What is the importance of the density of the insulation when choosing a material?

One of the parameters that people pay attention to when choosing a heater is density. What does this or that indicator mean and what characteristics of the heat-insulating material are affected by its density - this and much more will be discussed below.

The density of a material means the weight of a given substance, in one cubic meter of material. The unit of measurement is kg / m3 (kilogram per cubic meter). Another name for the density parameter is the specific gravity of the material.

The easiest way to understand what density is by considering mineral wool insulation. It can be loose and perceptibly soft, disassembling into fibers (a material with a low density, the molecules of which have weak bonds). You experience completely different sensations when touching mineral wool mats - their fibers are tougher, but most importantly, they seem to be pressed together (higher density of insulation).

Depending on what criterion is the basis for the classification, heaters are divided into different groups. Within the framework of this article, we are interested in density differentiation. In this case, the following types of thermal insulation materials are distinguished:

• Lungs. They are lightweight and have low thermal conductivity. This group primarily includes mineral wool materials.
• Average. An example of such a heater is foam glass. Such thermal insulation materials are usually produced in the form of slabs and blocks with high thermal and acoustic insulation values.
• Tough. This is a dense insulation, usually obtained by pressing, for example, mineral wool mats. In addition to low thermal conductivity, they are characterized by moisture resistance and the ability to withstand heavy loads.

As already mentioned, all thermal insulation materials are divided into several types, depending on the specific gravity. The scope of its application depends on the latter.

This is clearly reflected in the table:

It is important that certain types of insulation have their own classification depending on the specific weight. For example, according to GOST, polystyrene is divided into grades PSB 15 (density is less than 15 kg / m3), PSB 25 (indicators 15-25 kg / m3), PSB 35 (specific gravity from 25 to 35 kg / m3) and PSB 50 ( 50 kg / m3 or more).

The hardness classification of mineral wool is as follows:

• P-75 (material density, respectively, 75 kg / m3) suitable for lightly loaded and horizontal surfaces;
• P-125 (the specific gravity of this wool is 125 kg / m3, but insulation with a density of 110, 120 and 130 kg / m3 belongs to the same type) wall insulation;
• PZh-175 (density indicators are clear from the name) - high density material for outer skin;
• PZh-200 (specific gravity is 200 kg / m3 and above) - used for outdoor work, has increased fire resistance.

Different types of insulation have different average density values.

• Mineral wool heaters have a density of 30 to 200 kg / m3, which ensures their versatility - you can choose the material for any part of the house.
• Maximum density of polyethylene foam is 25 kg / m3, while the material is quite thin - 8-10 mm. An increase in density to 55 kg / m3 is achieved through the use of a foil layer on one side. Interestingly, its appearance only slightly increases the density of the product, significantly increasing the heat efficiency of the material. This is ensured by the ability of the foil coating to reflect up to 97% of thermal energy.

• Popular material for insulation Styrofoam has a specific gravity of 80-160 kg / m3, and extruded polystyrene foam - 28 to 35 kg / m3. It is no coincidence that the latter is one of the lightest materials for thermal insulation, which, moreover, has a low thermal conductivity.
• Due to the peculiarities of the composition and application technology (it is sprayed with a semi-liquid mass on the surface, after which it solidifies), penoizol also has a low density - 10 kg / m3. However, like most similar materials, it requires additional protection at least - a layer of plaster.
• A wide range of specific gravity indicators is characteristic of for foam glass - foamed or honeycomb glass. Interestingly, the standard figures are 200–400 kg / m3, while the light version has a density of 100–200 kg / m3. In combination with high thermal efficiency, because the thermal conductivity coefficient is equal to those of mineral wool, the material allows using a lightweight version for insulating facade structures, that is, having less weight and cost.

Most of the characteristics of the insulation are interrelated. So, the density index affects the thermal conductivity.

As you know, air is the best heat insulator. A large number of air bubbles are located between chaotically directed fibers of mineral wool insulation, for example, stone wool. but if the specific gravity of the material is increased (in fact, the fibers are compressed more strongly), then the volume of air bubbles will decrease, which will lead to an increase in thermal conductivity.

