THE ADVANTAGES OF GLASS WOOL

THERMAL INSULATION

 Thermal dispersions measure the inability of a building or of an appliance to keep the heat or the cold. The insulating materials applied to the walls restrict the heat flow from the hotter side to the colder: the higher the insulating capability, the lower the heat loss. In fact, the heat loss varies according to the wall thickness and the difference in temperature between the inside and the outside.

Insulation is necessary in order to minimise dispersions and glass wool is one of the best insulating solutions on the market.

Its thermal properties come from the technical features as at section "what is it and how it works".
Eurofibre offers products and solutions with certified and reliable performance that are able to reduce thermal dispersions in an efficient and long-lasting manner. The main feature of any insulating material is its thermal conductivity or "lambda" (X).

Thermal performance of two or more insulating products must be compared by this parameter and not, as it often happens, by their densities: the lower the thermal conductivity the better the insulating capability.

Those products with a thermal conductivity lower than 0,065 W/(m·K) are defined as "insulating products". Glass wool has a thermal conductivity between 0,045 W/mK and 0,030 W/mK, when measured at 10°C. This value also varies with the density of glass wool.

Energy efficiency and cost/efficiency ratio.

In order to make a fair assessment of energy efficiency and cost/efficiency ratio, it's necessary to take into consideration the Thermal Resistance. This is defined as the ratio between the thickness of the insulating material and the thermal conductivity (R = s / λ as m²W/K). Since the retail price of the product depends on the ratio between the quantity of insulating material over a certain surface (expressed in kg/m²), sometimes it may be more convenient to use thicker and less dense materials with the same thermal efficiency. This becomes clear with the chart below. 

density
thickness weight conductivity resistance
kg/m3 mm kg/m2 W/(mK) m2K/W
20 60 1,200 0,034 1,76
30 50 1,500 0,032 1,56
60 30 1,800 0,031 0,97
80 30 2,400 0,030 1,00

A higher thermal resistance can be obtained by using a material with a lower density but a higher thickness. As a result of this the cost per sqm becomes more convenient. 

ACOUSTIC INSULATION

The weaving of glass wool products also ensures excellent acoustic insulation.
The principle by which glass wool absorbs sound energy is called "absorption by porosity".
The structure of the material is characterized by a large amount of small gaps all linked to each other. The sound wave propagates into it and it's transformed into heat by friction.
The comparison between the acoustic performances of the products should not be based on the density but on a property called "resistance to airflow" (EN 29053). It is a well-known fact that the resistance to airflow of fibre-based materials is a feature that allows an indirect assessment of some properties, such as acoustic absorption and attenuation.The higher the values of resistance to air flow the better the absorption, attenuation, and dynamic stiffness.
In the following chart we can see a comparison between the resistances to airflow of glass and rock wool products.
 
ROCK WOOL
stated density
 kg/m3  30  50 70 100 
Resistance to airflow  kNs/m4  >5 >10   >15 >25 
GLASS WOOL
stated density
kg/m3 12 20 30 50
Resistance to airflow kNs/m4 >5 >12 >18 >30

 

THE ADVANTAGES OF GLASS WOOL_960x450.jpg
What shown above is a result of the difference in production of the two materials, which is, in turn, due to the different raw materials used.
Glass wool presents longer and thinner fibres than rock wool, which is a non-fibred material. This feature is the main reason for the results shown in the chart above. At equal thickness (resistance to airflow is not related to the product's dimension), it's therefore possible to use glass wool products, which are lighter than those in rock wool. 
the advantages of glass wool_960x450.jpg
Example of thermal insulation and acoustic correction with an insulation product made of self-extinguishing black polythene placed on the ceiling of a commercial premises.
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