Vapor permeability of building materials. Air permeability of building envelopes How to find defects in sealing exterior walls and other fences at home

To create a climate favorable for living in the 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.

For the most part, they are porous bodies. The size and structure of the pores in different materials is not the same, therefore, the air permeability of materials, depending on the pressure difference, manifests itself in different ways.

Figure 11 shows a qualitative picture of the dependence of air permeability G from pressure difference ΔР for building materials, given by K.F. Fokin.

Fig.11. Effect of material porosity on its air permeability.1 - materials with uniform porosity (such as foam concrete); 2 - materials with pores of various sizes (such as fillings); 3 - low air-permeable materials (such as wood, cement mortars), 4 - wet materials.

Straight line from 0 to point a on curve 1 indicates the laminar movement of air through the pores of the material with uniform porosity at small values ​​of the pressure difference. Above this point, turbulent motion occurs on the curved section. In materials with different pore sizes, the air movement is turbulent even at a small pressure difference, which can be seen from the curvature of line 2. In materials with low air permeability, on the contrary, the air movement through the pores is laminar and at fairly large pressure differences, therefore, the dependence G from ΔР linear for any pressure difference (line 3). In wet materials (curve 4) at low ΔР, less than a certain minimum pressure difference ΔP min, there is no air permeability, and only when this value is exceeded, when the pressure difference is sufficient to overcome the forces of surface tension of the water contained in the pores of the material, air movement occurs. The higher the moisture content of the material, the greater the value ΔP min.

With laminar air movement in the pores of the material, the dependence is valid

where G is the air permeability of the fence or layer of material, kg / (m 2. h);

i- air permeability coefficient of the material, kg / (m. Pa. h);

δ - thickness of the material layer, m.

Air permeability coefficient of the material similar to the coefficient of thermal conductivity and indicates the degree of air permeability of the material, numerically equal to the air flow in kg passing through 1 m 2 of an area perpendicular to the direction of flow, at a pressure gradient of 1 Pa / m.

The values ​​of the air permeability coefficient for various building materials differ significantly from each other.

For example, for mineral wool i ≈ 0.044 kg / (m. Pa. h), for non-autoclaved foam concrete i ≈ 5.3.10 - 4 kg / (m. Pa. h), for solid concrete i ≈ 5.1.10 - 6 kg / (m. Pa. h),

With turbulent air movement in formula (2.60) should be replaced ΔР on the ΔР n. At the same time, the exponent n varies within 0.5 - 1. However, in practice, formula (2.60) is also used for the turbulent regime of air flow in the pores of the material.

In modern regulatory literature, the concept of air permeability coefficient is not used. Materials and designs are characterized air permeability R and, kg / (m. h). with a pressure difference on different sides? P o \u003d 10 Pa, which, with laminar air movement, is found by the formula:

where G is the breathability of a layer of material or structure, kg / (m 2. h).

The resistance to air penetration of fences in its dimension does not contain the dimension of air transfer potential - pressure. This situation arose due to the fact that in regulatory documents, by dividing the actual pressure difference? P by the standard pressure value? P o \u003d 10 Pa, the air permeability resistance is reduced to a pressure difference? P o \u003d 10 Pa.

The values ​​are given breathability for layers of some materials and structures.

For windows, in the leaks of which the movement of air occurs in mixed mode, the resistance to air penetration , kg / (m. h), is determined from the expression:

Questions for self-control

1. What is the breathability of the material and fence?

2. What is breathability?

3. What is infiltration?

4. What is exfiltration?

5. What quantitative characteristic of the process of air permeability is called air permeability?

6. Through what two types of leaks is air filtered in fences?

7. What are the three types of filtration, according to the terminology of R.E. Brilinga?

8. What is the breathability potential?

9. What two natures form the pressure difference on opposite sides of the fence?

10. What is the air permeability coefficient of the material?

11. What is the air permeability of the building envelope?

12. Write a formula for determining the resistance to air penetration during laminar movement of air through the pores of construction materials.

