Determination of the dew point at negative temperatures. How to determine the position of the dew point when insulating a house? How to properly insulate a house: from the inside or outside

Construction technologies involve taking into account many nuances that affect the durability of the structure and the ability to resist the negative influence of external factors. One of the main enemies of most buildings and structures is constant high humidity. To combat it, various methods are used.

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. An important place in such a situation is given to competent calculations for the insulation of buildings. A mandatory attribute in them is the determination of the dew point temperature.

Basic Knowledge

Large construction projects use complex and cumbersome programs for calculations. Many coefficients and mathematical formulas are used. In domestic conditions, the technique is greatly simplified. A lot of rounding 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 the involvement of third-party specialists.

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

The 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 to the maximum with liquid and can no longer receive replenishment from it without passing into condensate, then it is said that in this case the relative humidity has reached 100%. Subsequent saturations turn the air into fog, which is a large number of water droplets in the air that are suspended.

The peculiarity of this event lies in the fact that different air temperatures can provide different degrees of moisture saturation before passing into condensate. There is a direct dependence on the high temperature and the amount of dissolved liquid in the air. At the same time, when air with a moisture content of 70-80% gets 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

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

• relative humidity at the moment;
• current air temperature;
• air speed;
• material thickness.

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

VIDEO: Why condensation falls on the walls

The role of the concept in the construction process

We recommend using a special table prepared by experts 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 many online calculators. Often, the built-in algorithms in them do not take into account important factors.

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

The table is easy to use. 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 desired temperature number. Visually it will look like this.

Consider an example. Imagine a house with brick walls. Inside the room, for example, the temperature will be +20°С, and outside it will be cooler, for example, -10°С. The 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 highest possible value (+20°С), and the outer part will have the lowest possible value (-10°С). In the middle of the brick there will be a plane with a temperature of + 12 ° C. Moisture will condense in this place. The process will also occur on the entire volume with lower values.

The use of various heaters helps to turn the situation in a positive direction. They help to shift the position of the dew point in the wall. Depending on which side the owners of the house 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 insulation fence. Thus, there will be no destruction of the structure.

It must be borne in mind that without insulation, the plane with the dew point in our climate will be located directly in the depth of the wall. This is shown in the first drawing, so moisture will harm 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 a particular building material.

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

Requirements for insulation and thermal insulation

It is customary to call vapor permeability a value that demonstrates how much water vapor a building material is able to pass through itself in a given time. Almost all popular materials are permeable by this criterion:

• tree;
• concrete;
• brick, etc.

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

You should not be afraid that there is some kind of stationary part with a dew point in the wall, as this happens in a certain area. Builders call the place a zone of possible condensation. Given that most fences are "breathable", a lot of moisture escapes to the outside.

The correct construction of the 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 be saturated with liquid.

Various polymer heaters offered by manufacturers, due to their design, practically do not let steam 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 close to this zone. Moisture will not form.

It is not recommended to use ekrudirovanny penosterol for facade insulation. It is used only for foundation or closed building systems. As a result of constant temperature changes and direct sunlight, after a year and a half, it begins to crumble.

It will also happen in the reverse process. It is not necessary to carry out the insulation of 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 a 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 transfer the point to the insulation material. Use high-quality ventilation in the room to remove water vapor.

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

The higher the relative humidity of the air, the higher the dew point value, respectively, the lower the humidity, the lower it is.

The dew point cannot exceed the air temperature.

At 100% humidity, the dew point will be equal to the air temperature.

Dew point calculation

T p \u003d (b * f (T, Rh)) / (a-ƒ (T, Rh))

ƒ(T, Rh) = (a*T)/(b+T)+ln⁡(Rh/100)

• Т р – dew point temperature, °С;
• a (constant) = 17.27;
• c (constant) = 237.7;
• Т – air temperature, °С;
• Rh – relative air humidity, %;
• ln is the natural logarithm.

This formula has an error of ±0.4 °С in the range:

• 0 °C
• 0,01
• 0 °C

Dew Point Instruments

To determine the temperature of condensation, various instruments are used:

1. Psychrometer A device that measures relative humidity and air temperature. It consists of two thermometers: one - dry, the second - with constant moisture. As moisture evaporates, the humidified thermometer gradually cools. The lower the relative humidity of the air, the lower its temperature. The psychrometer is used in laboratory conditions.
2. Portable thermohygrometer- a digital device that shows humidity and air temperature, and some models also display the dew point value. Used in construction to survey buildings.
3. Thermal imagers. Some instruments include a dew point calculation function. At the same time, zones with a temperature below its value are shown on the screen of the thermal imager.

