Advice 1: How to calculate the thermal conductivity

The thermal conductivity represents the ability of a material to conduct heat. Conductivity is accomplished by thermal transfer of kinetic energy between particles inside of the material, and in contact with others. Calculation of thermal conductivity is widely used in construction for the development of special materials, protecting the house from the cold.
How to calculate the thermal conductivity
Instruction
1
Determination of the thermal conductivity of materials is carried out using a conductivity coefficient which is a measure of the ability to transmit heat flow. The lower the value of this index, the higher the insulating properties of the material. In this case the conductivity does not depend on density.
2
The numerical value of the conductivity is equal to the amount of thermal energy that passes through a section of material with a thickness of 1 m and 1 sq m over 1 second. The temperature difference on opposite surfaces is taken equal to 1 Kelvin. The amount of heat is the energy that gains or loses material by heat transfer.
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The formula of heat conduction as follows:Q = λ*(dT/dx)*S*dτ, where:Q – thermal conductivity;λ – thermal conductivity coefficient;(dT/dx) is the temperature gradient;S is the cross-sectional area.
4
When calculating the thermal conductivity of construction structures divided into components and summed their conductivity. This allows to determine the measure of the ability of the house construction (walls, roofs, Windows, etc.), cutting off the heat flow. In fact, the thermal conductivity of the building structure is a combined thermal conductivity of its material, including air gaps and a film of the outside air.
5
Based on the value of the thermal conductivity of the structure is determined by the amount of heat loss through it. This value is obtained by multiplying the thermal conductivity on the calculated time period, the total area of the surface as well as on the temperature difference between the outer and inner surfaces of the structure. For example, for walls of 10 square m with a conductivity of 0.67 at temperature difference of 13°, the heat loss in 5 hours will be 0,67*5*10*13 = of 435.5 j*m.
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The thermal conductivity coefficients of different materials are contained in the table of thermal conductivity, for example, for vacuum it is equal to 0, and for silver, one of the most teploprovodny materials, 430 W/(m*K).
7
During the construction together with the thermal conductivity of the materials should take into account the phenomenon of convection, which is observed in materials in liquid and gaseous state. This is especially true in the development of system of water heating and aeration. To reduce heat loss in these cases establish cross dividers made of felt, wool and other insulation materials.

Advice 2: How to calculate the thickness of insulation

During the construction of the building, be sure to remember about the thermal insulation. Areas where building regulations on insulation are violated, is called cold bridges. Usually they are from the higher temperatures (indoors) appear wet, or the point of "dew" that brings the formation of mildew and mold. Improper insulation of their homes will bring about depletion of the family budget.
How to calculate the thickness of insulation
Instruction
1
Determine the construction of the outer walls. It depends on the following factors: climatic, economic, structural features of the object and others. Determine the surface finishing of external walls (internal and external). Diagram of interior and exterior decoration depends on the solution of the exterior and interior of the structure. This automatically adds several layers to the thickness of the wall of the house.
2
Calculate the heat-transfer resistance of the selected wall (Rпр.) This value can be found by the formula, it is necessary to know the material from which made the wall and its thickness: Rпр.=(1/α (V))+R1+R2+R3+(1/α (n)), where R1, R2, R3 – resistance of heat transfer of each layer of the wall, α – the heat transfer coefficient of the inner surface of the wall, α(n) is the heat transfer coefficient of the outer surface of the wall.
3
Calculate the minimum allowable values of thermal resistance of (Rmin) for the climate zone where the building is carried out according to the formula R=δ/λ, δ – thickness of the layer of material in meters, λ is the thermal conductivity of material (W/m*K). The thermal conductivity can be seen on the packaging material, or define a special table thermal conductivity material, for example, for polystyrene PSB-s 15, density 15 kg/m3 , it is equal to 0,043 W/m mineral wool with a density of 200 kg/m3, and 0.08 W/m.
Thermal conductivity – the ability of a material to exchange heat with the environment. The higher the conductivity, the material is colder. The higher the thermal conductivity of concrete, metal, marble, low - air. Thus, materials which are based on air, for example, polystyrene are extremely warm. 40mm foam = 1m of brickwork. The coefficient has a constant value for each climate zone, it can be found in the directory DBN V. 2.6-31:2006 (Thermal insulation of buildings).
4
Compare Rmin with Rпр. find the difference Δ R. If the result of the calculation of Rmin< or = Rпр., the wall insulation is not necessary because existing regulatory layers provide insulation. When Rmin>Rпр., then determine the difference, subtract the larger value from a smaller ΔR= Rmin- Rпр.
5
Find the thickness of insulation according to ΔR. The insulation should provide the missing heat-transfer resistance. Choosing the insulation material, be aware of the following its characteristics, such as coefficient of thermal conductivity, coefficient of water absorption, density, Flammability class. The coefficient of water absorption - the ability of a material to keep the absorbed water. The smaller its value is of greater interest in this material as insulation. Used in the construction of materials with a high coefficient of water absorption, for example, glass wool or mineral wool. Additionally, in this case, a vapor - and waterproofing. To do this, so as not to allow material to get wet. If this happens, the conductivity strongly increases, for example, mineral wool twice.
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Also important is the Flammability and density of insulation. The latter characterizes the load on the supporting structures. Building materials are divided into non-combustible and combustible, which are divided into 4 groups: low-flammable (G1); ameranouche (G2); normalnaya (G3); zelenogorye (G4). The denser the material, the less flammable the cost is higher. After choosing the material, calculate by the formula the thickness of the insulation: ΔR= δ/λ, where δ= λ/ΔR, δ is the required thickness of the selected insulation, expressed in metres.
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