Dew point - formula, calculation and visualization. Dew point during construction and insulation of a house Dew point in simple words

Everything in human life is interconnected! And even the romance and beauty of nature become a way to designate the processes occurring in the narrow spheres of science. For example, dew point - what is it if not a physical phenomenon that can naturally be seen early in the morning at the end of spring or in summer.

Physical term

All physical phenomena that are studied in a school physics course surround us without breaks for lunch, sleep and holidays. All life is physics, one way or another already mastered by humanity and still completely unexplored. For example, many natural phenomena known by physicists have found their scientific embodiment in the practical activities of man. Here is the morning dew - the beauty of a summer morning. But from the same dew that falls in residential areas due to improper installed windows, broken hydro- and thermal insulation can lead to a huge number of problems. And certain parameters when moisture falls on surrounding surfaces were obtained beautiful name- Dew point. If we use the correct language of subject definitions, then this parameter is the temperature value of a gas cooled isobarically (at constant pressure), at which the water vapor contained in this gas becomes saturated.

Air humidity

In a competent definition of the concept of “dew point” there is another important physical term - isobaric cooling of air. Few, looking at the puddles on the windowsill formed from moisture accumulated on the glass, will remember the Gay-Lossac law - the relative change in the volume of a given mass of gas at constant pressure is proportional to the change in temperature. Although people hear about air humidity every day in the weather forecast. The amount of water vapor in the surrounding air taken in a volume of 1 cubic meter. m is called absolute humidity. But relative air humidity is an indicator of the ratio of the amount of water vapor in the air (calculated as a percentage) to the maximum possible at the existing temperature. And it is when considering this characteristic that the concept of “dew point” arises. What it is? This is the temperature at which water vapor becomes saturated and precipitates into water droplets at the existing pressure. If the weather forecast indicates high relative humidity, the dew point temperature will be close to the ambient air temperature.

Life, air, water

In everyday life, people rarely think about such a concept as dew point. Determining it is important only in some industries, in construction, medicine. But for everyone, a certain humidity of the surrounding air is important for good health. When the air has sufficient humidity, one can breathe easily and freely, but as soon as this indicator changes at constant pressure and temperature environment, then either dryness or excess moisture is felt. It is on the basis of the relative humidity of the air that the dew point can be determined. This phenomenon is a very complex and significant aspect of atmospheric physics. It is also important for human life. For example, builders know from experience that dew point is a significant parameter of high-quality construction, influencing the entire life of future residents or users.

Why is it necessary to determine the dew point in construction?

Dew point measurement is enough simple task, if you use certain formulas and rules. But why do people involved in construction need to know this natural parameter? Everything is very simple here - to understand the process of insulating a room, because the layer that serves as a barrier to cold and moisture can be located either with inside indoors and outdoors, or may be absent altogether. In addition, the thickness of the insulation also depends on the dew point. When calculating this parameter from the point of view of construction and insulation of buildings, the following parameters must be taken into account:

• material and material thickness of all wall components;
• room temperature;
• outside temperature;
• indoor air humidity;
• air humidity outside the room.

The closer the dew point is physically located to the inner surface of the wall, the longer period the wall will be damp for some time. This will happen when the air temperature drops both outside and indoors. Professional builders They know that in order to create an optimal indoor microclimate in areas with a significant annual temperature variation, the building must first be insulated from the outside, calculating the thickness of the insulating layer to correctly determine the physical location of the dew point in it.

The windows are "crying"

New technologies make life more comfortable. For example, plastic windows have made it possible to make buildings more protected from the vagaries of weather and external sounds, to retain heat more effectively, and to abandon the routine autumn-spring responsibility of caulking and uncaulking window frames. But this option works 100% only if the windows are installed in compliance with all parameters, including taking into account such factors as dew point temperature. Wooden frames windows, even if they are well caulked, have natural micropores that serve as a kind of ventilation ducts. Such frames are said to be “breathable”. But plastic windows are devoid of such required component to create a comfortable microclimate. That is why, when humidity and temperature are no longer in a certain balance, the windows begin to “cry” - moisture accumulates on the glass and plastic partitions, flowing down and forming puddles on the window sills. This negatively affects the condition of the premises - humidity increases, objects in it can become damp and moldy. When installing plastic windows You should always remember that the dew point depends on two factors - the surface temperature of the window and the air humidity in the room. A single-chamber window in a climate with low air temperatures will in any case “cry” if such a window is located in a heated residential room. Therefore, it is recommended in this case to install not even two, but three-chamber windows. Then the inner glass will have a high enough temperature compared to the outer glass to remain dry. It is also necessary to normalize the air humidity in the apartment by establishing high-quality ventilation. If the apartment is dry and the windows are installed correctly, then the dew point will not manifest itself in any way and the glass surface will remain dry.

