According to environmental studies, up to 40% of the electricity and heat generated in the Northern Hemisphere is spent on heating industrial, residential and other facilities. This is due to the fact that high-quality thermal insulation of buildings brings significant benefits in terms of saving finances. Among other things, this allows you to achieve a comfortable stay. Styrofoam acts as one of the most common heat insulators, it is also called polystyrene foam, or PPS.
Vapor permeability
The vapor permeability of the foam is quite low. In practice, this means that on the way the steam moves from inside the house to the outside, there will be a barrier in the form of polystyrene foam. Outside buildings, temperatures are often lower than indoors. Therefore, the steam will turn into condensate, as a result of this, water will accumulate in the areas where the thermal insulation joins the wall structure. This leads to the risk of wetting materials that are nearby.
In order for the vapor permeability of the foam not become a minus when using this insulation, it is necessary to correctly calculate the dew point and determine which insulation thickness to choose. The removal of the dew point in this case can be carried out beyond the limits of the installed material. A reasonable solution in this matter is the installation of a ventilated facade. The vapor transmission characteristics of the heat insulator are not considered in isolation from the details of a particular design. It is important to consider what the walls are made of, how high the foundation is, and whether the installation of steam and waterproofing was carried out.
How to make vapor permeability a plus
The vapor permeability of the foam is 0.05 mg / (m · year · Pa). In this regard, its use can cause mold. In general, this characteristic is not only negative, but also a positive feature. The advantage is that when laying thermal insulation there is no need to create a vapor-permeable barrier. But a minus may occur if the installation technology has been violated. Under the foam, as mentioned above, moisture will form, which will certainly lead to the destruction of both the construction material itself and the insulation layer.
The vapor permeability of the foam will not affect the microclimate of the premises, if it is installed outside the building. Do not assume that polystyrene foam with different vapor permeability can be found on sale. This characteristic remains the same, regardless of density and foaming. This indicator is similar to a treehouse of oak or pine.
Structure and composition
Polyfoam is a white material with a rigid foam structure in which 2% polystyrene and 98% air. For manufacturing, a technology has been developed for foaming polystyrene granules. In the next step, these microscopic particles are treated with hot steam. This procedure is repeated several times, which reduces the weight and density of the material. The prepared mass is dried to remove residual moisture. The raw materials are in the open air in drying tanks. At this stage, the structure takes on its final form.
The granules have a size that ranges from 5 to 15 mm. When they are dried, they are given the appropriate form. Pressing is carried out on plants or machines that turn the material into something like a compact package. As soon as the foam is compressed, it is exposed to hot steam, resulting in the formation of blocks with certain parameters. They are cut with a tool in size. Sheets may have custom sizes. The thickness of the web varies from 20 to 1000 mm, while the dimensions of the plates can have dimensions from 1000 x 500 mm to 2000 x 1000 mm.
Basic properties
When you know the vapor permeability of the foam, you can ask about other characteristics as well as features. Among others, it should be highlighted:
- low thermal conductivity;
- high sound and windproof properties;
- low water absorption;
- durability;
- strength;
- resistance to chemical and biological effects.
With regard to thermal conductivity, it is an indisputable advantage of foam. This is due to the fact that the cells in the base have the shape of a polyhedron. Their size reaches 0.5 mm. A closed cell cycle reduces heat transfer and limits cold penetration.
Sound and windproof properties
The thickness and vapor permeability of the foam is not all that you should know when buying a material. It is important to take an interest in sound and windproof properties as well. If the walls are insulated with polystyrene foam, they will not need wind protection. Sound insulation of the building will increase. Thus, the soundproofing properties are explained by the cellular structure.
In order to ensure high-quality insulation from external noise, it will be necessary to lay a layer of material, the thickness of which is 3 cm. If you increase this figure, you will be able to achieve better sound insulation. The vapor permeability of the facade foam was mentioned above. However, this characteristic is not the only one you should know. It is also necessary to take an interest in durability. The plates of this insulator do not change their physical properties for a long time. They are ready to undergo high pressure without collapsing or deforming. An excellent example of this is the construction of runways, where expanded polystyrene has long been widely used. The degree of strength depends on the thickness of the plates and proper installation.
The vapor permeability of the foam density 25 remains the same as mentioned above. The first indicator does not depend on other characteristics. But before purchasing this heat insulator, it is also important to know about resistance to chemical and biological influences. Plates are resistant to aggressive environments, solutions of alkalis, salts and acids, sea water, gypsum and lime. Expanded polystyrene can be in contact with bitumen, cement, water-soluble and silicone paints. Substances can affect the canvas only with prolonged exposure. This applies to materials that contain vegetable and animal oils, as well as diesel fuel and gasoline.
The vapor permeability of the foam and extruded polystyrene foam was mentioned above. Before buying this material, it is also important to know that you can use insulation as a building material, excluding contact with aggressive chemical compounds, among which are saturated hydrocarbons and organic solvents.
Fire safety
Vapor permeability and fire safety of foam are one of the important characteristics. Modern building materials must meet fire safety requirements and be resistant to open flame during operation. Expanded polystyrene does not support combustion and flares up at a temperature that is 2 times higher than that of wood. Energy during the burning of foam is 8 times less than when burning a tree. This suggests that the temperature of the fire will be significantly lower.
What to fear
Expanded polystyrene can ignite only during direct contact with the flame. Upon termination of such contact, the foam self-extinguishes within 4 seconds. These indicators characterize it as a fireproof material suitable for construction.
Application
The breathability of the foam is quite low, which does not allow its use indoors. But the structure of the material is cellular, which makes the material a universal sound and heat insulator in the field of construction. Expanded polystyrene is used to make industrial products by the type of sheet foam, insulation for pipes and shells. The compartments of the vessels are filled with material, which increases their buoyancy. Bibs, life vests and floats are made from polystyrene foam. It is used for transportation of donor organs, medical containers are made, and used for other medical needs.
PPS has found its wide application in construction and decoration; it is used as a fixed formwork. He serves as a heat insulator in instrumentation. It can be used as packaging for expensive and fragile goods. It acts as a substrate for food products and as a raw material for the manufacture of disposable plates. Styrofoam often makes decorative elements. This may be the exterior and interior decoration of buildings, as well as premises for various purposes. Ceiling tiles, skirting boards, Christmas decorations, architectural decor, and garden decor are made from it.
Styrofoam classification
Polyfoam today is known in many varieties, among them are:
- polystyrene;
- polyurethane;
- extrusion foam;
- polyvinyl chloride;
- extruded polystyrene;
- polyethylene foam.
PPS can be made by pressing or by a non-press method. Distinguishing these materials is not difficult. The press variety is made by the method of strong adhesion of granules, so such canvases are more difficult to break. Extruded polystyrene is almost the same as non-foam polystyrene. The material has disadvantages, expressed in that there are cavities between the granules where water vapor can penetrate. At minus temperatures, moisture accumulates there, which leads to the gradual destruction of the material. In this regard, extrusion foam wins somewhat. In appearance, it has a homogeneous structure. Among the advantages of this material should be highlighted:
- long term of operation;
- great strength.
Polyethylene foam is very flexible. It often takes the form of translucent sheets of different thicknesses, which are flexible. The most used in everyday life is polyurethane foam. In the people it is called foam rubber and is characterized by elasticity.