Vapor permeability - typical misconceptions. Vapor permeability of mineral wool Review of hygroscopicity of thermal insulation

First, let’s refute the misconception - it is not the fabric that “breathes,” but our body. More precisely, the surface of the skin. Man is one of those animals whose body strives to maintain a constant body temperature, regardless of conditions. external environment. One of the most important mechanisms of our thermoregulation is the sweat glands hidden in the skin. They are also part of the body's excretory system. The sweat they produce, evaporating from the surface of the skin, carries with it some of the excess heat. Therefore, when we are hot, we sweat to avoid overheating.

However, this mechanism has one serious drawback. Moisture, quickly evaporating from the surface of the skin, can cause hypothermia, which leads to colds. Of course, in Central Africa Where humans have evolved as a species, this situation is rather rare. But in regions with changeable and predominantly cool weather, a person constantly had and still has to supplement his natural thermoregulation mechanisms with various clothes.

The ability of clothing to “breathe” implies its minimal resistance to the removal of vapors from the surface of the skin and the “ability” to transport them to the front side of the material, where the moisture released by a person can evaporate without “stealing” the excess amount of heat. Thus, the “breathable” material from which the clothing is made helps the human body maintain optimal temperature body, avoiding overheating or hypothermia.

The “breathable” properties of modern fabrics are usually described in terms of two parameters - “vapor permeability” and “air permeability”. What is the difference between them and how does this affect their use in clothing for sports and active rest?

What is vapor permeability?

Vapor permeability is the ability of a material to transmit or retain water vapor. In the outdoor apparel and equipment industry important has a high ability of the material to water vapor transport. The higher it is, the better, because... This allows the user to avoid overheating and still remain dry.

All fabrics and insulation materials used today have a certain vapor permeability. However, in numerical terms it is presented only to describe the properties of membranes used in the production of clothing, and for a very small number not waterproof textile materials. Most often, vapor permeability is measured in g/m²/24 hours, i.e. the amount of water vapor that will pass through square meter material per day.

This parameter is indicated by the abbreviation MVTR (“moisture vapor transmission rate” or “speed of passage of water vapor”).

The higher the value, the greater the vapor permeability of the material.

How is vapor permeability measured?

MVTR numbers are obtained from laboratory tests based on various techniques. Due to the large number of variables affecting the operation of the membrane - individual metabolism, air pressure and humidity, area of ​​material suitable for moisture transport, wind speed, etc., there is no single standardized research method for determining vapor permeability. Therefore, in order to be able to compare samples of fabrics and membranes with each other, manufacturers of materials and finished clothing use a number of techniques. Each of them separately describes the vapor permeability of a fabric or membrane in a certain range of conditions. Today, the following test methods are most often used:

"Japanese" "upright cup" test (JIS L 1099 A-1)

The test sample is stretched and sealed on top of a cup, inside of which a strong desiccant - calcium chloride (CaCl2) - is placed. The cup is placed for a certain time in a thermohydrostat, in which the air temperature is maintained at 40°C and humidity at 90%.

Depending on how the weight of the desiccant changes during the control time, MVTR is determined. The technique is well suited for determining vapor permeability not waterproof fabrics, because the test sample is not in direct contact with water.

"Japanese" inverted cup test (JIS L 1099 B-1)

The test sample is stretched and hermetically fixed over a vessel with water. Afterwards it is turned over and placed over a cup with a dry desiccant - calcium chloride. After the control time, the desiccant is weighed, resulting in the calculation of MVTR.

Test B-1 is the most popular, as it demonstrates the highest numbers among all methods that determine the rate of passage of water vapor. Most often, it is its results that are published on labels. The most “breathable” membranes have an MVTR value according to the B1 test greater than or equal to 20,000 g/m²/24h according to test B1. Fabrics with values ​​of 10-15,000 can be classified as noticeably vapor permeable, at least under not very intense loads. Finally, for clothing that requires little movement, a vapor permeability of 5-10,000 g/m²/24h is often sufficient.

