What is the “dew point” and why is it needed? Dew point in the wall - calculation and finding Where the dew point should be.

Ecology of consumption. Estate: One of the conditions high-quality insulation at home is to calculate the dew point, which should be closer to external wall, and in no case - inside the house. To do this, you need to be able to determine where the dew point will be located at different conditions to eliminate the possibility of condensation forming on the walls inside the room.

Wall insulation is one of the main issues during construction. At first glance, it may seem that it is very simple to solve it - choose the one that suits the climatic conditions and finances, and insulate it. However, this is not true. There are a number technical specifications, which must be completed so that the walls of the house do not become damp inside or freeze outside during the cold season.

One of these conditions is to insulate the house so that the dew point is closer to the outer wall, and in no case - inside the house. To do this, you need to be able to determine where the dew point will be located under different conditions in order to eliminate the possibility of condensation forming on the walls inside the room.

What is dew point

The dew point is an indicator of the temperature at which maximum saturation of air with steam occurs and it begins to condense. This indicator depends on two main factors: temperature and air humidity.

When at least one of these two quantities changes, the dew point also changes, that is, it constantly moves, just as the temperature and humidity of the air are not constant all the time.

There is a table of dew points at different temperatures and air humidity, developed by specialists. From it you can see under what conditions steam begins to condense. For example, in winter time at a standard indoor air temperature of +200C and humidity from 50% to 60%, the dew point will range from 9.30C to 120C. That is, condensation should not form inside the room, since under the specified conditions there are no surfaces with such a temperature.

Let's look further. If the house is +200C, and the temperature outside is -200C, then in the wall there will be a dew point with a temperature of +120C at a relative humidity of 60%. The dew point can move across the thickness of the wall depending on the temperature inside and outside the room, as well as the humidity in the wall itself. The closer the dew point is to the inner surface, the more likely it is that the wall will be wet from the inside. And this is already creating unfavorable conditions for accommodation. By insulating a house, we can shift the dew point, since this changes the temperature of the wall itself.

Where will the dew point be?

There can be three options for wall construction: without insulation, with external and internal cladding. Let's consider where the dew point might be in each of these cases?

1. The design is without insulation, then the dew point is located:

• inside the wall closer to the outer surface;
• inside the wall it is shifted to the inner surface;
• on the inner surface - indoors the wall will remain wet throughout the winter period.

2. There is external insulation, then the dew point is:

• inside the insulation - this indicates that the calculation of the dew point and the thickness of the insulation was carried out correctly, and the wall in the room will be dry;
• any of the three cases described in paragraph 1 - the reason is the incorrect choice of insulation and its characteristics.

3. Done interior lining, then the dew point will be:

• inside the wall closer to the insulation;
• on the inner surface of the wall under the cladding;
• in the insulation itself.

From what has been discussed above, it becomes clear that the location of the dew point also depends on such characteristics of the fence as temperature and vapor permeability. Majority modern insulation materials practically does not allow steam to pass through, so it is recommended external cladding walls

If you choose internal insulation, then the following conditions must be met in order to:

• the wall was dry and warm;
• the insulation had good vapor permeability and small thickness;
• ventilation and heating functioned in the building.

Knowing possible areas of condensation formation, i.e. location of the dew point, for certain climatic zones it is possible to select a type and material of insulation that will not create conditions for damp walls inside the house.

There is an opinion that the house should be insulated from the outside, and the insulation in all respects must comply with GOST. Then the dew point will be inside the casing, that is, outside the house, and interior walls will be dry in any season. That is why external insulation is more profitable than internal insulation.

In climatic zones in which conditions vary depending on the time of year or time of day, builders face the difficult task of choosing and calculating correct amount building materials for furnishing a home and creating a comfortable microclimate in it. The question of protection from subzero temperature, winds and humidity. The answer is a simple word - insulation. But its effectiveness directly depends on the dew point, which shows how much water vapor is in the air.

Dew point: a little history

For a long time, people who did not even think about determining some kind of dew point, built homes for themselves in order to relax in conditions of complete silence, when neither insects nor animals disturbed you, not to mention weather phenomena. If a simple house made of natural materials is enough on a tropical island, since the air temperature in this area is comfortable all year round, then the situation may be completely different in another climatic zone, where the indoor temperature differs from the outdoor temperature by several tens of degrees. How to support comfortable conditions in a home under such weather conditions? That's right, build walls from the appropriate material that can withstand all these misfortunes, and insulate them. But this is not enough - you also need to know what the dew point is and learn how to calculate it correctly.

