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The concept of “breathing walls” is considered a positive characteristic of 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 good example 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 on cold water pipes. These are examples of water vapor forming inside a home.
What is vapor permeability
The design and construction rules give the following definition of the term: vapor permeability of materials is the ability to pass through droplets of moisture contained in the air due to different values of partial vapor pressures with 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 protective layers V roofing pie Proper ventilation gap must be ensured.
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 a forced exhaust of 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, thick layer extruded polystyrene foam.
The opposite method of using the vapor-conducting effects of building materials has been successfully used. It consists of covering a brick wall 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.
Ideal for inner layer reinforced concrete, its heat capacity, density and strength have maximum indicators. Concrete successfully smoothes out the difference between night and day temperature changes.
When carrying out construction work they make up wall pies 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 ensure better performance characteristics of multilayer structures, the rule is applied: 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.
If this rule is followed, it will not be difficult for water vapor trapped in the warm layer of the wall to quickly escape 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 mg/(m h Pa) |
| 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 table of vapor permeability 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 area engineering solutions in construction.
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Movement of water vapor
- foam concrete;
- aerated concrete;
- perlite concrete;
- expanded clay concrete.
Aerated concrete
The right finish
Expanded clay concrete
Structure of expanded clay concrete
Polystyrene concrete
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Vapor permeability of concrete: features of the properties of aerated concrete, expanded clay concrete, polystyrene concrete
Often in construction articles there is an expression - vapor permeability concrete walls. It means the material’s ability to pass water vapor, or, in popular parlance, “breathe.” This parameter has great importance, since waste products are constantly formed in the living room, which must be constantly removed outside.
The photo shows moisture condensation on building materials
General information
If you do not create normal ventilation in the room, dampness will be created in it, which will lead to the appearance of fungus and mold. Their secretions can be harmful to our health.
Movement of water vapor
On the other hand, vapor permeability affects the ability of a material to accumulate moisture. This is also a bad indicator, since the more it can retain it, the higher the likelihood of fungus, putrefactive manifestations, and damage due to freezing.
Improper removal of moisture from the room
Vapor permeability is denoted by the Latin letter μ and measured in mg/(m*h*Pa). The value shows the amount of water vapor that can pass through the wall material over an area of 1 m2 and with a thickness of 1 m in 1 hour, as well as the difference between the external and internal pressure 1 Pa.
High ability to conduct water vapor in:
- foam concrete;
- aerated concrete;
- perlite concrete;
- expanded clay concrete.
Heavy concrete closes the table.
Advice: if you need to make a technological channel in the foundation, this will help you diamond drilling holes in concrete.
Aerated concrete
- Using the material as an enclosing structure makes it possible to avoid the accumulation of unnecessary moisture inside the walls and preserve its heat-saving properties, which will prevent possible destruction.
- Any aerated concrete and foam concrete block contains ≈ 60% air, due to which the vapor permeability of aerated concrete is recognized to be at a good level, the walls in this case can “breathe”.
- Water vapor seeps freely through the material, but does not condense in it.
The vapor permeability of aerated concrete, as well as foam concrete, is significantly superior to heavy concrete - for the first it is 0.18-0.23, for the second - (0.11-0.26), for the third - 0.03 mg/m*h* Pa.
The right finish
I would especially like to emphasize that the structure of the material ensures that it effectively removes moisture into the environment, so that even when the material freezes, it does not collapse - it is forced out through open pores. Therefore, preparing the finish aerated concrete walls, should be considered this feature and select appropriate plasters, putties and paints.
The instructions strictly regulate that their vapor permeability parameters are not lower than aerated concrete blocks used for construction.
Textured facade vapor-permeable paint for aerated concrete
Tip: do not forget that vapor permeability parameters depend on the density of aerated concrete and may differ by half.
For example, if you use concrete blocks with density D400 - their coefficient is 0.23 mg/m h Pa, and for D500 it is already lower - 0.20 mg/m h Pa. In the first case, the numbers indicate that the walls will have a higher “breathing” ability. So when selecting finishing materials for walls made of aerated concrete D400, make sure that their vapor permeability coefficient is the same or higher.
Otherwise, this will lead to poor drainage of moisture from the walls, which will affect the level of living comfort in the house. Please also note that if you have used it for exterior finishing vapor-permeable paint for aerated concrete, and for the interior - non-vapor-permeable materials, steam will simply accumulate inside the room, making it damp.
