Air permeability of building materials. Vapor permeability of building materials Air permeability of building materials

1. Only a heater with the lowest coefficient of thermal conductivity can minimize the selection of internal space

2. Unfortunately, we lose the storage heat capacity of the outer wall array forever. But there is a win here:

A) there is no need to spend energy on heating these walls

B) when you turn on even the smallest heater in the room, it will almost immediately become warm.

3. At the junction of the wall and the ceiling, "cold bridges" can be removed if the insulation is applied partially on the floor slabs with subsequent decoration of these junctions.

4. If you still believe in the "breathing of the walls", then please read THIS article. If not, then there is an obvious conclusion: the heat-insulating material must be pressed very tightly against the wall. It is even better if the insulation becomes one with the wall. Those. there will be no gaps and cracks between the insulation and the wall. Thus, the moisture from the room will not be able to get into the dew point zone. The wall will always remain dry. Seasonal temperature fluctuations without moisture access will not adversely affect the walls, which will increase their durability.

All these tasks can be solved only by sprayed polyurethane foam.

Possessing the lowest coefficient of thermal conductivity of all existing thermal insulation materials, polyurethane foam will take up a minimum of internal space.

The ability of polyurethane foam to adhere reliably to any surface makes it easy to apply it to the ceiling to reduce "cold bridges".

When applied to walls, polyurethane foam, being in a liquid state for some time, fills all the cracks and microcavities. Foaming and polymerizing directly at the point of application, polyurethane foam becomes one with the wall, blocking access to destructive moisture.

VAPOR PERMEABILITY OF WALLS
Supporters of the false concept of “healthy breathing of the walls”, in addition to sinning against the truth of physical laws and deliberately misleading designers, builders and consumers, based on a mercantile urge to sell their goods by any means, slander and slander thermal insulation materials with low vapor permeability (polyurethane foam) or heat-insulating material and completely vapor-tight (foam glass).

The essence of this malicious insinuation boils down to the following. It seems like if there is no notorious “healthy breathing of the walls”, then in this case the interior will definitely become damp, and the walls will ooze with moisture. In order to debunk this fiction, let's take a closer look at the physical processes that will occur in the case of lining under the plaster layer or using inside the masonry, for example, a material such as foam glass, the vapor permeability of which is zero.

So, due to the heat-insulating and sealing properties inherent in foam glass, the outer layer of plaster or masonry will come into an equilibrium temperature and humidity state with the outside atmosphere. Also, the inner layer of masonry will enter into a certain balance with the microclimate of the interior. Water diffusion processes, both in the outer layer of the wall and in the inner one; will have the character of a harmonic function. This function will be determined, for the outer layer, by diurnal changes in temperature and humidity, as well as seasonal changes.

Particularly interesting in this respect is the behavior of the inner layer of the wall. In fact, the inside of the wall will act as an inertial buffer, the role of which is to smooth out sudden changes in humidity in the room. In the event of a sharp humidification of the room, the inner part of the wall will adsorb the excess moisture contained in the air, preventing the air humidity from reaching the limit value. At the same time, in the absence of moisture release into the air in the room, the inner part of the wall begins to dry out, preventing the air from “drying out” and becoming like a desert one.

As a favorable result of such an insulation system using polyurethane foam, the harmonics of fluctuations in air humidity in the room are smoothed out and thus guarantee a stable value (with minor fluctuations) of humidity acceptable for a healthy microclimate. The physics of this process has been studied quite well by the developed construction and architectural schools of the world, and in order to achieve a similar effect when using fiber inorganic materials as a heater in closed insulation systems, it is highly recommended to have a reliable vapor-permeable layer on the inside of the insulation system. So much for "healthy breathing walls"!

There is a legend about the "breathing wall", and legends about the "healthy breathing of the cinder block, which creates a unique atmosphere in the house." In fact, the vapor permeability of the wall is not large, the amount of steam passing through it is insignificant, and much less than the amount of steam carried by air when it is exchanged in the room.

Vapor permeability is one of the most important parameters used in the calculation of insulation. We can say that the vapor permeability of materials determines the entire design of insulation.

What is vapor permeability

The movement of steam through the wall occurs with a difference in partial pressure on the sides of the wall (different humidity). In this case, there may not be a difference in atmospheric pressure.

Vapor permeability - the ability of a material to pass steam through itself. According to the domestic classification, it is determined by the vapor permeability coefficient m, mg / (m * h * Pa).

The resistance of a layer of material will depend on its thickness.
It is determined by dividing the thickness by the vapor permeability coefficient. It is measured in (m sq. * hour * Pa) / mg.

For example, the vapor permeability coefficient of brickwork is taken as 0.11 mg / (m * h * Pa). With a brick wall thickness of 0.36 m, its resistance to steam movement will be 0.36 / 0.11 = 3.3 (m sq. * h * Pa) / mg.