There are building codes, in which for any regions are calculated different meanings, including the thickness of the building walls for a certain material, the thickness of insulation for a certain wall thickness, etc. Unfortunately, some customers, in order to save materials and reduce construction costs, take these indicators at the lower limits. Here they can stumble upon “underwater reefs”. In a constantly changing climate, there is no guarantee that the frost this winter will not be too severe. As a result, if during construction the determination of the dew point was incorrect or was not carried out at all, due to changes in temperature and humidity outside, the walls inside the room begin to get wet, and over time, mold and mildew appear.

Our ancestors tried many building materials, which provided in regions with harsh winters reliable protection from frost and snow, water and rain in spring and autumn and heat in summer. All they had to do was build a hut with thick, breathable walls (with a reserve, so to speak), and put a good stove inside, ensuring proper circulation warm air, and the job was done. In such a home, any person felt comfortable, without even wondering about calculating the dew point. But time passed...

With the advent of large cities and their development, people began to build multi-storey buildings. They began to use new materials in construction. Construction companies and private owners began to save on materials, guided during construction by the lower limits of the values ​​of construction regulations. In addition, during the cold and winter season in apartment buildings (and not only) they began to use not the heat from the stove, but central heating or individual heating systems operating on the same principle.

Why do you need to correctly calculate the dew point when insulating a house?

Have you ever seen an uninsulated house in which (especially when it’s below zero outside) the walls near the ceiling or floor are wet? What kind of moisture is this? It turns out it's dew. Indoors? Yes! And not only indoors, but also in the walls and floor.

Humidity, temperature and atmospheric pressure. When these three quantities change, precipitation occurs. Precipitation comes in the form of rain, snow and dew. Let's talk about the latter in more detail.

As a result of contact between a cold surface and moist warm air, its humidity drops and condensation begins to form on this surface. This process can be observed on the walls of a glass with a cold drink.

The temperature at which this condensation falls is called the dew point temperature (DTP). At a certain temperature and atmospheric pressure As air humidity increases, the dew point value, which is expressed in degrees, also increases. The walls of a glass with ice have a dew point temperature. Thus, this concept is used to somehow indicate the content of water vapor in the air. Having calculated everything correctly, you will find out the temperature value at which air humidity reaches 100 percent. If this temperature is equal to the air temperature (it cannot exceed it), then fog or rain will form (depending on pressure). If it is significantly less, there will be no precipitation.

So, if there is humid air and an object whose temperature is TTP, moisture will accumulate on this object. That is why it is necessary to determine the dew point at different construction work, including erection of walls, their insulation, pouring self-leveling floors, thermal insulation of building roofs, etc. For example, if the temperature outside is such that the dew point is in the area from the center of the wall, closer to its inner edge, you will see a wet spot in your room until the temperature outside rises. If this continues for some time, a fungus will form on these surfaces, loving the combination of humidity, heat and carbon dioxide(which we exhale from the lungs). Now we are approaching the main point.

Dew point determination

Example No. 1

Let's take, for example, a very common case in construction: the installation of self-leveling floors. The humidity in the room and the temperature of the base on which the coating will be applied plays a big role. After all, if the floor has a TTR, the moisture released in it can negatively affect the strength of the future coating - all sorts of deformations appear, which soon turn into peeling of the coating. To avoid this, you need to measure the humidity in the room (with a hygrometer) and the air temperature. We calculate the dew point using the formula:

Or based on the finished table:

Click to enlarge

For example, if the dew point is 11 degrees Celsius, and the base temperature is not 5 degrees higher than the dew point, it is not recommended to install a self-leveling floor.

Example No. 2

Arrangement external insulation at home with polystyrene foam or . In this case, the situation is much more complicated. After all, you need to measure temperature and humidity outside and inside the room in all possible combinations that occur in your climate zone. To help builders, standards SP 23-101-2004 “Design of thermal protection of buildings” and SNiP 23-02-2003 “Thermal protection of buildings” have been developed. Manufacturers of insulation systems also provide on their websites special calculators for calculating the thickness of the insulation depending on the parameters of the walls and climatic conditions, so that the dew point does not end up in the wrong place.

