How to understand dew point. Dew point: what is it, definition and calculation formula
When describing the installation of thermal insulation of structures, unknown phrases are encountered. For example, you should know what "dew point" means. This is easy to explain with an everyday example.
The higher the relative humidity, the higher the dew point and closer to the actual air temperature
Air is a mixture of nitrogen, oxygen, other gases and steam. The temperature at which steam condenses occurs has acquired the concept of dew point. This phenomenon is observed when the kettle boils, and the vapors form water droplets on cold surfaces.
Formula for calculation
This formula can be used to calculate relative humidity from a known dew point
Here Tr means the temperature of the point itself, b and a show equal (constant) values, ln is the natural logarithm, T is the temperature inside the room, Rh is the relative humidity value.
As can be seen from the formula, the value directly depends on the values of two parameters:
- moisture index;
- actual temperature readings.
At high relative humidity, the parameter becomes higher and closer to the actual temperature level. To calculate this variable, there is a table with a small parameter step. It can be used to find the required value by measuring the relative humidity and the actual temperature.
Table 1. Determination of the indicator using the ratio of influencing parameters on which the dew point depends According to the table, we calculate that at a temperature of, for example, 19 degrees and a humidity of 50%, the condensation parameter will be 8.3 degrees.
From this video it becomes clear how thick the insulation should be for the most comfortable conditions:
The term "dew point" in construction
The constantly growing and developing market for building products presents a wide range of materials for thermal insulation. The choice of thermal insulation for industrial and residential premises must be approached properly and during construction, pay attention to the indicator in question.
Incorrect dew point measurement often results in wall fogging, mold, and sometimes structural failure. The boundary of the transition from low temperatures outside the walls to higher temperatures inside heated structures with the possible formation of condensate is considered by experts to be the dew point. On any surface in the room, the temperature of which is close to the dew point parameter or falls below the value, drops of water will appear. The simplest example: in the middle of some rooms, during cold weather, condensation flows on the window panes.
The main factors influencing the determination of the value are:
- climatic factors (temperature value and air humidity outside);
- temperature values inside;
- humidity indicator inside;
- the thickness of the walls;
- vapor permeability of thermal insulation used in construction;
- availability of heating and ventilation systems;
- purpose of buildings.
The correct determination of the dew point is essential in construction Only if the indicator is measured correctly, in the future it is possible to comfortably operate the building and reduce maintenance costs in the future.
Precise definition
Water vapor most often condenses on the walls themselves or inside their structure if they are not adequately insulated or built. Without insulation, the value will be close to the temperature of the inside of the wall, and in some cases to the wall in the middle of the house. When the temperature inside the enclosing structures is below the value, then during a cold snap at a negative temperature outside, condensation will occur.
There are several places where the indicator can be located on non-insulated structures:
- inside the structure, close to its outer part, the wall will remain dry;
- inside the wall, but close to the inside, the wall becomes wet with temperature changes;
- the side of the wall that is in the building will constantly be covered with condensate.
Experts do not recommend insulating rooms from the inside, explaining that when using this method of thermal insulation, the parameter will be under the heat-insulating layer in the middle of the room . As a result, there will be a large accumulation of moisture..
- condensate can accumulate in the center of the wall and during cold weather move towards the placement of heat-insulating components;
- the place of accumulation of moisture can be the boundary of the building envelope and the insulation layer, which becomes damp and forms mold in the middle of the rooms;
- in the middle of the heat-insulating layer itself (it will gradually become saturated with moisture, begin to mold and rot from the inside).
The dew point is formed by three components: atmospheric pressure, air temperature and its humidity. Styrofoam, mineral wool or other type of insulation must be placed on the outside of the building, which will allow you to place the value in the insulating layer (with this arrangement, the walls inside will remain dry). For a clearer understanding of the parameter, there are graphs of its placement on the walls of houses with insulation, as well as on buildings that do not have an insulation layer. To independently make such a calculation, you can determine the dew point in the wall with a calculator.
Wrong definition of value
The result of errors made during the calculation of parameters will be the constant accumulation of condensate, high humidity, the development of fungal deposits and mold. An industrial, administrative or residential building will not be able to serve for a long time: negative processes will accelerate destruction. Additional costs for ongoing maintenance and overhaul will be required.
