Glass Wool is not Mineral Wool

By: Mr. Mushfiq Rahman, Director Pakistan Insulations (Pvt) Ltd

In industry, both glass wool and mineral wool are used for insulation. However, glass wool and mineral wool are very different from each other and they should not be confused for each other. Recently, it has come to our attention that people in Pakistan glass wool is being sold under the name of mineral wool. While this may not seem important to some, this is actually very important as this not being the same product as previously mentioned. If you take nothing else from this article, take this: Mineral Wool is the far superior product and in the current situation of Pakistan, Glass Wools only advantage is lower cost and this also is not true now a days.

Before tackling the major differences between the two, it is important to mention the similarities they have. Both glass wool and mineral wool are made by melting a substance and spinning into a centrifuge to form fibers. For glass wool, this is a combination of glass and sand, whereas for mineral wool, minerals are used for this purpose. The best mineral wool is made from basalt rock which is known as rockwool. Both glass wool and mineral wool are used for insulation purposes and both have similar thermal resistance values (R-values), though mineral wool has a slightly higher R-value than glass wool. This is where their similarities end.

There are several differences between glass wool and mineral wool that make mineral wool the far superior product. The most important reason in my opinion is that of fire safety. Glass Wool will melt and potentially even burn at the exposure at the slightest flame for more than a few minutes. Mineral wool, on the other hand will not melt till it reaches 1000 C and can withstand flames for several hours, which is typically more than enough time to stop the fire. What this means is that mineral wool is far better at containing fires than glass wool, and as such makes it a much safer material to use for insulation. Another advantage of mineral wool is that its R-value does not degrade and will maintain the same R-value several decades after it is initially installed, unlike glass wool. This is in comparison to glass wool which degrades very quickly after it is initially installed. This is due to mineral wool sagging much less than glass wool, which means its better at maintaining its structure, thus allowing it to maintain its R-value. For this same reason, mineral wool is also a better acoustic insulator than glass wool. Mineral Wool is also impenetrable to moisture whereas glass wool is not. This means there is a much higher chance of fungi and mold growing inside glass wool as opposed to mineral wool. The only potential advantage of glass wool is that it can sometimes be slightly cheaper but even that is not the case right now. As a matter of fact, mineral wool is cheaper than glass wool in Pakistan right now and will stay so for the foreseeable future.

Now that we all understand that glass wool and mineral wool are not the same, here is how to tell if the “mineral wool” you received is glass wool. Usually, glass wool is yellow, and mineral wool comes in a variety of colors. However, those who try to sell glass wool as mineral wool will often dye the glass wool to another color to disguise its true nature. The best way to tell if the insulation material you are receiving is mineral wool is to expose a small piece of it to flame from a lighter. If it melts quickly, it is not mineral wool. If it doesn’t melt after several minutes, it is most likely mineral wool.

Now that you know what the differences between mineral wool and glass wool are and how to tell the two apart, you can make avoid being defrauded by being sold glass wool that is being referred to as “mineral wool”.