Thermal conductivity of building materials. Thermal conductivity of basic building materials Heat transfer coefficient of building materials table

Construction of a private house is very not an easy process from start to finish. One of the main issues this process is a choice construction raw materials. This choice must be very competent and thoughtful, because it depends on most of life in a new house. What stands apart in this choice is the concept of thermal conductivity of materials. It will determine how warm and comfortable the house will be.

Thermal conductivity is an ability physical bodies(and the substances from which they are made) transfer thermal energy. Explaining more in simple language, this is the transfer of energy from a warm place to a cold one. For some substances, such transfer will occur quickly (for example, most metals), and for some, on the contrary, very slowly (rubber).

To put it even more clearly, in some cases, materials with a thickness of several meters will conduct heat much better than other materials with a thickness of several tens of centimeters. For example, a few centimeters of drywall can replace an impressive brick wall.

Based on this knowledge, it can be assumed that the most correct choice of materials will be with low values ​​of this quantity so that the house does not cool down quickly. For clarity, let’s denote the percentage of heat loss in different areas of the house:

What does thermal conductivity depend on?

Values ​​of this quantity may depend on several factors. For example, the thermal conductivity coefficient, which we will talk about separately, the humidity of building materials, density, and so on.

• Materials with high densities have, in turn, a high ability to transfer heat due to the dense accumulation of molecules inside the substance. Porous materials, on the contrary, will heat up and cool down more slowly.
• Heat transfer is also affected by the humidity of materials. If the materials get wet, their heat transfer will increase.
• Also, the structure of the material greatly influences this indicator. For example, a tree with transverse and longitudinal grains will have different meanings thermal conductivity.
• The indicator also changes with changes in parameters such as pressure and temperature. With increasing temperature it increases, and with increasing pressure, on the contrary, it decreases.

Coefficient of thermal conductivity

For quantification such a parameter are used special thermal conductivity coefficients, strictly declared in SNIP. For example, the thermal conductivity coefficient of concrete is 0.15-1.75 W/(m*C) depending on the type of concrete. Where C is degrees Celsius. On this moment Calculation of coefficients is available for almost all existing types of building materials used in construction. Thermal conductivity coefficients building materials very important in any architectural and construction work.

For convenient selection of materials and their comparison, special tables of thermal conductivity coefficients are used, developed in accordance with SNIP standards (building codes and regulations). Thermal conductivity of building materials, the table of which will be given below, is very important in the construction of any objects.

• Wood materials. For some materials, the parameters will be given both along the fibers (Index 1, and across – index 2)

• Various types of concrete.

• Various types of construction and decorative bricks.

Calculation of insulation thickness

From the above tables we see how different the heat conductivity coefficients can be for different materials. To calculate the thermal resistance of the future wall, there is a simple formula, which connects the thickness of the insulation and its thermal conductivity coefficient.

R = p / k, where R is the thermal resistance index, p is the layer thickness, k is the coefficient.

From this formula it is easy to extract the formula for calculating the thickness of the insulation layer for the required thermal resistance. P = R * k. Thermal resistance value is different for each region. There is also a special table for these values, where they can be viewed when calculating the thickness of the insulation.

Now let's give some examples the most popular insulation materials and their technical characteristics.

In recent years, when building a house or renovating it, much attention has been paid to energy efficiency. Given existing fuel prices, this is very important. Moreover, it seems that savings will continue to become increasingly important. In order to correctly select the composition and thickness of materials in the pie of enclosing structures (walls, floors, ceilings, roofs), it is necessary to know the thermal conductivity of building materials. This characteristic is indicated on the packaging of the materials, and it is necessary at the design stage. After all, you need to decide what material to build the walls from, how to insulate them, and how thick each layer should be.

What is thermal conductivity and thermal resistance

When choosing building materials for construction, you need to pay attention to the characteristics of the materials. One of the key positions is thermal conductivity. It is represented by the thermal conductivity coefficient. This is the amount of heat that a particular material can conduct per unit time. That is, the smaller this coefficient, the worse material conducts heat. And vice versa, the higher the number, the better the heat is removed.