13. Write a formula for determining the window's air permeability.

Breathability is the ability of materials to pass air. A necessary condition for the passage of air through the material is the presence of an air pressure difference (D R) on both sides of the material sample. The higher the pressure drop, the more intense the process of air passing through the material. At low speeds of air passing through materials, the dependence of the air speed on the magnitude of the pressure drop is linear and is expressed by the D'Arcy equation:

Such a dependence takes place at small values ​​or with a dense structure of the textile fabric. With an increase in the speed of air movement through materials, a deviation from the linear nature of the dependence of the speed on the pressure drop can be observed. In this regard, for household materials intended for the manufacture of clothing, in accordance with the standard (GOST 12088–77), breathability is estimated at a pressure drop = 49 Pa (5 mm water column), which corresponds to the operating conditions of clothing in the climatic conditions of central Russia , where the wind speed is no more than 8–10 m/s.

The generally accepted characteristic of air permeability is air permeability coefficient, dm 3 / (m 2 ∙ s):

, (58)

where is the volume of air, dm 3 , passing through the working part of the material sample, the area of ​​which is , m 2 , for a time equal to 1 s, at a pressure drop .

When using m 3 as a unit of measurement for the volume of air passing through a sample of material, the resulting value of the air permeability coefficient (m 3 / (m 2 × s)) is numerically equal to the speed of air movement through the material (m / s).

The air permeability of modern materials varies widely - from 3.5 to 1500 dm 3 / (m 2 ∙ s) ( tab. eight).

Table 8 Grouping fabrics by air permeability

(according to N. A. Arkhangelsky)

The air flow passes through the pores of the textile material, therefore, the air permeability indicators depend on the structural characteristics of the material, which determine its porosity, the number and size of through pores. Materials made of thin, strongly twisted threads have a large number of through pores and, accordingly, greater air permeability compared to materials made of thick fluffy threads, in which the pores are partially closed by protruding fibers or thread loops.

The most important structural characteristics of textile webs having through pores, which mainly determine their air permeability, are the thickness of the web, the amount of through porosity and the characteristic size of the diameter (diameter) of the through pores. It is possible to determine the values ​​of the speed of air passage through the material at different pressure drops using the mathematical model proposed by A.V. Kulichenko, which has the form

, (59)

where – air viscosity, mPa s; – diameter of through pores, m;

– through porosity; – material thickness, m.

In those cases where the materials do not have through pores, their air permeability is determined by the value of the total porosity, the pore size and the thickness of the sheets. So, for nonwoven materials based on fibrous canvases, the dependence of the air permeability coefficient on their structure is expressed by experimentally obtained by A. V. Kulichenko equations that have the general form

, (60)

where is the filling of the nonwoven material with fibers; L is the thickness of the material; is a parameter associated with the geometric characteristics of the fibers.

Humidity is one of the most important factors on which the breathability of materials depends. The value of this factor is the higher, the greater the density of the material and the higher the hygroscopic properties of the fibers from which it is made. So, according to B. A. Buzov, at 100% moisture content of woolen cloth fabrics, air permeability decreases by 2–3 times compared to their air-dry state. A decrease in the air permeability of materials when moistened is associated with swelling of the fibers and the appearance of micro- and macrocapillary moisture, which causes a sharp reduction in the number and size of pores and, ultimately, leads to an increase in the aerodynamic resistance of the material and, accordingly, to a decrease in the air permeability coefficient.

Deformation of textile materials causes significant changes in their structure (in particular, porosity is disturbed), which leads to a change in air permeability. Research conducted at the Ivanovo State Textile Academy prof..V. V. Veselov, showed that with asymmetric biaxial stretching of the fabric, there is initially a slight decrease in air permeability, and then its increase to 60% of the initial value. This is due to the complex nature of the restructuring of the material structure, which is associated with tension and compression of the warp and weft threads.