What is the vapor permeability of building materials

Below are the values of the coefficient of vapor permeability for several building materials (according to the regulatory document), which are most widely used, mg / (m * h * Pa).
Bitumen 0.008
Heavy concrete 0.03
Autoclaved aerated concrete 0.12
Expanded clay concrete 0.075 - 0.09
Slag concrete 0.075 - 0.14
Burnt clay (brick) 0.11 - 0.15 (in the form of masonry on cement mortar)
Lime mortar 0.12
Drywall, gypsum 0.075
Cement-sand plaster 0.09
Limestone (depending on density) 0.06 - 0.11
Metals 0
Chipboard 0.12 0.24
Linoleum 0.002
Polyfoam 0.05-0.23
Polyurethane hard, polyurethane foam
0,05
Mineral wool 0.3-0.6
Foam glass 0.02 -0.03
Vermiculite 0.23 - 0.3
Expanded clay 0.21-0.26
Wood across the fibers 0.06
Wood along the fibers 0.32
Brickwork from silicate bricks on cement mortar 0.11

Data on the vapor permeability of the layers must be taken into account when designing any insulation.

How to design insulation - according to vapor barrier qualities

The basic rule of insulation is that the vapor transparency of the layers should increase outward. Then in the cold season, with a greater probability, there will be no accumulation of water in the layers, when condensation occurs at the dew point.

The basic principle helps to decide in any cases. Even when everything is "turned upside down" - they insulate from the inside, despite the insistent recommendations to make insulation only from the outside.

In order to avoid a catastrophe with wetting the walls, it is enough to remember that the inner layer should most stubbornly resist steam, and based on this, for internal insulation, use extruded polystyrene foam with a thick layer - a material with very low vapor permeability.

Or do not forget to use even more “airy” mineral wool for a very “breathing” aerated concrete from the outside.

Separation of layers with a vapor barrier

Another option for applying the principle of vapor transparency of materials in a multilayer structure is the separation of the most significant layers by a vapor barrier. Or the use of a significant layer, which is an absolute vapor barrier.

For example, - insulation of a brick wall with foam glass. It would seem that this contradicts the above principle, because it is possible to accumulate moisture in a brick?

But this does not happen, due to the fact that the directional movement of steam is completely interrupted (at sub-zero temperatures from the room to the outside). After all, foam glass is a complete vapor barrier or close to it.

Therefore, in this case, the brick will enter into an equilibrium state with the internal atmosphere of the house, and will serve as an accumulator of humidity during its sharp jumps inside the room, making the internal climate more pleasant.

The principle of separation of layers is also used when using mineral wool - a heater that is especially dangerous for moisture accumulation. For example, in a three-layer construction, when mineral wool is inside a wall without ventilation, it is recommended to put a vapor barrier under the wool, and thus leave it in the outside atmosphere.

International classification of vapor barrier qualities of materials

The international classification of materials for vapor barrier properties differs from the domestic one.

According to the international standard ISO/FDIS 10456:2007(E), materials are characterized by a coefficient of resistance to steam movement. This coefficient indicates how many times more the material resists the movement of steam compared to air. Those. for air, the coefficient of resistance to steam movement is 1, and for extruded polystyrene foam it is already 150, i.e. Styrofoam is 150 times less vapor permeable than air.

Also in international standards it is customary to determine the vapor permeability for dry and moist materials. The boundary between the concepts of “dry” and “moistened” is the internal moisture content of the material of 70%.
Below are the values of the coefficient of resistance to steam movement for various materials according to international standards.

Steam resistance factor

First, data are given for dry material, and separated by commas for moist (more than 70% moisture).
Air 1, 1
Bitumen 50,000, 50,000
Plastics, rubber, silicone — >5,000, >5,000
Heavy concrete 130, 80
Medium density concrete 100, 60
Polystyrene concrete 120, 60
Autoclaved aerated concrete 10, 6
Lightweight concrete 15, 10
Artificial stone 150, 120
Expanded clay concrete 6-8, 4
Slag concrete 30, 20
Burnt clay (brick) 16, 10
Lime mortar 20, 10
Drywall, plaster 10, 4
Gypsum plaster 10, 6
Cement-sand plaster 10, 6
Clay, sand, gravel 50, 50
Sandstone 40, 30
Limestone (depending on density) 30-250, 20-200
Ceramic tile?, ?
Metals?
OSB-2 (DIN 52612) 50, 30
OSB-3 (DIN 52612) 107, 64
OSB-4 (DIN 52612) 300, 135
Chipboard 50, 10-20
Linoleum 1000, 800
Substrate for plastic laminate 10 000, 10 000
Substrate for laminate cork 20, 10
Polyfoam 60, 60
EPPS 150, 150
Polyurethane hard, polyurethane foam 50, 50
Mineral wool 1, 1
Foam glass?, ?
Perlite panels 5, 5
Perlite 2, 2
Vermiculite 3, 2
Ecowool 2, 2
Expanded clay 2, 2
Wood across grain 50-200, 20-50

It should be noted that the data on the resistance to the movement of steam here and "there" are very different. For example, foam glass is standardized in our country, and the international standard says that it is an absolute vapor barrier.