DEFINITION
Absolute air humidity is the amount of water vapor per unit volume of air:
In the SI system, the unit of measure for absolute humidity
Humidity is a very important environmental parameter. It is known that most of the Earth's surface is occupied by water (the World Ocean), from the surface of which evaporation continuously occurs. In different climatic zones, the intensity of this process is different. It depends on the average daily temperature, the presence of winds and other factors. Thus, in certain places the process of water vaporization is more intense than its condensation, and in some places it is vice versa.
The human body actively reacts to changes in air humidity. For example, the process of sweating is closely related to the temperature and humidity of the environment. At high humidity, the processes of evaporation of moisture from the surface of the skin are practically compensated by the processes of its condensation, and the removal of heat from the body is disturbed, which leads to violations of thermoregulation; at low humidity, the processes of evaporation of moisture prevail over the processes of condensation and the body loses too much fluid, which can lead to dehydration.
In addition, the concept of humidity is the most important criterion for evaluating weather conditions, which is known to all from weather forecasts.
The absolute humidity of the air gives an idea of the specific water content in the air by mass, but this value is inconvenient in terms of the susceptibility of humidity by living organisms. A person feels not the mass amount of water in the air, but its content relative to the maximum possible value. To describe the reaction of living organisms to changes in the water vapor content in the air, the concept of relative humidity is introduced.
Relative humidity
DEFINITION
Relative humidity- this is a physical quantity showing how far the water vapor in the air is far from saturation:
where is the density of water vapor in the air (absolute humidity); density of saturated water vapor at a given temperature.
Dew point
DEFINITION
Dew point is the temperature at which water vapor becomes saturated.
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 the temperatures match, fog is formed). Conversely, if the values of the dew point and air temperature at the time of measurement differ greatly, then we can talk about a low content of water vapor in the atmosphere.
When something is brought into a warm room from frost, the air above it cools, becomes saturated with water vapor, and water droplets condense on things. In the future, the thing warms up to room temperature, and all the condensate evaporates.
Another, no less well-known example is the fogging of windows in a house. Many people have condensation on their windows in the winter. This phenomenon is influenced by two factors - humidity and temperature. If a normal double-glazed window is installed and the insulation is correctly carried out, and there is condensate, it means that the room has high humidity; Possibly poor ventilation or ventilation.
Examples of problem solving
EXAMPLE 1
| Exercise | The photo shows two thermometers used to determine the relative humidity of the air using a psychrometric table. What will a wet bulb thermometer show if relative humidity increases by 7% at a constant air temperature? |
| Decision | Let's write down the readings of the dry and wet thermometers shown in the photo: Let's determine the difference in thermometer readings: According to the psychrometric table, we determine the relative humidity of the air: If the air humidity increases by 7%, it will become 55%. According to the psychrometric table, we determine the readings of a dry thermometer and the difference between the readings of dry and wet thermometers: So the wet bulb will show: |
| Answer | Wet bulb readings. |
EXAMPLE 2
| Exercise | Relative humidity in the evening at a temperature of 50%. Will dew fall if the temperature drops to ? at night? |
| Decision | Relative Humidity:
|
Why do windows, doors, walls sweat? Why do things that are brought from the cold into a warm room become covered with condensate? Why do cold water pipes get wet? - one answer, the surface temperature of the object is lower dew point temperature.
Dew point (Dew point temperature TP) is the temperature at which dew begins to form, i.e. the temperature to which the air must be cooled in order for the relative humidity to reach 100%
From the school physics course, we know that air humidity (water content in the air) is determined by two parameters:
absolute humidity;
relative humidity.
With absolute humidity(f ) everything is clear - this is the amount of water, in grams, contained in one cubic meter of air, the unit of measurement is grams in a cubic meter, g/m3.
f=m/V
V - volume of moist air;
m is the mass of water vapor contained in this volume.
Relative Humidity(RH ) is the amount of water contained in the air relative to the maximum possible amount of water at a given temperature and pressure, the unit of measurement is percent, % .
And with temperature increase, maximum possible amount of water contained in the air increases.
Accordingly, at decrease in temperature – decreases.
With a further decrease in temperature, superfluous» water will start to condense in the form of dew drops- That's what it is Dew point.
A few facts about the dew point.
- The dew point temperature cannot be higher than the current temperature.
- The higher the dew point temperature, the more moisture is in the air
- High dew point temperatures are in the tropics, low in deserts, polar regions.
- Relative humidity (RH) around 100% causes dew, frost (frost dew), fog.