The effect of tensile strains on air permeability is most significant in knitted fabrics. Unlike fabrics, knitted fabrics have a higher extensibility, which is associated with a greater mobility of their structure, which is sensitive even to low values ​​of tensile forces applied to them. Structural changes in knitted fabrics when such forces are applied to them consist primarily in changes in the configuration of the loops. The threads themselves, especially in easily stretched fabrics, can be slightly stressed. The high extensibility of knitted fabrics when external loads are applied to them is the cause of not only their structural changes, but also changes in the values ​​of their properties, in particular, permeability.

For such highly stretchable webs, the dependence of air permeability on the magnitude of their spatial tensile strain is linear ( rice.) and is expressed by an equation of the form ,

where is the coefficient of air permeability in the initial undeformed state; – spatial deformation; - coefficient characterizing the change in the air permeability of the fabric when it is stretched and depending on the structure of the fabric.

When designing products, information is needed not only on the breathability of the materials from which certain products are made, but also on the breathability of the clothing package. With an increase in the number of layers of material in the bag, the overall air permeability of the bag decreases ( fig.22). The most dramatic decrease in air permeability (up to 50%) is observed with an increase in the number of material layers to two; further increase in the number of layers affects to a lesser extent. With the introduction of air gaps between the layers, the air permeability of the bag depends on the thickness of the air gap.

Rice. 22 Dependence of the coefficient of air permeability

knitted fabrics on the magnitude of surface deformation:

1 - cross-knitted, interlock (PA thread elastic + PU elastomeric thread);

2 - cross-knitted, smooth surface (cotton yarn);

3 - cross-knitted patterned (PAN yarn);

4 – cross-knitted, interlock (woolen yarn)

Rice. 23 Dependence of air permeability of bags

fabrics depending on the number of layers: 1 - drape; 2 - cloth

The total breathability of a multilayer garment bag is calculated using the Clayton formula, which can be up to 10% inaccurate:

, (61)

where , , …, are the air permeability coefficients of each layer separately.

The air permeability of materials is also a technological property, since it affects the parameters of the wet-heat treatment of garments on steam-air presses and mannequins.

moisture permeability

The human body in the process of life constantly releases water vapor, the accumulation of which in the underwear and shoe space can cause discomfort, stickiness of clothing, wetting of adjacent layers, which leads to a decrease in the heat-shielding properties of the product.

The ability of materials to conduct moisture from an environment with high humidity to an environment with low humidity is their important hygienic property. Due to this property, the removal of excess vaporous and droplet-liquid moisture from the underwear and intra-shoe layer or the isolation of the human body from the effects of external moisture (precipitation, waterproof clothing and shoes, etc.) is ensured.

The process of transferring moisture through materials includes the following components:

– diffusion and convective transport;

– absorption of moisture from the interior(underwear or shoe) space, transfer through the polymer and desorption to the external environment;

– capillary condensation, capillary rise and subsequent desorption.

Depending on the pore size in the material, the predominance of certain components of the moisture transfer process can be observed. In macroporous materials (with a predominance of macrocapillaries with a diameter of 10 -7 m or more), the diffusion process predominates. In cases where the materials are hydrophilic, the manifestation of the second component is also observed. In microporous materials (with a predominance of microcapillaries with a transverse size of less than 10-7 m), there is a predominance of transfer due to sorption - desorption and capillary rise. For heteropose materials, i.e., having micro- and macropores, the presence of all three components of the moisture transfer process is characteristic.

The moisture permeability of the material significantly depends on the sorption properties of the fibers and threads of its constituents. The process of moisture transfer in hydrophilic and hydrophobic materials is not the same. Hydrophilic materials actively absorb moisture and thus, as it were, increase the evaporation surface, which is practically not typical for hydrophobic materials. The onset of dynamic equilibrium between the processes of sorption and desorption in hydrophilic materials requires a significant amount of time, while in hydrophobic materials it occurs very quickly.