Where did the legend of the breathing wall come from?

A lot of companies produce mineral wool. This is the most vapor-permeable insulation. According to international standards, its vapor permeability resistance coefficient (not to be confused with the domestic vapor permeability coefficient) is 1.0. Those. in fact, mineral wool does not differ in this respect from air.

Indeed, it is a "breathing" insulation. To sell mineral wool as much as possible, you need a beautiful fairy tale. For example, that if you insulate a brick wall from the outside with mineral wool, then it will not lose anything in terms of vapor permeability. And this is absolutely true!

An insidious lie is hidden in the fact that through brick walls 36 centimeters thick, with a humidity difference of 20% (outside 50%, in the house - 70%), about a liter of water will leave the house per day. While with air exchange, about 10 times more should come out so that the humidity in the house does not increase.

And if the wall is insulated from the outside or from the inside, for example, with a layer of paint, vinyl wallpaper, dense cement plaster (which, in general, is “the most common thing”), then the vapor permeability of the wall will decrease several times, and with complete insulation - tens and hundreds of times .

Therefore, it will always be absolutely the same for a brick wall and for households - whether the house is covered with mineral wool with “raging breath”, or “dull-sniffing” foam plastic.

When making decisions on the insulation of houses and apartments, it is worth proceeding from the basic principle - the outer layer should be more vapor-permeable, preferably at times.

If for some reason it is not possible to withstand this, then it is possible to separate the layers with a continuous vapor barrier (use a completely vapor-tight layer) and stop the movement of steam in the structure, which will lead to a state of dynamic equilibrium of the layers with the environment in which they will be located.

The term "vapor permeability" itself indicates the property of materials to pass or retain water vapor in its thickness. The table of vapor permeability of materials is conditional, since the calculated values of the level of humidity and atmospheric action do not always correspond to reality. The dew point can be calculated according to the average value.

Each material has its own percentage of vapor permeability

Determining the level of steam permeability

In the arsenal of professional builders, there are special technical tools that allow you to diagnose the vapor permeability of a particular building material with high accuracy. To calculate the parameter, the following tools are used:

devices that make it possible to accurately determine the thickness of the layer of building material;
laboratory glassware for research;
scales with the most accurate readings.

In this video you will learn about vapor permeability:

With the help of such tools, it is possible to correctly determine the desired characteristic. Since the experimental data are recorded in the tables of the vapor permeability of building materials, it is not necessary to establish the vapor permeability of building materials during the preparation of a dwelling plan.

Creation of comfortable conditions

To create a favorable microclimate in a dwelling, it is necessary to take into account the characteristics of the building materials used. Particular emphasis should be placed on vapor permeability. With knowledge of this ability of the material, it is possible to correctly select the raw materials necessary for housing construction. Data is taken from building codes and regulations, for example:

vapor permeability of concrete: 0.03 mg/(m*h*Pa);
vapor permeability of fiberboard, chipboard: 0.12-0.24 mg / (m * h * Pa);
vapor permeability of plywood: 0.02 mg/(m*h*Pa);
ceramic brick: 0.14-0.17 mg / (m * h * Pa);
silicate brick: 0.11 mg / (m * h * Pa);
roofing material: 0-0.001 mg / (m * h * Pa).

Steam generation in a residential building can be caused by human and animal breathing, food preparation, temperature differences in the bathroom, and other factors. No exhaust ventilation also creates a high degree of humidity in the room. In winter, it is often possible to notice the occurrence of condensate on windows and on cold pipelines. This is a clear example of the appearance of steam in residential buildings.

Protection of materials in the construction of walls

Building materials with high permeability steam cannot fully guarantee the absence of condensation inside the walls. In order to prevent the accumulation of water in the depths of the walls, the pressure difference of one of the components of the mixture of gaseous elements of water vapor on both sides of the building material should be avoided.

Provide protection from the appearance of liquid actually, using oriented strand boards (OSB), insulating materials such as foam and vapor barrier film or a membrane that prevents steam from seeping into the thermal insulation. Simultaneously with the protective layer, it is required to organize the correct air gap for ventilation.

If the wall cake does not have sufficient capacity to absorb steam, it does not risk being destroyed as a result of the expansion of condensate from low temperatures. The main requirement is to prevent the accumulation of moisture inside the walls and provide its unhindered movement and weathering.

