Dew point in the wall - calculation and finding

Determine the dew point in the wall is very simple. Below will be an example how to make a calculation. It can do anyone who is interested in the issue of proper insulation.

The dew point is the temperature at which water vapor begins to condense.

What is a dew point

The dew point in the wall can move in its thickness when the temperature changes inside the room and outside. For example, if there is a stable temperature indoors, and it's cold on the street, the dew point will move around the wall thickness closer to the room.

The temperature of the subject on which steam will be condensed, i.e. The dew point depends mainly from two parameters:

  • air temperature;
  • Air humidity.

For example, at an indoor temperature of +20 degrees and humidity 50%, the temperature of the dew point will (approximately) +12.9 degrees. If an item with such a temperature appears in the room or below, condensate is formed on it.

For example, when the refrigerator opens, the dew from the incoming warm air drops inside it. It looks like "Fog running out of the refrigerator."

If the street is cold, then somewhere in the wall there will be a temperature at which steam condensation will begin, and at this point will be moisturizing. If the wall is thin, "cold", and its inner surface will coolest up to 12.9 degrees or less (with the indicated values ​​of temperature and humidity of the air), then the dew will fall on it, it will become wet, and very quickly acquires mold.

When insulation of walls, house designs, it is useful to make the calculation of the dew point for the largest and smallest values ​​of humidity and temperature in order to know what borders of the space will move the dew point when these parameters change.

How the calculation is performed

In the calculations of the dew point and insulation thickness, some parameters are not taken into account - pressure, air movement speed, material density ... Therefore, it is possible to speak only about approximate values. But it is not critical when it comes to determining the thickness of the insulation.

To determine the dew point in the wall, the easiest way to use the tables of ready-made exemplary values, and do not try to deal with the calculations. Moreover, you should not trust homemade programs from the Internet, they often do not take into account the parameters and give false values, and sometimes - and on the principle of random numbers.

Dew appears everywhere with sufficient coolingBelow is the table of the calculated dew point values ​​depending on the air temperature and its humidity. These are exemplary values, since the influence of other factors is not taken into account.

Table of dew point definition. Calculation

For example, it can be determined that for room with a temperature inside +22 degrees, and a humidity of 60%, the temperature at which water steam (dew point) will be condensed with 13.9 degrees.

Wall with insulation - how to determine the place of condensation

Solve the task of finding a point of dew in the wall is very simple. It's easy to know:

  • coefficient of thermal resistance of the wall ,? 1, W / (M • K);
  • thermal resistance coefficient of insulation ,? 2, W / (M • K);
  • Wall thickness, H1, m;
  • the thickness of the insulation, H2, m;
  • temperature indoor, T1, hail. WITH;
  • air humidity that will reach the dew point,%;
  • Dew point for temperature and humidity data, hail. WITH;
  • Temperature outside, t2, hail. WITH.

In the rough approximation, it is assumed that the thickness of each layer will change linearly.

The desired value is the temperature on the boundary of the walls of the wall and insulation. When it is found, you can construct a chart of temperature change in the "Wall-insulation" layer and to find the position of the dew point.

To do this, there is the ratio of thermal resistance of the wall to the thermal resistance of the insulation, based on which the temperature change is determined in one of the layers, which will give the opportunity to find out the temperature at the border.

Consider on the example.

Example of calculation

An example of conditions The following. Zeles-concrete wall H1 = 36 cm, is insulated with foam h2 = 10 cm. The coefficient of thermal resistance of the reinforced concrete? 1 = 1.7 W / SMK, foam -? 2 = 0.04 W / SMK. Temperature inside T1 = + 20 degrees, outside T2 = 10 degrees. Humidity indoors and outside is accepted the same - 50%. According to the table, the dew point will be 9.3 degrees.

Example. Calculation of the dew point in the wallThermal resistances of the wall and insulation are defined as H /?, W / M2K. In this example, the thermal resistance of the wall will be 0.36 / 1.7 = 0.21 W / m2k., Insulation 0.1 / 0.04 = 2.5 W / m2k.

The ratio of thermal resistance of the first layer to the second (walls to the foam) will be: n = 0.21 / 2.5 = 0.084.Then the temperature drop in the first layer (wall) will be, T = T1- T2HN = 20 - (- 10) x0 , 084 = 2.52 degrees.

Accordingly, the temperature on the boundary of the layer will be t1-T = 20-2.52 = 17.48 degrees.

Now we can build an approximate flow of temperature drops in the wall layer - insulation and note the dew point on it.

From exemplary calculations and approximate graphics, you can find out the main thing - the dew point is in the insulation, far from the wall, i.e. Even deterioration of the conditions, taking into account the error of the calculations, will not entail the female moistening of the wall.

An example of determining the location of the temperature of condensation inside the wall

The temperature inside is +22 degrees, outside - 15 degrees (region north), humidity - 50%, dew point - 11.1 degrees. A wall thickness 38 cm made of bricks (1.5 bricks + seam + plaster is accepted by everything as "brickwork").

The thermal resistance coefficient for brickwork is 0.7 W / SMK, for mineral wool - 0.05 W / SMC (taking into account its moisturizing in real operating conditions). Position point of dew under normal conditionsThermal resistance of the wall: 0.38 / 0.7 = 0.54 W / m2k., Insulation 0.1 / 0.05 = 2.0 W / m2k. The heat of thermal resists of the first layer to the second will be: n = 0.54 / 2.0 = 0.27, and the temperature difference within the first layer will be t = 22 - (-15) x0.27 = 9.99 degrees. Temperature on the border of the layers: 22- 9.99 = 12 degrees.

As you can see, the situation is "right." With the increase in humidity, that the usual phenomenon, with a drop in the temperature indoors, or in a cold winter, the dew point will "walk" inside the wall.

Such insulation for a relatively "warm" brick wall will already be considered insufficient, and on the position of the dew point and on the regulatory values ​​of the heat loss, through the enclosing structures.

The dew point can be shifted and the heating of the room with the help of internal heating and its drainage. Naturally, this is an extreme measure that is used only when it came to "dry the walls". Dew point in the wall - calculation and finding

What values ​​need to be taken to calculate

Usually, the indoor temperature is taken 22 degrees, more often on the floor it is lower, and under the ceiling reaches 27 degrees. For the central regions, it is considered the minimum temperature outside the premises -15 degrees, (short-term decreases of temperature up to -20 - -25 degrees are allowed).

For the southern regions - -7 degrees, with a short-term decrease of -15 - -20 degrees. (The minimum temperature can be chosen on your own, - What temperature keeps in winter all the time? To what values ​​does it go short-time?)

The air humidity in the room is usually accepted average (but not small) - 50%,. There is usually some stock here, as often in winter air in land, due to actively working heating, - 30 - 40%. But in many homes are struggling with dryness air, installing humidifiers and raising plants. The optimal moisture is 50%, it is also calculated.

In the fall and spring for bandwidth, couples will go in the opposite direction - from the street. To calculate the "demi-season" on vapor-permeable insulation, humidity must be taken about 90%.

Where the dew point should be

The warming of the fence is considered "normal" only when the dew point in the cold time is mainly (!) Is in the insulation and does not shifted into the wall.

