The dew point is called the cooled air to a certain temperature, in which the vapor begins to condense and turn into dew. In general, this parameter depends on the air pressure in the room and on the street. It is not always easy to determine the value, but it is necessary to do this, since this is one of the most important factors in construction and for a comfortable life and human existence in the room.
With an overestimated dew point, concrete, metal, wood and many other building materials will not give the desired effect when building or repairing a house and will not last long. During the laying of polymer floors, if condensate gets on the surface of the material, in the future, such defects as: swelling of the floor, shagreen, peeling of the coating and much more may occur. It is impossible to visually determine the parameter in the room, for this it is necessary to use a non-contact thermometer and a table.
What factors influence
- wall thickness in the room and what materials were used for insulation;
- temperature, in different parts of the world it is different and the temperature coefficient of north from south is very different;
- humidity, if the airspace contains moisture, the dew point will be larger.
To better understand what it is, and how certain factors can affect the value, consider an illustrative example:
- Insulated wall in the room. The dew point will shift depending on the outdoor weather conditions. In the case of stable weather without sharp fluctuations, the dew point will be located closer to the outer wall, towards the street. In this case, there are no harmful indicators for the room itself. If a sharp cold snap occurs, the dew point will slowly move closer to the inside of the wall - this can lead to saturation of the room with condensate and slow wetting of the wall surface.
- Externally insulated wall. The dew point has a position inside the walls (insulation). When choosing a material for insulation, you should rely on this factor and correctly calculate the thickness of the selected material.
- Insulated wall from the inside. The dew point is between the center of the wall and the insulation. This is not the best option if the weather conditions are too humid, because with a sharp cold snap, in this case, the dew point will sharply shift to the junction between the insulation and the wall, and this, in turn, can lead to disastrous consequences for the wall of the house itself. It is possible to insulate a wall from the inside in a humid climate if the house has a good heating system that is able to maintain a uniform temperature in each room.
If the repair of the house is made without taking into account the weather conditions, it will be almost impossible to eliminate the problems that have arisen, the only way out is to start work again and clean up everything that has been done, which entails a lot of money.
How to correctly identify and calculate (table and formula)
Dew point can be affected by temperature and humidity
It is quite difficult for a person to live in comfort with high humidity. Condensation causes problems both for health (there is a possibility of getting sick with asthma) and for the house itself, especially for its walls. The ceiling and walls from high humidity can become covered with mold that is harmful to humans and difficult to remove, in rare cases it is necessary to completely change the walls and ceiling in order to kill all harmful microorganisms present.
In order to prevent this from happening, you should make a calculation and find out whether it is worth starting repairs in a particular building, insulating walls, or even building housing in this place. It is important to know that for each building the dew point is individual, which means that its calculation will be carried out with slight differences.
Before proceeding with the calculation, one should take into account such factors as: climatic conditions in a particular region, the thickness of the walls and the material from which they are made, and even the presence of strong winds. Absolutely all materials contain low, permissible humidity, a person should make sure that this humidity does not increase and a dew point does not form. When you call a specialist to measure the value in case of high humidity, you will most likely be given an answer that the thermal insulation of the house is not done correctly, the thickness of the material is not suitable, or a mistake was made during installation. To some extent, this person will be right, since it is the correct repair in the house that to a greater extent affects the change in the dew point and the appearance of condensation on the walls.
Table: indicators for determining the dew point
| C° | Dew point V S in CO at relative humidity in % | |||||||||||||
| 30% | 35% | 40% | 45% | 50% | 55% | 60% | 65% | 70% | 75% | 80% | 85% | 90% | 95% | |
| 30 | 10,5 | 12,9 | 14,9 | 16,8 | 18,4 | 20 | 21,4 | 22,7 | 23,9 | 25,1 | 26,2 | 27,2 | 28,2 | 29,1 |
| 29 | 9,7 | 12 | 14 | 15,9 | 17,5 | 19 | 20,4 | 21,7 | 23 | 24,1 | 25,2 | 26,2 | 27,2 | 28,1 |
| 28 | 8,8 | 11,1 | 13,1 | 15 | 16,6 | 18,1 | 19,5 | 20,8 | 22 | 23,2 | 24,2 | 25,2 | 26,2 | 27,1 |
| 27 | 8 | 10,2 | 12,2 | 14,1 | 15,7 | 17,2 | 18,6 | 19,9 | 21,1 | 22,2 | 23,3 | 24,3 | 25,2 | 26,1 |
| 26 | 7,1 | 9,4 | 11,4 | 13,2 | 14,8 | 16,3 | 17,6 | 18,9 | 20,1 | 21,2 | 22,3 | 23,3 | 24,2 | 25,1 |
| 25 | 6,2 | 8,5 | 10,5 | 12,2 | 13,9 | 15,3 | 16,7 | 18 | 19,1 | 20,3 | 21,3 | 22,3 | 23,2 | 24,1 |
| 24 | 5,4 | 7,6 | 9,6 | 11,3 | 12,9 | 14,4 | 15,8 | 17 | 18,2 | 19,3 | 20,3 | 21,3 | 22,3 | 23,1 |
