Heat transfer theories
Insulation of a wooden house
When starting construction, the future homeowner must choose not only the appearance and layout of the house, but also calculate the upcoming expenses for the maintenance and operation of his house. A significant share of these costs are the heating costs, ventilation and air conditioning. This raises a question: how to reduce heat loss and what materials to choose as insulation?
How to reduce heat loss?
The best assistant in this matter is knowledge of the processes of transferring water and heat in a building. Using this knowledge, you may choose the optimal materials for insulation, correctly place layers of thermal, steam and waterproofing, thereby protecting the house from fungal infections and dampness.
By the way, the thermal insulation properties of the glue bar are significantly superior to the same properties of brick and concrete. The thermal conductivity of solid wood is higher than that of glue. Adhesive interlayers in the timber are excellent heat insulators, and the spike joints on the lamellas create several sealing contours, preventing cold air from entering the house.
According to the theory of heat transfer, temperatures in different areas of a room are always approximately the same, regardless of the location of heat sources. This is explained by the fact that there are three methods of heat transfer: heat conduction, convection, and radiation. Through external walls, roofs, doors and windows (or enclosing structures), transmission is carried out mainly by thermal conductivity, which is characterized by the coefficient of thermal conductivity. The higher this coefficient of a material, the worse its thermal insulation properties.
The existing temperature difference on the internal and external surfaces of the enclosing structures is the reason for the occurrence of a heat flow, the movement of which is directed towards a decrease in temperature. The heat flux collides with the thermal resistance of the material from which the enclosing structure is made. Insulation is used to increase the thermal resistance of walls, doors, windows and roofs.
The insulation takes over the heat saving function. The durability, comfort and energy efficiency of a house directly depend on the ability of the insulation to perform this function for a long time.
The materials from which the structure of the house is made are never completely dry due to the processes of sorption and condensation of water vapor. Moisture in the house appears as a result of human activities: washing, cleaning, cooking, and caring of indoor plants. Other activities may also create vapors indoors. When the material is moistened, the thermal conductivity coefficient increases sharply, which is not a constant value and changes depending on humidity, density, and in the case of wood, on the direction of the heat flow. The structures of external fences must be made so that condensation does not occur in them and moisture does not accumulate. For good thermal protection at home, it is important that the insulation is protected from moisture.
What materials to choose as insulation?
Building materials with a thermal conductivity coefficient of less than 0.2 W/m2 are considered suitable for thermal insulation. Materials for thermal insulation are classified as follows:
Insulation of a wooden house
- Inorganic fibrous (basalt, mineral fibers and fiberglass);
- Foam inorganic (expanded perlite, foam glass);
- Foam organic (foams - polystyrene, polyurethane);
- Natural organic material (wood wool, cork, paper).
- Inorganic fiber insulation from natural materials (flint, basalt) and fiberglass. Heaters of this type have high thermal insulation properties and are fire-resistant, fungi and bacteria do not spread there.
The following types of this insulation are available:
- Mats - filler between wall posts and rafters;
- Semi-rigid slabs - used as an addition to the rostwerk, suitable for the construction of a sloped roof with ventilation, but without an air gap and between the rafters;
- Solid slabs are filler for floors and ceilings.
- Basalt wool is a collection of very thin and flexible vitreous fibers. Such fibers are formed by spraying the molten charge. High quality basalt wool does not crumble, being soft and pleasant to the touch.
- Glass wool consists of silky light flexible and thin glass filaments, which are obtained by drawing molten glass. Fiberglass is a type of mineral wool. This type of insulation has increased hygroscopicity, therefore, during storage, installation and operation, it requires reliable protection from all types of moisture.
If we compare glass wool and basalt wool, then the advantages are clearly the second one. Basalt wool surpasses fiberglass in some specifications: water absorption (lower than that of glass wool), hydrolytic resistance, and service life. Glass wool clods after several years, resulting in condensation.
Basalt wool keeps its original shape well as a result of the chaotic arrangement of the fibers.
Foam organic insulation (foam polystyrene) has a low cost, good thermal insulation properties, low bulk density. It retains its shape, is processable, has a low moisture content and is non-harmful to health. With all its advantages, the fire-fighting properties and acoustic performance are worse than those of inorganic fiber insulation. Because of its flammability, as well as because of its low vapor permeability, this type of insulation is the least suitable for insulating a wooden house.