Expanded clay concrete
The vapor permeability of expanded clay concrete blocks depends on the amount of filler in its composition, namely expanded clay - foamed baked clay. In Europe, such products are called eco- or bioblocks.
Advice: if you can’t cut the expanded clay block with a regular circle and grinder, use a diamond one. For example, cutting reinforced concrete with diamond wheels makes it possible to quickly solve the problem.
Structure of expanded clay concrete
Polystyrene concrete
The material is another representative cellular concrete. The vapor permeability of polystyrene concrete is usually equal to that of wood. You can make it yourself.
What does the structure of polystyrene concrete look like?
Today, more attention is beginning to be paid not only to thermal properties wall structures, and also the comfort of living in the building. In terms of thermal inertness and vapor permeability, polystyrene concrete resembles wooden materials, and heat transfer resistance can be achieved by changing its thickness. Therefore, poured monolithic polystyrene concrete is usually used, which is cheaper than ready-made slabs.
Conclusion
From the article you learned that building materials have such a parameter as vapor permeability. It makes it possible to remove moisture outside the walls of the building, improving their strength and characteristics. Vapor permeability of foam concrete and aerated concrete, as well as heavy concrete differs in its performance, which must be taken into account when choosing finishing materials. The video in this article will help you find additional information on this topic.
Page 2
During operation, a variety of defects may occur. iron concrete structures. At the same time, it is very important to identify problem areas in a timely manner, localize and eliminate damage, since a significant part of them is prone to expansion and aggravation of the situation.
Below we will look at the classification of main defects concrete covering, and also provide a number of tips for repairing it.
During the operation of reinforced concrete products, various damages appear on them.
Factors that influence strength
Before analyzing common defects in concrete structures, it is necessary to understand what may be causing them.
The key factor here will be the strength of the frozen concrete mortar, which is determined by the following parameters:
The closer the solution composition is to the optimal one, the less problems will be in operation of the structure
- Composition of concrete. The higher the grade of cement included in the solution, and the stronger the gravel that was used as filler, the more durable the coating or monolithic design. Naturally, when using high-quality concrete, the price of the material increases, so in any case we need to look for a compromise between economy and reliability.
Note! Excessively strong compositions are very difficult to process: for example, to perform the simplest operations, expensive cutting of reinforced concrete with diamond wheels may be required.
That's why you shouldn't overdo it with the selection of materials!
- Reinforcement quality. Along with high mechanical strength Concrete is characterized by low elasticity, therefore, when exposed to certain loads (bending, compression), it can crack. To avoid this, steel reinforcement is placed inside the structure. How stable the entire system will be depends on its configuration and diameter.
For sufficiently strong compositions, diamond drilling of holes in concrete is required: regular drill"Won't take it"!
- Surface permeability. If the material is characterized by a large number of pores, then sooner or later moisture will penetrate into them, which is one of the most destructive factors. Temperature changes at which the liquid freezes, destroying the pores due to an increase in volume, have a particularly detrimental effect on the condition of the concrete coating.
In principle, it is the listed factors that are decisive for ensuring the strength of cement. However, even in an ideal situation, sooner or later the coating is damaged, and we have to restore it. What can happen in this case and how we need to act will be discussed below.
Mechanical damage
Chips and cracks
Detection of deep damage using a flaw detector
The most common defects are mechanical damage. They can arise due to various factors, and are conventionally divided into external and internal. And if a special device is used to determine internal ones - a concrete flaw detector, then problems on the surface can be seen independently.
The main thing here is to determine the reason why the malfunction occurred and promptly eliminate it. For ease of analysis, we have structured examples of the most common damage in the form of a table:
| Defect | |
| Potholes on the surface | Most often they occur due to shock loads. It is also possible for potholes to form in areas of prolonged exposure to significant mass. |
| Chips | They are formed by mechanical influence on areas under which zones of low density are located. They are almost identical in configuration to potholes, but usually have less depth. |
| Peeling | It represents the separation of the surface layer of the material from the main mass. Most often it occurs due to poor drying of the material and finishing before the solution is completely hydrated. |
| Mechanical cracks | Occurs with prolonged and intense exposure to large area. Over time, they expand and connect with each other, which can lead to the formation of large potholes. |
| Bloating | Formed if surface layer compacted until air is completely removed from the solution mass. Also, the surface swells when treated with paint or impregnations (sealings) of undried cement. |
Photo of a deep crack
As can be seen from the analysis of the causes, the occurrence of some of the listed defects could have been avoided. But mechanical cracks, chips and potholes are formed due to the use of the coating, so they simply need to be repaired periodically. Instructions for prevention and repair are given in the next section.