An important condition is the installation of a ventilation system with forced exhaust, which will not allow excess liquid and steam to accumulate in the room. By fulfilling the requirements, you can protect the walls from cracking and increase the durability of the home as a whole.

Location of thermal insulation layers

To ensure the best performance of the multi-layer structure of the structure, the following rule is used: the side with a higher temperature is provided with materials with increased resistance to steam infiltration with a high coefficient of thermal conductivity.

The outer layer must have high vapor conductivity. For the normal operation of the enclosing structure, it is necessary that the index of the outer layer is five times higher than the values of the inner layer. Subject to this rule, water vapor that has entered the warm layer of the wall will leave it without much effort through more cellular building materials. Neglecting these conditions, the inner layer of building materials becomes damp, and its thermal conductivity becomes higher.

The selection of finishes also plays an important role in the final stages of construction work. Properly selected composition of the material guarantees effective removal of liquid into the external environment, therefore, even at sub-zero temperatures, the material will not collapse.

The vapor permeability index is a key indicator when calculating the size of the cross section of the insulation layer. The reliability of the calculations made will depend on how high-quality the insulation of the entire building will turn out.

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:


Short name of the country according to MK (ISO 3166) 004-97	Country code by MK (ISO 3166) 004-97	Abbreviated name of the national standards body
Azerbaijan		Azstandard
		Ministry of Economy of the Republic of Armenia
Belarus		State Standard of the Republic of Belarus
Kazakhstan		State Standard of the Republic of Kazakhstan
Kyrgyzstan		Kyrgyzstandart
		Moldova-Standard
		Rosstandart
Tajikistan		Tajikstandart
Uzbekistan		Uzstandard

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

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


Parameter	Designation	unit of measurement
Cross-sectional area of the sample perpendicular to the direction of air flow
Air flow density		kg/(m h)
Air permeability coefficient		kg/[m h (Pa)]
Filter mode indicator
Breathability		[m h (Pa)]/kg
Pressure drop
Air consumption
Sample thickness
Air density

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:

- air flow meters (rotameters) with air flow measurement limit 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 differential pressure 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

The vapor permeability of materials table is a building code of domestic and, of course, international standards. In general, vapor permeability is a certain ability of fabric layers to actively pass water vapor due to different pressure results with a uniform atmospheric index on both sides of the element.

The considered ability to pass, as well as retain water vapor, is characterized by special values \u200b\u200bcalled the coefficient of resistance and vapor permeability.

At the moment, it is better to focus your own attention on the internationally established ISO standards. They determine the qualitative vapor permeability of dry and wet elements.

A large number of people are committed to the fact that breathing is a good sign. However, it is not. Breathable elements are those structures that allow both air and vapor to pass through. Expanded clay, foam concrete and trees have increased vapor permeability. In some cases, bricks also have these indicators.

If the wall is endowed with high vapor permeability, this does not mean that it becomes easy to breathe. A large amount of moisture is collected in the room, respectively, there is a low resistance to frost. Leaving through the walls, the vapors turn into ordinary water.

When calculating this indicator, most manufacturers do not take into account important factors, that is, they are cunning. According to them, each material is thoroughly dried. Damp ones increase thermal conductivity by five times, therefore, it will be quite cold in an apartment or other room.

The most terrible moment is the fall of night temperature regimes, leading to a shift in the dew point in wall openings and further freezing of condensate. Subsequently, the resulting frozen waters begin to actively destroy the surface.

Indicators

The vapor permeability of materials table indicates the existing indicators:

, which is an energy type of heat transfer from highly heated particles to less heated ones. Thus, an equilibrium in temperature regimes is carried out and appears. With a high apartment thermal conductivity, you can live as comfortably as possible;
Thermal capacity calculates the amount of supplied and stored heat. It must necessarily be brought to a real volume. This is how temperature change is considered;
Thermal absorption is an 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-fledged comfort in the 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

Moisture located in the atmosphere, at a low level of relative humidity, is actively transported through the existing pores in building components. They take on an appearance similar to individual water vapor molecules.

In those cases when the humidity begins to rise, the pores in the materials are filled with liquids, directing the working mechanisms for downloading into capillary suction. Vapor permeability begins to increase, lowering the resistance coefficients, with an increase in humidity in the building material.

For internal structures in already heated buildings, dry-type vapor permeability indicators are used. In places where heating is variable or temporary, wet types of building materials are used, intended for the outdoor version of structures.

Vapor permeability of materials, the table helps to effectively compare the various types of vapor permeability.

Equipment

In order to correctly determine the vapor permeability indicators, experts use specialized research equipment:

Glass cups or vessels for research;
Unique tools required for measuring thickness processes with a high level of accuracy;
Analytical balance with weighing error.