Materials with low thermal conductivity are used for insulation, and materials with high thermal conductivity are used to transfer or remove heat. For example, radiators are made of aluminum, copper or steel, since they transfer heat well, that is, they have high coefficient thermal conductivity. For insulation, materials with a low thermal conductivity coefficient are used - they retain heat better. If an object consists of several layers of material, its thermal conductivity is determined as the sum of the coefficients of all materials. During calculations, the thermal conductivity of each of the components of the “pie” is calculated, and the found values ​​are summed up. In general, we obtain the thermal insulation capacity of the enclosing structure (walls, floor, ceiling).

There is also such a thing as thermal resistance. It reflects the ability of a material to prevent heat from passing through it. That is, it is the reciprocal of thermal conductivity. And, if you see a material with high thermal resistance, it can be used for thermal insulation. An example of thermal insulation materials is the popular mineral or basalt wool, foam, etc. Materials with low thermal resistance are needed to remove or transfer heat. For example, aluminum or steel radiators used for heating, as they give off heat well.

Table of thermal conductivity of thermal insulation materials

To make it easier to keep your house warm in winter and cool in summer, the thermal conductivity of walls, floors and roofs must be at least a certain figure, which is calculated for each region. The composition of the “pie” of walls, floor and ceiling, the thickness of the materials are taken into account so that the total figure is no less (or better yet, at least a little more) recommended for your region.

When choosing materials, it is necessary to take into account that some of them (not all) in conditions high humidity conduct heat much better. If such a situation may occur for a long period of time during operation, the thermal conductivity for this condition is used in the calculations. The thermal conductivity coefficients of the main materials used for insulation are given in the table.

Some of the information is taken from standards that prescribe the characteristics of certain materials (SNiP 23-02-2003, SP 50.13330.2012, SNiP II-3-79* (Appendix 2)). Those materials that are not specified in the standards are found on the manufacturers' websites. Since there are no standards, different manufacturers they can differ significantly, so when purchasing, pay attention to the characteristics of each material you purchase.

Table of thermal conductivity of building materials

Walls, ceilings, floors can be made from different materials, but it so happens that the thermal conductivity of building materials is usually compared with brickwork. Everyone knows this material, it’s easier to make associations with it. The most popular diagrams are those that clearly demonstrate the difference between various materials. One such picture is in the previous paragraph, the second is a comparison brick wall and walls made of logs - is shown below. That is why for walls made of brick and other materials with high thermal conductivity they choose thermal insulation materials. To make it easier to select, the thermal conductivity of the main building materials is summarized in a table.

Wood is one of the building materials with relatively low thermal conductivity. The table provides approximate data for different breeds. When purchasing, be sure to look at the density and thermal conductivity coefficient. Not everyone has them as they are prescribed in regulatory documents.

Metals conduct heat very well. They are often the bridge of cold in a structure. And this must also be taken into account, direct contact must be excluded using heat-insulating layers and gaskets, which are called thermal breaks. The thermal conductivity of metals is summarized in another table.

How to calculate wall thickness

In order for the house to be warm in winter and cool in summer, it is necessary that the enclosing structures (walls, floor, ceiling/roof) must have a certain thermal resistance. This value is different for each region. It depends on the average temperatures and humidity in a particular area.

Thermal resistance of enclosing
designs for Russian regions

In order for heating bills not to be too high, it is necessary to select building materials and their thickness so that their total thermal resistance is not less than that indicated in the table.

Calculation of wall thickness, insulation thickness, finishing layers

For modern construction A typical situation is when the wall has several layers. Except load-bearing structure There is insulation and finishing materials. Each layer has its own thickness. How to determine the thickness of insulation? The calculation is simple. Based on the formula:

R—thermal resistance;

p—layer thickness in meters;

k is the thermal conductivity coefficient.