Dew Point Calculation Table

To quickly calculate the dew point, use the table of its calculation. Knowing the actual temperature and relative humidity of the air, it is easy to determine the temperature of condensation.

So, for example, at an air temperature of 20°C and a relative humidity of 40%, condensation will occur on surfaces with a temperature of 6°C and below.

Dew Point Calculator

Calculation result

Comfortable dew point values ​​for humans

Dew point in construction

Dew point calculation is of great importance in construction. Thanks to her, it is determined:

• Wall thickness and material;
• Thickness, material and place of insulation;
• Ventilation and heating system in the room.

Ignoring or incorrect calculation of the dew point leads to the formation of mold and fungi. This has a negative impact on the durability of the building, significantly reducing its life.

In the window sphere - the dew point directly relates to the problem of condensation on. Knowing its definition, this can be easily eliminated - it is enough to lower the humidity of the air or increase the temperature of the glass surface.

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

The dew point is the temperature to which air must cool in order to condense into vapor and then into dew. In the cold season, the partial pressure increases, warm air, under the influence of the pressure difference, rushes to 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, a normal humidity level is considered to be between 40-60%.

Special thermotechnical tables help determine the dew point. For the correct measurement, 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 condensate.

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

What determines the occurrence of the dew point

The dew point is a physical phenomenon that exists in any room. It is important to learn how to manage it correctly: to prevent temperature extremes, drafts, and excessive humidity in the room.

Parameters affecting dew point indicators:

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

Situations that may arise:

Insufficient insulation of the house, in particular, a thin heat insulator. In this case, the dew point can affect 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 can be as follows:

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

The occurrence of a dew point with different options for wall insulation and without it

For a better understanding of the process, watch this video:

How to properly insulate a house: from the inside or outside

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

Related article:

: price, advantages of use, selection criteria, types of material, calculation of the required quantity, nuances of proper installation with your own hands - read in our article.

How to bring the dew point out

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

Important! Before deciding on a home insulation option, look at how the building behaves in the winter.

What you need to pay attention to first of all:

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

Conditions to consider

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

Learn the following important points:

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

Only after carefully studying the "input data" is a decision made about the method and technology of home insulation and working with the dew point.

What thermal insulation material to prefer

Knowing the location of the dew point in the wall allows you to better understand and imagine the physical processes associated with the loss of heat through the plane of the wall and to choose the right heat-insulating material, while determining the methods of its installation.

If you look from the point of view of the budget component, then you can opt for insulating materials based on mineral wool. They differ in vapor permeability and, when the dew point is found in their array, they do not interfere with the movement of steam and its release to the outside, into the atmosphere.

Thermal insulation materials made of basalt and fiberglass are resistant to moisture, are not affected by mold and perfectly tolerate repeated thawing and freezing cycles. 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 grooves-guides.

dire consequences

How to understand that everything is bad? Sometimes you have to deal with errors that occur when building technologies are not followed. What signs may indicate that there are problems:

• the house smells of dampness, traces of fungus and mold appear on the walls;
• flakes off in places;
• the integrity of building structures is violated.

Dew point calculation

In practice, it is not difficult to make dew point measurements. The main thing is to get the necessary tools.

You will need to stock up:

• tape measure;
• conventional thermometer;
• non-contact thermometer - pyrometer;

Advice! In order to save on the purchase of appliances, you can rent them.

Sequence of work:

• a mark is placed on the wall at a height of approximately 60 cm from the floor;
• using a thermometer to measure temperature and humidity;
• the resulting indicator is 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, then the room has high humidity. In view of this, insulation must be carried out under the supervision of a specialist.

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

The dew point is a kind of indicator of the amount of water vapor in the air. As humidity increases, so does the dew point value (at a certain temperature and pressure). The dew point value is expressed in degrees. This is the temperature at which the maximum saturation of the air with water vapor is achieved if they are constantly contained in the air at the same temperature.