What does "basically" mean? At maximum negative temperatures, which are usually for several days, week, and occur periodically, the dew point may be shifted into the wall.

For a wall of dense heavy materials, there is nothing dangerous. But for a wall of porous materials, which, as usual, skip the steam very well and absorb moisture, the appearance of the dew point must be short, especially when they are combined with steamers-steam insulators.

Such walls require the greatest insulation, especially with the fact that they themselves are warm. To shift the dew point will be required 2 times longer than the insulation. With regular insulation, they are combined much better, as moisture can be derived here, but only under the condition of excellent ventilation of the insulation.

A visual graphics of temperatures are given for various insulation schemes. The dew point is approximately listed as 16 degrees, it is achieved when there is a particularly comfortable setting of +25 degrees, 55 - 60% humidity inside the house. Examples, dew point positions, with different insulation schemes

  • 1 - wall without insulation;
  • 2 is an insufficient layer of insulation - the dew point is inside the wall. Its constant finding the wetting of a loose wall, an unhealthy atmosphere, the risk of material destruction, if the wall layer of insulation has a greater resistance to the movement of steam than the wall itself (incorrect insulation);
  • 3 - sufficient insulation, dew point in insulation (main time), normal preservation of wall materials and heat in the house, If the heat resistance of the structure is not less than the normative, because for very cold walls, it is possible to shift the dew point from them from them with a small layer of insulation ;
  • 4 - Internal insulation - the worst solution. The dew point on the wall surface or is close to it, shifts the wet wall, and damage to the health of tenants, wet freeze and destruction of structures. It is used in hopeless situations under the condition that the wall is continuously closed with a steam polypoletor, which prevents steam penetration to the dew point. Those. The formation of condensate is impossible due to the humidity close to 0.

In the standards, thermal resistance of the enclosing surfaces for specific climatic zones are indicated. This value to reduce the state forbids us.

More often, the standard requires a smaller thickness of the insulation than that that is needed to displace the dew point in the insulation. Therefore, to select the insulation under all surfaces, in principle, it is desirable and by the condition of displacement of the dew point in the insulation.

These values ​​are compared with the regulatory requirement, and is usually taken, as a rule, even greater importance, multiple the thickness of the insulation, which is on sale.

One of the most important concepts in construction is a dew point. At the stage of the insulation of the walls, it allows you to correctly select the type and thickness of the heat insulating material, form the optimal microclimate inside the structure. You can determine the dew point in several ways. However, you also need to know what to do with the result obtained.

Dew point in a skeleton house

Small excursion to physics phenomena

The dew point is the air temperature at which the excess moisture contained in it falls in the form of condensate. Why is it too much? The fact is that warm air keeps a large amount of water vapor, cold - much less. It is this difference when the temperature drops Forms condensate . An example of a phenomenon is droplets of water on cold water pipes or windows, fog.

What else needs to know about the dew point:

  • The higher the humidity, the more closer to the air temperature, and vice versa.
  • Its value can not be higher than air temperature.
  • Condensate always appears on cold surfaces . This is explained by the fact that the warm air is cooled next to them, and its humidity decreases.

Unit of measurement of the point of condensate loss - degrees Celsius.

Displacement of the dew point

Dew point in the wall of the house - why it is important to know

Most of the year between the temperature and humidity regime of the street and premises there is a significant difference. That is why in the thickness of the walls with the insulation, the condensation sections often appear. When changing weather conditions, they shift closer to the outer or inner surface of the wall . That is, to a colder or warm area.

Example: The air temperature is steadily equal to 25 ° C, and the humidity is 45%. In this case, condensate is formed on a plot with a temperature of 12.2 ° C. With increasing humidity up to 65%, the dew point is shifted to a warmer portion, where 18 ° C.

Why is it important to know the location of the condensate falling point? Because it defines exactly which layer of the wall "cake" is subjected to the destructive effects of moisture. The worst option is when the insulation is wet. Under such conditions, most thermal insulation materials loses their properties. They are deforming, skip cold air , rot, lose elasticity. Mineral wool is especially exposed to these processes.

Displacement point dew when temperature change

Variants of problem areas

The dew point has a property of shifting, but most often the three zones of its location are distinguished:

  • Closer to the outer surface of the wall. This option takes place if Wall is not insulated . The appearance of a problem zone is also possible with external insulation of insufficient thickness.
  • Closer to the inner surface of the wall. In the absence of insulation, condensate in this place is easily formed during the cooling period. Internal insulation shifts the section of condensate formation to the region between the surface of the wall and insulation . With outdoor insulation, this phenomenon is rarely found if all calculations were performed correctly.
  • In the thickness of the insulation. For outdoor thermal insulation, this is the optimal option. When internal insulation is a great risk of appearance from the mold room and, as a result, Disorders of microclimate .

Note! The formation of condensate in the wall affects not only the temperature and humidity regime from the street and the room. Determining factors are also the thickness of the structure, the thermal conductivity coefficient of the materials used.

Effect of dew point on well-being

Calculation of dew point

Calculate the value of the parameter in several ways. It can be an online calculator, a consolidated table, a special device, a mathematical formula.

Using Table data

Special table for calculating the dew point contains approximate values. This is due to the fact that during their excretion, only the air temperature and its relative humidity took into account. In the left column of the table, the air temperature is indicated, in the upper line - the relative humidity of the air in percent. At the intersection of columns and lines just the desired value.

There are several table options. However, the temperature range is -5 ° C. + 30 ° C, and humidity - 30-95%. The application of the table is convenient if you need to make calculations quickly. If possible The result is better to double-check In another way, for example, using a special calculator online.

Table for calculating the dew point

Calculation of mathematical formula

The mathematical formula for calculating the temperature of the condensal formation is complex and cumbersome. For calculations, two constant values ​​are used, The actual value of air temperature and relative humidity . The latter should be taken in bulk bodies.

Unlike working with a table, the range of the last two parameters is greater. The formula allows you to take into account the temperature from 0 to + 60 ° C, the humidity is from 1 to 100%. The error of the result does not exceed half the degree Celsius. However, it is convenient to use the formula only when it is free time.

Calculator calculation

Special calculators allow in online mode to calculate the dew point in the wall of the house. You can find them on specialized sites. To calculate, you will need to enter a number of source data. They differ from the resource to the resource, but the standard kit includes information on the following parameters:

  • Wall material;
  • The number of its layers and their thickness;
  • temperature outside and inside the house;
  • Humidity indoors and on the street.

Most calculators do not just count the desired value. They also issue graphs of its possible movement and moisture condensation zone.

Example Calculator

Application of devices for calculating

Regardless of the method to be performed by calculations, you will need initial data . To obtain them, you need to stock up with some devices. So, a conventional thermometer is suitable for determining the temperature, and to determine humidity - hygrometer. For convenience, they are combined in such a device as a digital thermohygrometer. All obtained values ​​are displayed on a small screen. Some devices are determined by the condensate flow temperature. Some models of building thermal imagers can determine the problem zone.

How to move the dew point in the wall

If after carrying out all the calculations you do not suit the location of the dew point, it is worth thinking over its displacement. For this you can:

  • Enlarge the insulation layer outside;
  • use material with high vapor permeability;
  • dismantle a layer of internal insulation, moved it out;
  • adjust the indoor microclimate - install Forced ventilation, Additionally heated air.

