materials with increased resistance to steam leakage with a high thermal conductivity coefficient.
The outer layer must have high vapor conductivity. For normal operation of the enclosing structure, it is necessary that the index of the outer layer is five times higher than the values of the inner layer. If this rule is observed, water vapor trapped in the warm layer of the wall will not special effort will leave it through more cellular building materials. Neglecting these conditions, the inner layer of building materials becomes damp, and its thermal conductivity coefficient becomes higher.
The selection of finishes also plays an important role in final stages construction work. The correctly selected composition of the material guarantees its effective removal of liquid into the external environment, therefore, even with sub-zero temperature the material will not collapse.
The vapor permeability index is a key indicator when calculating the cross-sectional size of the insulating layer. The reliability of the calculations made will determine how high-quality the insulation of the entire building will be.
The concept of “breathing walls” is considered positive characteristic the materials from which they are made. But few people think about the reasons that allow this breathing. Materials that can pass both air and steam are vapor permeable.
A clear example of building materials with high vapor permeability:
- wood;
- expanded clay slabs;
- foam concrete.
Concrete or brick walls are less permeable to steam than wood or expanded clay.
Indoor steam sources
Human breathing, cooking, water vapor from the bathroom and many other sources of steam in the absence of an exhaust device create high levels of humidity indoors. You can often observe the formation of perspiration on window glass in winter time, or in cold water pipes. These are examples of water vapor forming inside a home.
What is vapor permeability
Design and construction rules give following definition term: vapor permeability of materials is the ability to pass through droplets of moisture contained in the air due to various sizes partial pressures of steam from opposite sides at identical values air pressure. It is also defined as the density of the steam flow passing through a certain thickness of the material.
The table containing the coefficient of vapor permeability, compiled for building materials, is of a conditional nature, since the specified calculated values of humidity and atmospheric conditions do not always correspond to real conditions. The dew point can be calculated based on approximate data.
Wall design taking into account vapor permeability
Even if the walls are built from a material that has high vapor permeability, this cannot be a guarantee that it will not turn into water within the thickness of the wall. To prevent this from happening, you need to protect the material from the difference in partial vapor pressure from inside and outside. Protection against the formation of steam condensate is carried out using OSB boards, insulating materials such as penoplex and vapor-proof films or membranes that prevent steam from penetrating into the insulation.
The walls are insulated so that closer to the outer edge there is a layer of insulation that is unable to form moisture condensation and pushes back the dew point (water formation). In parallel with the protective layers in roofing pie it is necessary to ensure the correct ventilation gap.
Destructive effects of steam
If the wall cake has a weak ability to absorb steam, it is not in danger of destruction due to the expansion of moisture from frost. The main condition is to prevent moisture from accumulating in the thickness of the wall, but to ensure its free passage and weathering. It is equally important to arrange forced exhaust excess moisture and steam from the room, connect a powerful ventilation system. By observing the above conditions, you can protect the walls from cracking and increase the service life of the entire house. The constant passage of moisture through building materials accelerates their destruction.
Use of conductive qualities
Taking into account the peculiarities of building operation, the following insulation principle is applied: the most vapor-conducting insulating materials are located outside. Thanks to this arrangement of layers, the likelihood of water accumulating when the outside temperature drops is reduced. To prevent the walls from getting wet from the inside, the inner layer is insulated with a material that has low vapor permeability, for example, a thick layer of extruded polystyrene foam.
The opposite method of using the vapor-conducting effects of building materials has been successfully used. It consists in the fact that brick wall covered with a vapor barrier layer of foam glass, which interrupts the moving flow of steam from the house to the street during low temperatures. The brick begins to accumulate moisture in the rooms, creating a pleasant indoor climate thanks to a reliable vapor barrier.
Compliance with the basic principle when constructing walls
The walls must have a minimum ability to conduct steam and heat, but at the same time be heat-intensive and heat-resistant. When using one type of material, the required effects cannot be achieved. The outer wall part must retain cold masses and prevent their impact on internal heat-intensive materials that maintain a comfortable thermal regime inside the room.
Reinforced concrete is ideal for the inner layer; its heat capacity, density and strength are at their maximum. Concrete successfully smoothes out the difference between night and day temperature changes.
When carrying out construction work, wall pies are made taking into account the basic principle: the vapor permeability of each layer should increase in the direction from the inner layers to the outer ones.