Dew point and metal destruction

Technical developments have made it possible not to calculate the dew point using formulas, but to use a special device that automatically determines this parameter for moisture and hydrocarbons - this is the so-called dew point analyzer. It is used by specialists during certain types of work, for example when applying protective coating on devices and systems made of materials susceptible to corrosion due to high humidity. After all, if the surface is not dry enough before applying the coating, then the applied protection will not work, since sufficient adhesion, that is, adhesion between the materials, will not appear. The painted surface will become covered with blisters and cracks, and the base material will continue to deteriorate even under protection. It is for high-quality anti-corrosion protection that it is necessary to know the dew point, calculating it using formulas and analyzer devices.

Well-being and dew point

Dew point temperature is an important natural parameter that people almost never think about in Everyday life. But this factor has the most direct impact on well-being; it is here that relative air humidity, which is mentioned in weather forecasts, plays a role. Thus, scientists and doctors have noticed that a high dew point is felt as discomfort, and if the air temperature is high and the dew point approaches it close enough, then a person suffers from humid stuffiness.

World weather observations

Calculation of dew point is an important parameter for many types of technical work, for human health. It is part of physical natural phenomena and can relate to a science such as meteorology - weather observations. This field of study of nature originated a long time ago, but as a scientific field it was organized in the 17th century, when the thermometer was invented by Galileo Galilei and the barometer by Otto von Guericke. Measurements of temperature, air humidity, and atmospheric pressure made it possible to draw a conclusion about such a parameter as the dew point. When it was first recorded and began to be used in different areas human life is not known exactly, but observations and recording of this physical phenomenon are carried out constantly at all points globe. The highest dew point temperature was recorded in the Iranian town of Jask on July 20, 2012 and amounted to 35 0 C. Now you can understand why with an increase in air humidity and ambient temperature it becomes difficult to breathe - a parameter such as the dew point plays a role in this. What it is? Factor between air humidity and temperature at which moisture condenses.

Basic formula

The dew point itself, as a natural phenomenon, is calculated in several ways. The simplest one is represented by the formula in the figure below.

In it, T r is the dew point, RH is relative humidity, T is temperature, digital values 243.12 and 17.62 are constant.

This formula gives an error of 1 0 C, and if it is taken into account, the parameter will be calculated quite correctly.

Table for determining dew point

Calculating the dew point is a rather complex algorithm that requires not only knowledge of certain physical parameters, but also the ability to use certain mathematical formulas. The complex and rather lengthy calculation process can be eliminated if you use tabular values. Such tables indicate the relative air humidity and ambient temperature. The intersection of these parameters in the table grid gives the dew point temperature value.

Insulating a house - outside or inside?

The formula for calculating dew point is of little use to anyone in everyday life. But in some industries and areas of human activity it is impossible to do without it. The dew point, the definition of which was discussed above, is an important parameter for high-quality construction and arrangement of premises for any purpose. Whatever the building, it must be dry, which means that the dew point in the wall must either be eliminated completely or reduced to the maximum distance from the inner surface. For example, the construction and insulation of buildings will necessarily require such calculations. Today you can find many tabular indicators with already calculated values. But many use formulas to confirm the specified data and maximize precise definition dew points for high-quality thermal and waterproofing of premises under specific conditions. In this case, it is necessary to take into account the parameters of wall materials, insulation, and vapor barriers. Experienced builders they say that the dew point is not a stationary indicator, it constantly moves with changes in external factors. But it is necessary to insulate buildings located in areas with a wide temperature difference in the indoor-outdoor ratio from outside the premises, that is, from the street. Then the dew point will be located in the insulation, the moisture will evaporate outside and not inside, and the room will remain dry.