The appropriate option is chosen based on the climatic conditions of the region of residence, design features of the house, financial capabilities and used building materials.

Ignoring such a phenomenon as moisture condensation in the wall "Pie" may be too expensive to do. At least Unpleasant odor indoors, constant dampness . As a maximum - large colonies of mold mushrooms, spoiling the inner decoration of walls, destroying the insulation and hinder the health of households. Thus, the calculation of the dew point is essential if you want to build reliable and dry walls for your home.

On the physical condition of water contained in insulation, hygroscopic building materials, air, the ambient temperature affects the ambient temperature. According to the laws of heat engineering, the dew point is a kind of temperature at which steam water become condensate, that is, dew.

All about how to determine the dew point to take into account it when developing a construction project, you will learn from the articles submitted by us. We will tell you how the point is calculated in which steam turns into condensate, and how it reflects on the operation of the house. We give advice on the options for localizing this phenomenon.

Connection point of dew and construction

The numeric value of the dew point is directly dependent on such indicators: relative humidity and temperature on the street, and in the indoors itself. For example, if the window T = 8 ˚С, and in the house T = 22 ˚С and the relative humidity of 45%, then condensate is formed on the outer wall.

There are also additional factors that form the dew point, namely: the features of the regional climate, the degree of insulation of all enclosing surfaces, the quality and type of heating system, the period of residence - can be permanent (house, apartment) or temporary, for example, cottage or garage, ventilation .

For the builders it is very important to know the number of dew points to calculate the accurate localization of condensate on the walls, as well as to determine the necessary soaplitel thickness. After all, thanks to these knowledge, you can minimize the loss of heat during the cold weather.

The position of the dew point may wander around the wall thickness. It depends on the thickness and type of materials of the wall itself and insulation, from the temperature and humidity indicators in the room and on the street.

Each material used for construction and wall decoration, except metal, has its own degree of vapor permeability. This indicator, from the point of view of physics, shows the amount of steam that any material can skip over a certain time.

Parry permeability table

Parry permeability One of the decisive factors that affect the choice of materials for insulation, also this parameter is important for analyzing the state of external walls.

During periods of low temperatures, steam from the room under pressure will strive to go outside through all the layers of external walls. The lower the pharmaceous coefficient of the insulation, the smaller layer should be laid. Its coefficient should grow from the inside to the outer, as well as thermal conductivity.

If all calculations are carried out without errors, the location of the dew point will be in, closer to the outer surface. It is there that the couple will turn into condensate and only moisturize the wall. Thus, steam will accumulate in winter, and in the summer it is necessary to create conditions for evaporation of accumulated moisture.

High-quality insulation

The main condition for high-quality insulation is the creation of conditions for evaporation of accumulated moisture. For this, special calculations are carried out and finishing materials are selected.

A less suitable will be the position of the dew point in the bearing wall of the house. It happens if the type and thickness of the insulation is incorrectly selected.

The worst option involves the location of the condensate on the inside of the wall. This situation is possible if the wall is not insulated at all or the insulation is indoors. In the latter case, a mold can be formed under the insulation layer, moreover, wet heat insulation will not be able to maintain heat.

Dew point calculation options

Methods and rules for calculating the dew point are regulated at the legislative level with such documents as SNiP 23-02 Thermal protection of buildings and SP 23-101-2004 Design of thermal protection of buildings.

In SNiP in paragraph 6.2, three normalized importance on heat, namely:

  1. Resistance to the heat transfer of walls and insulation.
  2. The magnitudes of the temperature indoors and on the surface of the outer wall.
  3. Indicator of approximate heat consumption for heating taking into account ventilation.

The norms are considered to be fulfilled if the requirements 1 and 2 or 2 and 3 are observed.

In order to determine the most experts in the regional meteorological service as accurately as possible to obtain a certificate of accurate temperature and wind rose on a certain territory.

But each can have such calculations. There are several ways to determine the dew point.

Method number 1 - the use of formulas

For such calculations, several formulas were created. For example, a formula for deducting a dew point at T from 0 ° C to +60 ˚С. Its error is ± 0.4 ° C. To carry out calculations, you will need the temperature in the room at an altitude of 50-60 cm from the floor and air humidity. Then just substitute the data and get the result.

Formula for determining the dew point

This is one of the most popular formulas in which T temperature in degrees Celsius, RH relative humidity in%, LN natural logarithm

Method No. 2 - Application of a Finished Table

Experts have developed a table for instant computing. It should be borne in mind that the table shows approximate data. It contains temperature and humidity, and at their intersection you will find a dew point.

Table of dew point

You can find out the number of dew points due to the data from the table presented in the SP 23-101-2004. Need to choose a value at the intersection of temperature and humidity

Method number 3 - measuring instruments

Now there are several types of special devices for conducting such measurements. For example, some, except key characteristics, can display both the localization of the dew point and the thermogram of the room. They are used by professional builders and heating engineering specialists.

Teplogram thermal imager

The thermal imager is a professional device, with which you can create a gas tower. In some models there is a function of calculating the dew point

A portable heat-headerometer will help learn not only the temperature and humidity indoors, and will calculate the dew point.

The psychrometer will help measure the two key indoor indicators: humidity and air temperature. The device consists of wet and dry thermometers in one block.

Mobile heat-leveler

With the help of a mobile heat-hydroometer it is easy to find the humidity and temperature on all parts of the wall, the roofs in any room

Method number 4 - calculations on the online calculator

Services providing such calculators are very much. In this case, this method is considered one of the most unreliable, because as a result you can get numbers from the ceiling or with a big error.

If you are unsure of the results obtained, then trust the professionals and contact a specialized company. They will analyze the walls and offer the optimal option.

Localization of the dew point

The location of the dew point depends on what part the insulation is located. So, in the wall without insulation, it will be shifted by the wall thickness depending on the change in air temperature and humidity. With a minimum temperature drop, it will be located in the thickness of the wall between the center and the outer surface.

Subsequently, the inner side of the wall will remain dry. When its position is between the inner surface and the center of the wall, the latter wet inside during a sharp cooling or in the period of frost.

Dew point position

The wall can be insulated with outdoor or outer sides, or not be insulated at all. From this will depend on the location of the dew point

In the wall with the location of the dew point will be optimal. Indeed, in this case, it will be located inside the insulation, and thus the inner surface of the wall will be dry. This is the best option.

But, if the insulation thickness was picked up incorrectly, the dew point could occur, which is fraught with the appearance of fungus, mold, rapid destruction of the walls.

The wall with condensate is formed in the wall closer to the residential premises, the temperature of the wall under the heat insulation layer decreases, creating optimal conditions for the growing of mold.

Localization may be like this:

  • Between the center of the wall and insulation, and in the period of frost or a sharp decrease in temperature on their border;
  • on the inner surface of the wall, which the whole winter period under the insulation will be wet;
  • Inside the insulation, which, like a wall under it, will be wet during the whole cold period.

As can be seen, the point of dew point has a significant impact on the comfort and health of the person.

The consequences of incorrect calculations

During the choice of materials for insulation, remember that one of the effective ways to protect the outer walls from moisture is the correct location of the insulation layer.

