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Stone wool insulation vs alternatives

Paul Barrett, Head of Product Management
Paul Barrett, Head of Product Management
March 23, 2022

Insulation is an essential component of comfortable and efficient buildings. It not only reduces heat loss or heat gain by providing a barrier between inside and outside temperatures, but its use can also support some of today’s biggest sustainability and development challenges, from energy consumption to noise pollution and fire resilience.

There are many types of insulation, including stone wool - which ROCKWOOL manufactures - glass wool, sheep’s wool, wood wool and plastic foam insulations such as phenolic foam (PF), polyisocyanurate (PIR), extruded polystyrene (XPS), expanded polystyrene (EPS) and spray foam. In addition, you may come across cellulose (recycled newspaper), hemp, elastomeric rubber, polyethylene, cellular glass and ceramic fibre.

What are the different types of insulation?

1. Mineral wool insulation

Mineral wool is a term used to describe insulation made from minerals such as stone, silica or refractory ceramics (materials that are extremely resistant to heat). These raw materials are heated in a furnace to high temperature until molten, spun into fibres and formed into finished insulation products, such as rolls, slabs, loose wool (granulate) and pipe sections. 

Two common types of mineral wool are:

  • Stone wool: Stone wool is manufactured from abundant deposits of naturally occurring volcanic rock. ROCKWOOL® stone wool insulation is made from basalt rock, together with recycled and upcycled secondary materials.
  • Glass wool: Glass wool (also known as glass fibre) is manufactured from silica or glass cullet. 

Mineral wool typical applications 

Mineral wool is a versatile insulator and has many applications. It’s typically used to insulate residential lofts, but can also be used in ceilings, walls and under floors. In commercial and large-scale residential buildings it’s used in the External Thermal Insulation Composite System – or ETICS – a compact multilayer insulation solution designed to improve the energy efficiency of both new and existing buildings. It’s also typically found in Heating, Ventilation, and Air Conditioning - or HVAC - insulation in high-rise offices, apartments, airports, hospitals, warehouses and other industrial facilities. 

Mineral wool performance

Thermal performance

Mineral wool has tiny pockets of air trapped within its structure, which stop both hot and cold air passing through. By reducing airflow and heat flow, mineral wool works as a buffer against fluctuations in temperature. And because it’s vapour-permeable, it still allows moisture to pass out of the building. 

Fire properties

Mineral wool insulation is typically non-combustible (Euroclass A1 and A2-s1, d0). Non-combustible products do not burn and do not make any significant contribution to the fuel load in the event of a fire. 

Noise Reduction

Because mineral wool is extremely resistant to airflow, it’s also excellent at noise reduction and sound absorption. There’s a range of mineral wool products made specifically to better manage sound. 

2. Foam plastic insulation

Foam plastic (or plastic foam) is a term used to describe insulation materials derived from petrochemicals. These oil-based chemicals are used to create various insulation products, which are commonly formed into rigid slabs or pipe sections. 

Common types of plastic foam insulation include:

Polyurethane (PUR) insulation: PUR and PIR are both derived from polyurethane, a thermoset plastic, produced by reacting a polyol component and an isocyanate (MDI) component, formed into a closed-cell foam. A chemical blowing agent is used in the production of PUR and PIR, which is retained in the final products to improve thermal performance.
Polyisocyanurate (PIR) insulation: Although similar to PUR, PIR is produced using a different type of polyol and a higher proportion of isocyanate (MDI), resulting in a significantly different chemical structure. 
Phenolic foam (PF) insulation: PF is a closed-cell, rigid insulation produced using phenol and formaldehyde resin, which is expanded between two facing layers. The chemical mix bonds to both facings and is cured to form the final product.  A chemical blowing agent is used in the production of PF, which is retained in the final product to improve thermal performance. PF claims to have better thermal properties than other types of foam plastic insulation.
Expanded Polystyrene (EPS) insulation:  EPS is a semi-open-cell, rigid foam plastic material made from solid beads of polystyrene fused together. The beads are manufactured from styrene expanded using a pentane blowing agent that is not retained in the finished product. 

EPS insulation products are also available with particles of graphite integrated into the polystyrene beads to improve thermal performance.

Extruded polystyrene (XPS) insulation: Although similar to EPS, XPS is a closed-cell rigid foam plastic produced by melting polystyrene granules. The molten liquid is extruded through a die and expands during the cooling process. A chemical blowing agent is injected into the extruder and is retained in the final product to improve thermal properties.
Spray foam insulation: Spray foam is typically an open or closed-cell polyurethane liquid that is sprayed into position to form an insulating layer when set. 

Typical applications 

Rigid foam board insulation can be used almost anywhere insulation is needed in your home, for example in the roof, floor and cavity walls. It’s a popular choice in basements or near external foundations or walls, and can be used in external applications as well as internally. 


Thermal performance

The structure of rigid foam, with its tiny air bubbles, is what makes it a popular choice for thermal insulation. The air pockets work to slow the flow of air, warm or cold. 

Fire properties

All foam plastic insulation products are combustible, with Euroclass reaction to fire ratings of B, C, D, E or F. 

Noise reduction

Some foam plastics have noise-reduction properties, and some do not perform so well. There are also specific types of foam plastics made for sound insulation. It is best to look at the acoustic performance of the type of plastic foam insulation you are considering.


3. Sheep’s wool insulation

Sheep’s wool insulation is available with a 100% wool content or as a wool-polyester mix. To make sheep’s wool suitable as an insulation material, it must undergo a series of processes, which include scouring (washing) and carding (combing). The wool may be further treated with borax to enhance its reaction to fire and pest-repellent qualities. Sheep’s wool is typically available as batts or rolls.

Typical applications 

Sheep's wool insulation is typically used in roofs, walls or floors but can also be used around ducting, pipes and water tanks. It’s most commonly used as loft insulation. 



Thermal performance

Sheep’s wool is an effective insulation material, thanks to its air pockets and crimped structure. 

Fire properties

Sheep’s wool insulation typically obtains a Euroclass fire rating of around E, which means it is fire retardant. Some products are treated with borates to make them extra fire retardant. Sheep’s wool will likely char in the event of fire. 

Noise reduction

Thanks to its density and the millions of tiny air pockets present in its structure, sheep’s wool can act as an effective acoustic insulator, dampening noise and reverberations. 

4. Wood fibre insulation

Wood fibre insulation is made from waste softwood (sawdust, chips and off-cuts). The untreated wood is broken down into a fibrous pulp before being formed into insulation boards or quilts. Chemicals are added to some wood fibre insulation products to bind the fibres together, to improve their reaction to fire and pest-repellent properties.

Typical applications 

Wood fibre insulation products can be used in walls, ceilings and floors, as well as in the external envelope of a building. Some can be rendered or made watertight, and others can be used as load-bearing. 



Thermal performance

Wood fibre can perform as well as mineral wool in terms of its thermal properties. Wood is naturally a good insulator - its hollow cells are full of air and act as a barrier to heat transmission. 

Fire properties

Wood fibre insulation is rated as a class E combustible material. It will char and form a layer of ash on its surface, helping to slow the spread of fire. 

Noise reduction

The high density of many wood fibre insulation products makes them an effective sound absorber too. With the increased mass comes increased noise and reverberation absorption. 

Article History

Our experts continually review and update our articles when legislation changes or new information becomes available. 

Current version: 1

First published: 23/03/2022