The dew point cannot exceed the air temperature. As a result of the contact of a cold surface and warm air, the humidity drops - this phenomenon is called condensation.

Droplets of moisture are obtained, which can transform into fog, frost, cloud or rain. The simplest example is a kettle boiling on the stove, on the hot lid of which you can see droplets of moisture. The temperature of the lid is the dew point in this case.

Knowing the dew point temperature, you can get an idea of ​​the relative humidity of the air. If the dew point temperature is close to the ambient temperature, then the humidity is high ( when matched, fog is obtained!).

Conversely, if the values ​​of the dew point and temperature differ greatly, then we can talk about a low content of water vapor in the atmosphere.

Another simple example can be considered when something is brought into a warm room from a frost. The air above it is cooled, saturated with water vapor and droplets of water condense on things.

In the future, the thing warms up to room temperature and the condensate evaporates. By the way, this phenomenon is due to the recommendation not to immediately turn on household electrical appliances that have been brought in from the cold.

Another, no less well-known example is the misting of windows in the house. Many windows “cry” in winter, condensation falls on them. It must be understood that this phenomenon is largely influenced by two factors - humidity and temperature.

Therefore, if you have a normal double-glazed window and insulation is properly carried out, and there is condensate, it means that not everything is in order with humidity; Possibly poor ventilation.

One of the most interesting physical phenomena is the change in the state of aggregation of water, in particular, the boiling of water. Read more details in the article it is really very interesting. We are sure you will find a lot of new things here.

How to calculate dew point? ^

To find the dew point temperature, cumbersome formulas were previously used. Here is one of them that works fairly at a temperature from 0 to +60С. Tp=b((aT/b+T)+lnRH)/a-((aT/b+T)+lnRH); here a=17.27, b=237.7, RH- relative air humidity, expressed in fractions of a unit, ln is the natural logarithm, Tr- Dew point.

Now you can just go to the Internet and find a calculator on the relevant sites that will show the dew point temperature depending on air temperature and pressure (normal atmospheric pressure is usually taken at 762 mm Hg).

One of the "advanced" ways to calculate the dew point is to use thermal imagers. Some models have this feature. The display shows a thermogram that clearly shows places with temperatures below the dew point.

Table for determining the dew point ^

A more affordable method is to use a household psychrometer. This is a device in which two alcohol thermometers are combined. One of them has special moisturizing, the other is normal, dry.

As moisture evaporates, the humidified thermometer cools. The humidity is lower, the temperature is lower. A humidity value of 100% means that the readings of both thermometers are equal.

Knowing the humidity and temperature displayed on the display, you can calculate the dew point from the table. They are used for quick calculations. The value of the ambient air temperature, humidity and the corresponding dew point value is indicated.

And you know what should be Read this article, there is nothing more valuable than the health of our children!

You can read everything about water aerobics and its benefits for weight loss, the most important, relevant and useful information!

Read all about treatment with living and dead water in the article:
take care of your health!

How to determine the dew point? ^

The correct determination of this parameter is of paramount importance in construction. The possibility of condensation on the walls depends on the correctness of the calculations, which dramatically reduces the durability of structures, and in some cases makes living indoors simply impossible.

Any wall (if it is not made of metal) has this or that moisture. The reason for the formation of condensate lies not only in the material of the walls themselves, but in the thermal insulation, on the correct arrangement of which the place of condensate formation depends. The temperature at which it falls depends on:

• air temperature in the room;
• humidity in the room.

Using the tables, it can be determined that if the temperature, for example, in a room is + 20 ° C with a humidity of 60%, then moisture will form on any surface with a temperature of 12 ° C and below.

With a decrease in humidity to 40%, condensate will appear on the surface with a temperature below 6C. That is, the lower the humidity, the further the dew point is from the room temperature.

The location of the dew point depends on:

• outdoor humidity;
• internal humidity;
• temperature inside and outside the room;
• wall thickness, insulation.

1. How does the dew point behave in a wall without insulation? There are several options for finding it:

• between the center of the wall (in thickness) and the outer surface: in this case, the inner wall remains dry;
• between the center of the wall and the inner surface: the inner surface can freeze for several days with a sharp decrease in air temperature in the region;
• on the surface of the wall indoors: during the winter period, the wall will be wet.