The JIS L 1099 B-1 test method fairly accurately illustrates the performance of the membrane in ideal conditions(when there is condensation on its surface and moisture is transported to a drier environment with a lower temperature).

Sweating plate test or RET (ISO - 11092)

Unlike tests that determine the rate of water vapor transport through a membrane, the RET technique examines how much the test sample resists passage of water vapor.

A sample of fabric or membrane is placed on top of a flat porous metal plate, under which a heating element is connected. Plate temperature is maintained at surface temperature human skin(about 35°C). Water evaporating from heating element, passes through the plate and the test sample. This leads to heat loss on the surface of the plate, the temperature of which must be maintained constant. Accordingly, the higher the level of energy consumption to maintain a constant plate temperature, the lower the resistance of the tested material to the passage of water vapor through it. This parameter is designated as RET (Resistance of Evaporation of a Textile - “material resistance to evaporation”). The lower the RET value, the higher the breathability of the membrane or other material being tested.

RET 0-6 - extremely breathable; RET 6-13 - highly breathable; RET 13-20 - breathable; RET over 20 - non-breathable.

Equipment for carrying out the ISO-11092 test. On the right is a chamber with a “sweating plate”. A computer is required to obtain and process results and control the test procedure © thermetrics.com

In the laboratory of the Hohenstein Institute, with which Gore-Tex collaborates, this technique is complemented by testing real clothing samples by people on a treadmill. In this case, the results of the sweat plate tests are adjusted according to the testers' comments.

Testing Gore-Tex clothing on the treadmill © goretex.com

The RET test clearly illustrates the performance of the membrane in real conditions, but is also the most expensive and time-consuming on the list. For this reason, not all active clothing manufacturing companies can afford it. At the same time, RET is today the main method for assessing the vapor permeability of membranes from the Gore-Tex company.

The RET technique generally correlates well with the results of the B-1 test. In other words, a membrane that shows good breathability in the RET test will show good breathability in the inverted cup test.

Unfortunately, none of the test methods can replace the others. Moreover, their results do not always correlate with each other. We saw that the process of determining the vapor permeability of materials in various methods has many differences, simulating different conditions work.

In addition, various membrane materials work according to different principles. For example, porous laminates ensure relatively free passage of water vapor through the microscopic pores present in their thickness, and non-porous membranes transport moisture to the front surface like a blotter - with the help of hydrophilic polymer chains in their structure. It is quite natural that one test can simulate the advantageous conditions for the operation of a non-porous membrane film, for example, when moisture is closely adjacent to its surface, and another - for a microporous one.

Taken together, all this means that there is practically no point in comparing materials with each other based on data obtained from different test methods. It also makes no sense to compare the vapor permeability of different membranes if the test method for at least one of them is unknown.

What is breathability?

Breathability- the ability of a material to pass air through itself under the influence of its pressure difference. When describing the properties of clothing, a synonym for this term is often used - “breathability”, i.e. how wind-resistant the material is.

In contrast to methods for assessing vapor permeability, relative uniformity reigns in this area. To assess air permeability, the so-called Fraser test is used, which determines how much air will pass through the material during a control time. The test air flow rate is typically 30 mph, but may vary.

The unit of measurement is the cubic foot of air passing through the material in one minute. Denoted by the abbreviation CFM (cubic feet per minute).

How more value- the higher the air permeability (“blowability”) of the material. Thus, poreless membranes demonstrate absolute “windproofness” - 0 CFM. Test methods are most often defined by ASTM D737 or ISO 9237 standards, which, however, give identical results.

Exact numbers CFMs are published relatively rarely by fabric and ready-to-wear manufacturers. Most often this parameter is used to characterize windproof properties in descriptions various materials, developed and used within the production of SoftShell clothing.

