When working on insulating the facade of a building, investors often wonder which material is better: mineral wool or styrofoam? Both are characterized by good thermal insulation properties, but they have many differences. From the following article you will learn when it is better to use mineral wool and when styrofoam.
Wool or styrofoam
It is important to remember that both mineral wool and polystyrene foam can be used in new construction, as well as during the renovation of existing buildings. Although at first glance they may appear similar, there are important differences between them that can affect the choice of the appropriate material and the entire insulation system.
The two materials may seem very similar. However, as is often the case, differences and details matter. A mistake in choosing the right material can lead to:
a significant increase in insulation costs,
failure to achieve expected results, such as adequate sound insulation,
damage to the insulation material used,
problems with moisture and the appearance of fungi in the structure
What are the characteristics of mineral wool?
Mineral wool guarantees proper thermal conditions, protects against noise and increases fire protection. It is ideal for insulating roofs, walls, floors, ceilings, attic slants and various installations. Using mineral wool, we can count on constant thermal parameters throughout the use of the building, which is due to its thermal conductivity coefficient lambda (λ) and thermal resistance.
Photo: iStock © author's archive
The material comes from natural sources and is produced from rock raw materials. Its fibers begin to melt only after 2 hours of exposure to temperatures exceeding 1000°C. However, binders and hydrophobic agents added to wool are less resistant to high temperatures. Typically, wool is given the A1 fire resistance class. It has a high water vapor permeability coefficient, which allows vapor to flow freely through the building structure.
Added hydrophobizers make mineral wool have limited ability to absorb capillary water and water vapor from the environment. In addition, it is characterized by high resistance to most chemical agents.
Panels made of mineral wool are characterized by heavier weight, lower stiffness and limited tensile strength of TR ≥ 80 for fins and TR ≥ 7.5 for panels.
PN-EN 13162:2009 defines standards for mineral wool panels used in thermal insulation technology. According to it, there are two main types of panels. The first is panels with a disordered arrangement of fibers, which have a tensile strength exceeding 7.5 kPa. Their typical dimensions oscillate around 50-60 cm x 100-120 cm.
The second type are boards with a regular, laminar arrangement of fibers, which are arranged parallel and perpendicular to the wall surface. They are characterized by a much higher tensile strength, exceeding 80 kPa. Due to their elongated shape and the most common dimensions of 20x120 cm, they are sometimes called lamellas.
What distinguishes polystyrene foam?
Styrofoam is a material that does not absorb water, so even short-term exposure to moisture does not adversely affect its insulating properties. This means that if condensation occurs inside the styrofoam, it will not significantly affect its performance. Although it is produced from petroleum derivatives, it does not contain substances that are harmful to health. Styrofoam also has a low weight, is mechanically durable and has a very low vapor permeability.
However, this material does not perform well in case of high heat or direct fire. It begins to deform already at a temperature of about +80°C. It is also important to note that it is not resistant to most organic solvents.
In thermal insulation systems, it is recommended to use polystyrene foam compliant with PN-EN 13163:2009, which has a tensile strength of at least 80 kPa perpendicular to the surface. In addition, this material should meet the requirements of class E in accordance with PN-EN 13501-1 and have a manufacturer's guarantee of dimensional stability after a suitable storage period.
Styrofoam boards that are cut from properly seasoned blocks (usually stored for 6-8 weeks) retain their dimensional stability. Slabs with maximum dimensions of 120x60 cm can be used in insulation systems.
Currently available variants of polystyrene foam are traditional white boards, white with dark spots, called spotted, and graphite versions. Different types can have different values of thermal conductivity λ.
When to use wool and when to use styrofoam?
Styrofoam is ideal for applications in moisture-prone areas, such as basements, floors, insulation of plinths or green roofs. With acoustic styrofoam, we can effectively dampen the sound created by impacts that spread between floors of a building.
Photo: iStock © Author's archive
Mineral wool is often used in areas with high humidity, provided that it is properly protected by waterproofing and vapor barrier on the interior. Taking such precautions is aimed at eliminating condensation, which can weaken the material's thermal insulation properties.
Styrofoam is a common choice due to its more favorable price compared to facade wool. Additional advantages of styrofoam are easy transportation and storage, and simple processing. In practice, if you opt for an insulation system with wool, you must be prepared for costs higher by about 20-30% compared to polystyrene.
When polystyrene boards were widely used in insulation technology (the use of mineral wool has a shorter tradition), no cases were observed where fire was transmitted through these systems. In addition, by choosing styrofoam, we do not have to worry that the walls of the building will be overstressed.
In conclusion, if we have a limited budget, styrofoam will be a more favorable choice. Wool, on the other hand, is worth considering in areas with high humidity or where additional protection is needed. For insulating foundations, basements, balconies or terraces, styrofoam will suffice.
Are you building or renovating a house? Check out our tips on insulation
Compiled by:MAŁGORZATA BUCHKOVSKA