Depending on the average density of the material structure, one or another method of moisture passage prevails. In textile materials (with a surface filling of more than 85%), moisture transfer predominates by its sorption - desorption by the fibers of the material. The moisture permeability of such materials depends mainly on the ability of the fibers to absorb moisture. In materials with a surface fill of less than 85%, moisture passes mainly through the pores of the material. The moisture permeability of such materials depends on their structural parameters. When filling by weight is less than 30%, the ability of fabrics to pass moisture is practically independent of the hydrophilicity of fibers and threads.

The moisture conductivity of the material also has influence of air movement through the material. At low air speeds, the process of moisture passage by sorption - desorption prevails. With an increase in the speed of air movement, the process of diffusion of moisture through the pores becomes more active. At an air speed of 3–10 m/s, there is a close correlation between air and moisture permeability.

The ability of materials to pass moisture vapor is called vapor permeability.

Vapor permeability coefficient, g / (m 2 ∙ s), shows how much water vapor passes through a unit area of ​​\u200b\u200bthe material per unit time:

, (62)

where BUT is the mass of water vapor that has passed through the material sample, g; S– material sample area, m2; – test duration, s.

The vapor permeability coefficient depends on the size of the air gap - the distance from the surface of the material to the surface of moisture evaporation, mm. With its decrease, the coefficient increases. Therefore, in the designation of the vapor permeability coefficient, the value at which the tests were carried out is always indicated. The value should be minimal and the same when testing materials for their comparison, since the resistance to the passage of moisture vapor is the sum of the resistance of the air layer between the material and the evaporation surface and the resistance of the material itself.

An increase in temperature difference and relative humidity difference, i.e., partial pressure of water vapor, on both sides of the material causes an increase in the intensity of the vapor permeability process. Carrying out tests at a water temperature of 35–36 °C brings the test conditions closer to the operating conditions of clothing, since this temperature corresponds to the temperature of the human body.

Relative vapor permeability,%, - the ratio of the mass of moisture vapor BUT, evaporated through the test material, to the mass of moisture vapor AT, evaporated from the open surface of the water, which was under the same test conditions:

100 % . (63)

Due to the significant influence of the thickness of the air gap between the material sample and the moisture evaporation surface, a characteristic called vapor permeability resistance. This value is measured in mm of the thickness of a layer of still air that has the same resistance to the passage of water vapor as the material under test.

Depending on the resistance to vapor permeability, I. A. Dimitrieva proposed to divide fabrics into four groups ( tab. nine)

Table 9 Grouping, fabrics depending on

their resistance to water vapor transfer

The permeability of textile materials during the passage of drop-liquid moisture through them is estimated using the characteristics water permeability and water resistance.

Water permeability- the ability of textile materials to pass water at a certain pressure. The main feature of this property is water permeability coefficient dm 3 / (m 2 ∙ s). It shows how much water passes through a unit area of ​​the material per unit time:

, (64) where V- the amount of water that has passed through the sample of the material, dm 3;

S—sample area, m2; - time, s.

The water permeability coefficient is determined by measuring the time it takes for water to pass through a sample of 0.5 dm 3 material under pressure H = 5 ∙ 10 3 Pa. For materials with a film coating or water-repellent finish, the water permeability coefficient is determined by sprinkling for 10 minutes (GOST 30292–96).

Water resistance(water resistance) - the resistance of textile materials to the penetration of water through them. Water resistance is characterized by the lowest pressure at which water begins to penetrate through the material ( tab. ten).

Table 10 Norms of water resistance of raincoat fabrics

The water resistance of materials with water-repellent impregnation or film coating is estimated by the time of wetting during sprinkling (GOST 30292–96).

Water permeability, water resistance and water repellency depend on the structural parameters of filling the sheets, on their thickness, sorption properties and wetting ability. For a number of garments that protect people from atmospheric precipitation (raincoats, coats, suits, umbrellas, tents, etc.), the water resistance of materials is one of the most important quality indicators.