Recently, manufacturers have begun to “remember” air permeability much more often. The fact is that, along with the air flow, much more moisture evaporates from the surface of our skin, which reduces the risk of overheating and condensation accumulation under clothes. Thus, the Polartec Neoshell membrane has slightly greater air permeability than traditional porous membranes (0.5 CFM versus 0.1). Thanks to this, Polartec was able to achieve significant better work of its material in conditions of windy weather and rapid user movement. The higher the air pressure outside, the better Neoshell removes water vapor from the body due to greater air exchange. At the same time, the membrane continues to protect the user from wind cooling, blocking about 99% of the air flow. This turns out to be enough to withstand even stormy winds, and therefore Neoshell has even found its way into the production of single-layer assault tents ( shining example- BASK Neoshell and Big Agnes Shield tents 2).

But progress does not stand still. Today there are many offers of well-insulated mid-layers with partial breathability, which can also be used as an independent product. They use either fundamentally new insulation - like Polartec Alpha, or use synthetic volumetric insulation with a very low degree of fiber migration, which allows the use of less dense “breathable” fabrics. Thus, Sivera Gamayun jackets use ClimaShield Apex, Patagonia NanoAir uses insulation under the FullRange™ brand, which is produced by the Japanese company Toray under original name 3DeFX+. Identical insulation is used in Mountain Force ski jackets and trousers as part of the “12 way stretch” technology and Kjus ski clothing. The relatively high breathability of the fabrics in which these insulations are enclosed makes it possible to create an insulating layer of clothing that will not interfere with the removal of evaporated moisture from the surface of the skin, helping the user to avoid both getting wet and overheating.

SoftShell clothing. Subsequently, other manufacturers created an impressive number of their analogues, which led to the widespread use of thin, relatively durable, “breathable” nylon in clothing and equipment for sports and outdoor activities.

So I waited. I don’t know about you, but I’ve been wanting to experiment for a long time. Otherwise it’s all theory and theory. She didn't answer my questions. I mean thermal engineering calculation according to DBN. So I collected samples and decided to experiment with them. I'm interested in how the material will behave when exposed to steam.

Armed himself with whatever he could. Two steamers, pans with cold accumulators, a stopwatch and a pyrometer. Oh, yes... Another bucket of water for the fourth experiment with immersing samples. And off we went... :)

I summarized the results of the experiment on vapor permeability and inertia in a table.

In general, the experience went wrong. Despite the different thermal conductivity of the materials, the surface temperature of the samples in the first experiment with a vapor barrier layer was practically the same. I suspect that the steam from the steamer, which escaped, also heated the surface of the samples. As soon as I blew air on the samples, the temperature dropped by 1-2 degrees. Although, in principle, the dynamics of temperature growth remained the same. But I was more interested in this, because the very conditions of the experiment are far from real.

Which surprised me. This is Bethol. Second experiment without vapor barrier. This behavior of the insulation should not be considered a disadvantage. In my experience, Betol itself was a representative of vapor-permeable insulation. I think mineral wool insulation would behave the same way, but with faster dynamics.

Experience is very revealing. A sharp increase in temperature (large heat loss) due to vapor permeability and subsequent cooling of the material when water begins to evaporate from the surface. The insulation warmed up so much that it allowed it to release water in a vapor state and thus cool itself.

Gas block 420 kg/m3. He disappointed me. No! Not in terms of quality! He just clearly showed that he is selfish! 🙂 It’s better not to design with it multilayer walls. Due to its higher vapor permeability, it retained warm steam worse than a dense foam block. This suggests that if this material is used, the entire temperature and humidity shock will be taken vapor permeable insulation. In general, take a denser, thicker gas block, and interior walls glue materials with low vapor permeability ( vinyl wallpapers, plastic lining, oil painting etc)...

What do you think of high-density foam blocks (a representative of inertial materials)? Well, isn't this lovely? After all, he clearly showed us how inertial material behaves when heat accumulates. I would like to note that when I removed it from the steamer it was hot. Its temperature was clearly higher than Betol and Gas Block. During the same exposure time, he was able to accumulate more heat, which led to more high temperature material by 2-3 degrees.