- Relative humidity (RH) reaches 100% during the rainy season.
- High dew points usually occur before cold temperature fronts.
How to determine, calculate the dew point?
The answer is obvious -
1. To determine the dew point, there are special tables,
where the columns indicate the relative humidity in % , in rows – ambient air temperature in °С, in cells at the intersection - the dew point temperature, for the selected humidity and temperature.
For example, relative humidity of 60% is chosen, room temperature is 21 °C at the intersection we see dew point value 12.9 °C.
Accordingly, under these conditions, moisture condensation will occur on cold surfaces (for example, window panes) with surface temperature lower than 12.9 °C.
On specialized sites, there are more detailed tables for determining the dew point, but for "home use" it is quite enough, the table below can be saved, printed and used if necessary.
2. When calculating the dew point temperature, use formulas 1.1 and 1.2.
The formula for an approximate calculation of the dew point in degrees Celsius (only for positive temperatures):
Tp = (b f (T, RH)) / (a - f (T, RH)) , (1.1 )
f (T, RH) = a T / (b + T) + ln (RH / 100) , (1.2 )
Tr – dew point temperature, °C;
a = 17.27;
b = 237,7;
T – room temperature, °С;
RH – relative humidity, %;
ln is the natural logarithm.
Calculate dew point for the same temperatures and humidity.
T= 21 °С;
RH = 60 %.
First we 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 °С
So our calculation result Tr = 12.93167 °С .
3. It is much easier to calculate the dew point using " Dew Point Calculator" on our website.
Fill in the values:
Air temperature indoors, ° With . - 21 ;
relative humidity, % . – 60 .
As we see, the dew point value for all three methods is the same:
Tr= 12.9 °С;
Tr\u003d 12.93167 ° С;
Tr\u003d 12.93 ° С.
The difference is only in the number of decimal places.
There are fair questions why do we need this dew point, why do we spend so much time defining or calculating what practical application dew point has?
In places where moisture constantly accumulates, favorable conditions are created for the development of mold, fungal spores, which very negative impact on health nearby of people.
Knowing the dew point, we can prevent the formation of condensation on the surfaces of our room.
Wet grass underfoot, misted windows, droplets on the walls of a damp basement - all this is the result of the condensation of water vapor from the atmospheric air. Everyone has come across this, but not everyone was interested in how to determine the dew point. Most often, this task has to be solved by architects, builders and designers, and people who are far from this area are hardly familiar with this concept.
The nature of the appearance of dew
Condensation of water on various surfaces occurs as follows. Atmospheric air is always saturated to some extent with water vapor. Water changes from a gaseous state to a liquid state when its temperature drops. This occurs when atmospheric air comes into contact with colder surfaces and the subsequent loss of heat. The result is the appearance of water droplets.
The temperature at which water vapor from the air turns into a liquid state of aggregation is called dew point.
The higher the content of water vapor in the air (or other mixture of gases), the higher the dew point of water, or dew point. So, at a relative humidity of 100%, the dew point exactly coincides with its temperature. And vice versa: the lower the relative humidity, the lower the dew point. This means that for condensation to occur, the air will have to be cooled more strongly.
Scope of the concept
This term is widely used in industrial and civil construction. The need to determine this value arises when the walls of the room are insulated. If we neglect the calculation of this indicator, problems will appear after the insulation work. One of the options is damage to the wall decoration due to settling moisture. If the finish is tolerant of water, but drops of condensate will fall on the walls, there is nothing good in this either. Humid environment promotes the development of pathogenic microorganisms, mold.
In aviation, the dew point is also calculated. Condensation forms on some parts of the aircraft during the flight. In this case, the condensate freezes and parts of the aircraft freeze over.
This value is also used in forestry. Forest fire specialists use the dew point to calculate the fire hazard class, which characterizes the possibility of a forest fire catching fire. Based on this, protective measures are designed.
In agriculture, knowing the dew point, determine the likelihood of damage to crops by non-communicable diseases (damage caused by weather conditions). At the same time, one of the tasks of breeding is to develop varieties of cultivated plants capable of condensing moisture from the air on their vegetative organs. This will allow you to successfully engage in agriculture in conditions of low precipitation.
How to calculate dew point
By mathematical formula
Carrying out calculations manually according to the formula is a fairly accurate way. However, to use the formula, several other indicators must first be defined. The formula looks like this.