However, the relationship between density and thermal conductivity is due to the structure of the material. For example, when the density of expanded polystyrene changes, the volume of air contained in its capsules remains unchanged. This means that the thermal conductivity does not change in any way when the density of the insulation changes.

But the change in specific gravity always affects sound insulation. This is due to the fact that with a decrease in the air permeability of the heat insulator, its noise-absorbing indicators increase.

In other words, the denser the material, the better sound insulation it is characterized by... However, as the density increases, so does the weight and thickness of the material. It becomes inconvenient to work with him.

The way out of this situation will be the use of special heat-insulating panels with improved sound insulation properties. It can be lightweight glass wool or basalt insulation with twisted thin and long fibers. In this case, the density of the material may not exceed 50 kg / m3.

Strength indicators are also related to the material's ability to withstand heavy loads, and the relationship is directly proportional here. In this regard, more dense materials should be used in the loaded areas.This is the only way to avoid deformation of the insulation.

Finally, the method of installation depends on the specific gravity of the insulation. So, between the lags and the elements of the crate, lightweight heat insulators of low density can be used. If the same option is mounted on walls, it will simply slide, so the choice is made in favor of more durable mats and sheets.

Besides, dense insulation does not need additional mechanical protection, they are strong enough to withstand mechanical stress. And looser materials - polystyrene, expanded polystyrene, mineral wool - always need additional protection.

The density of the material should be chosen first of all, taking into account the scope of its application. When it comes to wall cladding, the type of cladding material should also be considered. So, for facades faced with siding, you can use lightweight insulation (40–90 kg / m3). If plastering is planned, the specific weight of the insulation should be increased to 140–160 kg / m3.

For pitched roofs, insulation with a density of up to 45 kg / m3 is sufficient, while a flat roof, subject to increased loads, requires a more "serious" heat insulator. For mineral wool insulation, this indicator will be at least 150 kg / m3, for expanded polystyrene insulation - at least 40 kg / m3. Under the subfloor, you need the most dense insulation, at least 180 kg / m3, and between the logs, you can also lay light, loose insulation, since they take all the load on themselves.

When choosing insulation, depending on its density, you should consider such criteria as:

• types of work (external or internal insulation);
• material installation method;
• the load to which the insulation is subjected;
• average temperature indicators in the winter season;
• the need for sound insulation.

The products of some companies have a small selection of materials, depending on the density. So, in the rulers Ursa Insulation is practically not found, the density of which is higher than 35 kg / m3.

Most well-known brands (Isover, Rockwool) produce both light and rigid insulation - a special type for each type of work, including under a loaded ventilation facade.

Paying attention to specific products, it is worth carefully studying the instructions for the material, paying attention not only to the density indicators, but also to the scope of application. So, in the Isover line there are medium density slabs (50-80 kg m3), which, however, are suitable for insulating facade systems.

Of interest are also slabs that combine 2 textures - their outer side is denser, hard, and the inner side is loose, soft. The use of such materials provides high-quality thermal insulation, reduces the load on the building, and also applies plaster directly over the insulation.

Some manufacturers, for example, TechnoNICOL, produce materials of different rigidity in different lines, while the lines of other brands include several types of material in terms of density. For example, Knauf is a line that includes material with a density of 35 kg / m3 and 150 kg / m3.

As for foam boards, manufacturers usually give a clear differentiation of the material by purpose, which is inextricably linked with density. For example, the density of TechnoNicol CARBON SAND boards is 28 kg / m3. Low density, which means low weight, allow them to be used as part of sandwich panels. And the CARBON PROF products of the same brand have a density of 30–35 kg / m3, which changes its purpose - now it serves as an independent insulation in residential buildings.

In other words, one of the main tips when buying insulation is to pay attention to the density and purpose of each specific manufacturer.

For example, for walls, a lightweight insulation is enough, which has a low thermal conductivity and will not overload the structure with its weight. Suitable material with indicators of 50-200 kg / m3.

For internal thermal insulation, even lighter insulation materials with a density of 28–55 kg / m3 should be used. But the foundation and basement parts require the use of rigid high-density insulation, at least 150 kg / m3.

Finally, we must not forget that heaters, the density of which is less than 250 kg / m3, necessarily need an additional protective layer. Moreover, when it comes to external thermal insulation.

For information on whether the density of thermal insulation materials is important, see the next video.