Insulating the walls and floors of a home is one of the most effective ways to keep warm. Currently, there are several types of thermal insulation materials to choose from. Before installation, the thickness of the insulation layer should be calculated in order to optimize procurement costs and reduce the labor intensity of the work. But how to calculate the thickness of the insulation correctly? To do this, you need to know its properties.
Thermal conductivity is the main characteristic of insulation
Each material, regardless of its purpose, is characterized by the ability to transmit heat waves. The coefficient of thermal conductivity determines the amount of thermal energy passing through a structure of a material with an area of 1 m² at a temperature difference on its surfaces of 1 degree Celsius. Measured in W / m² * C.
The less heat transfer, the better the insulation's ability to keep warm. Optimal performance is possessed by polymeric materials - polyurethane foam, expanded polystyrene and the like. A layer of expanded clay will be the least effective in terms of energy saving.
In practice, the value of the heat transfer resistance (m2 * C / W) is used to calculate the thickness of the insulation. To calculate it, you need to use a simple formula:
The ratio of the wall thickness (d) to the coefficient of thermal conductivity (K) makes it possible to calculate the optimal heat insulator layer.
Requirements for residential buildings
But the wall of the house itself also has a certain ability to retain heat. It directly depends on the material of manufacture of the structure. Reinforced concrete structures have the worst heat transfer rates. Wooden houses and aerated concrete walls are optimal in terms of energy savings.
Why do you need to know this indicator? There are certain requirements for the value of the heat transfer resistance of the outer walls of residential buildings. In particular, SNiP II-3-79 determines the value of this parameter depending on the climatic zone.
Knowing all the initial data, you can independently calculate the thickness of the insulation, depending on its type and material for making the walls.
Calculation example
The heat transfer value is influenced by the density of the material. This is especially true for basalt wool and expanded clay. Therefore, it is advisable to clarify the actual indicator of the insulation from a specific manufacturer.
As an example of calculation, let's take a brick wall with a standard thickness of 640 mm (two-row). You will also need other data necessary to calculate the optimal thickness of the insulation:
- Region - Tula. For him, the optimal indicator of heat transfer resistance (Rн) is 4.65 m2 * C / W.
- The outer heat-insulating layer will be made of expanded polystyrene - K = 0.029 W / m² * С.
First, you should find out the actual heat transfer resistance of the brickwork:
Based on this, an additional layer of insulation (RT) should compensate for the lack of heat transfer resistance:
Using the formula for the ratio of heat transfer resistance to the thickness of the material, you can calculate the depth of the insulation layer.
That is, in this case, in order to ensure optimal energy saving, it is necessary to install a layer of polystyrene foam with a thickness of at least 100 mm on the outer wall.
Using this technique, you can independently calculate the optimal depth of thermal insulation protection. The main thing is that the values of the thermal conductivity of the insulation coincide with the actual ones.
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