The coefficient of thermal conductivity of the material. Thermal conductivity of building materials: table

The process of transferring energy from a warmer part of the body to a less heated part is called thermal conductivity. The numerical value of such a process reflects the coefficient of thermal conductivity of the material. This concept is very important in the construction and repair of buildings. Properly selected materials allow you to create a favorable microclimate in the room and save a significant amount on heating.

The concept of thermal conductivity

Thermal conductivity is the process of exchange of thermal energy, which occurs due to the collision of the smallest particles of the body. Moreover, this process will not stop until the moment of equilibrium of temperatures. This takes a certain period of time. The more time it takes to heat exchange, the lower the thermal conductivity.

This indicator is expressed as the coefficient of thermal conductivity of materials. The table contains the measured values ​​for most materials. The calculation is based on the amount of thermal energy transmitted through a given surface area of ​​the material. The larger the calculated value, the faster the object will give up all its heat.

Factors Affecting Thermal Conductivity

The thermal conductivity of a material depends on several factors:

• The density of the material. With an increase in this indicator, the interaction of material particles becomes stronger. Accordingly, they will transfer temperature faster. This means that with an increase in the density of the material, heat transfer improves.

• The porosity of the substance. Porous materials are heterogeneous in structure. Inside them is a large amount of air. And this means that it will be difficult for molecules and other particles to transfer thermal energy. Accordingly, the thermal conductivity increases.

• Humidity also affects thermal conductivity. Wet material surfaces allow more heat to pass through. Some tables even indicate the calculated coefficient of thermal conductivity of the material in three states: dry, medium (normal) and wet.

When choosing material for insulation of premises, it is important to take into account the conditions in which it will be operated.

The concept of thermal conductivity in practice

Thermal conductivity is taken into account at the design stage of the building. This takes into account the ability of materials to retain heat. Thanks to their proper selection, residents will always be comfortable indoors. During operation, money for heating will be significantly saved.

Thermal insulation at the design stage is an optimal, but not the only solution. It is not difficult to insulate an already finished building by conducting internal or external works. The thickness of the insulation layer will depend on the selected materials. Some of them (for example, wood, foam concrete) can in some cases be used without an additional layer of thermal insulation. The main thing is that their thickness exceeds 50 centimeters.

Particular attention should be paid to the insulation of the roof, window and doorways, floor. Most of the heat goes through these elements. Visually, this can be seen in the photograph at the beginning of the article.

Structural materials and their indicators

For the construction of buildings using materials with a low coefficient of thermal conductivity. The most popular are:

• Concrete. Its thermal conductivity is in the range 1.29-1.52W / m * K. The exact value depends on the consistency of the solution. This indicator is also affected by the density of the starting material, which is 500-2500 kg / m ³ . Use this material in the form of a solution for foundations, in the form of blocks - for the construction of walls and foundations.
  

• Reinforced concrete, the thermal conductivity of which is 1.68 W / m * K. The density of the material reaches 2400-2500 kg / m ³ .

• Wood, since ancient times used as a building material. Its density and thermal conductivity depending on the rock are 150-2100 kg / m ³ and 0.2-0.23 W / m * K, respectively.

Another popular building material is brick. Depending on the composition, it has the following indicators:

• adobe (made of clay): 0.1-0.4 W / m * K;

• ceramic (made by firing): 0.35-0.81 W / m * K;

• silicate (from sand with lime): 0.82-0.88 W / m * K.

Concrete materials with added porous aggregates

The coefficient of thermal conductivity of the material allows you to use the latter for the construction of garages, sheds, summer houses, baths and other structures. This group includes:

• Foam concrete. It is produced with the addition of foaming agents, due to which it is characterized by a porous structure with a density of 500-1000 kg / m ³ . Moreover, the ability to transfer heat is determined by the value of 0.1-0.37W / m * K.
  

• Expanded clay, the performance of which depends on its type. Solid blocks have no voids or holes. With voids inside, hollow blocks are made , which are less durable than the first option. In the second case, the thermal conductivity will be lower. If we consider the general figures, then the density of expanded clay concrete is 500-1800 kg / m3. Its indicator is in the range of 0.14-0.65W / m * K.

• Aerated concrete, within which pores 1-3 mm in size are formed. This structure determines the density of the material (300-800kg / m ³ ). Due to this, the coefficient reaches 0.1-0.3 W / m * K.

Indices of thermal insulation materials

The coefficient of thermal conductivity of heat-insulating materials, the most popular in our time:

• polyfoam, which has a density of 15-50 kg / m ³ , with thermal conductivity - 0,031-0,033W / m * K;
  

• polystyrene foam, the density of which is the same as that of the previous material. But at the same time, the heat transfer coefficient is at the level of 0.029-0.036W / m * K;

• glass wool. It is characterized by a coefficient equal to 0.038-0.045W / m * K;

• stone wool with a rating of 0.035-0.042W / m * K.

Scorecard

For convenience, the coefficient of thermal conductivity of the material is usually entered in the table. In addition to the coefficient itself, such indicators as the degree of humidity, density, and others can be reflected in it. Materials with a high coefficient of thermal conductivity are combined in the table with indicators of low thermal conductivity. A sample of this table is shown below:

Using the coefficient of thermal conductivity of the material will allow to erect the desired building. The main thing: to choose a product that meets all the necessary requirements. Then the building will turn out comfortable for living; a favorable microclimate will remain in it.

Properly selected insulating material will reduce heat loss, which is why it will no longer be necessary to "heat the street." Thanks to this, the financial costs of heating will significantly decrease. Such savings will soon return all the money that will be spent on the purchase of a heat insulator.