Coefficient of thermal conductivity of the material. Thermal conductivity of building materials: table
The process of transferring energy from the heated partbody to less heated is called thermal conductivity. The numerical value of this process reflects the thermal conductivity of the material. This concept is very important in the construction and repair of buildings. Correctly selected materials allow creating a favorable microclimate in the room and saving a significant amount of heating.
The concept of heat conduction
Thermal conductivity is the process of heat exchangeenergy, which occurs due to the collision of the smallest particles of the body. And this process will not stop until the moment of equilibrium of temperatures comes. This takes a certain amount of time. The more time spent on heat exchange, the lower the thermal conductivity index.
This indicator is expressed as the coefficientthermal conductivity of materials. The table contains already measured values for most materials. The calculation is based on the amount of thermal energy that has passed through a given surface area of the material. The larger the calculated value, the faster the object will give all its heat.
Factors affecting the thermal conductivity
The coefficient of thermal conductivity of a material depends on several factors:
- Density of the material. When this parameter is increased, the interaction of the material particles becomes stronger. Accordingly, they will transmit the temperature faster. And this means that as the density of the material increases, heat transfer improves.
- Porosity of the substance. Porous materials are heterogeneous in their structure. Inside of 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 coefficient rises.
- Humidity also affectsthermal conductivity. Wet surfaces of the material allow more heat. In some tables, even the calculated coefficient of thermal conductivity of the material in three states is indicated: dry, medium (normal), and wet.
The concept of heat conductivity in practice
Thermal conductivity is taken into account at the stagedesigning a building. This takes into account the ability of materials to retain heat. Due to their correct selection of residents inside the premises will always be comfortable. During operation, money will be saved for heating.
Warming at the design stage isoptimal, but not the only solution. It is not difficult to insulate an already finished building by carrying out internal or external works. The thickness of the insulation layer will depend on the materials selected. 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 given to the insulation of the roof, window and door openings, floor. Through these elements, the most heat is lost. Visually, you can see this in the photo at the beginning of the article.
Structural materials and their indicators
For the construction of buildings use materials with a low coefficient of thermal conductivity. The most popular are:
- Concrete. Its thermal conductivity is in the range of 1.29-1.52 W / m * K. The exact value depends on the consistency of the solution. This index is also affected by the density of the initial material, which is 500-2500 kg / m3. Use this material in the form of a solution for foundations, in the form of blocks - for the erection of walls and foundations.
- Reinforced concrete, the value of thermal conductivity of which is 1.68 W / m * K. The density of the material reaches 2400-2500 kg / m3.
- Wood, since ancient times used as a building material. Its density and thermal conductivity, depending on the rock, are 150-2100 kg / m3 and 0.2-0.23 W / m * K, respectively.
Another popular building material is brick. Depending on the composition, he has the following indicators:
- Saman (made of clay): 0.1-0.4 W / m * K;
- ceramic (manufactured by firing): 0.35-0.81 W / m * K;
- silicate (from sand with the addition of lime): 0.82-0.88 W / m * K.
Concrete materials with the addition of porous aggregates
The coefficient of thermal conductivity of the material makes it possible 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 is characterized by a porous structure with a density of 500-1000 kg / m3. At the same time, the ability to transmit heat is determined by a value of 0.1-0.37 W / m * K.
- Keramzitobeton, the indices of which depend onits kind. Solid blocks do not have voids or holes. With cavities inside, hollow blocks are made that are less durable than the first option. In the second case, the thermal conductivity will be lower. If we consider the general figures, the density of claydite-concrete is 500-1800kg / m3. Its value is in the range of 0.14-0.65 W / m * K.
- Aerated concrete, inside which pores are formed in the size of 1-3 millimeters. Such a structure determines the density of the material (300-800kg / m3). Due to this, the coefficient reaches 0.1-0.3 W / m * K.
Indicators of thermal insulation materials
The coefficient of thermal conductivity of heat-insulating materials, the most popular in our time:
- foam, which has a density of 15-50kg / m3, with a thermal conductivity of 0.031-0.033 W / m * K;
- polystyrene, the density of which is the same as that of the previous material. But 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 0,038-0,045 W / m * K;
- stone wool with an index of 0.035-0.042W / m * K.
Table of indicators
For convenience of operation the thermal conductivity coefficientIt is customary to add a material to the table. In it, in addition to the coefficient itself, such indicators as the degree of humidity, density, and others can be reflected. Materials with a high coefficient of thermal conductivity are combined in the table with the indices of low thermal conductivity. A sample of this table is shown below:
Using the coefficient of thermal conductivitymaterial will allow to build the desired construction. The main thing is to choose a product that meets all the necessary requirements. Then the building will be comfortable for living; it will retain a favorable microclimate.
Correctly selected insulating materialwill reduce heat losses, for which reason it will no longer be necessary to "heat the street". Due to this, the financial costs for heating will be significantly reduced. Such savings will soon return all the money that will be expended to purchase a heat insulator.