The waterproofness of raincoat fabrics is also evaluated by the ability of raincoat materials to water repellency, which is determined by the state of the wet surface of the sample after it has been sprinkled and shaken ( tab. eleven).

Table 11 Surface condition of materials after sprinkling

In accordance with GOST 28486-90, water repellency standards are set in points and for raincoat and jacket fabrics made of synthetic threads with a film coating in 3 layers - at least 80 points, in 1 layer - at least 70 points, with a water-repellent finish - up to 70 points.

Dust tightness

Materials in the process of wearing products are able to pass into the underwear layer or retain dust particles in their structure. This leads to contamination of both the materials themselves and the layers of the product located under them. Dust particles penetrate through the material mainly in the same way as air - through the through pores of the material. Dust particles are retained in the structure of the material due to their mechanical adhesion to the surface irregularities of the fibers and oil lubrication. In addition, the process of capture of dust particles by the material is facilitated by their electrification during friction. The smallest dust particles (less than 50 microns) do not have charges, but are capable of rubbing against each other or against a material to acquire a charge of a short duration. In the presence of static electricity on the surface of the material, charged dust particles are attracted to the surface of the fibers, where they are subsequently held by mechanical adhesion or lubrication. Thus, the higher the electrification of the material, the more it becomes contaminated. The loose porous structure of a material made of fibers with an uneven surface has the ability to capture more dust and retain it for a longer time than a dense structure of a material having smooth, even fibers. For these reasons, woolen and cotton fabrics have the highest dust capacity. The addition of polyester fibers to them reduces the dust capacity.

Dust tightness– the ability of materials to pass dust particles. It is characterized dust penetration coefficient ,g/(cm 2 s):

, (65)

where is the mass of dust that has passed through the material sample, g; – sample area, m2; – test time, s.

Relative dust penetration , %, shows the ratio of the mass of dust passed through the material to the mass of dust used in the test, :

100 % . (66)

Dust capacity – the ability of the material to receive and retain dust. It is characterized relative dust capacity, %, - the ratio of the mass of dust absorbed by the material, , to the mass of dust used in the test, :

100 % . (67)

The indicators of dust permeability and dust capacity are determined by sucking through the material with a vacuum cleaner a sample of dust having a certain composition and particle size. By weighing, the amount of dust that has passed through the material and settled on the material is determined.

Materials of different types have different values ​​of dust permeability and dust capacity ( table 12).

Table 12 Dust permeability and dust holding capacity of materials

(according to M.I. Sukharev)

Figure 1 - vapor permeability of a galvanized flashing

According to SP 50.13330.2012 "Thermal protection of buildings", Appendix T, table T1 "Designed thermal performance of building materials and products", the vapor permeability coefficient of a galvanized flashing (mu, (mg / (m * h * Pa)) will be equal to:

Conclusion: the internal galvanized flashing (see Figure 1) in translucent structures can be installed without a vapor barrier.

For the installation of a vapor barrier circuit, it is recommended:

Vapor barrier of the fastening points of the galvanized sheet, this can be provided with mastic

Vapor barrier of joints of galvanized sheet

Vapor barrier of elements joining points (galvanized sheet and stained-glass crossbar or rack)

Ensure that there is no steam transmission through fasteners (hollow rivets)

Terms and Definitions

Vapor permeability- the ability of materials to pass water vapor through their thickness.

Water vapor is the gaseous state of water.

The dew point characterizes the amount of humidity in the air (water vapor content in the air). The dew point temperature is defined as the ambient temperature to which the air must be cooled in order for the vapor it contains to reach saturation and begin 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, for 1 hour, at a pressure difference of 1 Pa. (according to SNiP 23-02-2003). 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

The vapor permeability of air 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 material layer 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 "Designed thermal performance of building materials and products", the vapor permeability coefficient (mu, (mg / (m * h * Pa)) will be equal to:

Steel rod, reinforcing (7850kg/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 mortar) (1600) = 0.14;

Brickwork from hollow brick (ceramic hollow brick with a density of 1300 kg / m3 on cement sand mortar) (1400) = 0.16;

Brickwork from 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 density 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 grain (700) = 0.05

Oak along the grain (700) = 0.3

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.

