Rock wool or fiberglass: Which insulates better?

In today’s article we are going to talk about two of the materials that are most taken into account when performing insulation work.

Rock wool or fiberglass? This question is one of the most asked by technicians when doing this type of work, and although both have a similar behavior, sometimes it is very worthwhile to choose one of the two.

In general, both materials have similar characteristics and are a great option when it comes to achieving good insulation and, therefore, good energy efficiency in a home. This translates into significant savings that amortize the initial investment in a short period of time.

But sometimes choosing one or the other can bring greater benefits. Let’s analyze what their essential differences are in case you ever find yourself in the situation of choosing between one of them.

Differences between rock wool and fiberglass

Both fiberglass and stone wool are used in much the same way in insulation.

Both are usually part of the blows of the air chambers and, also, are part of the filling of solutions such as in the core of sandwich panels or various coatings used on facades, floors and interior walls.

Although their characteristics are very similar, there are certain aspects in which placing one or the other can represent certain advantages.

If we have to talk about the difference between rock wool and fiberglass, we will cite the following:

  • Its origin: rock wool comes from volcanic rocks, while glass wool comes from glass threads. Both are treated at high temperatures, so their behavior against fire is very good.
  • Thermal insulation: both materials have almost the same qualities of thermal insulation, although we must consider that rock wool helps a little better to contain heat and avoid its losses.
  • Sound insulation – the thickness of rock wool is higher than that of fiberglass, so its ability to insulate acoustically will be better.
  • Water resistance: rock wool is very resistant to water, as it does not get wet easily and prevents the appearance of bacteria and mold very well over time. In those very humid places, or in facades facing north, it presents better behavior than fiberglass.
  • Sustainability: if you are concerned about caring for the environment, you should know that rock wool is made with 70% recycled materials, while glass wool is made with 30%.
  • Price: In this aspect, fiberglass is usually cheaper than rock wool.
Rock wool Fiberglass
Thermal insulation Very high High
Sound insulation High High
Water resistance Very good Good
Sustainability 70% recycled materials 30% recycled materials
Price 3,5 – 4,5 €/m2 2 – 3 €/m2
Is fiberglass or stone wool better?

Is glass wool or rock wool better?

Choosing between rock wool or fiberglass is to take into account the differences described above. The behavior of both materials is very similar, however, there are small nuances in which it may be convenient to choose one or the other.

Basically, it is not a question of which is better, but which one is more convenient depending on the intrinsic characteristics of the work where they are going to be installed.

For example, if we have to choose between fiberglass or rock wool and we need good sound insulation, rock wool is usually the most used, however, it will also be more expensive, so the decision must be based on both aspects.

The normal thing is that it is an experienced professional who weighs the pros and cons of each of the materials, and depending on the constructive typology make the best choice.

In general, in those works where there is a fairly tight budget, it is usually chosen to insulate with glass wool. Also if the volume of work is considerable, this choice is much cheaper.

With regard to blowing, one or the other is usually chosen depending on what has been said above, but if it is installed in panels, those composed of glass fibers are much more manageable and adaptable to any surface where they are going to be installed.

On the other hand, glass wool is more flaccid than rock wool, so depending on the areas, it can be more complicated to install.

They are the characteristics of the building, the location it has, the needs that are required and the budget that is had, the four factors that will generally tip the balance between one material and another.

Rock wool Fiberglass
✔ Better thermal insulation ✔ More economical
✔Increased water resistance ✔ More manageable
✔More sustainable option

My recommendation: if you live in a cold climate and can afford it, opt for rock wool. Otherwise use fiberglass, which will still be a good option.

Difference between rock wool and fiberglass

In summary, you have already seen what their small differences are, so you should consider them when making your choice.

Although our advice is that you consult by a professional, since he knows how to understand those small nuances by which one material may be more appropriate than the other.

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By Catharine Bwana