| 23 | 4,5 | 6,7 | 8,7 | 10,4 | 12 | 13,5 | 14,8 | 16,1 | 17,2 | 18,3 | 19,4 | 20,3 | 21,3 | 22,2 |
| 22 | 3,6 | 5,9 | 7,8 | 9,5 | 11,1 | 12,5 | 13,9 | 15,1 | 16,3 | 17,4 | 18,4 | 19,4 | 20,3 | 21,1 |
| 21 | 2,8 | 5 | 6,9 | 8,6 | 10,2 | 11,6 | 12,9 | 14,2 | 15,3 | 16,4 | 17,4 | 18,4 | 19,3 | 20,2 |
| 20 | 1,9 | 4,1 | 6 | 7,7 | 9,3 | 10,7 | 12 | 13,2 | 14,4 | 15,4 | 16,4 | 17,4 | 18,3 | 19,2 |
| 19 | 1 | 3,2 | 5,1 | 6,8 | 8,3 | 9,8 | 11,1 | 12,3 | 13,4 | 14,5 | 15,3 | 16,4 | 17,3 | 18,2 |
| 18 | 0,2 | 2,3 | 4,2 | 5,9 | 7,4 | 8,8 | 10,1 | 11,3 | 12,5 | 13,5 | 14,5 | 15,4 | 16,3 | 17,2 |
| 17 | 0,6 | 1,4 | 3,3 | 5 | 6,5 | 7,9 | 9,2 | 10,4 | 11,5 | 12,5 | 13,5 | 14,5 | 15,3 | 16,2 |
| 16 | 1,4 | 0,5 | 2,4 | 4,1 | 5,6 | 7 | 8,2 | 9,4 | 10,5 | 11,6 | 12,6 | 13,5 | 14,4 | 15,2 |
| 15 | 2,2 | 0,3 | 1,5 | 3,2 | 4,7 | 6,1 | 7,3 | 8,5 | 9,6 | 10,6 | 11,6 | 12,5 | 13,4 | 14,2 |
| 14 | 2,9 | 1 | 0,6 | 2,3 | 3,7 | 5,1 | 6,4 | 7,5 | 8,6 | 9,6 | 10,6 | 11,5 | 12,4 | 13,2 |
| 13 | 3,7 | 1,9 | 0,1 | 1,3 | 2,8 | 4,2 | 5,5 | 6,6 | 7,7 | 8,7 | 9,6 | 10,5 | 11,4 | 12,2 |
| 12 | 4,5 | 2,8 | 1 | 0,4 | 1,9 | 3,2 | 4,5 | 5,7 | 6,7 | 7,7 | 8,7 | 9,6 | 10,4 | 11,2 |
| 11 | 5,2 | 3,4 | 1,8 | 0,4 | 1 | 2,3 | 3,5 | 4,7 | 5,8 | 6,7 | 7,7 | 8,6 | 9,4 | 10,2 |
| 10 | 6 | 4,2 | 2,6 | 1,2 | 0,1 | 1,4 | 2,6 | 3,7 | 4,8 | 5,8 | 6,7 | 7,6 | 8,4 | 9,2 |
| For intermediate indicators not listed in the table, the average value is determined | ||||||||||||||
Schedule
Thanks to the graph, you can determine the optimal performance
How to calculate: necessary tools and sequence of actions
- thermometer;
- hygrometer;
- non-contact thermometer (can be replaced with a regular one).
Formula for calculation in frame, brick, multilayer walls with insulation
To calculate the dew point with insulation, the following formulas are used: 10.8 ° C
Using the obtained indicators, draw up a graph with the temperature range T1 placed in the wall and the remaining °C for the insulation. Mark the dew point at the desired location.
What if the value is defined incorrectly?
Consider the places where the dew point can be located in an uninsulated wall:
- Closer to the outer surface of the wall. In this case, the appearance of a dew point in the house is minimal, as a rule, the inner wall remains dry.
- Closer to the inner surface of the wall. In this case, condensation may occur during a sharp cold snap outside.
- In the rarest of cases, the dew point is on the inside wall of a building. In this case, it is almost impossible to get rid of it, and most likely the walls in the house will be a little damp all winter.
In these cases, the problem can be solved by adding vapor barrier layers to the walls. This will help keep water vapor from escaping through the walls into the room, preventing dew points from appearing on the walls and ceiling. If the climate is too cold and most of the year the temperature is more than minus 10 degrees, it is worth considering the option of forced entry of heated air into the room. This can be done using a heat exchanger or an air heater.
Video: why condensation and mold appear on the walls
It is important to correctly determine the dew point during the construction phase. This will help to correctly insulate the wall and in the future to avoid the appearance of condensation and mold in the house.
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
BUT 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 according to the required thickness according to the thermal 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 the reader in the next branch be insulated from the inside, but I can’t, because we have the same layout of the apartment with him (further options), or the 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 factors of influence 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),
- the 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.
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°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°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°C | -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°C | -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°C | -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°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°C | -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°C | -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°C | -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°C | 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°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°C | 2,5 | 5 | 6,9 | 8,8 | 10,5 | 11,9 | 13,5 | 14,8 | 16 | 17 | 18 | 19 | 20 | 21 |
| +23°C | 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°C | 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°C | 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°C | 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°C | 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°C | 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°C | 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°C | 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°C | 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 paintwork.
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, Tp means the point temperature itself, b and a show equal (constant) values, ln is the natural logarithm, T is the indoor temperature, 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 indicator, 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.