The higher the relative air humidity, 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% air humidity, the dew point will be equal to the air temperature.

Dew point calculation

Т r = (b*f(T, Rh))/(a-ƒ(T, Rh))

ƒ(T, Rh) = (a*T)/(b+T)+ln⁡(Rh/100)

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

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

• 0 °C
• 0,01
• 0 °C

Instruments for calculating dew point

Various instruments are used to determine the condensation temperature:

1. Psychrometer- a device that measures relative humidity and air temperature. It consists of two thermometers: one is dry, the second is with constant humidification. As moisture evaporates, the moistened 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 inspect buildings.
3. Thermal imagers. Some instruments include a dew point calculation function. At the same time, zones with temperatures below its value are shown on the screen of the thermal imager.

Dew point calculation table

To quickly calculate the dew point, use its calculation table. Knowing the actual temperature and relative humidity of the air, you can easily determine the condensation temperature.

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 has great value in construction. Thanks to it, it is determined:

• Wall thickness and material;
• Thickness, material and place of insulation;
• Indoor ventilation and heating system.

Ignoring or incorrectly calculating the dew point leads to the formation of mold and mildew. This has negative influence on the durability of the building, significantly reducing its service life.

In the window sphere, the dew point directly relates to the problem of condensation on. Knowing its definition, you can easily eliminate this - just lower the air humidity or increase the temperature of the glass surface.

The concept of dew point

The dew point is the temperature at which moisture precipitates or condenses from the air, which was previously in a vapor state. In other words, the dew point in construction is the boundary of transition from the low air temperature outside the enclosing structures to the warm temperature of the internal heated rooms, where moisture may appear; its location depends on the materials used, their thickness and characteristics, the location of the insulating layer and its properties.

In a regulatory document SP 23-101-2004 “Design of thermal protection of buildings” (Moscow, 2004) and SNiP 23-02 “Thermal protection of buildings” the conditions relating to the accounting and value of the dew point are regulated :

“6.2 SNiP 23-02 establishes three mandatory mutually related standardized indicators for the thermal protection of a building, based on:

“a” – standardized values ​​of heat transfer resistance for individual building envelopes for thermal protection of the building;

“b” – standardized values ​​of the temperature difference between the temperatures of the internal air and on the surface of the enclosing structure and the temperature on the internal surface of the enclosing structure above the dew point temperature;

“c” – a standardized specific indicator of thermal energy consumption for heating, which allows one to vary the values ​​of the heat-protective properties of enclosing structures, taking into account the choice of systems for maintaining standardized microclimate parameters.

The requirements of SNiP 23-02 will be met if, when designing residential and public buildings the requirements of the indicators of groups “a” and “b” or “b” and “c” will be met.

Condensation of water vapor most easily occurs on some surface, but moisture can also appear inside the thickness of structures. With regard to wall construction: in the case where the dew point is located close to or directly on the inner surface, under certain temperature conditions during the cold season, condensation will inevitably form on the surfaces. If the enclosing structures are not sufficiently insulated or are constructed without installing an additional insulating layer at all, then the dew point will always be located closer to the internal surfaces of the premises.

The appearance of moisture on the surfaces of structures is fraught with unpleasant consequences - this creates a favorable environment for the proliferation of microorganisms, such as fungus and mold, the spores of which are always present in the air. In order to avoid these negative phenomena, it is necessary to correctly calculate the thickness of all elements that make up the enclosing structures, including calculating the dew point.

According to the instructions of the regulatory document SP 23-101-2004 “Design of thermal protection of buildings” (Moscow, 2004):

“5.2.3 Temperature of the internal surfaces of the external fences of the building, where there are heat-conducting inclusions (diaphragms, through inclusions of cement-sand mortar or concrete, interpanel joints, rigid connections and flexible connections in multilayer panels, window frames etc.), in corners and on window slopes should not be lower than the dew point temperature of the air inside the building...”

If the temperature of the surface of the wall indoors or window units is lower than the calculated dew point value, then condensation is likely to appear in the cold season, when the outside air temperature drops to negative values.

Solving the problem - how to find the dew point, its physical value, is one of the criteria for ensuring the required protection of buildings from heat loss and maintaining normal microclimate parameters in the premises, in accordance with the conditions of SNiP and sanitary and hygienic standards.