Measuring Tools

The concept of dew point is widely used at gas measuring stations, at automobile gas-filling compressor stations, at underground natural gas storage and drying stations, for calibrating hygrometers and wet gas generators. Dew point - important characteristic for high-quality operation both for residential and industrial premises, and for gas pipelines and gas storage systems. A device for measuring dew point allows you to abandon complex calculations using formulas and calculate this parameter by independently measuring environmental factors - temperature, humidity and pressure. The very first device developed was a psychrometric hygrometer, also called a psychrometer. Currently this is a laboratory device not used in practice. The development of electronic computing analyzers did not miss such a physical parameter as the ratio of humidity and ambient air temperature, and therefore the calculation of the dew point. Such devices are easy to operate, although some models, including those with the properties of a thermal imager, require processing of the received information using special computer programs. A dew point analyzer is a significant device in construction, as well as in the maintenance of gas pipelines and gas distribution stations, significantly simplifying human activities.

The importance of dew point for human activity

Comfort is warmth and coziness, impossible without a certain balance of temperature and air humidity, which in many cases is provided using a heating system operating on natural gas. This is where you can see how important the dew point is physical characteristics, because the appearance of dampness, violation of waterproofing, destruction of materials, and deterioration of their quality depend on it.

Natural gas is important for both domestic and industrial needs of humans. And the gas dew point plays important role in its transportation and storage. A correctly calculated gas dew point allows you to prevent the occurrence of dangerous situations during transportation and storage of blue fuel, and the same parameter, taken into account during the construction of the building, will avoid the appearance of mold, which is dangerous to the health and even life of people.

An important physical parameter of practical importance is the dew point. What is this in human life? This is the temperature factor on which many areas of human life and activity depend: from well-being to the high-quality operation of buildings, machines and mechanisms.

When describing the work of installing thermal insulation of buildings, unknown phrases are encountered. For example, you should know what “dew point” means. This is easy to explain using an everyday example.

The higher the relative humidity, the higher the dew point and the closer to the actual air temperature

Air is a mixture of nitrogen, oxygen, other gases and steam. The temperature at which steam condenses occurs has acquired the concept of dew point. This phenomenon occurs when a kettle boils and the vapor forms water droplets on cold surfaces.

Formula for calculation

This formula can be used to calculate relative humidity from a known dew point

Here Tr means the temperature of the point itself, b and a show equal (constant) values, ln - natural logarithm, T - indoor temperature, Rh - relative humidity value.

As can be seen from the formula, the value directly depends on the values ​​of two parameters:

• humidity indicator;
• actual temperature readings.

At high relative humidity, the parameter becomes higher and closer to the actual temperature level. To calculate this variable value, there is a table with a small step of parameters. From it you can find the required value by measuring the relative humidity and actual temperature.

​From the table we calculate that at a temperature of, for example, 19 degrees and a humidity of 50%, the condensation parameter will be 8.3 degrees.

From this video it becomes clear how thick the insulation should be for the most comfortable conditions:

The term "dew point" in construction

The constantly growing and developing construction products market represents wide choose materials for thermal insulation. The choice of thermal insulation for industrial and residential premises must be approached properly and during construction, pay attention to the indicator in question.

Experts consider the boundary of transition from low temperatures outside the walls to higher temperatures inside heated structures with the possible formation of condensation to be the dew point. Drops of water will appear on any surface in the room whose temperature is close to the dew point parameter or reaches a value lower. The simplest example: in the middle of some rooms in cold weather window glass condensation drains.

The main factors influencing the determination of the value are:

• climatic factors (temperature and air humidity outside);
• temperature values ​​inside;
• indoor humidity indicator;
• wall thickness;
• vapor permeability of thermal insulation used in construction;
• availability of heating and ventilation systems;
• purpose of structures.

Only if the indicator is measured correctly can the building be used comfortably in the future and will reduce maintenance costs in the future.

Precise definition

Water vapor most often condenses on the walls themselves or inside their structure if they are not insulated or built properly. Without insulation, the value will be close to the temperature of the inside of the wall, and in some cases, the wall in the middle of the house. When the temperature inside the enclosing structures is below this value, condensation will occur during a cold snap at negative temperatures outside.

There are several places where the indicator may be located on non-insulated structures:

• inside the structure, close to its outer part, the wall will remain dry;
• inside the wall, but close to the inside, the wall becomes wet with temperature changes;
• the side of the wall that is located in the building will constantly be covered with condensation.