As can be seen from the figure, a and b are constant values. T is the air temperature. Rh is the relative humidity of the air. This calculation method will give a result with an error of 0.5ºС.
Using an online calculator
Since manually calculating the formula is not suitable for everyone (due to insufficient knowledge in mathematics or lack of time), online calculators are available on the Internet that calculate the dew point based on the information entered. Using them is absolutely simple: you just need to enter the initial data (temperature of atmospheric air and relative humidity). The calculation result will appear on the screen.
Calculator programs
Linking the dew point indicator and the expected consequences of improper insulation is not possible for everyone. This requires specific knowledge in physics and construction. Therefore, in addition to conventional calculators that calculate this value, programs with advanced features have been created. They are also freely available and can be used online.
Such programs take into account many parameters when calculating:
- The locality in which the building was built (under construction). The statistics of average monthly temperatures, relative humidity, and pressure in this region immediately appear.
- Room type. Obviously, the humidity in the bathroom will be higher than in the room, and this in turn affects the type of insulation that is acceptable.
- Construction type. Here you can choose from a wall, floor, attic floor and other positions.
- Construction layers. Here it is taken into account what is behind the insulated wall - another room or street.
- floor or wall material.
- Temperature and relative humidity of indoor and outdoor air.
After filling in all the required fields, the program will plot the dew point.
Dew point table
If you need to quickly get the dew point value, tables are used. The data in the tables is very inaccurate and gives an approximate result. But using them is easy and fast: you just need to find the desired cell at the intersection of the column and row with the desired temperature and relative humidity.
Table 1. Determination of the dew point by two indicators.
Special tools
In meteorology, special tools have been invented to determine the dew point. However, even to calculate using a mathematical formula or any other method described above, you need your own tools.
Temperature is measured with a thermometer, humidity with a hygrometer. For convenience, in this case, an instrument that can measure both temperature and air humidity is suitable - a digital thermohygrometer.
In addition, there are devices that combine several functions: measuring temperature, humidity, calculating the dew point and storing information.
In most cases, working with such a device is as follows.
- Turn on the device. Pay attention to battery charge.
- Bring the sensor tip to the surface to be examined at a right angle.
- To freeze the measurement data, press the Hold button in the menu. So you can see the result in a comfortable position of the device.
- To save the data, click the Save button.
- If you need to transfer information to a computer, connect the device to the network via USB.
- Copy the data to your computer.
Working with instruments for measuring dew point is easy even for a person without special training. The interface is intuitive, and if you have questions, you should 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, a series of negative events will follow.
The insulation material quickly becomes unusable, the life of the material of the wall itself is reduced. The finish will not hold due to regular wetting: the wallpaper gradually peels off, the plaster crumbles, the paint peels off. Due to excessive humidity in the room, a mold layer, fungus and other pathogenic microorganisms develop in a short time on walls, ventilation systems, ceilings and other surfaces.
How dew behaves with non-insulated walls
With non-insulated walls, there are several variations in the behavior of the dew point. 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 place of steam condensation will shift to the inner surface of the wall. Then drops of condensate will certainly form on its surface.
In some cases (cold building frame material), the dew point can be located indoors all year round, that is, on the inner surface of the wall. Then it is necessary to make applied calculations and take care of wall insulation, taking into account the climatic features of the settlement in which the building is located.
In general, the location of the dew point in a floor or wall is related to a number of physical factors:
- humidity of outdoor air and indoor air;
- outdoor and indoor air temperatures;
- floor or wall thickness.
Dew point in externally insulated walls
With the correct selection of material and well-calculated thickness of the insulation layer, the dew point will always be in the insulation and will never move towards the inner surface. The walls are dry all year round. Only the insulation is damaged by weather conditions, the wear of the walls slows down.
If the thickness of the insulation is less than necessary, or the thermal conductivity of the material was not taken into account, the dew point will behave in the same way as in an uninsulated wall, that is, moisture will continue to accumulate in the room if it accumulated before insulation. If this happens, there is only one way out - to increase the thickness of the insulation material. This can be done by adding another layer of thermal insulation or by replacing the old material with a new one of suitable thickness.
With an excessive thickness of the insulation layer, the dew point will not go beyond its limits throughout the year. This will not entail any negative consequences: the wall will be dry all year round. However, calculations are made in order to avoid unreasonable financial expenses. After all, if you can save yourself from moisture and keep warm with less insulation, then why spend more?