GOST 32493-2013

INTERSTATE STANDARD

MATERIALS AND PRODUCTS HEAT-INSULATING

Method for determining air permeability and air permeability

Materials and products the construction heatinsulating. Method of determination of air permeability and resistance to a air permeability

MKS 91.100.60

Introduction date 2015-01-01

Foreword

Goals, basic principles and the basic procedure for work on interstate standardization are established by GOST 1.0-92 "Interstate standardization system. Basic provisions" and GOST 1.2-2009 "Interstate standardization system. Interstate standards, rules and recommendations for interstate standardization. Rules for the development, adoption, application , updates and cancellations"

About the standard

1 DEVELOPED by the Federal State Budgetary Institution "Research Institute of Building Physics of the Russian Academy of Architecture and Building Sciences" (NIISF RAASN)

2 INTRODUCED by the Technical Committee for Standardization TC 465 "Construction"

3 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes of November 14, 2013 N 44-P)

Voted for the adoption of the standard:

4 By order of the Federal Agency for Technical Regulation and Metrology dated December 30, 2013 N 2390-st, the interstate standard GOST 32493-2013 was put into effect as the national standard of the Russian Federation from January 1, 2015.

5 INTRODUCED FOR THE FIRST TIME


Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments - in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly information index "National Standards". Relevant information, notification and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet

1 area of ​​use

1 area of ​​use

This International Standard applies to building insulation materials and prefabricated products and specifies a method for determining air permeability and air resistance.

2 Normative references

This standard uses normative references to the following interstate standards:

GOST 166-89 (ISO 3599-76) Calipers. Specifications

GOST 427-75 Measuring metal rulers. Specifications

Note - When using this standard, it is advisable to check the validity of reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or according to the annual information index "National Standards", which was published as of January 1 of the current year, and on issues of the monthly information index "National Standards" for the current year. If the reference standard is replaced (modified), then when using this standard, you should be guided by the replacing (modified) standard. If the referenced standard is canceled without replacement, the provision in which the reference to it is given applies to the extent that this reference is not affected.

3 Terms, definitions and symbols

3.1 Terms and definitions

In this standard, the following terms are used with their respective definitions.

3.1.1 material breathability: The property of a material to pass air in the presence of a difference in air pressure on opposite surfaces of a material sample, determined by the amount of air passing through a unit area of ​​a material sample per unit time.

3.1.2 air permeability coefficient: An indicator characterizing the breathability of the material.

3.1.3 air permeation resistance: An indicator that characterizes the property of a material sample to prevent the passage of air.

3.1.4 pressure drop: The difference in air pressure on opposite surfaces of the sample during the test.

3.1.5 air flow density: The mass of air passing per unit of time through a unit area of ​​the surface of the sample, perpendicular to the direction of air flow.

3.1.6 air consumption: The amount (volume) of air passing through the sample per unit time.

3.1.7 filter mode indicator: The indicator of the degree of pressure drop in the equation for the dependence of the mass air permeability of the sample on the pressure drop.

3.1.8 sample thickness: The thickness of the sample in the direction of air flow.

3.2 Notation

The designations and units of measurement of the main parameters used in determining the air permeability are given in Table 1.


Table 1

4 General provisions

4.1 The essence of the method is to measure the amount of air (air flow density) passing through a sample of material with known geometric dimensions, with the sequential creation of specified stationary air pressure drops. Based on the measurement results, the air permeability coefficient of the material and the air permeability of the material sample are calculated, which are included in the air filtration equations (1) and (2), respectively:

where - air flow density, kg / (m h);

- pressure drop, Pa;

- sample thickness, m;

- air permeability, [m·h·(Pa)]/kg.