First you need to decide on the materials that you will use during construction. Moreover, you need to know exactly what type of wall material, insulation, finishing, etc. will be. After all, each of them makes its contribution to thermal insulation, and the thermal conductivity of building materials is taken into account in the calculation.

First, the thermal resistance of the structural material (from which the wall, ceiling, etc. will be built) is calculated, then the thickness of the selected insulation is selected based on the “residual” principle. You can also take into account thermal insulation characteristics finishing materials, but usually they are a plus to the main ones. This is how a certain reserve is laid down “just in case.” This reserve allows you to save on heating, which subsequently has a positive effect on the budget.

An example of calculating the thickness of insulation

Let's look at it with an example. We are going to build a brick wall - one and a half bricks long, and we will insulate it with mineral wool. According to the table, the thermal resistance of walls for the region should be at least 3.5. The calculation for this situation is given below.

If the budget is limited, you can take 10 cm of mineral wool, and the missing will be covered finishing materials. They will be inside and outside. But if you want to keep your heating bills to a minimum, better finish let "plus" to calculated value. This is your reserve for the most time low temperatures, since thermal resistance standards for enclosing structures are calculated based on the average temperature over several years, and winters can be abnormally cold. Therefore, the thermal conductivity of building materials used for finishing is simply not taken into account.

Construction of any home, be it a cottage or a modest one country house, must begin with project development. At this stage, not only the architectural appearance of the future structure is laid down, but also its structural and thermal characteristics.

The main task at the project stage will be not only the development of strong and durable constructive solutions, capable of maintaining the most comfortable microclimate with minimal costs. A comparative table of thermal conductivity of materials can help you make your choice.

The concept of thermal conductivity

In general terms, the process of thermal conduction is characterized by the transfer of thermal energy from hotter particles solid to less heated ones. The process will continue until thermal equilibrium occurs. In other words, until the temperatures become equal.

In relation to the building envelope (walls, floor, ceiling, roof), the heat transfer process will be determined by the time during which the temperature inside the room becomes equal to the ambient temperature.

The longer this process takes, the more comfortable the room will feel and more economical in operating costs.

Numerically, the heat transfer process is characterized by the thermal conductivity coefficient. The physical meaning of the coefficient shows how much heat passes through a unit of surface per unit time. Those. the higher the value of this indicator, the better the heat is conducted, which means the faster the heat exchange process will occur.

Accordingly, at the stage design work it is necessary to design structures whose thermal conductivity should be as low as possible.

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Factors influencing the thermal conductivity value

The thermal conductivity of materials used in construction depends on their parameters:

1. Porosity - the presence of pores in the structure of a material disrupts its homogeneity. When a heat flow passes, part of the energy is transferred through the volume occupied by pores and filled with air. It is accepted to take the thermal conductivity of dry air (0.02 W/(m*°C)) as a reference point. Accordingly, the larger the volume occupied by air pores, the lower the thermal conductivity of the material will be.
2. Pore ​​structure - the small size of the pores and their closed nature help reduce the rate of heat flow. In the case of using materials with large communicating pores, in addition to thermal conductivity, heat transfer processes by convection will be involved in the heat transfer process.
3. Density - at higher values, particles interact more closely with each other and contribute more to the transfer of thermal energy. In general, the thermal conductivity values ​​of a material depending on its density are determined either on the basis of reference data or empirically.
4. Humidity - the thermal conductivity value for water is (0.6 W/(m*°C)). When wet wall structures or insulation, dry air is displaced from the pores and replaced with drops of liquid or saturated moist air. Thermal conductivity in this case will increase significantly.
5. The effect of temperature on the thermal conductivity of a material is reflected through the formula:

λ=λо*(1+b*t), (1)

where, λо - thermal conductivity coefficient at a temperature of 0 °C, W/m*°C;

b - reference value of the temperature coefficient;

t - temperature.

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Practical application of the thermal conductivity value of building materials

The concept of the thickness of the material layer directly follows from the concept of thermal conductivity to obtain the required value of heat flow resistance. Thermal resistance is a standardized value.