Calculation of dew point value

• using the table of the regulatory document;
• according to the formula;
• using an online calculator.

Calculation using a table

Calculation of the dew point when insulating a house can be done using the table of the regulatory document SP 23-101-2004 “Design of thermal protection of buildings” (Moscow, 2004)

To determine the temperature of condensation, it is enough to look at the intersection of the temperature and humidity values ​​​​established by the standards for each category of premises.

Calculation by formula

Another way to determine the dew point in a wall is using a simplified formula:
$$\quicklatex(size=25)\boxed(T_(p)= \frac(b\times \lambda (T,RH))(a — \lambda(T,RH)))$$

Values:

Тр – desired dew point;

a – constant = 17.27;

b – constant = 237.7 °C;

λ(Т,RH) – coefficient calculated by the formula:
$$\quicklatex(size=25)\boxed(\lambda(T,RH) = \frac(((a\times T)))((b + T) + (\ln RH)))$$
Where:
Т – indoor air temperature in °C;

RH – humidity in fractions of volume ranging from 0.01 to 1;

ln – natural logarithm.

For example, let’s calculate the required value in a room where it should be maintained optimal temperature 20 °C with a relative humidity of 55%, which is established by standards for residential buildings. In this case, we first calculate the coefficient λ(T,RH):

λ(T,RH) = (17.27 x 20) / (237.7 + 20) + Ln 0.55 = 0.742

Then the temperature of condensation from the air will be equal to:

Tr = (237.7 x 0.742)/(17.27 – 0.742) = 176.37/ 16.528 = 10.67 °C

If we compare the temperature value obtained from the formula and the value obtained from the table (10.69°C), we will see that the difference is only 0.02°C. This means that both methods allow you to find the desired value with high accuracy.

Calculation using an online calculator

The examples show that such a task as determining the dew point is not particularly difficult. Online calculators are developed based on tables and formulas, so if you are faced with the problem of how to calculate the dew point in a wall, a calculator for this is available on the website. To make the calculation, it is enough to fill in two fields - enter the indicators of the established standard indoor temperature and relative humidity.

Determining the position of the dew point in the wall

In order to ensure the normal thermal protection qualities of the enclosing structures, it is necessary not only to know the value of the condensation temperature, but also its position within the enclosing structure. The construction of external walls is now carried out in three main options, and in each case the location of the condensation boundary can be different:

• the structure was built without a device additional insulation- from masonry, concrete, wood, etc. In this case, in the warm season, the dew point is located closer to the outer edge, but if the air temperature drops, it will gradually shift towards the inner surface, and there may come a time when this boundary will end up indoors, and then condensation will appear on the internal surfaces.

It should be noted that the dew point at wooden house with the correct thickness of the walls - made of logs or timber - will be located closer to the outer surfaces, since wood is natural material With unique properties, having very low thermal conductivity with high vapor permeability. Wooden walls in most cases do not require additional insulation;

• the structure was built with an additional layer of insulation with outside. With the correct calculation of the thickness of all materials, the dew point when insulating with foam plastic or other types effective insulation materials will be located inside the insulating layer, and condensation will not appear indoors;
• the structure is insulated with inside. In this case, the boundary of the appearance of condensation will be located close to the inner side and during severe cold weather it may shift by inner surface, at the junction with the insulation. In this case, it is also likely that moisture will appear indoors, leading to unpleasant consequences. Therefore, this insulation option is not recommended and is carried out only in cases where there are no other solutions. At the same time, it is necessary to provide additional measures to prevent negative consequences– provide an air gap between the insulation and the cladding, holes for ventilation, arrange additional ventilation of the rooms to remove water vapor, air conditioning to reduce humidity.