4.2 The number of samples required to determine air permeability and air permeability should be at least five.

4.3 The temperature and relative humidity of the air in the room in which the tests are carried out should be (20 ± 3) ° C and (50 ± 10)%, respectively.

5 Means of testing

5.1 Test rig, including:

- hermetic chamber with an adjustable opening and devices for hermetic fastening of the sample;

- equipment for creating, maintaining and quickly changing air pressure in a sealed chamber up to 100 Pa when testing heat-insulating materials and up to 10,000 Pa - when testing structural and heat-insulating materials (compressor, air pump, pressure regulators, differential pressure regulators, air flow regulators, shut-off fittings).

5.2 Measuring instruments:

- flowmeters (rotameters) of air with a measurement limit of air flow from 0 to 40 m/h with a measurement error of ±5% of the upper measurement limit;

- indicating or self-recording pressure gauges, pressure sensors that provide measurements with an accuracy of ± 5%, but not more than 2 Pa;

- a thermometer for measuring air temperature within 10 °C - 30 °C with a measurement error of ±0.5 °C;

- psychrometer for measuring relative air humidity within 30%-90% with a measurement error of ±10%;

- metal ruler according to GOST 427 with a measurement error of ±0.5 mm;

- caliper according to GOST 166.

5.3 Drying cabinet.

5.4 Test equipment and measuring instruments must comply with the requirements of the current regulatory documents and be verified in the prescribed manner.

5.5 A diagram of the air permeability test setup is shown in Figure 1.

1 - compressor (air pump); 2 - control valves; 3 - hoses; 4 - air flow meters (rotameters); 5 - a sealed chamber that provides a stationary mode of air movement; 6 - a device for hermetic fastening of the sample; 7 - sample; 8 - indicating or self-recording manometers, pressure sensors

Figure 1 - Diagram of a test setup for determining the air permeability of thermal insulation materials

5.6 The test facility must ensure tightness in the range of test modes, taking into account the technical capabilities of the test equipment.

When checking the tightness of the chamber, an airtight element (for example, a metal plate) is installed in the opening and carefully sealed. The loss of air pressure at any stage of the test shall not exceed 2%.

6 Test preparation

6.1 Before testing, a test program is drawn up, in which the final control pressure values ​​\u200b\u200band a graph of pressure drops should be indicated.

6.2 Samples for testing are made or selected from products of full factory readiness in the form of rectangular parallelepipeds, the largest (front) faces of which correspond to the dimensions of the sample holder, but not less than 200x200 mm.

6.3 Samples are accepted for testing in accordance with the act of sampling, drawn up in the prescribed manner.

6.4 If the selection or production of samples is carried out without the involvement of a testing center (laboratory), then when registering the test results, an appropriate entry is made in the test report (protocol).

6.5 Measure the thickness of the specimens with a ruler with an accuracy of ± 0.5 mm at four corners at a distance of (30 ± 5) mm from the top of the corner and in the middle of each side.

With a product thickness of less than 10 mm, the thickness of the sample is measured with a caliper or micrometer.

The arithmetic mean of the results of all measurements is taken as the thickness of the sample.

6.6 Calculate the difference in thickness of the specimens as the difference between the largest and smallest thickness values ​​obtained by measuring the specimen in accordance with 6.5. With a sample thickness of more than 10 mm, the thickness difference should not exceed 1 mm, with a sample thickness of 10 mm or less, the thickness difference should not exceed 5% of the sample thickness.

6.7 Samples are dried to constant weight at the temperature specified in the normative document for the material or product. Samples are considered dried to constant weight if the loss of their weight after the next drying for 0.5 h does not exceed 0.1%. After drying, determine the density of each sample in a dry state. The sample is immediately placed* into the air permeability test rig. Before testing, it is allowed to store dried samples in a volume isolated from the surrounding air for no more than 48 hours at a temperature of (20 ± 3) ° C and relative humidity of (50 ± 10)%.
_________________
* The text of the document corresponds to the original. - Database manufacturer's note.