A simplified formula that determines the thickness of the layer will look like:

where, H - layer thickness, m;

R - heat transfer resistance, (m2*°C)/W;

λ - thermal conductivity coefficient, W/(m*°C).

This formula, when applied to a wall or ceiling, has the following assumptions:

• the enclosing structure has a homogeneous monolithic structure;
• the building materials used have natural moisture.

When designing, the necessary standardized and reference data are taken from the regulatory documentation:

• SNiP23-01-99 - Construction climatology;
• SNiP 02/23/2003 - Thermal protection of buildings;
• SP 23-101-2004 - Design of thermal protection of buildings.

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Thermal conductivity of materials: parameters

A conventional division of materials used in construction into structural and thermal insulation has been accepted.

Structural materials are used for the construction of enclosing structures (walls, partitions, ceilings). They differ large values thermal conductivity.

The values ​​of thermal conductivity coefficients are summarized in Table 1:

Table 1

By substituting into formula (2) the data taken from the regulatory documentation and the data from Table 1, you can obtain the required wall thickness for a specific climatic region.

When making walls only from structural materials without using thermal insulation, required thickness(in the case of using reinforced concrete) can reach several meters. The design in this case will turn out to be prohibitively large and cumbersome.

Allows the construction of walls without using additional insulation, perhaps, only foam concrete and wood. And even in this case, the thickness of the wall reaches half a meter.

Thermal insulation materials have fairly low thermal conductivity values.

Their main range lies from 0.03 to 0.07 W/(m*°C). The most common materials are extruded polystyrene foam, mineral wool, polystyrene foam, glass wool, and polyurethane foam-based insulation materials. Their use can significantly reduce the thickness of enclosing structures.

It is better to start the construction of each facility with project planning and careful calculation of thermal parameters. Accurate data will be obtained from a table of thermal conductivity of building materials. Proper construction of buildings contributes to optimal indoor climate parameters. And the table will help you choose the right raw materials to be used for construction.

Thermal conductivity of materials affects the thickness of walls

Thermal conductivity is a measure of the transfer of thermal energy from heated objects in a room to objects at a lower temperature. The heat exchange process is carried out until the temperature indicators are equalized. To indicate thermal energy, a special thermal conductivity coefficient of building materials is used. The table will help you see all the required values. The parameter indicates how much thermal energy is passed through a unit area per unit time. The larger this designation, the better the heat exchange will be. When constructing buildings, it is necessary to use material with minimum value thermal conductivity.

The thermal conductivity coefficient is a value that is equal to the amount of heat passing through a meter of material thickness per hour. Usage similar characteristics necessary to create better thermal insulation. Thermal conductivity should be taken into account when selecting additional insulating structures.

What influences the thermal conductivity index?

Thermal conductivity is determined by the following factors:

• porosity determines the heterogeneity of the structure. When heat is passed through such materials, the cooling process is insignificant;
• an increased density value affects close contact of particles, which contributes to faster heat transfer;
• High humidity increases this indicator.

Using thermal conductivity values ​​in practice

The materials are presented in structural and thermal insulation varieties. The first type has high thermal conductivity. They are used for the construction of floors, fences and walls.

Using the table, the possibilities of their heat transfer are determined. In order for this indicator to be low enough for a normal indoor microclimate, walls made of some materials must be especially thick. To avoid this, it is recommended to use additional thermal insulating components.

Thermal conductivity indicators for finished buildings. Types of insulation

When creating a project, you need to consider all ways of heat leakage. It can come out through walls and roofs, as well as through floors and doors. If you do the design calculations incorrectly, you will have to be content only with the thermal energy received from heating devices. Buildings built from standard raw materials: stone, brick or concrete need to be additionally insulated.

Additional thermal insulation is carried out in frame buildings. Wherein wooden frame imparts rigidity to the structure, and insulating material is laid in the space between the posts. In buildings made of brick and cinder blocks, insulation is done from the outside of the structure.

