Stone Wool Insulation for Energy Efficiency | 11 Features

Stone wool was invented thanks to discovering that lava could be mixed with wool tassels 150 years ago in a volcanic eruption. It was later developed and converted into the stone wool insulation material and started to be produced in the 1850s and patented in the USA in 1875. It is no coincidence that this material continues to be preferred today after 1.5 centuries. Strong features and some advantages over materials in the same category make this material stand out.

What is Rockwool Insulation

Stone wool, aka rockwool, is a thermal insulation material that produced by melting inorganic stones in the nature at very high temperatures, around 1500 degrees, obtained from recycled slag [1]. The rockwool insulation material, which is made of melting these inorganic materials, contains 97% fiber. This fibrous thermal insulation material is generally marketed as standard sized boards or rolls. This makes the rockwool for insulation easier to install and transport.

Stone wool insulation panel
Stone wool insulation panel [2]

Characteristics of Stone Wool Insulation

Just like other thermal insulation materials, since the thermal conductivity factor is low, it keeps the interior cool in summer and warm in winter. In short, mineral wool insulation slows down the transfer of heat energy from the hot space to the cold space.

Thermal Conductivity of Rockwool

The thermal conductivity r value of rockwool insulation material is between 0.035 – 0.040 W/mK. This range is very close to the values of other thermal insulation materials.

Is stone wool fire proof?

Compared to EPS and XPS thermal insulation materials, rockwool insulation is safe against fire and in the A1 fire proofing class. It also begins to melt at temperatures above 1000 degrees. In this way, it also provides effectiveness in protection against fire. Thanks to the fire-stopping feature of the stone wool insulation in the case of a fire, the spread of the blazes are delayed and it gives time for the people inside to escape.

Does stone wool provide sound insulation?

The material has a surface that absorbs sound waves thanks to its fibrous structure. For this reason, yes, rockwool insulation panels are extremely useful building materials in terms of sound insulation. The sound-absorbing criss-cross fiber structure converts this sound energy into heat energy. Generally, in cases where sound insulation is more important, rockwool insulation material with a lower density should be used. By this way, the rate of air inside it increases and this helps to dampen sound waves.


Rockwool insulation is a waterproof material. The fiber in its structure repels water. For this reason, the water in contact with the surface remains on its surface. This feature makes the material extremely effective in terms of waterproofing.

Rock wool, which is a vapor permeable material, prevents moisture from condensing. It is expected that the layers in the structure shell will not pass water, and the vapour will pass from the outer layer to the inner layer at a decreasing rate. Because if the vapor permeability is too low, the vapor may liquefy and turn into water leaking between the layers due to the temperature difference between the two environments. This damages the materials used in the building.

Other Features of Rockwool Insulation

  • Stone wool is offered in the market in boards with a thickness of 3 to 12 cm. The length of these rockwool insulation boards, which are 60-120 cm in width, can reach up to 8 meters, and this length can be increased according to the need. The dimensions of the mineral wool insulating material are not affected by temperature differences or change.
  • The melting temperature is above 1000 degrees. The temperature range in which the product can be used efficiently is between -50 and +650 degrees.
  • Stone wool insulation material fills the gaps in the frame walls very easily. This is one of the best benefits of rockwool insulation and makes it better than other materials that alternatives to rockwool in this manner.
  • It is a material that can be used throughout the life of the building, does not deacay, and cannot be ate by harmful organisms and insects. The reason why it keeps microorganisms away is its inorganic structure.
  • It is usually with a form of a panel. It is possible to cover the surfaces of the boards with glass tulle or aluminum foil, depending on the need.
  • The density of stone wools sold in the market varies between 40 and 150 kg/m³. In this direction, you can choose different densities according to the using area and climate.

As a result, this material is highly preferred due to its high thermal insulation values as well as good levels of sound absorption and fire resistance.

Features of Rockwool thermal insulation
Rockwool thermal insulation [2]

Where is stone wool insulation used?

There are different usage areas like XPS and EPS and other similar thermal insulation materials used in the building sector. However thanks to its non-rigid, compressible and formable structure; Efficiency of it and ease of application are higher on rough surfaces and in amorphous frames. In this way, rockwool insulation is used for insulation purposes in many areas of our lives, except for the building sector. It is widely used in exterior walls, roofs, suspended ceilings, separating walls, electrical appliances, insulation of aluminum and steel doors, outer shells of ships and airplanes.

To summarize, the stone wool thermal insulation material, which was first produced 150 years ago, has become one of the effective insulation materials of the building sector thanks to its features like that high thermal insulation, sound proofing, water resistance, fire proofing and high compressibility.

Ceiling installation of thermal insulation
Ceiling installation [3]


[1]Discovery Channel. “How It’s Made (Belgesel)”. Date accessed May 11 2021.

[2]Achim Hering – Own work, CC BY 3.0, Date accessed May 11 2021.

[3]Recomandari Bellcraft. Flickr. Date accessed May 11 2021.

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