• wall thickness, including base material (h1, in meters) and insulation (h2, m);
• thermal conductivity coefficients for load-bearing structure(λ1, W/(m*°C) and insulation (λ1, W/(m*°C);
• standard room temperature (t1, °C);
• outdoor air temperature, taken for the coldest time of year in a given region (t2, °C);
• standard relative humidity in the room (%);
• standard dew point value at given temperature and humidity (°C)

We will accept the following conditions for calculation:

• wall brick thick h1 = 0.51 m, insulation – polystyrene foam thickness h2 = 0.1 m;
• thermal conductivity coefficient established according to regulatory document For sand-lime brick, laid on cement-sand mortar, according to the table in Appendix “D” SP 23-101-2004λ1 = 0.7 W/(m*°C);
• thermal conductivity coefficient for EPS insulation - expanded polystyrene, having a density of 100 kg/m² according to the table in Appendix “D” SP 23-101-2004λ2 = 0.041 W/(m*°C);
• indoor temperature +22 °C, as established by standards within 20-22 °C according to table 1 SP 23-101-2004 for residential premises;
• outside air temperature –15 °C for the coldest time of year in a conventional area;
• indoor humidity – 50%, also within the standard range (no more than 55% according to Table 1 SP 23-101-2004) for residential premises;
• the dew point value for the given values ​​of temperature and humidity, which we take from the table above, is 12.94 °C.

First, we determine the thermal resistances of each layer that makes up the wall and the ratio of these values ​​to each other. Next, we calculate the temperature difference in the load-bearing layer of the masonry and at the boundary between the masonry and the insulation:

• the thermal resistance of the masonry is calculated as the ratio of the thickness to the thermal conductivity coefficient: h1/ λ1 = 0.51/0.7 = 0.729 W/(m²*°C);
• the thermal resistance of the insulation will be equal to: h2/ λ2 = 0.1/0.041 = 2.5 W/(m²*°C);
• thermal resistance ratio: N = 0.729/2.5 = 0.292;
• temperature difference in the layer brickwork will be: T = t1 – t2xN= 22 - (-15) x 0.292 = 37 x 0.292 = 10.8 °C;
• the temperature at the junction of the masonry and insulation will be: 24 – 10.8 = 13.2 °C.

Based on the calculation results, we will plot the temperature change in the wall mass and determine the exact position of the dew point.

According to the graph, we see that the dew point, the value of which is 12.94 °C, is within the thickness of the insulation, which is the best option, but very close to the junction between the wall surface and the insulation. When the outside air temperature decreases, the condensation boundary may shift to this joint and further inside the wall. In principle, this will not cause any special consequences and condensation cannot form on the surface indoors.

The calculation conditions were accepted for middle zone Russia. In the climatic conditions of regions located in more northern latitudes, a greater thickness of the wall and, accordingly, the insulation is accepted, which will ensure that the boundary of condensation formation is located within the insulating layer.

In the case of insulation from the inside under all the same conditions: thickness of the supporting structure and insulation, external and internal temperature, humidity, accepted in the calculation example given, the graph of temperature changes in the thickness of the wall and at the boundaries will look like this:

We see that the boundary of condensation from the air in this case will shift almost to the inner surface and the likelihood of moisture appearing in the room as the outside temperature drops will increase significantly.

Dew point and vapor permeability of structures

When designing enclosing structures and ensuring standard thermal protection of premises, taking into account the vapor permeability of materials is of great importance. The amount of vapor permeability depends on the volume of water vapor that can pass through this material per unit of time. Almost all materials used in modern construction, - concrete, brick, wood and many others - have small pores through which air carrying water vapor can circulate. Therefore, designers, when developing enclosing structures and selecting materials for their construction, must take into account vapor permeability. In this case, three principles must be observed:

• there should be no obstacles to removing moisture in case of condensation on one of the surfaces or inside the material;
• the vapor permeability of enclosing structures should increase from the side interior spaces out;
• the thermal resistance of the materials from which external walls are constructed should also increase towards the outside.

In the diagram we see the correct composition of the structure of the external walls, providing regulatory thermal protection of the interior and removing moisture from the materials when it condenses on surfaces or inside the thickness of the wall.

The above principles are violated when internal insulation, therefore this method of thermal protection is recommended only as a last resort.

All modern designs external walls are based on these principles. However, some insulation materials that are included in wall construction have almost zero vapor permeability. For example, polystyrene foam, which has a closed cellular structure, does not allow air and, accordingly, water vapor to pass through. In this case, it is especially important to accurately calculate the thickness of the structure and insulation so that the boundary of condensation formation is within the insulation.