Heat loss in insulated and tightwood walls

High-quality heat dissipation will help significantly reduce heat loss and save the comfort in the house, as well as extend the life of the walls

A dense layer that pairs will not miss, it should be placed on the inside of the carrier wall, and the porous, passing moisture - outside.

It is also necessary to create conditions for ventilation at the point of condensation. In this case, condensate will evaporate without obstacles.

Correct location of the dew point

Properly insulated external wall will help reduce heat loss during a heating period from 45 to 95% and create a comfort in the house

If the insulation was chosen incorrectly, then the moisture in it will accumulate gradually and will decrease the number of thermal resistance of the wall. Therefore, on the second, maximum for the fifth heating season, heating costs will increase, if it is a private house, in the winter it will simply be much colder.

Professional insulation is a long and expensive process. Today there are many materials for insulation. Do not attempt to save them, as cheap materials will come into disrepair in a few heating seasons and begin to collapse.

The consequences of incorrect settlements are several, but some of them can negatively affect the quality of life. The main consequence will be constantly wet walls, as a result of fungus, mold, microbes on the walls, which entails the emergence of many chronic diseases.

Mold and fungus on the walls

Constantly wet walls become a seating for the growth of fungus and mold, because their disputes fly in the air and can cause diseases

Since the wet room is difficult to heat, the level of comfort falls. And the high humidity inside such walls can provoke diseases of the respiratory organs.

Another unpleasant consequence of improper calculations is the destruction of finishing materials - the tile crumbles, the brick is shred on the outer wall, and inside the room the surface will begin to swell on the walls.

Wall destruction

Low condensate, is the key cause of the appearance on the outer wall of the bloating and separation of finishing materials

To correct the situation, you should contact the specialists for analyzing the status of walls and insulation. Having properly calculated, you can correct all errors and create comfortable and warm conditions in your home.

With the rules and formulas for conducting a heat engineering calculation for competent design of the house, you will familiarize yourself, read which we highly recommend.

Conclusions and useful video on the topic

How to determine the dew point and that it represents it can be found from the next video:

On the ways of insulation of walls and the right choice of materials will be discussed in the next video:

You can find out the dew point as independently and contacting professionals. The number of dew points allows the specialist to competently choose the material and high qualityly insulate the walls of a residential building or any other room.

Not only heat and comfort in the house, as well as the health of its inhabitants depends on the accuracy of measurements. Professionals are recommended to insulate the wall from the inside just as a last resort and after professional advice.

Please write comments and ask questions on controversial moments, publish photos and posts with your opinion in the block below. Share useful information and methods for determining the dew point, not described in the article. Tell us about personal experience in solving this issue.

Signs of dew on the grass, water leaks on the windows, droplets on the walls of the base - all this is the result of the condensate of the water vapor, which takes out of wet air. Most faced with this, but not everyone was interested, is it possible to eliminate this and how to do it. Determining the dew point will help eliminate moisture penetration and protect the structure from its destructive impact. Methods for determining the dew point and expert advice - hereinafter.

How to determine the dew point? Methods of Definition, Table, Expert Tips

What is a dew point

The concept of dew point is explained as the temperature in which pairs of air turns into a liquid. Depending on the difference between the air temperature in the room and beyond, the dew point can be shifted in the thickness of the wall. For example, if the room is stable +20 ° C, and the temperature fell on the street, the dew point will be shifted closer to the inner space of the house.

How to determine the dew point? Methods of Definition, Table, Expert Tips

The dew point depends on the tempera and humidity. For example, if in the room +24 ° C and 60% humidity, then the dew point will be approximately +15.5 ° C. So, if you put in the room, for example, water bucket with a temperature of + 10-15.5 ° C or less, condensate droplets will appear on the outer walls. At the cold air temperature on the street begins to moisturize the wall at the dew point. As a result, it wet and quickly turns mold. Solve the problem will help insulation, for which you need to correctly determine the dew point.

Methods for performing the calculation

To accurately calculate the dew point can only architect using special equipment, so you can only talk about approximate values. However, according to the advice of experts, when choosing a method of insulation and material itself, it is not too critical.

There is a table of finished parameters to determine the dew point in the wall, which eliminates ordinary people from independent calculations.

How to determine the dew point? Methods of Definition, Table, Expert Tips

The values ​​shown in this table depend on air humidity and its temperature. It is possible to rely on these values ​​only as on the exemplary, because the calculations are made with regard to only the main factors.

Also to calculate the dew point (the temperature of the transformation of steam into the liquid, tr (° C) there is a formula, the value of which is determined by the parameters of the air temperature, T (° C) and relative humidity, Rh (%):

How to determine the dew point? Methods of Definition, Table, Expert Tips

Professionals in their work apply:

  • Psychrometers,
  • portable thermohygrometers
  • Thermal imagers.

These devices differ in the method of action and use method, but are usually a more accurate result.

How to determine the dew point? Methods of Definition, Table, Expert Tips

For more accurate calculations, climate features in the region, thickness and material of walls and insulation are also taken into account. Do not trust online calculators and calculating programs from the Internet. They often give inaccurate data, given not all setpoints. More in-depth calculations are important in the construction of the house, and in order to insulation the walls there will be enough of the above parameters.

See also:

5 Errors when insulating a private house that cannot be performed!

Comparison of thermal conductivity insulation: What do experts choose?

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Wet grass under his feet, swollen windows, droplets on the walls of the raw basement - all this is the result of condensation of water vapor from atmospheric air. Everyone came across this, but not everyone was interested in how to determine the dew point. Most often this task is to solve architects, builders and designers, and people far from this sphere are hardly familiar with such a concept.

How to determine the dew point
How to determine the dew point

The nature of the appearance of dew

Condensation of water on various surfaces occurs as follows. The atmospheric air is always saturated with water vapor to one degree or another. Water from a gaseous state into liquid moves in case of lowering its temperature. This occurs when there is a touch of atmospheric air with cooler surfaces and the subsequent loss of heat. As a result - the appearance of water droplets.

Morning Rosa is easily explained by the laws of physics
Morning Rosa is easily explained by the laws of physics

Temperature, to achieve which pairs of water from the air are moving into a liquid aggregate state, is called Dew's point .

The higher the content of water vapors in the air (or another mixture of gases), the higher the temperature of the condensation of water, or the dew point. So, with a relative humidity of a 100% dew point exactly coincides with its temperature. Conversely: the smaller the relative humidity of the air, the lower the dew point. It means that condensate will have to cool the air is stronger.

We study the dew point in construction
We study the dew point in construction

Scope of application

This term in industrial and civil construction is widely applied. The need to determine this magnitude occurs when the walls of the room are insulated. If you neglect the calculation of this indicator, problems will appear after work on insulation. One of the options is damage to the walls of the walls by depositing moisture. If the finish is tolerant to the effects of water, but the condensate drops will fall on the walls, there is also nothing good in this. Wet environment contributes to the development of pathogenic microorganisms, mold.

The aviation also calculates the dew point. During the flight, condensate falls on some parts of the aircraft. In this case, the condensate is frozen and parts of the aircraft are ignitiated.