Analyzing the table, I received many answers and was even more convinced that in our climate it is necessary to build inertial houses and you will definitely save on heating...

Sincerely, Alexander Terekhov.

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

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

Vapor permeability table indicates the following indicators:

1. Thermal conductivity is a kind of indicator of the energetic transfer of heat from more heated particles to less heated particles. Consequently, equilibrium is established in temperature conditions. If the apartment has high thermal conductivity, then this is the most comfortable conditions.
2. Thermal capacity. Using it, you can calculate the amount of heat supplied and heat contained in the room. It is imperative to bring it to a real volume. Thanks to this, temperature changes can be recorded.
3. Thermal absorption is the enclosing structural alignment during temperature fluctuations. In other words, thermal absorption is the degree to which wall surfaces absorb moisture.
4. Thermal stability is the ability to protect structures from sudden fluctuations in heat flow.

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

On the one hand, vapor permeability has a good effect on the microclimate, and on the other hand, it destroys the materials from which the house is built. In such cases, it is recommended to install a vapor barrier layer with outside Houses. After this, the insulation will not allow steam to pass through.

Vapor barriers are materials that are used from negative impact air vapor to protect the insulation.

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

Table of vapor permeability of materials.

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

Table of vapor permeability of materials.

Material	Vapor permeability coefficient, mg/(m*h*Pa)
Aluminum
Arbolit, 300 kg/m3
Arbolit, 600 kg/m3
Arbolit, 800 kg/m3
Asphalt concrete
Foamed synthetic rubber
Drywall
Granite, gneiss, basalt
Chipboard and fibreboard, 1000-800 kg/m3
Chipboard and fibreboard, 200 kg/m3
Chipboard and fibreboard, 400 kg/m3
Chipboard and fibreboard, 600 kg/m3
Oak along the grain
Oak across the grain
Reinforced concrete
Limestone, 1400 kg/m3
Limestone, 1600 kg/m3
Limestone, 1800 kg/m3
Limestone, 2000 kg/m3
Expanded clay (bulk, i.e. gravel), 200 kg/m3	0.26; 0.27 (SP)
Expanded clay (bulk, i.e. gravel), 250 kg/m3
Expanded clay (bulk, i.e. gravel), 300 kg/m3
Expanded clay (bulk, i.e. gravel), 350 kg/m3
Expanded clay (bulk, i.e. gravel), 400 kg/m3
Expanded clay (bulk, i.e. gravel), 450 kg/m3
Expanded clay (bulk, i.e. gravel), 500 kg/m3
Expanded clay (bulk, i.e. gravel), 600 kg/m3
Expanded clay (bulk, i.e. gravel), 800 kg/m3
Expanded clay concrete, density 1000 kg/m3
Expanded clay concrete, density 1800 kg/m3
Expanded clay concrete, density 500 kg/m3
Expanded clay concrete, density 800 kg/m3
Porcelain tiles
Clay brick, masonry
Hollow ceramic brick (1000 kg/m3 gross)
Hollow ceramic brick (1400 kg/m3 gross)
Brick, silicate, masonry
Large format ceramic block(warm ceramics)
Linoleum (PVC, i.e. unnatural)
Mineral wool, stone, 140-175 kg/m3
Mineral wool, stone, 180 kg/m3
Mineral wool, stone, 25-50 kg/m3
Mineral wool, stone, 40-60 kg/m3
Mineral wool, glass, 17-15 kg/m3
Mineral wool, glass, 20 kg/m3
Mineral wool, glass, 35-30 kg/m3
Mineral wool, glass, 60-45 kg/m3
Mineral wool, glass, 85-75 kg/m3
OSB (OSB-3, OSB-4)
Foam concrete and aerated concrete, density 1000 kg/m3
Foam concrete and aerated concrete, density 400 kg/m3
Foam concrete and aerated concrete, density 600 kg/m3
Foam concrete and aerated concrete, density 800 kg/m3
Expanded polystyrene (foam), plate, density from 10 to 38 kg/m3
Extruded polystyrene foam (EPS, XPS)	0.005 (SP); 0.013; 0.004
Expanded polystyrene, plate
Polyurethane foam, density 32 kg/m3
Polyurethane foam, density 40 kg/m3
Polyurethane foam, density 60 kg/m3
Polyurethane foam, density 80 kg/m3
Block foam glass	0 (rarely 0.02)
Bulk foam glass, density 200 kg/m3
Bulk foam glass, density 400 kg/m3
Glazed ceramic tiles
Clinker tiles	low; 0.018
Gypsum slabs (gypsum slabs), 1100 kg/m3
Gypsum slabs (gypsum slabs), 1350 kg/m3
Fiberboard and wood concrete slabs, 400 kg/m3
Fiberboard and wood concrete slabs, 500-450 kg/m3
Polyurea
Polyurethane mastic
Polyethylene
Lime-sand mortar with lime (or plaster)
Cement-sand-lime mortar (or plaster)
Cement-sand mortar (or plaster)
Ruberoid, glassine
Pine, spruce along the grain
Pine, spruce across the grain
Plywood
Cellulose ecowool