Dew point in internally insulated walls
Wall insulation only from the inside inevitably leads to a shift in the dew point towards the room. This is due to the fact that the thermal insulation material retains heat in the room, thereby making the wall colder. And, as you know, the colder the surface, the more likely the fact of condensation of air moisture on it.
If, at normal temperatures for a given region, the dew point is located close to the inner surface of the wall and does not cause inconvenience, then on especially cold days it can shift into the room, that is, onto the inner surface of the wall. Then the wall will get wet under the insulation.
If moisture constantly accumulated on an uninsulated wall, then after work on the internal insulation of the room, the wall will continue to get wet under the insulation throughout the cold season. This will lead to gradual deterioration of all layers of building materials located on the inside of the wall, including the finish.
In some cases, after the internal insulation of a normal wall, the dew point changes location to the insulation. Then, throughout the winter, not only the wall will be wet, but also the thermal insulation material itself.
One way or another, in order to avoid damage to the finish and internal insulation layers, one simple rule must be remembered: the insulation of the inner surface of the wall is carried out only after its outer insulation.
About the dew point in plastic windows
When it comes to, then many imagine some specific mysterious place. In reality, the dew point cannot be seen, which we have already managed to find out. To reiterate, dew point refers to the temperature at which the vapor in the air is cooled to saturate and condense. 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.
On a note! Let's say the humidity is 50%, and the temperature is +21 degrees. Under these 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, then condensation will begin to appear on it (surface). As a rule, the coldest surfaces in the apartment are plastic windows, and therefore it is on them that in most cases excess moisture falls.
People often encounter condensation on double-glazed windows. Based on everything that has been said above, we can conclude that condensate can be dealt with in two ways - by increasing the temperature of the glasses and reducing the humidity in the apartment. So, comfortable humidity can be achieved by ensuring normal air exchange. All excess moisture - from washing, boiling pots and so on. - must leave the room, and not accumulate in it. First of all, the apartment should be regularly ventilated. The frequency of airing is determined on an individual basis, but we recommend doing this for at least 10 minutes twice a day. Do not forget about special ventilation valves.
Video - What is a dew point?
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 an extremely important factor in the installation of any polymeric floors, coatings and self-leveling floors on any grounds: concrete, metal, wood, etc. The occurrence of a dew point and, accordingly, water condensate on the surface of the base at the time of laying polymer floors of self-leveling floors and coatings can cause the appearance of a variety of defects: shagreen, swelling and shells; complete delamination of the coating from the base. Visual determination of the dew point - the appearance of moisture on the surface - is almost impossible, so the technology below is used to calculate the dew point.
Dew point table
The dew point table is very simple to use − hover your mouse over it... Dew Point table - download
For example: air temperature +16°С, relative air humidity 65%.
Find the cell at the intersection of +16°С air temperature and 65% humidity. It turned out + 9 ° С - 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.
For the application of polymer coatings, the surface temperature must be at least 4°C above the dew point!
| Tempe- ratura air | Dew point temperature at relative 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°С | -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°С | -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°C | -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°C | -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°C | -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°C | -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°C | -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°C | -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°C | -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°C | -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°C | -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°C | 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°C | 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°C | 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°C | 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°C | 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 devices: a thermometer, a hygrometer.
- Measure the temperature at a height of 50-60 cm from the floor (or from the surface) and the relative humidity of the air.
- Determine the dew point temperature from the table.
- 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. Take readings after 10-15 minutes.
- The surface temperature must be at least 4 (four) degrees above the dew point.
Otherwise, it is IMPOSSIBLE to carry out work on the application of polymer floors and polymer coatings!
There are devices that immediately calculate the dew point in degrees C.
In this case, the thermometer, hygrometer and dew point table are not required - they are all combined in this device.
Different polymer coatings “treat” the moisture on the surface in different ways during application. Polyurethane materials are the most “sensitive” to the occurrence of the dew point: paint coatings, polyurethane self-leveling floors, varnishes, etc. This is due to the fact that water is a hardener for polyurethane, and with an excess of moisture, the polymerization reaction proceeds 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 delamination 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 the time of their initial curing is quite long (up to a day).
Epoxy self-leveling floors and coatings are "less sensitive" to moisture, but, nevertheless, the determination of the dew point is a guarantee of quality when installing any polymer floors and paint coatings.