Ignoring the dew point can lead to the crash of the aircraft
Ignoring the dew point can lead to the crash of the aircraft

Use this magnitude and in forestry. Forest protection professionals from fires use a dew point to calculate the fire hazard class, which characterizes the possibility of fires of forest arrays. Based on this, protective measures are designed.

The dew point is applied in calculations for planning fire fighting events
The dew point is applied in calculations for planning fire fighting events

In agriculture, knowing the point of dew, determine the likelihood of damage to the crops of non-infectious diseases (damage caused by weather conditions). At the same time, one of the tasks of selection is to derive a variety of cultural plants that can condense moisture from the air on their vegetative organs. This will allow us to successfully engage in agriculture under conditions of low precipitation.

Placing the point of dew
Placing the point of dew

How to calculate dew point

In mathematical formula

Calculation manually by the formula is a fairly accurate way. However, to use the formula, it is pre-identifying several other indicators. Looks like a formula as follows.

Formula for calculating dew point
Formula for calculating dew point

As can be seen from the figure, A and B are constant values. T - air temperature. Rh - relative air humidity. This method of calculation will give the result with an error of 0.5ºС.

Using an online calculator

Since the calculation with the help of the manual formula is not suitable for all (due to insufficient knowledge in mathematics or lack of time), online calculators are placed on the Internet in the Internet, which calculate the dew point on the basis of the information entered. It is completely easy to use: it is necessary only to introduce the source data (atmospheric air temperature and relative humidity). The result of calculations will appear on the screen.

Calculatory programs

To link the indicator of the dew point and the alleged consequences of improper insulation are not at all. This requires specific knowledge in physics and construction. Therefore, in addition to conventional calculators, calculating this magnitude, programs with advanced features have been created. They are also in free access and they can be used online.

Such programs in the calculation take into account many parameters:

  1. The settlement in which the building is built (constructed). The statistics of average monthly temperatures, relative humidity, pressure in this region appear immediately.
  2. View of the room. Obviously, air humidity in the bathroom will be higher than in the room, and this in turn affects the type of permissible insulation.
  3. Design type. Here the choice is offered a wall, overlap, attic overlap and other positions.
  4. Layers of construction. It takes into account that it is located behind a warmed wall - another room or street.
  5. Overlapping material or wall.
  6. Temperature and relative humidity of indoor and outdoor air.

After filling out all the necessary fields, the program will make a graph of the dew point.

Dew point definition table

If necessary, quickly get the value of the dew point apply to tables. These tables are very inaccurate and give an approximate result. But it is easy to use them easily and quickly: it is enough just to find the desired cell at the intersection of the column and strings with the desired temperature and relative humidity.

Table 1. Definition of dew point in two indicators.

Definition of dew point in two indicators
Definition of dew point in two indicators

Special tools

Special tools are invented in meteorology, allowing to determine the dew point. However, even for calculating the mathematical formula or any other method described above, their tools are needed.

The temperature is measured by the thermometer, humidity - hygrometer. For convenience, in this case, a tool can measure and temperature and air humidity - a digital thermohygrometer.

This tool combines the functions of a thermometer and a hygrometer
This tool combines the functions of a thermometer and a hygrometer

In addition, there are devices that combine several functions: measurement of temperature, humidity, calculation of the dew point and memorization of information.

In most cases, work with such an appliance is as follows.

  1. Turn on the device. Pay attention to the battery charge.

    This looks like one of the popular devices.
    This looks like one of the popular devices.

  2. Apply the sensor tip to the surface under the right angle.

    The correct position of the device will ensure the accuracy of measurements.
    The correct position of the device will ensure the accuracy of measurements.

  3. To fix the measurement data, press the HOLD button in the menu. So you can get acquainted with the result in a comfortable position of the device.

    Fix - does not mean to save
    Fix - does not mean to save

  4. To save data, press the SAVE button.

    The ability to save eliminates the need to record data in the notebook
    The ability to save eliminates the need to record data in the notebook

  5. If necessary, transfer information to the computer Connect the device to the network via USB.

    Connect the dew point meter to the computer is not more difficult than a mobile phone.
    Connect the dew point meter to the computer is not more difficult than a mobile phone.

  6. Copy the data to the computer.

    Computer - reliable data warehouse
    Computer - reliable data warehouse

Working with devices for measuring the dew point is simple even for a person without special training. The interface is intuitive, and if there are questions, refer to the instructions.

The importance of determining the dew point

If you do not take into account the position of the dew point in the wall, follows a number of negative events.

Insulation material quickly comes in disrepair, the service life of the material itself is reduced. Finishing because of regular wetting will not hold on: wallpaper is gradually dug, the plaster rolls, the paint is peeling. Due to excessive humidity in the room in a short time on the walls, ventilation systems, the ceiling and other surfaces, a mold layer, fungus and other pathogenic microorganisms develop.

Ignoring the physical nature of condensation is fraught with an antisanitation indoor
Ignoring the physical nature of condensation is fraught with an antisanitation indoor

How does the dew behave with the lavety walls

With tangled walls there are several variations of the dew point behavior. In some situations, it is located in the inner space of the wall - closer to the street or closer to the room. In the second case, with a strong decrease in temperature, the condensation place of the steam will be shifted to the inner surface of the wall. Then the condensate drops are defensive on its surface.

Reworked walls often wedge
Reworked walls often wedge

In some cases (cold material of the building frame) The dew point may be located all year round indoors, that is, on the inner surface of the wall. Then it is necessary to make applied calculations and take care of the insulation of the wall, taking into account the climatic features of the settlement in which the building is located.

In general, the location of the dew point in the overlap or the wall is interconnected with a number of physical factors:

  • humidity of outdoor air and indoor air;
  • Outdoor air and air indoor temperatures;
  • Overlapping thickness or walls.

Dew point in warmed outside walls

With a correct selection of material and a competently calculated thickness of the insulation layer, the dew point will always be in the insulation and will never move towards the inner surface. Wall dry all year round. It is damaged by weather conditions only insulation, wear walls slows down.

Outdoor insulation - loyal protection against condensate falling in the apartment
Outdoor insulation - loyal protection against condensate falling in the apartment

In the event that the thickness of the insulation is less necessary, or the thermal conductivity of the material was not taken into account, the dew point will behave in the same way as in a tangled wall, that is, the moisture will continue to accumulate indoors if it accumulated before insulation. If this happens, the output one is to increase the thickness of the insulating material. This can be done by adding another layer of thermal insulation or replacing the old material on a new, suitable in thickness.

With an excessive thickness of the insulation layer, the dew point will not go beyond its limits throughout the year. No negative consequences for themselves will not entail: the wall will be dry all year round. However, the calculations are made to avoid unreasonable financial spending. After all, if you can escape from moisture and save heat with fewer insulation, then why spend more?

Inside or outside warming walls
Inside or outside the walls?

Dew point in warmed inside walls

Wall insulation is only on the inside inevitably leads to a shift of the dew point towards the room. This is due to the fact that thermal insulation material holds heat in the room, thereby making the wall is colder. And, as you know, the colder surface, the most likely the fact of condensation of air moisture on it.