2. When using a heater, the picture will be somewhat different. The place of condensation formation can be located (insulation from the outside):

• inside the insulation: this is true with correct thermal calculations - the wall will be dry, the point is calculated correctly;
• in any place described above (item 1): this happens if the thickness of the insulation is chosen incorrectly.

3. Internal insulation. In this case, the place of condensate formation moves inside the room; at the same time, the temperature under the heater decreases. The dew point can be:

• between the center of the wall and the insulation or at their border in case of a sharp cold snap;
• only under insulation: the wall will partially get wet all winter;
• inside the insulation: it will get wet during the entire cold period.

How is dew point used? ^

Knowing the location of the dew point, you can correctly calculate the thickness of the insulation, thereby preventing the formation of condensate in an undesirable place.

But there is another question: in what situation should the wall be insulated from the inside, and in which - from the outside? To answer it, it is necessary to take into account all the factors that affect the dew point and its position:

• climatic zone;
• mode of residence (permanent, temporary) indoors;
• what the insulated wall borders on (another room or street);
• operation of the ventilation system (including exhaust and correct calculations of the entire system);
• the quality of the heating system in the room;
• material, wall thickness;
• temperature outside and inside the room;
• external and internal humidity;
• insulation of all elements of the house (floor, walls, ceiling).

Insulation of the room from the inside is possible if the situation is as follows:

• permanently reside in the premises;
• ventilation functions in accordance with the standards for this room;
• the heating works just as well;
• all structural elements are insulated in accordance with the requirements for a specific climatic zone;
• the wall intended for insulation is sufficiently thick (according to the climatic zone): i.e. insulation thickness in any case must not exceed 50 mm.

Speaking quite simply, then all of the above can be formulated as follows: the warmer the region, the better the heating, ventilation, and the thicker the wall, the greater the likelihood of internal wall insulation.

Practice shows that in the vast majority of cases it is preferable to equip external insulation. In this option, there is much more chance that the dew point will be in the right place.

Why are the windows "crying" ^

There are specific recommendations for the microclimate in a residential area. This humidity -40-50% and temperature +18-23С. Maintaining these parameters minimizes the possibility of condensation on the glass surface.

Its appearance is also associated with human activity (it also releases moisture!). That is, there should be as many people in the room as sanitary standards allow.

High humidity can also be associated with improper air exchange. Here, too, there are rules: at least 3 "cubes" per "square" area in one hour.

For kitchens, these requirements are even tougher: from 6 to 9 "cubes" per hour, depending on the type of plate ( 9 cu. m/h - for gas). Therefore, it all depends on the quality of ventilation.

There is a contradictory situation; the house was overhauled, the old windows were replaced with double-glazed windows, and mold began to appear in the rooms. What is it connected with?

The fact is that in the course of a complete reconstruction, the heating is changed, modern boilers are installed instead of old gas water heaters, and windows are insulated. By and large, there are fewer opportunities for natural ventilation.

If earlier moisture from the room could escape through leaky window slots, through the exhaust of an old gas column, then now there is no such possibility.

There is only one way out - the development and installation of a new ventilation system. If this is not possible, then just ventilate the rooms and the kitchen more often.

The operational characteristics of a double-glazed window (coefficient "K", in particular) are important, but already secondary.

Possible consequences of choosing the wrong dew point ^

In the cold season, the air coming from a warm room outside is supercooled, manifesting itself in the form of precipitating moisture. The surface is any material that has a temperature below the dew point. As a result, at low outside temperatures, the walls are constantly wet. This leads to the formation of mold, promotes the development of various microorganisms. Subsequently, they can easily end up in the air inhaled by the residents, which leads to diseases of various kinds; for example, asthma.

A building with damp walls will not last long; the process of destruction will inevitably accelerate. Affected by mold, fungus, houses do not “live” for a long time. Therefore, it is important to calculate the correct point at the design stage of the building. Must be correctly selected:

• wall material and thickness;
• insulation material, its thickness;
• method of wall insulation (outside, inside);
• a variant of the heating and ventilation system that provides an optimal microclimate (18-23C at 40-50% humidity).

You can calculate the dew point yourself. In this case, it is necessary to take into account the climatic features of the region of residence. If you do not rely on your own strength, then you can contact any serious construction company. Surely there will be a specialist involved in such calculations.

