Q&A

Stone wool knowledge

Can stone wool be used for ETICS?

Stone wool is a Class-A, non-combustible insulation material, with high compressive and tensile strength, low water absorption and hygroscopicity and good dimensional stability. Not subject to thermal expansion, contraction or aging, stone wool is also exterior system compatible, energy saving and fire resistant, protecting buildings from extreme weather.

Its tensile strength meets relevant standards of the nation and technical requirements. The material can be used in the external wall plastering, roof insulation, curtain wall insulation and industrial insulation; compared with other thermal insulation board, such as XPS, stone wool board may not outperform them in tensile strength, but it is hard to be pulled apart in the real practice of project which proves itself qualified to specifications and application.

Is stone wool harmful to people?

ROCKWOOL insulation materials are made from stone wool. Although cutting the material may produce a small amount of powder, stone wool is still a non-toxic fiber material that does not cause any harm.

Stone wool has been recognized by the World Health Organization's International Agency for Research on Cancer (IARC) as a material with no risk to lung cancer. IARC has decided to withdraw stone wool from the list of possible carcinogens, because no evidence from epidemiological studies can indicate that working with stone wool will increase the risk of lung diseases; the inhalation of rock wool fiber over the long term also does not lead to the increased of tumor in animal experiments. There is no proof suggesting that stone wool is related to the increased risk of pulmonary fibrosis.

What is the difference between stone wool and slag wool?

Stone wool is mainly made from natural rocks while slag wool is from blast furnace cinder, phosphate slag, fly ash etc.

Iron ions inside the basalt allow finished stone wool products to have a higher content of iron oxide, enhancing its resistance to fire and high temperature. The content of slag or cinder is neither known nor evenly distributed, their pellet size irregular which causes the fact that some do not melt due to uneven heating. Furnace cinder may contain harmful heavy metals that are unknown. Acidic oxides containing sulfur, phosphorus and other elements will turn into acid with water, developing to metal corrosion; the exposure to water plus a high content of chloride ion will also generate acid that corrodes metals.

Melting basalt requires a temperature of more than 1,500 ° C, while slag and furnace cinder melt at 800 to 1,000 ° C. They start to shrink and deform at above 800 ° C, and even can be witnessed with holes, crystallization and carbonation. The burning test proved that slag wool performs poorly in fire resistance.

Slag wool has very coarse fiber and a high content of slag ball, which results in high thermal conductivity and poor performance in insulation. It often causes skin irritation and allergies. Raw materials being industrial waste or blast furnace cinder, slag cotton contains lots of powder and dust that carry heavy metal ions and sulfide. The contact with skin or inhalation will cause long-term harm on people.

What is the production process of stone wool?

The production of stone wool uses basalt as raw material, coke as fuel. After passing through vibration feeder, materials go to the cupola for melting at 1,400 degrees Celsius; and then the melt begins fiberization in the four-axis centrifuge as being spraying with agent. When wool collecting, curing, cooling, cutting and other processes completed, the finished stone wool products are finally wrapped by machine and delivered to storage.

What is the relationship between the acidity coefficient and the quality of the stone wool?

Generally, the line of acidity coefficient is drawn at 1.6, above 1.6 being stone wool, below 1.6 being slag wool. The overall performance of material whose acidity coefficient is above 1.6 is significantly better than that of material below 1.6; slag wool is normally lower than 1.4, its chemical stability poor.

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