If, with normal temperatures for this region, the dew point is located close to the inner wall surface and does not cause inconvenience, then in particularly cold days it can shift into the room, that is, on the inner surface of the wall. Then the wall will wet under the insulation.

If there was constantly on a tightened moisture wall, then after the work on the inner insulation of the room, the entire cold season of the wall will continue to worsch under the insulation. This will lead to a gradual damage of all layers of building materials located on the inside of the wall, including decoration.

Internal insulation does not save from wetting
Internal insulation does not save from wetting

In some cases, after the internal warming of the normal wall, the dew point changes the location to the insulation. Then throughout the winter will be wet not only the wall, but also the thermally insulating material itself.

Anyway, to avoid damage to the finishes and internal insulation layers, one simply rule must be remembered: the insulation of the inner surface of the wall is carried out only after its outdoor insulation.

On the dew point in plastic windows

If it comes to a dew point in double-glazed windows, then many are some specific mysterious place. In reality, the dew point cannot be seen that we have already found out. Repeat: under the point of dew, the temperature is meant, when cooled to which steam in the air is saturated and condensed. There are special tables that allow you to calculate the dew point at relative humidity and a specific temperature. One such table is shown below.

Dew point with relative humidity
Dew point with relative humidity

On a note! Suppose the humidity of the air is 50%, and the temperature is +21 degrees. Under such circumstances, the dew point will be +10.2. What does it mean? If the temperature of some surface in the apartment drops to +10.2 degrees, condensate will begin to appear on it. As a rule, the coldest surfaces in the apartment are plastic windows, and therefore it is precisely on them in most cases an excess moisture falls out.

People often face condensate on the glass packages. If we proceed from the whole above, we can conclude that with condensate you can fight in two ways - increase the temperature of glass and decrease in humidity in the apartment. So, comfortable humidity can be achieved by providing a normal air exchange. All excess moisture is from washing, boiling saucepan and so on. - Must leave the room, and not accumulate in it. First of all, the apartment should be regularly ventilated. The air frequency is determined individually, however, we advise you to make it at least 10 minutes a day. Do not forget about special ventilation valves.

Video - What is the dew point?

Dew point.

Why do windows, doors, walls sweat? Why are the condensate are covered with cold in a warm room? Why wet cold water pipes? - answer one, surface temperature of the subject below Dew point temperatures .

Dew point (Deva point temperature TR ) - this temperature at which the dew begins to form, i.e. The temperature to which you need to cool the air is that relative humidity achieved 100%

The content of the article:

From the school year of physics, we know that air humidity (water content in the air) is determined by two parameters:

Absolute humidity; Relative humidity.

С absolute humidity ( f ) Everything is clear - this is the amount of water in grams contained in one cubic meter of air, a unit of measure - grams in a cubic meter, g / m3. .

F = M / V

Where:

V - volume of wet air;

m- The mass of the water vapor contained in this volume.

Relative humidity ( Rh. ) - this is the amount of water contained in the air relative to the maximum possible amount of water at a temperature and pressure, the unit of measurement is percent, %.

And S. increasing temperature , Maximum possible Number of water contained in the air - Increases .

Table of maximum absolute humidity.

According to Temperature decrease decreases .

With a further decrease in temperature " Lying »Water will begin to condense in the form of drops of dew - That's what it is Dew point .

Dew point.

Several facts about the dew point.

  • The dew point temperature cannot be higher than the current temperature.
  • The higher the temperature point of the dew, the more moisture is in the air
  • High dew point temperatures are in the tropics, low in the deserts, polar regions.
  • The relative humidity (Rh) is about 100% leads to the dew loss, the inlet (frozen dew), fog.
  • Relative humidity (RH) reaches 100% in the period of rain.
  • High dew points usually occur in front of cold temperature fronts.

How to determine, calculate the dew point?

The answer is obvious -

Determine on the table, calculate by the formula, calculate on the "dew point calculator calculator".

1. To determine the dew point there are special tables,

where the columns indicate the relative humidity in %in lines - ambient temperature in ° S. In the cells at the intersection - the temperature of the dew point, for the selected humidity and temperature.

Table of dew point definition.

For example, relative humidity is selected 60%, room temperature 21 ° С At the intersection we see The value of the dew point 12.9 ° C.

Accordingly, under these conditions, the condensation of moisture will occur on cold surfaces (for example, window windows) with The surface temperature is lower than 12.9 ° C .

Specialized sites exist more detailed tables of dew point defining, but for "home use" is quite sufficient, below the table below, it can be saved, print and use if necessary.

Table of dew point definition.

2. When calculating the temperature of the dew point, we use formula 1.1 and 1.2.

Formula for approximate calculation of the dew point in degrees Celsius (for positive temperatures):

TP = (B f ​​(t, Rh)) / (A - F (T, Rh)) , ( 1.1. )

Where:

f (t, Rh) = a t / (b + t) + ln (rh / 100) , ( 1.2. )

Tr. Dew point temperature, ° С ;

a= 17.27;

b= 237.7;

ТRoom temperature, ° С ;

Rh. relative humidity,%;

LN. - Natural logarithm .

Calculate Dew's point For the same temperature and humidity values.

Т= 21 ° C;

Rh. = 60%.

First calculate the function F (T, RH)

f (t, rh) = a t / (b + t) + ln (rh / 100),

F (T, RH) = 17,27 * 21 / (237,7 + 21) + ln (60/100) =

= 1,401894 + (-0,51083) = 0.891068.

Then Dew point temperature

Tp = (b f (t, rh)) / (a ​​- f (t, rh)),

TP. =(237.7 * 0,891068) / (17.27 - 0,891068) =

= 211,807 / 16,37893 = 12.93167 ° C.

So, our result of calculations Tr. = 12.93167 ° C. .

3. It is much easier to calculate the dew point using " Dew point calculator calculator " on our website.

Fill the values:

Air temperature indoors, ° С. - 21. ;

Relative humidity %. - 60. .

Click on the button " Calculate "And immediately get the value Dew point temperatures - 12.93 ° C.

Dropping the result, we can calculate Tr. For other values.

Calculator calculating dew point.

As you can see The value of the dew point for all three ways coincides :

Tr. = 12.9 ° C;

Tr. = 12.93167 ° C;

Tr. = 12.93 ° C.

The difference is only in the number of marks after the comma.

Fair questions arise - Why do we need this dew point Why do we pay so much time to determine or calculate, what practical application has a dew point?

In places where moisture constantly accumulates, are created, favorable conditions for the development of mold, fungal dispute, which very negative effect on health located near of people .

Mold, fungus in places of moisture accumulation.

Knowing the dew point, we can prevent condensate formation on the surfaces of our room.

Using:

one." Calculator for calculating the temperature of the glass glass (window profile) ", determining the temperature of the internal glass of the TWIS glass glass in the cold period, you can predict the presence or absence of moisture condensation on the glass (profile) of your window.

We have an example (we want to order) a window made with:

  • Window profile Kbe Etalon. having a heat transfer resistance - 0.65 (m2 ° C / W).
  • Single-chamber glass glass 4m-16-4m. having resistance to heat transfer -0.32 (m2 ° C / W).

We want to know the inner temperature of the window profile and the glass pump at a temperature of 21 ° C, and an external temperature - 20 ° C.