IN Lately Various external insulation systems are increasingly used in construction: “wet” type; ventilated facades; modified well masonry etc. What they all have in common is that they are multilayer enclosing structures. And for multilayer structures questions vapor permeability layers, moisture transfer, quantification falling condensate are issues of paramount importance.

As practice shows, unfortunately, both designers and architects do not pay due attention to these issues.

We have already noted that the Russian construction market is oversaturated with imported materials. Yes, of course, the laws of construction physics are the same and operate in the same way, for example, both in Russia and in Germany, but the approach methods and regulatory framework are very often very different.

Let us explain this using the example of vapor permeability. DIN 52615 introduces the concept of vapor permeability through the vapor permeability coefficient μ and air equivalent gap s d .

If we compare the vapor permeability of a layer of air 1 m thick with the vapor permeability of a layer of material of the same thickness, we obtain the vapor permeability coefficient

μ DIN (dimensionless) = air vapor permeability/material vapor permeability

Compare the concept of vapor permeability coefficient μ SNiP in Russia is introduced through SNiP II-3-79* "Construction Heat Engineering", has the dimension mg/(m*h*Pa) and characterizes the amount of water vapor in mg that passes through one meter of thickness of a particular material in one hour at a pressure difference of 1 Pa.

Each layer of material in the structure has its own final thickness d, m. Obviously, the amount of water vapor passing through this layer will be less, the greater its thickness. If you multiply μ DIN And d, then we get the so-called air equivalent gap or diffuse equivalent thickness of the air layer s d

s d = μ DIN * d[m]

Thus, according to DIN 52615, s d characterizes the thickness of the air layer [m], which has equal vapor permeability with a layer of a specific material thickness d[m] and vapor permeability coefficient μ DIN. Resistance to vapor permeation 1/Δ defined as

1/Δ= μ DIN * d / δ in[(m² * h * Pa) / mg],

Where δ in- coefficient of air vapor permeability.

SNiP II-3-79* "Construction Heat Engineering" determines vapor permeation resistance R P How

R P = δ / μ SNiP[(m² * h * Pa) / mg],

Where δ - layer thickness, m.

Compare, according to DIN and SNiP, vapor permeability resistance, respectively, 1/Δ And R P have the same dimension.

We have no doubt that our reader already understands that the issue of linking the quantitative indicators of the vapor permeability coefficient according to DIN and SNiP lies in determining the vapor permeability of air δ in.