Experts do not recommend insulating rooms from the inside, explaining that when using this method of thermal insulation, the parameter will be located under the heat-insulating layer in the middle of the room . As a result, a large accumulation of moisture will occur.

• condensation can accumulate in the center of the wall and, during cold weather, move towards the placement of heat-insulating components;
• the place where moisture accumulates can be the boundary of the enclosing structure and the insulating layer, which becomes damp and forms mold in the middle of the rooms;
• in the middle of the heat-insulating layer itself (it will gradually become saturated with moisture and begin to mold and rot from the inside).

Polystyrene foam, mineral wool or other type of insulation must be placed with outside building, which will allow you to place the value in the insulating layer (with this arrangement, the walls inside will remain dry). For a clearer understanding of the parameter, there are graphs for its placement on the walls of houses with insulation, as well as on buildings that do not have an insulating layer. To make this calculation yourself, you can determine the dew point in the wall with a calculator.

Wrong definition of value

The result of errors made during the calculation of parameters will be a constant accumulation of condensation, increased humidity, and the development of fungal deposits and mold. Industrial, administrative or residential premises will not last long: negative processes will accelerate destruction. Additional costs will be required for routine maintenance and major repairs.

Construction technologies require taking into account many nuances that affect the durability of the structure and its ability to resist damage. negative influence external factors. One of the main enemies of most buildings and structures is constant high humidity. A variety of techniques are used to combat it.

It is necessary to take into account all factors at the initial design stage, when it is possible to influence the use of materials and the formation of the exterior of buildings. Important place In such a situation, it is necessary to make competent calculations when insulating buildings. A mandatory attribute in them is the determination of dew point temperature.

Basic knowledge

Large construction projects use complex and cumbersome calculation programs. Many coefficients are used and mathematical formulas. In domestic conditions, the technique is significantly simplified. Many roundings and approximations are used in the calculation, while the error is minimal.

Homeowners or builders will be able to independently calculate the dew point in the wall without involving third-party specialists.

To understand how to find a point, you need knowledge about the surrounding air and the presence of water vapor in it. It is formed as a result of many events, for example, particles of water are separated from residents, any sources of liquid, containers with water, appear after wet cleaning premises, etc.

Air capacity has a certain maximum. When this parameter is obtained, water particles begin to interact with each other, forming larger water droplets. This is how condensation occurs. In nature, it is noticeable in the form of fog or droplets on plants.

When the air is saturated with liquid as much as possible and can no longer receive recharge from it without turning into condensation, it is said that in this case the relative humidity has reached the level of 100%. Subsequent saturations turn the air into fog, which is a large number of suspended water droplets in the air.

The peculiarity of this event is that different air temperatures can provide different degrees of saturation with moisture before turning into condensation. There is a direct dependence on high temperature and the amount of dissolved liquid in the air. Moreover, when air with a moisture content of 70-80% comes into contact with a cooled object, the saturation limit occurs, and the degree of humidity in the contact plane instantly reaches 100%.

What causes condensation to form

Events lead to condensation. This interaction largely explains what a dew point is. Considering this example, it is obvious that this parameter in construction or in another field is a variable value. It is expressed in degrees. The main parameters that affect it:

• current relative humidity;
• current air temperature;
• air speed;
• thickness of materials.

To obtain calculated values, use measuring instruments: psychrometers and thermometers. A special table helps calculate the location of the desired value in the wall. Values ​​for development can not only be measured, but also learned from the current weather forecast. Many websites provide information not only about temperature, but also about humidity.

VIDEO: Why condensation appears on the walls

The role of the concept in the construction process

We recommend using a special table prepared by specialists to determine the location of the dew point in the wall. It is preferable to use your own definition of the parameter, without resorting to the help of a set online calculators. Often, the built-in algorithms in them do not take into account important factors.

The table below uses the step principle. For values ​​intermediate between two adjacent ones, the arithmetic mean can be used.

The table is easy to use. We draw a horizontal line from the measured room temperature. We draw a vertical line from the measured humidity value. At the intersection we obtain the required temperature number. Visually it will look like this.