We substitute the values ​​in the calculator and get the result:

Calculator calculating the temperature of the internal glass glass package (window profile).

The temperature of the inner wall of the window profile above the dew point

13,12> 12.93 .

Therefore, condensate on the wall of the window profile, under the selected conditions there will be no.

Calculator calculating the temperature of the internal glass glass package (window profile).

The temperature of the inner wall of the glass pack below the dew point,

4.98 <12.93.

So, on the inner wall of the glass package will be condensate .

Conclusion: glass windows 4m-16-4m. Not suitable for these conditions.

Let's try glass with a large heat transfer resistance, such as a two-chamber bag with and-glass 4m-10-4m-10-and4 having R ORD = 0.64 ( m2 ° C / W).

Calculator calculating the temperature of the internal glass glass package (window profile).

At the same time, 12.99> 12.93,

Exceeding insignificant, for these conditions it is desirable to use profiles and double-glazed windows with heat transfer resistance from 0.7 (m2 ° C / W).

2. " Calculator calculating the temperature of the outer air at which the dew point will come on the inner surface of the glass package »Knowing the heat transfer resistance of the glass glass, temperature and humidity in the room can calculate the outer temperature at which the temperature of the inner glass of the glass package will be equal to the temperature of the dew point.

Those. The external temperature is lower to which the inner glass will sweat .

In the previous example, we determined that the KBE etalon profile and 4m-10-4m-10-and4 double-glazed windows will not sweat at an internal temperature of 21 ° C and external - 20 ° C, but I would like to know Is there a reserve By reducing the external temperature and what is its value.

Calculator calculating the temperature of the outer air at which the dew point will occur on the inner surface of the glass package (window profile).

Calculator calculating the temperature of the outer air at which the dew point will occur on the inner surface of the glass package (window profile).

As can be seen according to the results of the calculation, already With a decrease in temperature to - 20,96 ° C for window profile and up to - 20,31 ° С For the glass package, the temperature of the inner wall will be equal temperature point dew .

Output:

This set of window profile and glass package is well suited in localities where Average air temperature Cold period of the year do not fall Below minus 15-18 ° C .

3. " Calculator for calculating the heat transfer resistance glass package ", You can calculate Minimal heat transfer resistance glass package, At which the temperature of the inner glass will be higher than the temperature of the dew point.

Those. The minimum resistance of the heat transfer heat transfer, in which the glasses will not sweat.

Calculator for calculating the resistance of the heat transfer heat transfer (window profile).

For selected conditions The heat transfer resistance of the window profile and the glass should be more than 0.635 (M2 ° C / W) .

Thus, using the results of the calculations, At the selection stage Window elements can Quantity estimate how it will behave in the cold period of the year Pick up the optimal option configuration.

See also:

Swipe windows

For many questions, why windows sweat: plastic; wooden; in the House; in the apartment; in the room; on the kitchen; on the balcony; On Read more

Soundproofing windows

The noise level of the residential premises is regulated by sanitary standards. This means that its maximum level is defined, which does not affect health and Read more

During the construction and design of any home, it is very important to the correct calculation of the dew point and its observance, when the walls are erected. Incorrect calculation of the dew point and or complete ignoring this indicator will destroy your home from the inside. Accounting dew point in construction will protect your project from the devastating effects of the external environment.

What is a dew point

      Dew point - This is a certain limit of air temperature, below which the paces are contained in the air, becomes saturated and converted into a liquid.

Dew point - This is the place where the cold air is found with warm, and then the place where the fluid is formed in the form of condensate. On the example of building structures, the dew point is manifested in the form of condensate on the windows. Always, with a sharp cooling on the street, we see how fading and drops of water are formed on previously dry window glasses. This is the most nearest and harmless manifestation of the dew point.

dew point

Condensate on the window

In nature, the dew point is manifested in the form of droplets of morning dew on the leaves of plants and other objects. It is formed as a result of the interaction of cold night air and heated with solar rays of warm morning air.

Dew point

Manifestation of condensate dew point in nature

In the case of heated premises, the dew point is created artificially at any time of the day, under the conditions of temperature below zero on the street.

It is quite another thing if the formation of such condensate dew point will be detected on the inside of the wall of the house. Not even a very experienced builder is concerned with the formation of an extra liquid, in a previously dry room. Since the consequences of such clusters of humidity can be the most unfavorable. But the inner wall of the house is not the only destructive place where it can show itself not the correct calculation of the dew point or its absence.

Wrong calculation and location of the dew point for the house is the destructive enemy number one in construction. Which, from the inside, slowly, but confidently destroys any strong structure.

Where the dew point should be

The ideal place of the appearance of the dew point in the wall is the insulation, located on the outside of the wall. The thickness of the insulation on the wall should be such that in the coldest time the condensate would not shifted into the wall itself or if he shifted, then not for a long time.

Dew point

dew point in insulation

On the devastating consequences of finding a point of dew in the body of the bearing wall, see below in the article.

Walls, the basis of which is porous materials, such as foam and gas blocks, sewer and this kind of materials, require a larger layer of insulation, as they absorb well and retain moisture. That is, even non-plum (several days), staying in a porous wall of the dew point can be destructive way to affect internal integrity. Therefore, the so-called warm materials for wall masonry can only be effective in certain regions, with not the frosty winter.

If, according to the calculations, the dew point will periodically move to the wall itself or the likelihood of such a shift itself, then this fact should be considered when choosing a material for masonry wall. For such cases, wall materials with high density are well suited and which, withstand a large number of freezing and thawing cycles, without damage. With a large coefficient of frost resistance. Such frost-resistant materials include brick, ceramzitobeton.

Material dew point

Indicators of frost resistance of the most common wall materials

How to calculate the dew point in the wall with insulation

Calculate one, well-defined place in the wall, where the condensate will be manifested. Since the dew point is depends on several parameters and this is a changeable indicator. It is possible to calculate only a certain distance in the thickness of the wall, where the liquid will be formed with a different temperature change outside the house.

For example, if there is a stable temperature indoors, and it's cold on the street, the dew point will move around the wall thickness closer to the room.

With the help of the formula, you can get the most accurate calculations of the dew point as a homogeneous so and a multilayer wall.

Calculate the place of appearance of the dew point in any multi-layer wall, it is quite simple, for this we need the following indicators:

  • Outdoor air temperature
  • Air temperature indoors
  • separately the thickness of each layer of the wall
  • The coefficient of thermal resistance of the materials from which the walls of the house are erected
  • Dew duration with relative air humidity in your region (table below)

Dew point

In order to determine in which part of the planned wall there will be a dew point and the allocation of condensate, you need to know two indicators.

  1. Dew point temperature in our region, With the indicators of humidity and air temperature and indoor temperature. We can see this indicator in the table above. Let's call this indicator - Tr (dew point)
  1. The air temperature that will arise on the border of two layers of the wall, With the indicators you are interested in. Let's call this indicator - TC (point between layers)

Table of dew point

If the difference of the above indicators will be positive, then the dew point is in the insulation, if the indicator is negative, the dew point will be a liquid inside the wall or at home.

Other words if the temperature at the junction of the insulation and the wall will be higher with a plus sign than the temperature of the dew point from the table, then the condensate will be formed in the insulation.