According to DIN 52615, air vapor permeability is defined as

δ in =0.083 / (R 0 * T) * (p 0 / P) * (T / 273) 1.81,

Where R0- gas constant of water vapor equal to 462 N*m/(kg*K);

T- indoor temperature, K;

p 0- average indoor air pressure, hPa;

P- atmospheric pressure at in good condition, equal to 1013.25 hPa.

Without going deeply into the theory, we note that the quantity δ in depends to a small extent on temperature and can be considered with sufficient accuracy in practical calculations as a constant equal to 0.625 mg/(m*h*Pa).

Then, if the vapor permeability is known μ DIN easy to go to μ SNiP, i.e. μ SNiP = 0,625/ μ DIN

Above we have already noted the importance of the issue of vapor permeability for multilayer structures. No less important, from the point of view of building physics, is the issue of the sequence of layers, in particular, the position of the insulation.

If we consider the probability of temperature distribution t, pressure saturated steam Rn and unsaturated (real) vapor pressure Pp through the thickness of the enclosing structure, then from the point of view of the process of diffusion of water vapor, the most preferable sequence of layers is in which the resistance to heat transfer decreases, and the resistance to vapor permeation increases from the outside to the inside.

Violation of this condition, even without calculation, indicates the possibility of condensation in the section of the enclosing structure (Fig. A1).

Rice. P1

Note that the arrangement of layers of different materials does not affect the value of the overall thermal resistance, however, the diffusion of water vapor, the possibility and location of condensation predetermine the location of the insulation on the outer surface of the load-bearing wall.

Calculation of vapor permeability resistance and checking the possibility of condensation loss must be carried out according to SNiP II-3-79* “Construction Heat Engineering”.

Recently we have had to deal with the fact that our designers are provided with calculations performed using foreign computer methods. Let's express our point of view.

· Such calculations obviously have no legal force.

· Methods are designed for higher winter temperatures. Thus, the German “Bautherm” method no longer works at temperatures below -20 °C.

· Many important characteristics as initial conditions are not linked to ours regulatory framework. Thus, the thermal conductivity coefficient for insulation materials is given in a dry state, and according to SNiP II-3-79* “Building Heat Engineering” it should be taken under conditions of sorption humidity for operating zones A and B.

· The balance of moisture gain and loss is calculated for completely different climatic conditions.

It is obvious that the number of winter months from negative temperatures for Germany and, say, for Siberia are completely different.

1. Only insulation with the lowest thermal conductivity coefficient can minimize the extraction of internal space

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

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

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

3. At the junction of the wall and the ceiling, “cold bridges” can be removed if the insulation is partially applied to the floor slabs and then decorated with these junctions.

4. If you still believe in the “breathing of walls,” then please read THIS article. If not, then the obvious conclusion is: thermal insulation material should be pressed very tightly against the wall. It’s even better if the insulation becomes one with the wall. Those. there will be no gaps or cracks between the insulation and the wall. This way, moisture from the room will not be able to enter the dew point area. The wall will always remain dry. Seasonal temperature fluctuations without access to moisture will not have an impact negative influence on the walls, which will increase their durability.

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

Having the lowest thermal conductivity coefficient of all existing thermal insulation materials, polyurethane foam will occupy a minimum of internal space.

The ability of polyurethane foam to reliably adhere 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 cracks and microcavities. Foaming and polymerizing directly at the point of application, polyurethane foam becomes one with the wall, blocking access to destructive moisture.

VAPIROPER PERMEABILITY OF WALLS
Supporters of the false concept of “healthy breathing of walls”, in addition to sinning against the truth of physical laws and deliberately misleading designers, builders and consumers, based on a mercantile motive to sell their goods by any means, slander and slander thermal insulation materials with low vapor permeability (polyurethane foam) or The thermal insulation material is 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 moisture. In order to debunk this fiction, let's take a closer look at the physical processes that will occur in the case of cladding under a plaster layer or using inside a masonry, for example, a material such as foam glass, the vapor permeability of which is zero.

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

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

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