Opinion of portal experts

According to experts on the website portal, calculating the dew point value and its position in the enclosing structures is one of the defining moments in ensuring the protection of buildings from heat loss. Most best option- this is when the boundary of condensation is within the thickness of the insulation in a structure with external insulation. It is necessary to calculate the thickness of the layers of enclosing structures for certain materials so as to prevent the dew point from shifting into the thickness of the wall and towards the surfaces inside the premises.

Dew point determines the ratio of air temperature, air humidity and surface temperature at which water begins to condense on the surface.

Production and sale of materials, performance of work: Polymer floors Self-leveling floors

Dew point definition

Dew point determination is extremely important factor when installing any polymer floors, coatings and self-leveling floors on any base: concrete, metal, wood, etc. The appearance of a dew point and, accordingly, water condensation on the surface of the base at the time of laying polymer floors, self-leveling floors and coatings can cause the appearance of a variety of defects: shagreen, swelling and cavities; complete detachment of the coating from the base. Visually determining the dew point - the appearance of moisture on the surface - is almost impossible, so the technology given below is used to calculate the dew point.

Dew point table

The dew point table is very easy to use - hover your mouse over it... Dew point table - download

For example: air temperature +16°C, relative humidity 65%.
Find a cell at the intersection of air temperature +16°C and air humidity 65%. It turned out to be +9°C - this is the dew point.
This means that if the surface temperature is equal to or below +9°C, moisture will condense on the surface.

To apply polymer coatings, the surface temperature must be at least 4°C above the dew point!

Tempe- ratio air	Dew point temperature at relative air humidity (%)
	30%	35%	40%	45%	50%	55%	60%	65%	70%	75%	80%	85%	90%	95%
-10°С	-23,2	-21,8	-20,4	-19	-17,8	-16,7	-15,8	-14,9	-14,1	-13,3	-12,6	-11,9	-10,6	-10
-5°C	-18,9	-17,2	-15,8	-14,5	-13,3	-11,9	-10,9	-10,2	-9,3	-8,8	-8,1	-7,7	-6,5	-5,8
0°C	-14,5	-12,8	-11,3	-9,9	-8,7	-7,5	-6,2	-5,3	-4,4	-3,5	-2,8	-2	-1,3	-0,7
+2°С	-12,8	-11	-9,5	-8,1	-6,8	-5,8	-4,7	-3,6	-2,6	-1,7	-1	-0,2	-0,6	1,3
+4°С	-11,3	-9,5	-7,9	-6,5	-4,9	-4	-3	-1,9	-1	0	0,8	1,6	2,4	3,2
+5°С	-10,5	-8,7	-7,3	-5,7	-4,3	-3,3	-2,2	-1,1	-0,1	0,7	1,6	2,5	3,3	4,1
+6°С	-9,5	-7,7	-6	-4,5	-3,3	-2,3	-1,1	-0,1	0,8	1,8	2,7	3,6	4,5	5,3
+7°С	-9	-7,2	-5,5	-4	-2,8	-1,5	-0,5	0,7	1,6	2,5	3,4	4,3	5,2	6,1
+8°С	-8,2	-6,3	-4,7	-3,3	-2,1	-0,9	0,3	1,3	2,3	3,4	4,5	5,4	6,2	7,1
+9°С	-7,5	-5,5	-3,9	-2,5	-1,2	0	1,2	2,4	3,4	4,5	5,5	6,4	7,3	8,2
+10°С	-6,7	-5,2	-3,2	-1,7	-0,3	0,8	2,2	3,2	4,4	5,5	6,4	7,3	8,2	9,1
+11°С	-6	-4	-2,4	-0,9	0,5	1,8	3	4,2	5,3	6,3	7,4	8,3	9,2	10,1
+12°С	-4,9	-3,3	-1,6	-0,1	1,6	2,8	4,1	5,2	6,3	7,5	8,6	9,5	10,4	11,7
+13°С	-4,3	-2,5	-0,7	0,7	2,2	3,6	5,2	6,4	7,5	8,4	9,5	10,5	11,5	12,3
+14°С	-3,7	-1,7	0	1,5	3	4,5	5,8	7	8,2	9,3	10,3	11,2	12,1	13,1
+15°С	-2,9	-1	0,8	2,4	4	5,5	6,7	8	9,2	10,2	11,2	12,2	13,1	14,1
+16°С	-2,1	-0,1	1,5	3,2	5	6,3	7,6	9	10,2	11,3	12,2	13,2	14,2	15,1
+17°С	-1,3	0,6	2,5	4,3	5,9	7,2	8,8	10	11,2	12,2	13,5	14,3	15,2	16,6
+18°С	-0,5	1,5	3,2	5,3	6,8	8,2	9,6	11	12,2	13,2	14,2	15,3	16,2	17,1
+19°С	0,3	2,2	4,2	6	7,7	9,2	10,5	11,7	13	14,2	15,2	16,3	17,2	18,1
+20°С	1	3,1	5,2	7	8,7	10,2	11,5	12,8	14	15,2	16,2	17,2	18,1	19,1
+21°С	1,8	4	6	7,9	9,5	11,1	12,4	13,5	15	16,2	17,2	18,1	19,1	20
+22°С	2,5	5	6,9	8,8	10,5	11,9	13,5	14,8	16	17	18	19	20	21
+23°С	3,5	5,7	7,8	9,8	11,5	12,9	14,3	15,7	16,9	18,1	19,1	20	21	22
+24°С	4,3	6,7	8,8	10,8	12,3	13,8	15,3	16,5	17,8	19	20,1	21,1	22	23
+25°С	5,2	7,5	9,7	11,5	13,1	14,7	16,2	17,5	18,8	20	21,1	22,1	23	24
+26°С	6	8,5	10,6	12,4	14,2	15,8	17,2	18,5	19,8	21	22,2	23,1	24,1	25,1
+27°С	6,9	9,5	11,4	13,3	15,2	16,5	18,1	19,5	20,7	21,9	23,1	24,1	25	26,1
+28°С	7,7	10,2	12,2	14,2	16	17,5	19	20,5	21,7	22,8	24	25,1	26,1	27
+29°С	8,7	11,1	13,1	15,1	16,8	18,5	19,9	21,3	22,5	22,8	25	26	27	28
+30°С	9,5	11,8	13,9	16	17,7	19,7	21,3	22,5	23,8	25	26,1	27,1	28,1	29
+32°С	11,2	13,8	16	17,9	19,7	21,4	22,8	24,3	25,6	26,7	28	29,2	30,2	31,1
+34°С	12,5	15,2	17,2	19,2	21,4	22,8	24,2	25,7	27	28,3	29,4	31,1	31,9	33
+36°С	14,6	17,1	19,4	21,5	23,2	25	26,3	28	29,3	30,7	31,8	32,8	34	35,1
+38°С	16,3	18,8	21,3	23,4	25,1	26,7	28,3	29,9	31,2	32,3	33,5	34,6	35,7	36,9
+40°С	17,9	20,6	22,6	25	26,9	28,7	30,3	31,7	33	34,3	35,6	36,8	38	39

