The comfort in a constructed building depends on many factors. The indoor microclimate, for example, is influenced by the thermal conductivity coefficient of building materials. The table of these parameters will allow you to choose the most suitable material to create comfortable conditions in the house.
Thanks to the correct calculation, in the future you can save on heating the house. Even if at the initial stage the construction is made from more expensive materials, over time they will fully pay off. In case if materials intensively transmitting heat are used for construction, it is necessary to carry out an additional amount of work to warm the house. It is carried out both outside and inside buildings. But in any case, this incurs additional costs of both time and money.
The concept of thermal conductivity
In physics, heat conduction is understood to mean the transfer of heat from more heated particles to less heated ones as a result of their direct contact. By particles here we mean atoms, molecules or free electrons.
In simple terms, thermal conductivity is the ability of a particular material to transmit heat. It is worth noting that the movement of heat will continue until a temperature equilibrium occurs.
Heat losses for different sections of buildings are different. If we talk about a private house, before heat loss will occur:
- through the roof - up to 30 percent;
- through chimneys, natural ventilation, and so on - up to 25 percent;
- through walls - up to 15 percent;
- in half - up to 15 percent;
- through windows - up to 15 percent;
- through adjoining - up to 15 percent.
For apartment buildings, these figures are slightly different. Losses through the roof and walls will be lower. But much more heat will go through the windows.
Coefficient of thermal conductivity
The thermal conductivity of the material is characterized by a time interval during which the temperature indicators reach equilibrium. This is evidenced by the coefficient of thermal conductivity of building materials. The table shows that in this case there is an inverse relationship between time and thermal conductivity. That is, the less time it takes to transfer heat, the greater the value of thermal conductivity.
In practice, this means that the building will cool faster if there is a greater coefficient of thermal conductivity of building materials. The table of values in this case is simply necessary. It shows how much heat a building will lose through a unit of area.
Consider an example. Brick has a thermal conductivity of 0.67 kW / (m 2 * K) (the value is taken from the corresponding tables). This means that 1 square meter of surface with a thickness of one meter will transmit 0.67 watts of heat. This value will be provided that the difference in temperature between the two surfaces is one degree. When the difference increases to 10 degrees, heat loss will amount to 6.7 watts. Under such conditions, when the wall thickness is reduced by 10 times (i.e., up to 10 centimeters), heat loss will be 67 watts.
Change in thermal conductivity
The thermal conductivity of building materials is influenced by various factors. The main parameters are:
- The density of the material. If the density is higher, then the particles inside the material interact with each other more strongly. Accordingly, the transfer of thermal energy and the establishment of equilibrium of temperatures will occur faster. Therefore, the higher the density, the better the material transmits heat.
- Porosity. Here the opposite situation is observed. Materials with high porosity have an inhomogeneous structure. Most of the volume is occupied by air, which has a minimum coefficient. The transfer of thermal energy through small pores is difficult. Accordingly, thermal conductivity will increase.
- Humidity. With increasing humidity, the thermal conductivity of building materials will also be higher.
The table above shows the exact values for some materials.
Comparison of thermal conductivity of materials in practice
It is difficult for an inexperienced person to understand what the coefficients of thermal conductivity of building materials are. SNiP gives the exact values that are contained in the table.
To better understand the difference in these values, consider an example. Compare several different materials. The amount of heat transmitted by them can be made the same if the wall thickness is changed . So, a wall of concrete panels (with insulation) with a thickness of 14 centimeters will correspond to a wooden wall with a thickness of 15 centimeters. The same value of thermal conductivity will be characteristic of expanded clay concrete with a thickness of 30 centimeters, hollow bricks with a thickness of 51 centimeters. If you take an ordinary brick, then to obtain this thermal conductivity it is necessary to build a wall 64 cm thick.
State standards
The coefficient of thermal conductivity of building materials (table) SNiP and other documents is determined. So, to compile the table that is posted above, such documents as SNiP 11-3-79, SNiP 23-02-2003, SP 50.13330.2012 were used.
If the standards do not give the value of the coefficient of thermal conductivity of the required building material, you can contact the manufacturer. Look at the packaging to see if this parameter is listed there. Another way out is to go to the official website of the manufacturer.
As you can see, the calculation of heat loss plays an important role in the process of building construction. The level of comfortable stay indoors will depend on this. Therefore, even at the design stage, it is necessary to carefully approach the issue of choosing building materials. This will reduce the cost of heating. In this case, the thickness of the selected material for each region will differ. And it will depend on the climatic conditions of the zone of residence.