Glass Wool: Everything You Need to Know About This Mineral Insulator

Glass Wool

Glass Wool

The glass wool is used as insulation to insulate the attic. Inexpensive and easy to install, it offers a very good level of thermal insulation. Available in many forms, glass wool makes it easy to achieve performance levels defined by thermal regulations.

What is glass wool?

To limit its ecological impact, the raw material used for the manufacture of glass wool is crushed recycled glass. Other materials of natural origin are added, such as sand, feldspar, limestone or dolomite. The whole is melted at high temperature, then cooled and ground. Passing through the wind tunnel produces a light and stringy product. Glass wool fibers are available in several forms:

  • Rolls; Coils
  • rigid or semi-rigid panels
  • flakes

Glass wool is the cheapest and most widely used thermal insulation for attic insulation. Very fire resistant, it is classified in category A1 (unless it is covered with kraft paper). In addition, it does not emit toxic fumes in the event of a fire. It is rot-proof and is not eaten by insects or pests such as rodents. Glass wool blowing offers superior longevity because it is not sensitive to settling. To achieve an optimal level of insulation, glass wool must be protected from air passages.

The thickness of the insulation is defined according to the thermal resistance objective to be reached. Here are some indicative values of glass wool thickness to provide for insulation of lost attics:

RT 2012R = 8320 mm375 mm
RT 2020R = 10400 mm465 mm

The thicknesses defined in relation to the thermal insulation are sufficient to achieve the required levels of sound insulation. Certain types of glass wool provide enhanced acoustic comfort.

The advantages of glass wool for roof insulation

Glass wool is used for thermal insulation and sound insulation of residential buildings or non-residential buildings. Its characteristics also allow it to be used as an absorber for acoustic correction or in fire protection. The advantages offered by glass wool are numerous:

  • very good level of thermal and sound insulation
  • moderate cost
  • quick installation

Glass wool is fully recyclable. Recovery channels have been set up to limit site waste.

Glass wool is most often used to insulate lost attics, but it can also be used in the form of panels to insulate convertible attics. Several techniques can be implemented:

  • insulation between rafters
  • bilayer insulation
  • sarking insulation

Glass wool price

Here are the different costs of glass wool depending on the type of product chosen:

Type of productthicknessPrice per m²
Roller100 mm€3.50
Kraft coated roll200 mm€8
Semi-rigid bare panel30 mm€7.50
Semi-rigid panel aluminum face30 mm€9

Glass wool for blowing is available from € 2.80 per kg. In some cases, it is necessary to provide a vapor barrier, which can increase the final bill.

Rock wool in rolls costs on average 20% more than glass wool. This mineral wool is less sensitive to humidity and offers better sound insulation than glass wool. This is why it can be recommended in damp or very noisy homes.


Glass wool and behavior in the face of humidity

By its constituents, glass wool is  a material that does not absorb moisture  and is therefore classified as non-hydrophilic when it is used in buildings.

What to do with wet glass wool? If a glass wool has been accidentally moistened by climatic conditions for example, it is not necessary to intervene by various manipulations. By simply letting it dry naturally, it will retain its properties as thermal and acoustic insulation while regaining its thickness.

Glass wool: characteristics

  • Glass wool raw material and manufacturing:

Glass wool is created from sand and recycled or cullet glass. These raw materials are weighed and mixed, thus forming the glass composition. Then comes the melting in the oven and then the fiberizing which allows the fibers to be entangled and to create the glass wool mattress.

  • Conditioning  of glass wool:

Glass wool mattresses are packaged in the form of rolls, panels and flakes. The choice of one or the other packaging is made according to the intended application, the insulation conditions (accessibility, configuration of the house) as well as according to the insulation performance objectives.

  • Soundproofing :

The  porous and elastic structure of glass wool makes it an excellent absorber of airborne noise and impact noise. Acoustic correction from one room to another is thus ensured.

  • Glass wool incombustible by nature:

The reaction to fire  is passive and efficient since mineral wools are made from materials that are inherently incombustible. They do not fuel the fire and do not spread flames in a fire.

  • Lifetime :

The lifespan of glass wool depends more on external conditions than on the fibers that constitute it. Implemented according to the rules of the art and well chosen according to the targeted application, the glass wool does not settle and retains its thickness for preserved insulation performance. It thus has a lifespan of several decades and conventionally identical to that of the building.

Is glass wool dangerous for health?

Glass wool has often been criticized for its irritant and volatile side. Considerable efforts have been made by the manufacturers to limit the inconveniences that may arise when handling the product. As with all DIY work, it is important to respect the conditions of use, whether it is for installing or removing insulation. Wearing a mask, glasses and long clothing and rinsing off after work is sufficient to limit the risk of irritation. Calling on a professional makes it possible to guard against all the hazards associated with the installation and opens the right to financial aid for energy renovation.


Author Bio Vikas Rastogi holds the position of managing partner atVK Brothers. Keeping up with the current trends in marketing, he thinks about the marketing of ideas in the digital age. His interest and creative approach to marketing bring him to the industry.

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