Video of the Usadba TV channel about the importance of determining the dew point before starting construction:

This article will address the following questions:

• What happens in a wall insulated from the inside;
• How to determine when you can insulate from the inside, and when you can’t. Factors on which it depends.

Definition of "dew point"

In order to understand the processes taking place in the wall, I will first dwell on such a concept as the dew point in construction.

Dew point determination- This is the temperature at which condensation occurs (moisture from the air turns into water). A point with this temperature is located in a certain place (on the wall outside, somewhere in the thickness of the wall or on the wall inside). Depending on the location of the dew point (further or closer in wall thickness to the interior), the wall is either dry or wet inside. The dew point (condensation temperature) depends on:

• indoor humidity;
• indoor air temperature.

1. If the indoor temperature is +20 degrees, and the indoor humidity is 60%, then condensation will form on any surface with a temperature below +12 degrees.

The lower the indoor humidity, the lower the dew point is the actual indoor air temperature.

2. At an indoor temperature of +20 degrees, and indoor humidity of 40%, then condensation will fall on any surface with a temperature below +6 degrees.

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

3. At an indoor temperature of +20 degrees, and indoor humidity of 80%, then condensation will fall on any surface with a temperature below +16, 44 degrees.

If the relative humidity is 100%, then the dew point is the same as the actual indoor temperature.

4. When the indoor temperature is +20 degrees, and indoor humidity is 100%, then condensation will fall on any surface with a temperature below +20 degrees.

Dew point location

A dew point position in the wall depends on:

• thickness and material of all layers of the wall,
• indoor temperature,
• outside temperature,
• indoor humidity,
• humidity outside.

Let's analyze what happens to the position of the dew point:

• in a wall not insulated at all;
• in a wall insulated from the outside;
• in a wall insulated from the inside.

Immediately, for each option, we will consider the consequences of such an arrangement of the dew point.

Location of the dew point in an uninsulated wall

By dew point location there may be options not insulated walls:

1. The location of the dew point between the middle of the wall and the outer surface of the wall.

The location of the dew point in the wall between the middle of the wall and the outer surface, the wall is not insulated

In this case, the wall is dry.

2. The location of the dew point between the middle of the wall and the inner surface.

The location of the dew point between the middle of the wall and the inner surface, the wall is not insulated

In this case, the wall is dry, it can freeze with a sharp drop in outside temperature (lower than the design temperature according to DBN / SNiP in the region for several days). The position of the dew point in these few days may shift to the inner surface of the wall.

3. The location of the dew point on the inner surface.

The location of the dew point on the inner surface of the wall, the wall is not insulated

The wall is wet inside almost the entire winter period.

As already discussed, the position of the dew point depends on the 5 factors described in the part above.

The location of the dew point in the wall insulated from the outside

By dew point location in the wall, insulated outside, there may be such options:

1. If the insulation is taken with the thickness required according to the heat engineering calculation, then the position of the dew point is inside the insulation.

The location of the dew point in the insulation, the wall is insulated from the outside

This is the correct position of the dew point. This wall is dry.

2. If the insulation is taken with a smaller thickness than it should be according to the heat engineering calculation, then all three options described above for an uninsulated wall are possible. The consequences are described there.

The location of the dew point in the wall, insulated from the outside (if the insulation is taken less than the calculated thickness)

The location of the dew point in the wall insulated from the inside

According to the location of the dew point in the wall, insulated from within. When we insulate a wall from the inside, we kind of “fence off” it from the room heat. Thus, we shift the position of the dew point inside the room and lower the temperature of the wall itself under the insulation. That is, both the dew point (temperature) and its position become such that condensation is more likely to form. There may be such options:

1. The location of the dew point in the thickness of the wall.

The location of the dew point in the thickness of the wall, the wall is insulated from the inside

In this case, the wall is dry, it can freeze with a sharp drop in outside temperature (lower than the design temperature according to DBN \ SNiP in the region for several days). The position of the dew point in these few days may shift to the inner surface of the wall.

2. The location of the dew point on the inner surface of the wall, under the insulation.

The location of the dew point on the inner surface of the wall, under the insulation, the wall is insulated from the inside

The wall in this case freezes under the insulation for the entire winter period.