For example, take the following conditions:

Dew point temperature in the region with humidity 60% and room temperature 21ᵒs According to the table will be 12.9 ᵒС. The temperature of the air on the border of the insulation and the wall is equal to 15 ° C.

The difference between these indicators 15 ᵒС - 12.9 ᵒС = +2.1

Dew point

If the difference of the above indicators will be positive, as in our case, the dew point is in the insulation, if the indicator will be negative, the dew point will scap the liquid inside the wall or at home.

In our case, the selection temperature of the liquid from the steam occurs earlier than the saturated air will reach the main wall. And the condensate falls in the insulation, and not in the bearing wall of the house or inside it.

The question arises if the temperature of the dew point at a given humidity we take from the existing table, how to calculate the temperature between the layers of the wall.

Calculate the air temperature on the border of two layers of the wall simply using the following formula:

TC (temperature between the layers of the wall) = (T2 - T1) x (S1x0.01 / k) / (S1x0.01 / k), where:

T2 - indoor air temperature

T1 - Air temperature on the street

S1 - Wall material thickness

k - thermal coefficient of the wall material

Dew point

Simple example:

Take an example of a region where the dew point is 12.9 ° C in the region with a humidity of 60%, room temperature 21ᵒС and the temperature on the street - 12 ᵒc below zero.

Now we need to calculate for these conditions, which will be the temperature between the standard wall in the brick 38 cm thick and the outer insulation of the polyfoam thickness 10 cm. What would take the temperature point of the dew from the table from it.

To do this, we use the above formula.

TC (temperature between the layers of the wall) = (T2 - T1) x (S1x0.01 / K1) / (S2X0.01 / K2)

By condition, we:

T2 = + 21ᵒC (indoor air temperature)

T1 = - 13 ᵒC Air temperature on the street)

S1 = 38 cm (wall material thickness)

K1 = 0.6 (the coefficient of thermal resistance of bricks)

S2 = 10 cm (insulation thickness of foam)

K2 = 0.04 (coefficient of thermal resistance of foam)

The calculation of the temperature between the brick wall insulation from the foam, in the climatic conditions we selected will be the following:

(+21 - (-13ᵒc)) x (38x0.01 / 0,6) / (10x0.01 / 0.04) = 9.52

According to our calculations, the temperature of the air between the insulation from the foam of a 10 cm and a brick wall of 38 cm, at an air temperature on -13 degrees Celsius and a temperature inside the house +21 degrees Celsius, equal to 9.52 degrees Celsius.

Thus, if deducting from the temperature between the insulation and the wall equal to 9.52 degrees Celsius, the temperature of the dew point is 12.9 degrees Celsius, it turns out to be 9.52-12.9 = -3.38.

Dew point

The dew point according to the calculations is in the wall

As we see, it turns out a negative indicator, that is, the state of condensate is wet air to reach the brick wall and humidity will accumulate in it.

The above calculation of the dew point is more accurate, with an accuracy of up to 0.5 degrees Celsius, unlike some online calculators and other devices that do not take into account the different structure of the material.

Calculation of dew point online calculator

On the Internet there are many online programs -Calculators with which you can calculate the approximate location of the location in the wall. The program calculates the dew point, based on a number of indicators that must be administered manually. This is the information of the petaterial, of which it is planned to build a wall, the number of walls of the wall and the occasion, the air temperature inside and the air temperature is outside the building, air humidity. Online calculator is convenient in the calculations. Together with digital paintings, you can see diagrams and charts of moving the dew point depending on the air temperature change. However, many calculators are distinguished by the counting results and how clear is unknown.

Online calculator to determine dew point

Calculation of the dew point using the device

The dew point can also be defined in real time using a special TV. This is an electronic device with a monitor, which will display information about indoor humidity, the air temperature and dew point will appear. Such devices are relevant to measure the dew point for the already erected and completed construction design. In the design of the wall thickness and buildings, this device will not help.

Thermal imager for dew point

Damper Curries for Wall Houses

We figured out that the dew point can be located in three different sections of the wall:

  1. In the outer insulation of the wall
  2. in the wall closer to the outer part
  3. in the wall, closer inner

Entry from the listed places, the dew point will manifest itself in different ways. If one place it will be harmless, then inside the house or in the wall there will be no expectation of the destructive effect on the integrity of the wall. Below, we will analyze the behavior of the dew point in each of the listed places.

Dew dawn with an unloading insulation

This is the most harmless to home to find the dew point. In this case:

  • Condensate in the occurrence of the dew point is formed directly, the Soaplitel is solar.
  • The insulation is not hygroscopic, because the moisture does not delay the wall structure and evaporates when the air temperature changes.
  • Due to the vapor insulation properties of the insulation, the humidity, which forms the evaporation of condensate, goes to the street and does not interact with the wall of the house.
  • The walls of the house are dry within the course of the year, both with the outer and from the internal source
  • Walls retain their strength and integrity of many decades
insulation outside

Dew point in the wall of the house, closer to the outside

  • The behavior of the wall depends largely on the material from which it is posted. Better tolerate dew point, walls of dense and heavy building materials, such as brick, ceramzite concrete, stone, wood. Since they are less susceptible to destruction and have a greater coefficient of frost resistance.
  • Walls of houses erected from porous materials, well absorbing moisture and passing steam. Such like, foam blocks, gas blocks and this kind of materials, the action of the dew point should be minimally short.
Dew point
Wall destruction under the influence of humidity
  • If condensate occurs inside the wall, the wall material is saturated with liquid. With the subsequent decrease in the air temperature below zero, the accumulated fluid freezes and increases in volumes. Increasing the volume of fluid destroys any wall material from the inside. This leads to the formation of both small and large cracks in the wall structure. Walls crumble and finally lose their strength.
  • In the event that the wall in which the dew point inside and is insulated outside, then the insulation will not prevent the output of the accumulated moisture. Therefore, the entire liquid will accumulate on the surface, between the insulation and the wall. It entails the formation of mold and fungus, with all the consequences, harmful both for the building and for human health.
  • If the wall of the house is not insulated outside, the liquid will go out with an increase in air temperature, but it will not save the wall from the internal destruction after the freezing of water. Similar evaporation of fluid, from a wet wall, we can observe in the form of a white plaque on brick walls.
Warm selection of brick wall in the form of a white plaque

Dew dawn at home, closer to the inner surface

It occurs when the pairs passes the middle of the thickness of the wall and condensate begins to form a closer to the wall surface, which is inside the house.

Consequences of dew for interior decoration at home:

  • The masonry saturated with humidity begins to highlight on the inner wall, in the house liquid in the form of water droplets.
  • Wet surface of the wall destroys the inner decoration of the room: putty, wallpaper other finishing materials.
  • On the walls and in the corners, mold and fungus are formed, from which it is already difficult to get rid of
  • In the house there is an unfortunate smell of decomposition, which is harmful to health.
  • Falls the total heat temperature in the house.
Mold on the wall inside the house

The most destructive and harmful consequences of the house is when the dew point is closer to the inner surface of the wall.

The dew point is an important parameter that should be processed in the design and construction of walls, roofs and construction of the whole house. It is not compliance with the irreversible and critical consequences of the building.

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