Let's look at an example. Let's imagine a house whose walls are made of brick. Inside the room, for example, the temperature will be +20°C, and outside it will be cooler, for example -10°C. The air humidity in the room is 60%. By connecting the horizontal and vertical lines in the table (20 and 60), we get 12°C at the intersection.

Each brick will have a non-uniform temperature. Its inner surface will have the maximum high value(+20°C), and the outer part will be with the lowest possible parameter (-10°C). In the middle of the brick there will be a plane with a temperature of +12°C. Moisture will begin to condense in this area. The process will also occur throughout the entire volume with lower values.

Turn the situation around positive side The use of various insulation materials helps. They help shift the position of the dew point in the wall. Depending on which side the home owners installed the insulation, the condensation plane will move. If everything is done correctly, then this point will not be in the wall of the house, but in the insulating fence. This way there will be no structural damage.

It must be taken into account that without insulation, the plane with the dew point in our climate will be located directly in the depths of the wall. This is shown in the first picture, so moisture will cause damage to the structure, ensuring the spread of fungus and mold in the room. The dew point in the wall will be located at a depth that depends on the vapor permeability of the specific building material.

It is necessary that water vapor penetrates to a place with a design temperature. This factor is taken into account when choosing a material.

Requirements for insulation and thermal insulation

Vapor permeability is usually called a value that demonstrates how much water vapor is capable of passing through. construction material for the allotted time. Almost all popular materials are permeable by this criterion:

• tree;
• concrete;
• brick, etc.

From some builders you can hear such a concept as “walls breathe.” Porous materials may also be included in the list (expanded clay, mineral wool, etc.).

There is no need to be afraid that there is some kind of stationary part with a dew point in the wall, since this happens in a certain area. Builders call the area a possible condensation zone. Considering that most fences are “breathable,” a lot of moisture escapes outside.

The correct construction of a building is such an arrangement of materials in which the determination of the dew point in the wall falls into the outer insulation layer. It is also important to provide the room with high-quality ventilation, in which excess moisture leaves the apartment or house. Under such conditions, the material does not have time to become saturated with liquid.

The various polymer insulation materials offered by manufacturers, due to their design, practically do not allow steam to pass through. Due to this property, they are recommended to be placed outside the walls. In this case, the dew point at which condensation occurs will move inside the foam or polystyrene. However, water vapor will not be able to get to this zone. No moisture will form.

It is not recommended to use extruded foam sterol for façade insulation. It is used only for foundations or closed building systems. As a result of constant temperature changes and exposure to direct sun rays after only a year and a half it begins to crumble.

The same will happen in the reverse process. You should not insulate internal walls with polymers, because the dew point will be located in the wall. In this case, unwanted moisture will seep into the joint of materials.

It is reasonable to use internal insulation in the following cases:

• the wall is almost always warm and dry;
• the residential building has high-quality ventilation;
• It is necessary to use high-quality permeable insulation that ensures the removal of excess moisture.

Conclusion

It is quite difficult to identify a specific place with a dew point, since this zone is floating and depends on external factors. It is advisable to use external insulation to move the point into the insulation material. Use good ventilation in the room to remove water vapor.

VIDEO: Proper insulation or How to remove dew point from a wall

Determining the dew point is an indispensable condition for correct dew point. It is from this stage that the selection of insulating materials, strategy and technology for work begins. Accurate calculations, which are based on determining the dew point in construction, will avoid the occurrence of condensation during operation of the house.

The dew point is the temperature to which air must cool in order to condense into steam and then into dew. In the cold season, the partial pressure increases, warm air, under the influence of the pressure difference, rushes into a colder zone, simultaneously turning into steam, and then into dew.

The dew point value is directly related to the concentration of water vapor in the air. The higher it is, the higher the dew point temperature.

For your information! In a residential area, the normal humidity level is considered to be between 40-60%.

Special thermotechnical tables help determine the dew point. To measure correctly, you only need to determine the temperature.

Typically, the average dew point is between 6ºC and 12ºC. Consequently, all surfaces, including walls, having a temperature equal to or below the dew point temperature will form condensation.

A simple example of how condensation manifests itself - dew drops on windows

What determines the occurrence of the dew point

Dew point is a physical phenomenon that exists in any room. It is important to learn how to manage it correctly: avoid temperature changes, drafts, and excessive room humidity.