Dew point calculation

To calculate the dew point, you need instruments: a thermometer, a hygrometer.

1. Measure the temperature at a height of 50-60cm from the floor (or from the surface) and the relative humidity.
2. Use the table to determine the “dew point” temperature.
3. Measure the surface temperature. If you do not have a special non-contact thermometer, place a regular thermometer on the surface and cover it to insulate it from the air. After 10-15 minutes, take readings.
4. The surface temperature must be at least four (4) degrees above the dew point.
   Otherwise, it is IMPOSSIBLE to carry out work on applying polymer floors and polymer coatings!

There are devices that immediately calculate the dew point in degrees C.
In this case, a thermometer, hygrometer and dew point table are not required - they are all combined in this device.

Different polymer coatings they “treat” moisture on the surface differently during application. Most “sensitive” to the occurrence of dew point polyurethane materials: paint coatings, polyurethane self-leveling floors, varnishes, etc. This is due to the fact that water is a hardener for polyurethane, and when there is excess moisture, the polymerization reaction occurs very quickly. As a result, a variety of coating defects appear. A particularly unpleasant defect is a decrease in adhesion, which cannot be immediately determined, and over time this leads to partial or complete peeling of the coating or polymer floor.

It is important to consider that the dew point is dangerous not only at the time of coating application, but also during its curing. This is especially dangerous for self-leveling floors, since their initial curing time is quite long (up to a day).

Epoxy self-leveling floors and coatings are “less sensitive” to moisture, but, nevertheless, determining the dew point is a guarantee of quality when installing any polymer floors and paint coatings.