If necessary, it is allowed to test wet samples, indicating in the report the moisture content of the samples before and after testing.

7 Testing

7.1 The test sample is installed in the device for hermetic fixation of the sample so that its front surfaces are turned into the chamber and into the room. The sample is carefully sealed and fixed in such a way as to exclude its deformation, gaps between the ends of the chamber and the sample, as well as the penetration of air through leaks between the clamping frame, the sample and the chamber. If necessary, the end faces of the sample are sealed in order to exclude the penetration of air through them from the chamber into the room, achieving complete passage of air during the test only through the front surfaces of the sample.

7.2 The ends of the manometer hoses (pressure sensors) are placed at the same level horizontally on both sides of the test sample in the chamber and in the room.

7.3 With the help of a compressor (air pump) and control valves, the pressure differences specified in the test program are created sequentially (in steps) on both sides of the sample. The air flow through the sample is considered steady (stationary) if the readings of the pressure gauge and flowmeters differ by no more than 2% for 60 s with a chamber volume of up to 0.25 m inclusive, 90 s - with a volume of 0.5 m 3, 120 s - with a volume of 0.75 m3, etc.

7.4 For each value of the pressure drop , Pa, the value of the air flow , m/h is recorded using the flow meter (rotameter).

7.5 The number of stages and the values ​​of the pressure drop corresponding to each test stage are specified in the test program. The number of test steps must be at least three.

The following values ​​of differential pressure in stages during the test to determine the coefficient of air permeability are recommended: 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100 Pa. When determining the resistance to air penetration, the same values ​​of pressure drop are recommended up to the limit values ​​of the test equipment, but not more than 1000 Pa.

7.6 After reaching the value of the final pressure specified by the test program, the load is successively reduced using the same pressure stages, but in reverse order, by measuring the air flow at each stage of the pressure drop.

8 Processing of test results

8.1 The test result for each pressure difference is taken to be the highest air flow rate for each stage, regardless of whether it was achieved with an increase or decrease in pressure.

8.2 According to the accepted values ​​for each pressure stage, calculate the value of the air flow (air flow density) passing through the sample, kg / (m h), according to the formula

where is the air density, kg/m;

- the area of ​​the front surface of the sample, m.

8.3 To determine the air permeability characteristics of a material from the test results obtained, equation (1) is expressed as:

According to the values ​​and in logarithmic coordinates, a plot of the air permeability of the sample is plotted.

The logarithms of the values ​​are plotted on the coordinate plane as a function of the logarithms of the corresponding pressure drops. A straight line is drawn through the marked points. The value of the filtering mode indicator is determined as the tangent of the slope of the straight line to the abscissa axis.

8.4 The coefficient of air permeability of the material, kg / [m h (Pa)], is determined by the formula

where is the ordinate of the intersection of the line with the axis;

- thickness of the test sample, m.

Air penetration resistance of a material sample, [m h (Pa)]/kg, is determined by the formula

8.5 The value of the coefficient of air permeability of the material and the resistance to air penetration of the samples of the material is determined as the arithmetic mean of the test results of all samples.

8.6 An example of processing test results is given in Appendix A.

Annex A (informative). Example of processing test results

Annex A
(reference)

This annex provides an example of processing the results of a test to determine the air permeability coefficient of stone wool with a density of 90 kg/m and the air permeability of a stone wool sample with dimensions of 200x200x50 mm.

The area of ​​the front surface of the sample is 0.04 m.

The density of air at a temperature of 20 ° C is 1.21 kg / m.

The results of measurements and processing of results are given in Table A.1. The first column shows the measured values ​​of the air pressure drop on different sides of the sample, the second column shows the measured values ​​of the air flow through the sample, the third column shows the values ​​of the air flow density through the sample calculated by formula (3) according to the data of column 2. The fourth and the fifth column presents the values ​​of the natural logarithms of the values ​​and given in columns 1 and 3, respectively.


Table A.1