When insulating the working surfaces of buildings, common types of thermal insulators are traditionally used: mineral wool, expanded polystyrene or foam. Their properties are subject to special requirements regarding hygroscopicity and density.
Influence of insulation density on performance
Density affects the following parameters of the material used for wall insulation:
- declared thermal insulation properties;
- sound insulation quality;
- resistance to deformation;
- features of installation in certain conditions of work.
For any heat insulator, there really is a rule: the less it weighs (the less its density), the more convenient the material for installation, and therefore more preferable. The density factor of stone wool is estimated by experts with great reservations. Its low thermal conductivity is due to the presence of an air gap between the threads. When this indicator reaches a certain minimum, the material ceases to retain heat.
When evaluating a material, it is always taken into account that the density of mineral wool affects not only its weight, but is also directly related to other performance characteristics.
Basic criteria and building codes
The resistance to heat transfer of the walls of buildings under construction is regulated by the current standards SNB 2.04.01 (chapter 5.1), which contains information for all types of walls and ceilings. In addition, for external fences and coatings, parameters for air and vapor permeability are necessarily calculated. In multilayer protective structures, the materials used are calculated as a whole, consistent with the main technical indicators.
The selection of products that are supposed to insulate the walls is preceded by heat engineering calculations. Based on their results, the type of material required and its specific brand is determined. When using synthetic substances (polystyrene or polyethylene), it is taken into account that they are impermeable not only to water, but also to steam. Therefore, when choosing them, it will be necessary to provide for special measures to create good air exchange in the premises.
Special requirements are imposed on materials formed in the form of slabs (including glass wool):
- the geometry is chosen so that the corners and edges of the workpieces do not have clearly distinguishable damage and noticeable irregularities;
- the structure of the plates is dense, the presence of poorly connected fibers and falling out granules is considered completely unacceptable;
- surfaces on both sides are made rough, or one of them is made with a complex texture.
Fulfillment of the latter requirement guarantees good adhesion to the insulated walls.
Density of heaters of various classes
Densities of mineral wool for facades are differentiated according to the class of a particular insulation material, and also vary for different modifications of the same type. To assess the density of mineral wool (basalt or any other), it is taken into account that this insulation refers to practically weightless materials.Moreover, the coefficient of its thermal conductivity does not, on average, exceed 0.026 W / cubic meter.
There are several types of basalt wool used for different purposes and differing only in the orientation of the fibers. The density values for facade mineral wool for different samples are given in tables widely available on the Internet. It can be seen from them that this indicator, depending on the modification and purpose of the product, varies in the range from 30 to 200 kilograms per unit volume. With such a wide range of densities of various heat insulators, the types used in floor slabs or when insulating roofs of buildings are of maximum importance.
Basalt "Technonikol" with the declared indicator equal to 195 units is traditionally considered as an example of estimating the density of mineral wool. This material is usually purchased for thermal insulation of joints of roof structures and cornice parapets. Rockwool basalt wool has an indicator of 190 units of account. It is ideal for installation under roofing. The well-known brand of modern insulation "Knauf Insulation" has a relatively low density - no more than 35 kg per unit volume. They are intended exclusively for thermal insulation of frame structures and walls of buildings being erected at high speed.
Special varieties of facing insulation materials with a low density of mineral wool for facades are produced by almost all large and well-known manufacturers of these materials. Some of them prefer to sell such a product as a separate category of products with a declared value of about 30-40 units. The Knauf company has adapted to produce a product with a "floating" density, reaching a maximum value of 150 units.
Insulation density limit depending on the area of application
The density index for synthetic materials such as foam ranges from 100 to 150 units. Such compacted slabs are intended for insulating the roofs of buildings made of timber or for thermal insulation of floors between floors. Most manufacturers try to classify them according to their purpose, according to which the minimum allowable values change. The density index of expanded polystyrene, for example, depending on the technology used in its manufacture, averages from 28 to 35 kg. It is classified as one of the lightest materials with a very low thermal conductivity.
The use of heat insulators with variable density for various declared purposes can be clearly seen on specific samples of insulation materials. Products CARBON SAND "TechnoNIKOL" have a density of 28 kilograms per unit volume. They are traditionally used in the manufacture of sandwich panels, minimizing the weight of workpieces and giving the coating the required thermal insulation characteristics. Another well-known thermal insulator from TechnoNIKOL of the CARBON PROF brand is used in housing construction to insulate walls and other loaded structures. This sample is designed for a density of 30-35 kilograms per cubic meter. For slab insulation used in the manufacture of roadbeds, an indicator of 50 and 60 kg per cubic meter is characteristic. In this case, the load on the coating increases; it needs heat protection of increased strength.
Penoplex is one of the common insulation materials that also have a density that depends on the intended purpose. Insulation samples with an indicator of 25 units are intended for insulation of typical vertical structures. Materials designed for use in road construction have an indicator reaching 47 units.
Penoizol and expanded polyethylene (VP)
This type of heat insulator differs from other materials in that the preparation procedure is directly tied to the place of its use. Penoizol is applied to the protected surfaces in liquid form and has a very low density index, not exceeding 10 kg per unit volume. The increased porosity of this material guarantees high quality insulation, and the liquid form of the filling provides excellent adhesion to any surfaces. At the same time, like most samples of insulation with a low density index, penoizol needs an outer protective layer - at least in plastering.
The density index for VP varies in a wide range, it is determined by its thickness and the use of reinforcing (reinforcing) materials. Standard products for floor insulation in rolls have a density of about 24 kilograms per unit volume. Heat insulators, designed for insulation and serving as the basis for protecting other structures, including refrigeration units, are noticeably different from them. These objects need to be reinforced with aluminum sheets, the required density reaches 50-60 kg / cubic meter.
Foam glass
Cellular or foamed glass is used to insulate facades, roofs or foundations of any building being built. A mixture of glass and gas components in baked form are represented by materials of various densities. For external insulation, samples with a density of 200-400 kilograms per cubic meter are used. These indicators are sufficient to achieve the required resistance to the effects of various factors, including strong gusts of wind and random mechanical deformations.
Insulation blanks of foam glass with a density of 200 units are traditionally used for brick facades, heaters with a density of 300-400 kg / cubic meter are used for insulating roofs and foundations. For thermal protection of lightweight frame structures, an option with an indicator of 100-200 units is suitable.
For thermal insulation of individual building structures and their elements, insulation materials are used, the choice of which is determined by their direct purpose. For wall and non-reinforced frame structures, lightweight samples with a low density index will be required, which excludes excessive stress on the protected structure. For this, materials are used, the declared figure of which is 50-200 kilograms per cubic meter. For warming the interior spaces of a house, for example, it is allowed to use materials of lower density, which fit within the boundaries of 28 to 50 units.
For the foundation and roof of any object, other methods of insulation will be required, for which substances with a high indicator are suitable. For this, products with a declared density characteristic from 150 to 400 units are suitable. At the same time, relatively light heaters with a low density (up to 250 kg / cubic meter) require a special protective layer. Otherwise, it is necessary to use products with more stringent requirements for the indicator in question.