Prevention and repair of defects
To minimize the risk of mechanical damage, first of all you need to follow the technology for arranging concrete structures.
Of course, this question has many nuances, so we will give only the most important rules:
- Firstly, the class of concrete must correspond to the design loads. Otherwise, saving on materials will lead to the fact that the service life will be reduced significantly, and you will have to spend effort and money on repairs much more often.
- Secondly, you need to follow the pouring and drying technology. The solution requires high-quality compaction of concrete, and when hydrated, the cement should not lack moisture.
- It is also worth paying attention to the timing: without the use of special modifiers, surfaces cannot be finished earlier than 28-30 days after pouring.
- Thirdly, the coating should be protected from excessively intense impacts. Of course, loads will affect the condition of concrete, but we can reduce the damage from them.
Vibration compaction increases strength significantly
Note! Even a simple limitation of the speed of transport in problem areas leads to defects asphalt concrete pavement occur much less frequently.
Another important factor is the timeliness of repairs and compliance with its methodology.
Here you need to follow a single algorithm:
- We clean the damaged area from fragments of the solution that have broken off from the main mass. For small defects you can use brushes, but large chips and cracks are usually cleaned with compressed air or sandblaster.
- Using a concrete saw or hammer drill, we open up the damage, deepening it to a durable layer. If we are talking about a crack, then it must not only be deepened, but also widened to facilitate filling with the repair compound.
- We prepare a mixture for restoration using either a polyurethane-based polymer complex or non-shrinking cement. When eliminating large defects, so-called thixotropic compounds are used, and small cracks are best sealed with a casting agent.
Filling open cracks with thixotropic sealants
- We apply the repair mixture to the damage, then level the surface and protect it from loads until the product has completely polymerized.
In principle, these works are easy to do with your own hands, so we can save on hiring craftsmen.
Operational damage
Drawdowns, dust and other malfunctions
Cracks on a subsiding screed
Experts classify so-called operational defects into a separate group. These include the following:
| Defect | Characteristics and possible reason emergence |
| Screed deformation | It is expressed in a change in the level of the poured concrete floor (most often the coating sinks in the center and rises at the edges). Can be caused by several factors: · Uneven density of the base due to insufficient compaction. · Defects in the compaction of the mortar. · Difference in moisture content of the top and bottom layers of cement. · Insufficient reinforcement thickness. |
| Cracking | In most cases, cracks do not arise from mechanical stress, but from deformation of the structure as a whole. It can be triggered by both excessive loads exceeding the design ones and thermal expansion. |
| Peeling | Peeling of small scales on the surface usually begins with the appearance of a network of microscopic cracks. In this case, the cause of peeling is most often the accelerated evaporation of moisture from the outer layer of the solution, which leads to insufficient hydration of the cement. |
| Surface dusting | It is expressed in the constant formation of fine cement dust on concrete. May be caused by: · Lack of cement in the solution. · Excess moisture during pouring. · Water entering the surface during grouting. · Insufficiently high-quality cleaning of gravel from the dust fraction. · Excessive abrasive effect on concrete. |
Peeling of the surface
All of the above disadvantages arise either due to a violation of technology or due to improper operation of the concrete structure. However, eliminating them is somewhat more difficult than mechanical defects.
- Firstly, the solution must be poured and processed according to all the rules, preventing it from stratifying and peeling when dried.
- Secondly, the base needs to be prepared equally well. The more densely we compact the soil under a concrete structure, the less likely it will be to subsidence, deformation and cracking.
- To prevent poured concrete from cracking, a damper tape is usually installed around the perimeter of the room to compensate for deformations. For the same purpose on screeds large area seams with polymer filling are installed.
- You can also avoid the appearance of surface damage by applying polymer-based strengthening impregnations to the surface of the material or “ironizing” the concrete with a flowing solution.
Surface treated with a protective compound
Chemical and climatic effects
A separate group of damages consists of defects that arise as a result of climatic exposure or a reaction to chemicals.