When choosing insulation materials, you need to pay attention to factors such as humidity levels, the influence of elevated temperatures and the type of structure. Consider certain parameters of insulating structures:

• the thermal conductivity indicator affects the quality of the heat-insulating process;
• moisture absorption has great importance when insulating external elements;
• thickness affects the reliability of insulation. Thin insulation helps maintain usable area premises;
• Flammability is important. High-quality raw materials have the ability to self-extinguish;
• thermal stability reflects the ability to withstand temperature changes;
• environmental friendliness and safety;
• Sound insulation protects against noise.

The following types of insulation are used:

• mineral wool is fire resistant and environmentally friendly. TO important characteristics low thermal conductivity;

• polystyrene foam is lightweight material with good insulation properties. It is easy to install and is moisture resistant. Recommended for use in non-residential buildings;
• basalt wool, unlike mineral wool, has better resistance to moisture;
• Penoplex is resistant to humidity, elevated temperatures and fire. It has excellent thermal conductivity, is easy to install and durable;

• polyurethane foam is known for such qualities as non-flammability, good water-repellent properties and high fire resistance;
• Extruded polystyrene foam undergoes additional processing during production. Has a uniform structure;

• penofol is a multi-layer insulating layer. The composition contains foamed polyethylene. The surface of the plate is covered with foil to provide reflection.

Bulk types of raw materials can be used for thermal insulation. These are paper granules or perlite. They are resistant to moisture and fire. And from organic varieties you can consider wood fiber, flax or cork covering. When choosing, Special attention pay attention to such indicators as environmental friendliness and fire safety.

Note! When designing thermal insulation, it is important to consider the installation of a waterproofing layer. This will avoid high humidity and will increase resistance to heat transfer.

Table of thermal conductivity of building materials: features of indicators

The table of thermal conductivity of building materials contains indicators various types raw materials used in construction. Using this information, you can easily calculate the thickness of the walls and the amount of insulation.

How to use the table of thermal conductivity of materials and insulation?

The table of heat transfer resistance of materials presents the most popular materials. When choosing a specific thermal insulation option, it is important to consider not only physical properties, but also such characteristics as durability, price and ease of installation.

Did you know that the easiest way to install penoizol and polyurethane foam. They are distributed over the surface in the form of foam. Similar materials Easily fills structural cavities. When comparing solid and foam options, it should be emphasized that foam does not form joints.

Values ​​of heat transfer coefficients of materials in the table

When making calculations, you should know the heat transfer resistance coefficient. This value is the ratio of the temperatures on both sides to the amount of heat flow. In order to find the thermal resistance of certain walls, a thermal conductivity table is used.

You can do all the calculations yourself. To do this, the thickness of the heat insulator layer is divided by the thermal conductivity coefficient. This value is often indicated on the packaging if it is insulation. Home materials are measured independently. This applies to thickness, and the coefficients can be found in special tables.

The resistance coefficient helps to select a specific type of thermal insulation and the thickness of the material layer. Information on vapor permeability and density can be found in the table.

At correct use tabular data you can choose quality material to create a favorable indoor microclimate.

Thermal conductivity of building materials (video)

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Thermal conductivity- the ability of a material to transfer heat from one part to another due to the thermal movement of molecules. Heat transfer in a material is carried out by conduction (by contact of particles of the material), convection (the movement of air or other gas in the pores of the material) and radiation.

Thermal conductivity depends on the average density of the material, its structure, porosity, humidity and average temperature of the material layer. As the average density of the material increases, thermal conductivity increases. The higher the porosity, i.e. less average density material, the lower the thermal conductivity. With increasing humidity of the material, thermal conductivity increases sharply, while its thermal insulation properties. Therefore, all heat-insulating materials in a heat-insulating structure are protected from moisture by a covering layer - a vapor barrier.

Comparative data of building materials with the same thermal conductivity

Thermal conductivity coefficient of materials