Parameters influencing dew point indicators:

• quality of house insulation, including interpanel seams;
• adequate and timely work to reduce humidity in the room, in case of excess;
• technology that was used, in particular the choice correct thickness heat-insulating materials.

Situations that may arise:

Insufficient insulation of the house, in particular, thin thermal insulation. In this case, the dew point can influence the occurrence of condensation, both inside the heat insulator and on the inner surface of the wall.

If there is no insulation near the wall, then the location of the dew point may be as follows:

• shifted closer to the outer surface of the wall - the structure is dry;
• on interior wall– the structure is wet in frosty weather;
• approximately average location in the plane of the wall - the internal structure is dry, but with a sharp temperature change it can get wet.

To make the process more clear, watch this video:

How to properly insulate a house: inside or outside

If you rely on the “golden” rule of construction, the insulation of the house should be on the outside. When designing external structure layers should be arranged with a decrease in their vapor barrier and an increase in thermal insulation ability in the direction from the inside to the outside.

Related article:

: price, advantages of use, selection criteria, types of material, calculation of required quantities, nuances correct installation with your own hands - read our article.

How to bring the dew point out

At proper thermal insulation The dew point will be located closer to the outer layer of insulation. Moreover, the thicker the layer of thermal insulation, the further the dew point will be from the load-bearing wall.

Important! Before making a decision regarding the thermal insulation option for your home, look at how the building behaves in winter period.

What you need to pay attention to first of all:

• if in winter the wall of the house is consistently dry, you can insulate it from the inside;
• the wall is usually dry, but with sudden temperature changes it can become damp - it is advisable not to take risks and not do internal insulation;
• if the wall is constantly wet, insulation should be done only with outside, from the inside - it’s impossible.

Conditions to consider

In addition, the choice of insulation option depends on the characteristics of the structure itself and its functions.

Please review the following important points:

• how the building works, whether it exists at all;
• the building is used throughout the year or seasonally;
• number of residents;
• quality of work ;
• how well the building insulation work was carried out;
• wall material and thickness;
• room microclimate: temperature regime, humidity;
• climate and location of the house.

Only after carefully studying the “input data” is a decision made on the method and technology of insulating the house and working with the dew point.

Which thermal insulation material should you prefer?

Knowing the location of the dew point in the wall allows you to better understand and imagine the physical processes associated with heat loss through the plane of the wall and choose the right thermal insulation material, having determined the methods of its installation.

If you look from the point of view of the budget component, you can opt for insulating materials based on mineral wool. They are characterized by vapor permeability and, when the dew point is in their mass, do not interfere with the movement of steam and its release out into the atmosphere.

Thermal insulation materials made of basalt and fiberglass are resistant to moisture, are not affected by mold and can withstand repeated cycles of thawing and freezing. So the position of the dew point in the thermal insulation layer will not harm it.

In this case, it is important to remember that moisture accumulates on its inner surface. To remove moisture, you need to use special guide grooves.

Dire consequences

How to understand that everything is bad? Sometimes you have to deal with errors that occur when you don't follow construction technologies. What signs may indicate that problems have arisen:

• the house smells damp, traces of fungus and mold appear on the walls;
• peels off in places;
• the integrity of building structures is compromised.

Dew point calculation

In practice, measuring dew point is not difficult. The main thing is to acquire the necessary tools.

You will need to stock up:

• tape measure;
• an ordinary thermometer;
• non-contact thermometer - pyrometer;

Advice! In order to save on purchasing devices, you can rent them.

Sequence of work:

• A mark is placed on the wall approximately at a height of 60 cm from the floor;
• using a thermometer, temperature and humidity are measured;
• the resulting indicator is located in the above table;
• the temperature of the wall surface is measured with a pyrometer;
• two indicators are compared;
• the result is determined: if the surface temperature differs from the dew point by more than 4ºС, it means that there is high humidity in the room. Therefore, insulation must be carried out under the supervision of a specialist.

Determination of dew point – the most important moment in the construction of a house, as well as during its proper insulation. If you do not track all of the above indicators, you can end up with a lot of problems, both with home maintenance and with the health of your loved ones.

I built the walls, put a roof on the house and installed windows - the box is ready. It is at this stage that the “constructive” period of construction ends and the installation of equipment, insulation of the walls of the house and its further preparation for final finishing begin.