This may include:
- The appearance of streaks and light spots on the surface - so-called efflorescence. Typically, the cause of the formation of salt deposits is a violation of the humidity regime, as well as the ingress of alkalis and calcium chlorides into the solution.
Efflorescence formed due to excess moisture and calcium
Note! It is for this reason that in areas with highly carbonate soils, experts recommend using imported water to prepare the solution.
Otherwise, a whitish coating will appear within a few months after pouring.
- Destruction of the surface under the influence of low temperatures. When moisture enters porous concrete, the microscopic channels in the immediate vicinity of the surface gradually expand as water expands in volume by about 10-15% when it freezes. The more often freezing/thawing occurs, the more intense the solution will degrade.
- To combat this, special anti-frost impregnations are used, and the surface is also coated with compounds that reduce porosity.
Before repairs, the fittings must be cleaned and treated
- Finally, corrosion of reinforcement can also be included in this group of defects. Metal embeds begin to rust where they are exposed, which leads to a decrease in the strength of the material. To stop this process, before filling the damage with a repair compound, the reinforcing bars must be cleaned of oxides and then treated with an anti-corrosion compound.
Conclusion
The defects in concrete and reinforced concrete structures described above can manifest themselves in a variety of forms. Despite the fact that many of them look quite harmless, when the first signs of damage are detected, it is worth taking appropriate measures, otherwise the situation may worsen dramatically over time.
Well and in the best possible way To avoid such situations is to strictly adhere to the technology for arranging concrete structures. The information presented in the video in this article is another confirmation of this thesis.
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Vapor permeability of materials table
To create favorable microclimate indoors, it is necessary to take into account the properties of building materials. Today we will analyze one property - the vapor permeability of materials.
Vapor permeability is the ability of a material to pass vapors contained in the air. 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.
This graph shows the resistance to permeation. Brick wall practically does not allow or allow moisture to pass through. 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 fact, the situation is better - in modern home about 95% of the steam escapes through the vent 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 particularly suffer from this parameter. Also, the walls, regardless of the material, will not allow moisture to pass through due to vinyl wallpaper. There are “breathing” walls and 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 wall can contain moisture, 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 really 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.
The figure demonstrates in detail the effect of pressure and the penetration of steam into the material. If the insulation is located with inside at home, 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.
Let's understand the coefficient
The table becomes clear if you look at 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 allows moisture to pass through as well as 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 on the outside of the house. After this, the insulation will not allow steam to pass through.
Vapor permeation resistance 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 wood materials require a special varnish.
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 about materials with high rate vapor permeability should be completely forgotten.
The vapor permeability of a material is expressed in its ability to transmit water vapor. This property of resisting the penetration of steam or allowing it to pass through the material is determined by the level of the vapor permeability coefficient, which is denoted by µ.
This value, which sounds like “mu,” acts as a relative value for vapor transfer resistance compared to air resistance characteristics. There is a table that reflects the ability of the material to vapor transfer, it can be seen in Fig. 1. Thus, the value of mu for mineral wool
equal to 1, this indicates that it is capable of transmitting water vapor as well as air itself. While this value for aerated concrete is 10, this means that it copes with conducting steam 10 times worse than air. If the mu index is multiplied by the layer thickness, expressed in meters, this will allow us to obtain an air thickness Sd (m) equal to the level of vapor permeability.
The table shows that for each position the vapor permeability indicator is indicated under different conditions. If you look at SNiP, you can see the calculated data for the mu indicator when the moisture ratio in the body of the material is equal to zero.
Figure 1. Table of vapor permeability of building materials For this reason, when purchasing goods that are intended to be used in the process country house construction
, it is preferable to take into account the international ISO standards, since they determine the mu value in a dry state, with a humidity level of no more than 70% and a humidity level of more than 70%.
When choosing building materials that will form the basis of a multilayer structure, the mu index of the layers located on the inside must be lower, otherwise, over time, the layers located inside will become wet, as a result of which they will lose their thermal insulation qualities. When creating enclosing structures, you need to take care of them normal functioning
. To do this, you should adhere to the principle that states that the mu level of the material located in the outer layer should be 5 times or more higher than the mentioned indicator of the material located in the inner layer.
Vapor permeability mechanism Under conditions of slight relative humidity
When the moisture level of a layer increases, its mu index increases, thus the level of vapor permeability resistance decreases.
Indicators of vapor permeability of undetected materials are applicable in conditions internal structures buildings that have heating. But the vapor permeability levels of moistened materials are applicable to any building structures that are not heated.
