Styrofoam or Mineral Wool for the Façade
On an almost daily basis, Knauf Insulation gets questions such as these sent to its email address: “I plan to have a Demit façade on a residential building. It is a family house, built from hollow clay bricks, which has not had mortar applied on the exterior. I wanted to use styrofoam, but some say that mineral wool is better. What do you recommend? What is a better insulating material and what is the price difference? Which material is quicker to work with?”
The decision to have a contact façade (known in everyday speech as Demit façade) on your building is certainly a serious step, primarily in the financial sense, because it requires investments which are an important item in the home budget. That is why everything needs to be well thought out and why the selection and the decision on the type and quality of the materials which you will build in should be approached in a thorough way.
Let’s start from the beginning and try to identify what’s most important for the user of the space when it comes to the new façade:
1. You only do the contact façade once within the facility’s life cycle – the façade should last as long as the house lasts – so, you need a permanent solution.
2. Which problems should the contact façade solve? In addition to heating insulation in the winter, you should also consider the thermal protection in the summer, sound insulation from the outside noise and the fire resistance of the façade.
3. The interior comfort in the rooms after the façade is installed – the walls need to “breathe after the insulation material is installed, that is, diffusion needs to be enabled – the passing of water steam from the interior through the exterior walls, so as to prevent condensation.
To further explain our answer – if, per our recommendation, you opt for mineral wool, you also get the following in the package:
– A material whose main ingredient is stone – so, a stable and permanent insulation which retains its characteristics through time – the characteristics of mineral wool are not affected by extreme changes in the external temperature and your façade will last as long as the facility lasts.
– Heating protection which is slightly better than EPS (styrofoam) insulation (of course, for the same chosen insulation thicknesses).
– Excellent sound insulation of the space – protection from external noise (the traffic, the neighborhood, children playing).
– Fireproof façade – because mineral wool is a non-flammable material and, in case of a fire, does not contribute to its spreading. Important: only systems with mineral wool can be classified as non-flammable, whereas ETICS (contact) systems with EPS (styrofoam) cannot be classified as such and they always belong in flammable systems.
– Steam-permeable façade; steam-permeability – the ability of the material to let through water steam, which is inevitably created inside a space, is defined with the µ coefficient (the lower the µ value is, the more easily the steam passes through the material). In order to understand this more easily, let’s take air as an example, where the value of µ=1. For mineral wool, it is µ=1.2, and for EPS, it is µ=30-40. This comparison clearly shows that the diffusion (the passing) of water steam through the walls featuring mineral wool goes without a problem, so the quality of the interior air and the microclimate are certainly better compared to the systems which have extremely non-steam-permeable materials in them.
Our additional recommendation – always buy the whole façade system, because that guarantees you the consistency and the permanence. When you’re buying a system, pay special attention for all components of the façade system (in addition to mineral wool, there are also anchors, the adhesive, reinforcement and smooth coating, the primer base and the finishing decorative façade layer) to be adapted to the insulation material such as mineral wool – so, the anchors need to be non-flammable and other materials steam-permeable.
The decision to have a contact façade (known in everyday speech as Demit façade) on your building is certainly a serious step, primarily in the financial sense, because it requires investments which are an important item in the home budget. That is why everything needs to be well thought out and why the selection and the decision on the type and quality of the materials which you will build in should be approached in a thorough way.
Let’s start from the beginning and try to identify what’s most important for the user of the space when it comes to the new façade:
1. You only do the contact façade once within the facility’s life cycle – the façade should last as long as the house lasts – so, you need a permanent solution.
2. Which problems should the contact façade solve? In addition to heating insulation in the winter, you should also consider the thermal protection in the summer, sound insulation from the outside noise and the fire resistance of the façade.
3. The interior comfort in the rooms after the façade is installed – the walls need to “breathe after the insulation material is installed, that is, diffusion needs to be enabled – the passing of water steam from the interior through the exterior walls, so as to prevent condensation.
To further explain our answer – if, per our recommendation, you opt for mineral wool, you also get the following in the package:
– A material whose main ingredient is stone – so, a stable and permanent insulation which retains its characteristics through time – the characteristics of mineral wool are not affected by extreme changes in the external temperature and your façade will last as long as the facility lasts.
– Heating protection which is slightly better than EPS (styrofoam) insulation (of course, for the same chosen insulation thicknesses).
– Excellent sound insulation of the space – protection from external noise (the traffic, the neighborhood, children playing).
– Fireproof façade – because mineral wool is a non-flammable material and, in case of a fire, does not contribute to its spreading. Important: only systems with mineral wool can be classified as non-flammable, whereas ETICS (contact) systems with EPS (styrofoam) cannot be classified as such and they always belong in flammable systems.
– Steam-permeable façade; steam-permeability – the ability of the material to let through water steam, which is inevitably created inside a space, is defined with the µ coefficient (the lower the µ value is, the more easily the steam passes through the material). In order to understand this more easily, let’s take air as an example, where the value of µ=1. For mineral wool, it is µ=1.2, and for EPS, it is µ=30-40. This comparison clearly shows that the diffusion (the passing) of water steam through the walls featuring mineral wool goes without a problem, so the quality of the interior air and the microclimate are certainly better compared to the systems which have extremely non-steam-permeable materials in them.
Our additional recommendation – always buy the whole façade system, because that guarantees you the consistency and the permanence. When you’re buying a system, pay special attention for all components of the façade system (in addition to mineral wool, there are also anchors, the adhesive, reinforcement and smooth coating, the primer base and the finishing decorative façade layer) to be adapted to the insulation material such as mineral wool – so, the anchors need to be non-flammable and other materials steam-permeable.
System installation: if installed according to the rules, both systems are equal regarding the difficulty of the installation, or more likely – the easiness of the installation. Contact systems have equal rules of installation, regardless of the insulation material (mineral wool or EPS). The key difference is that mineral wool panels must be anchored, unlike EPS panels, for which anchoring is not mandatory (it depends on the height of the facility, exposure to wind etc.).
Price of the system: the fact is that a contact façade with mineral wool is more expensive than the one with EPS (styrofoam). However, the recent styrofoam price increase has considerably reduced this difference and brought the two systems closers together in terms of the price. More precisely: if you pick other system components so that they are similar in quality, a mineral wool system is only some 30-40% more expensive than an EPS system, for the same thickness of the insulation.
The final decision – styrofoam of mineral wool, as always, is the result of many factors. Still, we recommend asking yourself – what is the most important to you – only the (lower) price, or all the other advantages that we mentioned above? We are sure that, all things considered, you have narrowed down your choice to a mineral wool system!
Finally – take a look around yourself and see – all the important public facilities (schools, hospitals, medical centers, kindergartens and nursing homes) as well as high-quality new buildings – opt for mineral wool as the insulation material. It’s no coincidence that most system producers put the mineral wool system in the “premium” solution category.
We are sure that you and your home deserve the premium Knauf Insulation façade!