Rules for the location of vapor barrier layers
To provide the best performance characteristics multi-layer structures of buildings, the rule applies: on the side with more high temperature, materials with increased resistance to steam penetration and increased thermal conductivity are used. Layers located on the outside must have high vapor conductivity. For the normal functioning of the enclosing structure, it is necessary that the coefficient of the outer layer is five times higher than that of the layer located inside. 
When this rule is followed, water vapor trapped in warm layer walls, it will not be difficult to quickly exit through more porous materials.
If this condition is not met, the inner layers of building materials harden and become more thermally conductive.
Introduction to the table of vapor permeability of materials
When designing a house, the characteristics of building materials are taken into account. The Code of Rules contains a table with information about what coefficient of vapor permeability building materials have under normal conditions. atmospheric pressure and average air temperature.
Material | Vapor permeability coefficient |
extruded polystyrene foam | |
polyurethane foam | |
mineral wool | |
reinforced concrete, concrete | |
pine or spruce | |
expanded clay | |
foam concrete, aerated concrete | |
granite, marble | |
drywall | |
chipboard, osp, fibreboard | |
foam glass | |
roofing felt | |
polyethylene | |
linoleum |
The importance of the vapor permeability table of materials
The vapor permeability coefficient is an important parameter that is used to calculate the layer thickness insulation materials. The quality of insulation of the entire structure depends on the correctness of the results obtained.
Sergey Novozhilov - expert on roofing materials with 9 years experience practical work in the field of engineering solutions in construction.
The vapor permeability table of materials is building code domestic and, of course, international standards. In general, vapor permeability is a certain ability of fabric layers to actively transmit water vapor due to different pressure results with a uniform atmospheric indicator on both sides of the element.
The ability to transmit and retain water vapor under consideration is characterized by special values called the coefficient of resistance and vapor permeability.
At this point, it is better to focus your attention on the internationally established ISO standards. They determine the high-quality vapor permeability of dry and wet elements.
A large number of people believe that breathing is a good sign. However, it is not. Breathable elements are those structures that allow both air and vapor to pass through. Expanded clay, foam concrete and trees have increased vapor permeability. In some cases, bricks also have these indicators.
If a wall is endowed with high vapor permeability, this does not mean that breathing becomes easy. A large amount of moisture accumulates in the room, which results in low resistance to frost. Coming out through the walls, the vapor turns into ordinary water.
Most manufacturers do not take into account when calculating this indicator important factors, that is, they are being cunning. According to them, each material is thoroughly dried. Damp ones increase thermal conductivity five times, therefore, it will be quite cold in an apartment or other room.
The most terrible moment is the drop in night temperature conditions, leading to a shift in the dew point in the wall openings and further freezing of the condensate. Subsequently, the resulting frozen water begins to actively destroy surfaces.
Indicators
The table indicates the vapor permeability of materials:
- , which is an energetic type of heat transfer from highly heated particles to less heated ones. Thus, equilibrium is achieved and appears in temperature conditions. With high indoor thermal conductivity, you can live as comfortably as possible;
- Thermal capacity calculates the amount of heat supplied and contained. It must be brought to a real volume. This is how temperature change is considered;
- Thermal absorption is the enclosing structural alignment in temperature fluctuations, that is, the degree of absorption of moisture by wall surfaces;
- Thermal stability is a property that protects structures from sharp thermal oscillatory flows. Absolutely all full comfort in a room depends on the general thermal conditions. Thermal stability and capacity can be active in cases where the layers are made of materials with increased thermal absorption. Stability ensures the normalized state of structures.
Vapor permeability mechanisms
At low levels of relative humidity, moisture in the atmosphere is actively transported through existing pores in building components. They acquire appearance, similar to individual molecules of water vapor.
In cases where humidity begins to rise, the pores in the materials are filled with liquids, directing the working mechanisms to be downloaded into capillary suction. Vapor permeability begins to increase, lowering the resistance coefficients, as the humidity in the building material increases.
For internal structures in already heated buildings, dry-type vapor permeability indicators are used. In places where the heating is variable or temporary, wet types of building materials are used, intended for external construction.
Vapor permeability of materials, the table helps to effectively compare various types vapor permeability.
Equipment
In order to correctly determine vapor permeability indicators, specialists use specialized research equipment:
- Glass cups or vessels for research;
- Unique tools required for thickness measuring processes with high level accuracy;
- Analytical type balances with weighing error.