The vapor permeability levels that form part of our standards are not in all cases equivalent to those that belong to international standards. Thus, in domestic SNiP the level of mu of expanded clay and slag concrete is almost the same, while according to international standards the data differ from each other by 5 times. The vapor permeability levels of gypsum board and slag concrete in domestic standards are almost the same, but in international standards the data differs by 3 times.
Exist various ways Determining the level of vapor permeability, as for membranes, the following methods can be distinguished:
- American test with a vertical bowl.
- American inverted bowl test.
- Japanese vertical bowl test.
- Japanese test with inverted bowl and desiccant.
- American vertical bowl test.
The Japanese test uses a dry desiccant that is placed under the material being tested. All tests use a sealing element.
According to SP 50.13330.2012 " Thermal protection buildings", Appendix T, table T1 "Calculated thermal performance indicators of building materials and products" the vapor permeability coefficient of galvanized covering (mu, (mg/(m*h*Pa)) will be equal to:
Conclusion: internal galvanized stripping (see Figure 1) in translucent structures can be installed without vapor barrier.
To install a vapor barrier circuit, it is recommended:
Vapor barrier for fastening points of galvanized sheets, this can be achieved with mastic
Vapor barrier of joints of galvanized sheets
Vapor barrier of joints of elements (galvanized sheet and stained glass crossbar or stand)
Ensure that there is no vapor transmission through fasteners (hollow rivets)
Terms and Definitions
Vapor permeability- the ability of materials to transmit water vapor through their thickness.
Water vapor is the gaseous state of water.
Dew point - The dew point characterizes the amount of humidity in the air (water vapor content in the air). Dew point temperature is defined as the ambient temperature to which the air must cool before the vapor it contains reaches saturation and begins to condense into dew. Table 1.
Table 1 - Dew point
Vapor permeability- measured by the amount of water vapor passing through 1 m2 of area, 1 meter thick, within 1 hour, at a pressure difference of 1 Pa. (according to SNiP 02/23/2003). The lower the vapor permeability, the better the thermal insulation material.
Vapor permeability coefficient (DIN 52615) (mu, (mg/(m*h*Pa)) is the ratio of the vapor permeability of a layer of air 1 meter thick to the vapor permeability of a material of the same thickness
Air vapor permeability can be considered as a constant equal to
0.625 (mg/(m*h*Pa)
The resistance of a layer of material depends on its thickness. The resistance of a layer of material is determined by dividing the thickness by the vapor permeability coefficient. Measured in (m2*h*Pa) / mg
According to SP 50.13330.2012 "Thermal protection of buildings", Appendix T, Table T1 "Calculated thermal performance indicators of building materials and products" the vapor permeability coefficient (mu, (mg/(m*h*Pa)) will be equal to:
Rod steel, reinforcing steel (7850 kg/m3), coefficient. vapor permeability mu = 0;
Aluminum(2600) = 0; Copper(8500) = 0; Window glass (2500) = 0; Cast iron (7200) = 0;
Reinforced concrete (2500) = 0.03; Cement-sand mortar (1800) = 0.09;
Brickwork from hollow brick (ceramic hollow brick with a density of 1400 kg/m3 on cement sand solution) (1600) = 0,14;
Brickwork made of hollow bricks (ceramic hollow brick with a density of 1300 kg/m3 on cement sand mortar) (1400) = 0.16;
Brickwork made of solid brick (slag on cement sand mortar) (1500) = 0.11;
Brickwork made of solid brick (ordinary clay on cement sand mortar) (1800) = 0.11;
Expanded polystyrene boards with a density of up to 10 - 38 kg/m3 = 0.05;
Ruberoid, parchment, roofing felt (600) = 0.001;
Pine and spruce across the grain (500) = 0.06
Pine and spruce along the grain (500) = 0.32
Oak across the grain (700) = 0.05
Oak along the grain (700) = 0.3
Glued plywood (600) = 0.02
Sand for construction work (GOST 8736) (1600) = 0.17
Mineral wool, stone (25-50 kg/m3) = 0.37; Mineral wool, stone (40-60 kg/m3) = 0.35
Mineral wool, stone (140-175 kg/m3) = 0.32; Mineral wool, stone (180 kg/m3) = 0.3
Drywall 0.075; Concrete 0.03
The article is given for informational purposes
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 results pressure at 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 are committed to the idea that breathing is 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 of vapor permeability.