And it is at this stage that it is important to correctly install the insulation, and indeed the entire insulation pie, on the walls of the house, so that in the future you do not get such a headache as the dew point in the wall from the side of the living room.

What kind of beast is the dew point and why is the dew point in the wall bad, what does it look like in practice?

First, a little theory, and then practically examples from my own experience, which I received when purchasing a box at home with an already installed layer of insulation.

Dew point temperature

The dew point tends to move. This moment depends on two indicators - temperature and humidity.

Each of them is also divided in half - into indoor and outdoor temperatures, indoor and outdoor humidity.

All calculations and formulas that are used to calculate the dew point assume that moisture will condense from the steam as it moves from the inside to the outside. This is exactly the situation observed in winter, when the temperature and humidity indoors are higher than the temperature and humidity outside. The dew point temperature will be calculated based on the design values ​​for outdoor and indoor conditions.

In summer, when the humidity and temperature outside are usually higher than the humidity and temperature indoors, the dew point is not as important. Why? Because the temperature difference is low and both temperature indicators, street and house, are in positive values.

And also because even if a dew point in the wall could form at positive values ​​of both temperatures, this would not have a strong impact on the comfort of living in the house.

It's a different matter in winter. At low temperatures, moisture condensed from steam enters the insulation and wall and freezes there. For insulation, getting wet is fraught with either complete loss of thermal insulation properties ( basalt wool), or destruction when water freezes (foam plastic). For the wall everything is the same, especially for aerated concrete and gas silicate blocks.

I personally observed the sad picture of the destruction of the wall of a block house in winter due to improperly done insulation. By spring, there were almost through holes in the 400 mm thick gas silicate wall.

How to calculate dew point

To calculate the dew point, a table of water vapor condensation values ​​is used depending on humidity and temperature. The value of external and internal temperature and the value of external and internal humidity are taken. The dew point temperature at which water will drop out of water vapor (dew formation) is obtained.

What does this temperature give us? A lot of things. We are able to calculate where the steam will condense in the insulation cake, that is, where the dew point will be in the wall - in the insulation, in the load-bearing wall or on the inner surface of the load-bearing wall - right in the room.

Naturally, the most correct option- this is the dew point in the insulation. In this case there will be no negative aspects for interior spaces. To avoid any negative aspects for the insulation, it is worth choosing the right type of insulation for the walls at the planning stage.

A less acceptable option is the dew point in the wall of the house, which is load-bearing. Here, the negative aspects for the interior will depend on the wall material. This situation occurs when the insulation is installed incorrectly or the thickness of the insulation is incorrectly selected.

The most unacceptable option is the dew point inside the room, on the inner surface of the load-bearing wall. This usually happens when the house is not insulated at all or is insulated incorrectly - from the inside.

Dew point in the house - what to do?

So, the promised example is from my own experience. I purchased a box brick house, which was insulated from the inside with foam plastic. What the people who built this box were thinking about is anyone's guess. Thanks to this insulation, a dew point was obtained in the house, on the inner surface load-bearing walls, between brick and insulation.

What was the dew point in the house, in what negative aspects?

There were two of them. Firstly, the brick wall from the inside was always damp in small pluses and subzero temperatures. There was a musty smell in the rooms; when opened, there were large pockets of mold under all the foam.

Secondly, in sub-zero temperatures it was impossible to properly heat this house, brickwork was excluded from the thermal circuit of the house, due to the fact that it was cut off from warm air rooms with foam plastic.

What did I do to beat the dew point in the house?

Firstly, all the foam was dismantled from internal surfaces load-bearing walls.

Secondly, the insulation was installed externally and was plastered using the wet facade method.

And thirdly, instead of the previous internal insulation 50 millimeters, external insulation was installed at 150 millimeters.

With proper insulation, the dew point is outside, and the house is warm and dry.

What happened? It became warm, dry and comfortable.

FINAL NOTE. Do not do it air gap between load-bearing wall and the air of the room. Often walls are sheathed from the inside with gypsum boards - it’s cheaper and faster than plastering. However, in air gap micro-drafts form between the gypsum plasterboard and the brick, which prevent heat transfer and heating of the inside of the brickwork.

I'm mine brick walls plastered the inside with the most ordinary plaster mixture. The top can now be painted or wallpapered. The thickness of the wallpaper is such that it can be neglected as a heat insulator.