Sandwich panels today are considered a unique building material. If you compare with classic solutions, the panels win in many ways. They are often compared by characteristics with:
- concrete;
- silicate brick;
- brick;
- wood.
All these options lose in the matter of thermal conductivity to sandwich panels.
The concept of thermal conductivity
Thermal conductivity is the ability of a material to conduct heat. This parameter is calculated using a specific formula. It refers to the amount of heat that passes through a sample of material 1 m thick. Its area should be 1 m 2 . In this case, heat passes in one second at a unit temperature gradient.
Absolute vacuum is the best heat insulating material. Its thermal conductivity is zero. However, if in the production of thermoses it is possible to achieve the similarity of a cosmic vacuum, in construction it is necessary to be content with one of the effective heat insulating materials - air.
Thermal conductivity of panels with different insulating layers. The main characteristic
In order to determine the thermal conductivity of sandwich panels, it is necessary to deal with the material in the base. The coefficient of thermal conductivity will depend on this. For example, mineral wool with different densities has a thermal conductivity ranging from 0.38 to 0.7. The undoubted advantage of mineral wool panels is fire safety. However, cotton wool has the ability to absorb water, which contributes to the loss of heat-insulating characteristics. The material sags over time, among other things, such sandwich panels have quite impressive weight.
The thermal conductivity of the sandwich panels will be slightly different if polystyrene foam is the basis. The thermal conductivity coefficient will vary from 0.03 to 0.7, which depends on the density. The material does not absorb moisture, which is the main advantage of polystyrene foam. But there are quite a few drawbacks, among them it should be noted low resistance to chemicals, fragility, susceptibility to destruction at a temperature of 70 Β° C. In this regard, the material is assigned a fire resistance class G2. In addition, expanded polystyrene is loved by rodents. Under the influence of gasoline, acetone, the material melts and cannot resist oils.
The thermal conductivity of the sandwich panels will be the lowest if polyurethane foam is the basis. The parameter under consideration here varies from 0.019 to 0.25. The material is durable, dense and light. It is chemically stable and does not absorb moisture. Rodents are indifferent to polyurethane foam, fungi and mold do not develop inside it. Operating temperature reaches +160 Λ. The material belongs to the second class of fire resistance.
When you know the coefficient of thermal conductivity of sandwich panels, you can consider the manufacturing method. For example, structures with expanded polystyrene and mineral wool are made using gluing technology, while polyurethane foam foams inside the panels, which allows achieving a high-strength monolithic structure at the exit.
Thermotechnical calculation
This calculation is required to select the type of sandwiches and their thickness. The formula is quite complex, it takes into account the location of the house, the type of building, the average annual temperature, the estimated indoor temperature, the type of panels, the duration of the heating season, the relative humidity inside. Take into account all these parameters the average man is not within the power. And the school physics course here will not be enough. Therefore, for a long time, a thermal engineering calculation has been used, where you need to know only the required value.
For example, for the European part of Russia, wall panels should have a minimum thickness of 120 mm. This applies to expanded polystyrene. If we are talking about mineral wool, this value increases to 150 mm. In the case of roofing panels, these values ββwill be 180 and 250 mm, respectively. This calculation is relevant for rooms where the air temperature should be equal to 20 Λ. Thermal conductivity will be less if the panels have less impressive thickness. However, in addition to thermal conductivity, there is also a coefficient of thermal resistance. It is also important to consider the heat transfer coefficient.
If the thermal conductivity with thermal insulation of polyurethane foam is 0.02, then this value will remain with a decrease in thickness to 80 or 60 mm. In the first case, the thickness is 100 mm. As for the coefficient of thermal resistance, it will decrease from 5 to 3. An intermediate value is 4. The heat transfer coefficient will increase. For thicknesses of 100, 80 and 60 mm, this parameter is 0.193; 0.24; and 0.315, respectively.
In the heat engineering calculation, you may also be interested in the thermal conductivity of the sandwich panels for operating conditions. This indicator will be 0.034 at a temperature of 10 Β° C.
Thermal conductivity of Metal Profile products
The company Metal Profile delivers mineral wool sandwich panels to the market. The thermal conductivity of these products ranges from 0.046 to 0.048. The density is 110 kg / m 3 . The compressive strength is 55 kPa. You may also be interested in the coefficient of thermal conductivity of the insulation of the sandwich panels "Metalprofile" if polystyrene foam is laid inside. This indicator is 0.04 at 25 Β° C. The density here is 17 kg / m 3 . The compressive strength is 0.1 MPa. If the estimated thickness of the panels is greater than the maximum thickness of the manufactured products, the required wall or roof size should be typed with an additional layer of insulation.
When you know the coefficient of thermal conductivity of the insulation of sandwich panels "Metal Profile", you should also be interested in the area of ββuse of these products. They are designed to create internal and external walls, operated and non-operated ceilings, partitions and roofs. They can be involved in new construction and in the reconstruction of facilities for various purposes. This can be production and storage facilities, food and agricultural enterprises, construction complexes, etc. Products can be operated at temperatures from -65 to +85 Λ.
Sizes of sandwich panels on the example of Metal Profile products
Before buying a sandwich panel, you should inquire about their size. The minimum and maximum thickness are 50 and 250 mm, respectively. There is also such a thing as working width. It can be equal to 1000, 1160 and 1190 mm. Parameters other than those specified are ordered separately. Length can vary from 2000 to 14000 mm.
Technical specifications of polyurethane foam sandwich panels
The coefficient of thermal conductivity of 100 mm sandwich panels is 0.02. Work with such plates can be carried out at a temperature range from +5 to +30 Λ. The service life reaches 30 years.
The material is resistant to aggressive environments and moisture. It is safe, which means it can be used in residential buildings. Operating temperature varies from -80 to +85 Λ. Actual heat losses will be 1.7 times lower than standard.
Installation Rules
Installation of panels starts from the corner of the building. They begin installation from the basement and continue in separate tiers, moving from bottom to top until it is possible to achieve the desired height of the building. A compensation 20 mm seam is provided between the individual tiers. On the base with the help of an anchor dowel, a support element of the base is installed. If necessary, lay a layer of mineral wool.
The sandwich panel rises to the vertical position with the help of a lifting device and is mounted on the base. The verticality must be checked using a survey tool or plumb line. The product is pressed to the runs and fixed hardware.
Pros and cons of operation
Sandwich panels are good in that they can be operated at a wide temperature range from -65 to +85 Β° C. Products are environmentally friendly, durable and have a good locking connection with high reliability. The disadvantages of sandwich panels can be a heater, which over time cakes and absorbs moisture. This refers to mineral wool, which is saturated with water and loses its performance characteristics. This may also apply to other heat insulators that attract rodents and contribute to the development of mold and fungus.