Equipment
In order to correctly determine vapor permeability indicators, specialists use specialized research equipment:
- Glass cups or vessels for research;
- Unique tools necessary for thickness measuring processes with a high level of accuracy;
- Analytical type balances with weighing error.
Often in construction articles there is an expression - vapor permeability of concrete walls. It means the material’s ability to pass water vapor, or, in popular parlance, “breathe.” This parameter is of great importance, since waste products are constantly formed in the living room, which must be constantly removed outside.
General information
If you do not create normal ventilation in the room, dampness will be created in it, which will lead to the appearance of fungus and mold. Their secretions can be harmful to our health.
On the other hand, vapor permeability affects the ability of a material to accumulate moisture. This is also a bad indicator, since the more it can retain it, the higher the likelihood of fungus, putrefactive manifestations, and damage due to freezing.
Vapor permeability is denoted by the Latin letter μ and measured in mg/(m*h*Pa). The value shows the amount of water vapor that can pass through the wall material over an area of 1 m2 and with a thickness of 1 m in 1 hour, as well as a difference in external and internal pressure of 1 Pa.
High ability to conduct water vapor in:
- foam concrete;
- aerated concrete;
- perlite concrete;
- expanded clay concrete.
Rounding out the table is heavy concrete.
Advice: if you need to make a technological channel in the foundation, diamond drilling of holes in concrete will help you.
Aerated concrete
- Using the material as an enclosing structure makes it possible to avoid the accumulation of unnecessary moisture inside the walls and preserve its heat-saving properties, which will prevent possible destruction.
- Any aerated concrete and foam concrete block contains ≈ 60% air, due to which the vapor permeability of aerated concrete is recognized as good, the walls in this case can “breathe”.
- Water vapor seeps freely through the material, but does not condense in it.
The vapor permeability of aerated concrete, as well as foam concrete, significantly exceeds heavy concrete - for the first it is 0.18-0.23, for the second - (0.11-0.26), for the third - 0.03 mg/m*h* Pa.
I would especially like to emphasize that the structure of the material ensures that it effectively removes moisture into the environment, so that even when the material freezes, it does not collapse - it is forced out through open pores. Therefore, when preparing, you should take this feature into account and select the appropriate plasters, putties and paints.
The instructions strictly regulate that their vapor permeability parameters are not lower than aerated concrete blocks used for construction.
Tip: do not forget that vapor permeability parameters depend on the density of aerated concrete and may differ by half.
For example, if you use D400, their coefficient is 0.23 mg/m h Pa, and for D500 it is already lower - 0.20 mg/m h Pa. In the first case, the numbers indicate that the walls will have a higher “breathing” ability. So when selecting finishing materials for walls made of D400 aerated concrete, make sure that their vapor permeability coefficient is the same or higher.
Otherwise, this will lead to poor drainage of moisture from the walls, which will affect the level of living comfort in the house. You should also take into account that if you used vapor-permeable paint for aerated concrete for the exterior, and non-vapor-permeable materials for the interior, the steam will simply accumulate inside the room, making it damp.
Expanded clay concrete
The vapor permeability of expanded clay concrete blocks depends on the amount of filler in its composition, namely expanded clay - foamed baked clay. In Europe, such products are called eco- or bioblocks.
Advice: if you can’t cut the expanded clay block with a regular circle and grinder, use a diamond one.
For example, cutting reinforced concrete with diamond wheels makes it possible to quickly solve the problem.
Polystyrene concrete
The material is another representative of cellular concrete. The vapor permeability of polystyrene concrete is usually equal to that of wood. You can make it yourself.
Today, more attention is beginning to be paid not only to the thermal properties of wall structures, but also to the comfort of living in the structure. In terms of thermal inertness and vapor permeability, polystyrene concrete resembles wooden materials, and heat transfer resistance can be achieved by changing its thickness. Therefore, poured monolithic polystyrene concrete is usually used, which is cheaper than ready-made slabs.
Conclusion
From the article you learned that building materials have such a parameter as vapor permeability. It makes it possible to remove moisture outside the walls of the building, improving their strength and characteristics. The vapor permeability of foam concrete and aerated concrete, as well as heavy concrete, differs in its characteristics, which must be taken into account when choosing finishing materials. The video in this article will help you find additional information on this topic.