3. The location of the dew point inside the insulation.

The location of the dew point in the insulation, the wall is insulated from the inside

The wall in this case freezes the entire winter period, except for the wall, the insulation is also wet.

When it is possible or impossible to insulate the walls from the inside

Now we will analyze when it is possible to insulate the wall from the inside, when it is impossible, what it depends on and how it depends. What is this “no”, what are the consequences.

The main "possible or impossible" is what will happen to the wall after it is insulated from the inside. If the wall is dry, you can. If the wall is dry, and only with a sharp, unexpected (which happens once every ten years) cold snap can get wet, you can try to insulate from the inside (at the discretion of the customer). If the wall is consistently wet throughout the winter settlement period (with the usual winter temperature in the region), it is impossible to insulate from the inside. As we have already found out above, these consequences depend on the position of the dew point. And the position of the dew point in the wall can be calculated, and then it will be clear (BEFORE insulation) whether it is possible or not to insulate a particular wall from the inside.

Note: We do such a calculation, ask questions in the section and we will calculate your specific situation.

Now a little discussion on the topic of what affects the possibility of insulation from the inside, and how it affects. This part of the article is caused by questions from readers of the following nature: “Why can a reader in the next branch be insulated from the inside, but I can’t, because we have the same apartment layout with him (further options), or houses are built from the same material, or one city of residence, or the same thickness of the wall and so on.

Let's figure it out. As we have already found out above, the consequences of internal insulation depend on:

• dew points (condensation temperature);
• position of the dew point in the wall before and after insulation.

In turn, the dew point (temperature) depends on: the humidity in the room and the temperature in the room. And the humidity in the room depends on:

• Mode of residence (permanently or temporarily);
• Ventilation (both inflow and exhaust, are they enough according to the calculation).

And the temperature in the room depends on:

• The quality of the heating;
• The degree of insulation of other structures of the house / apartment, except for walls (ceiling / roof, windows, floor).

The position of the dew point depends on:

• thickness and material of all layers of the wall;
• indoor temperature. On what it depends - found out above;
• outside temperature. It depends on whether the street is outside or another room, as well as on the climatic zone;
• indoor humidity. On what it depends, found out above;
• humidity outside. It depends on whether the street is outside or another room (and on the mode of operation of this room), as well as on the climatic zone.

Now, if we collect ALL factors of influence on dew point and dew point position, we will get a list of influencing factors that must be taken into account when deciding whether it is possible or not in a particular situation to insulate a particular wall from the inside. Here is a list of these factors:

• mode of residence in the premises (permanently or temporarily);
• ventilation (both inflow and exhaust, are they enough according to the calculation);
• the quality of the heating in the room;
• the degree of insulation of other structures of the house / apartment, except for walls (ceiling / roof, windows, floor);
• thickness and material of all layers of the wall;
• indoor temperature;
• indoor humidity;
• outside temperature;
• humidity outside the room;
• climatic zone;
• what is behind the wall, street or other room (its mode of operation).

It becomes clear that there may not be two identical situations for warming from the inside. Let's see how (approximately, without specifics) the situation looks like when insulation from the inside is possible:

• permanent residence,
• ventilation is carried out according to the norm (for this room),
• heating works well and is carried out according to the norm,
• other structures are insulated according to the norm,
• the wall to be insulated is thick and warm enough. According to the calculation for additional insulation for it, it should not be more than 50 mm (polystyrene, cotton wool, EPS). In terms of heat transfer resistance, the wall “does not reach” the norm of 30% or less.

To simplify it completely, it turns out like this: the warmer the region, the better your heating and ventilation, the thicker and warmer the wall, the more likely it is that you can insulate from the inside. I think it is clear that in each specific case you need to consider your "incoming data" and then make a decision.

Everything that is written above gives the impression that there are very few cases when internal insulation is possible and not harmful. It really is. In our experience, out of 100 who came up with the idea of ​​internal insulation, only 10 can do it without consequences. In other cases, you need to insulate the outside.

The consequences of improper insulation from the inside

What are the consequences of insulation, when they insulated from the inside, but it was “impossible”. As a rule, these are wet walls at first. Then, depending on the type of insulation, wet insulation. Cotton wool gets wet, but Styrofoam or XPS does not. But that doesn't change things. The end result is mold and fungus on the walls. The time of occurrence of consequences is from one to three years.