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What’s the Best Insulation Board?

In the vast realm of building and construction, insulation plays a pivotal role in energy conservation, comfort, and sustainability. As buildings, whether residential or commercial, consume a significant portion of the world’s energy, the importance of insulation cannot be overstated. A well-insulated structure can reduce energy bills, enhance comfort by maintaining consistent indoor temperatures, and minimise the carbon footprint. With numerous insulation materials available in the market, selecting the ideal one can be a complex decision. Factors such as the desired thermal performance, installation location, cost, and environmental considerations can all influence the final choice. Among the myriad options, four insulation boards – mineral wool, EPS, phenolic foam, and wood fibre – often stand out due to their widespread use and distinctive characteristics. However, it is always crucial to ask, which is the best insulation board?

Mineral Wool

Mineral wool is produced by melting basaltic rock or industrial slag at high temperatures. This molten material is then spun into fine strands resembling wool, hence the name. Binders are often added to provide stability to the final product. While it may have a slightly lower R-value per inch than some synthetic insulations, mineral wool offers consistent thermal performance. This is because it doesn’t settle or deteriorate like some other insulations might over time.


  • Fire Resistance: Mineral wool is inherently non-combustible. It can withstand temperatures exceeding 1000°C, making it an excellent choice for fireproofing.
  • Sound Insulation: Its fibrous structure makes it an effective acoustic insulator, reducing the transmission of sound between rooms or spaces.
  • Moisture Resistance: Mineral wool is water-repellent. It does not readily absorb moisture and can maintain its insulating properties even when wet. Additionally, it is vapour permeable, allowing walls to breathe.
  • Durability: It has a long lifespan and retains its performance capabilities over time, resisting sagging or settling.
  • Eco-friendly: Made from natural and abundant materials, mineral wool can often be recycled at the end of its useful life.


  • Installation: It can be bulkier and heavier than some other insulation types, potentially making installation more challenging. Additionally, handling mineral wool may require protective clothing due to potential skin irritation from the fibres.
  • Environmental Concerns: Although made from natural materials, the energy-intensive production process and the potential inclusion of synthetic binders can impact its environmental profile.


EPS is a type of rigid foam insulation derived from petrochemicals. It starts as small beads containing a blowing agent. These beads are expanded using steam to many times their original size and then moulded into large blocks or shaped panels. The process is energy-efficient and produces consistent, high-quality insulation boards. EPS has a moderate R-value, which means it provides a fair amount of thermal resistance per inch.


  • Lightweight: EPS is light and easy to handle, which can simplify installation.
  • Moisture Resistance: While not entirely waterproof, EPS does not readily absorb water, making it suitable for various applications where moisture is a concern.
  • Cost-Effective: Among the foam insulation materials, EPS is typically one of the most affordable.
  • Versatility: Available in various densities, it can be tailored for different applications, including below-grade installations.
  • Compressive Strength: EPS can be manufactured to withstand significant loads, making it a suitable choice for insulating beneath concrete slabs.


  • UV Sensitivity: Direct exposure to sunlight can degrade EPS over time, causing it to become brittle.
  • Fire Resistance: While it can be treated with fire retardants, EPS is not inherently fire-resistant and can release toxic fumes when burned.
  • Environmental Concerns: Being a petroleum-based product, concerns arise about its long-term environmental impact, especially regarding its non-biodegradable nature.

Phenolic foam

Phenolic foam is made from phenol-formaldehyde resin. The foam results from the reaction between phenol and formaldehyde under controlled conditions. As the foam expands, an agent, typically air, is introduced, giving it its cellular structure. The foam is typically manufactured in board format or as foamed-in-place insulation. One of the stand-out attributes of phenolic foam is its high R-value per inch, which often surpasses other common insulation materials. This means that thinner boards can achieve the same insulating effect, making it advantageous in spaces where room is limited.


  • Low Thermal Conductivity: This allows for thinner boards, which can be especially beneficial in retrofit applications where space might be at a premium.
  • Fire Performance: Phenolic foam has superior fire resistance, producing minimal smoke and often achieving the highest fire ratings.
  • Low Smoke Emission: In the event of a fire, the foam emits a minimal amount of smoke, which can be crucial in ensuring safety.
  • Moisture Resistance: Phenolic foam has a closed-cell structure, giving it excellent resistance to moisture, and in turn, preventing a significant drop in its insulating performance when wet.


  • Cost: Phenolic foam tends to be more expensive than some other insulation options.
  • Potential for Shrinkage: Over time, there have been concerns about the potential for phenolic foam boards to shrink, especially when exposed to moisture. This can result in gaps and reduced insulating performance.
  • Durability: It can be more fragile compared to other foam insulations, making it susceptible to damage during installation or if subjected to mechanical stress.
  • Environmental Concerns: Phenolic foam’s manufacturing process uses formaldehyde, which raises some health and environmental concerns. However, once cured, the foam is stable and shouldn’t release significant amounts of formaldehyde.

Wood Fibre

Wood fibre insulation is produced from softwood, often sourced from sustainable forests. The wood is broken down into fibres, which are then bonded together using various methods. Some use natural binders like lignin (an inherent component of wood), while others might use synthetic or natural additives. The manufacturing process typically involves refining the wood to extract fibres, followed by forming, pressing, and drying the insulation boards.


  • Sustainability: Being renewable and biodegradable, wood fibre is a green choice, often appealing to those aiming for sustainable or passive house constructions.
  • Moisture Regulation: Its hygroscopic nature means that it can absorb and release moisture, helping to regulate indoor humidity and reducing the risk of condensation and mould growth.
  • Sound Insulation: The fibrous structure effectively dampens sound, offering good acoustic insulation properties.
  • Non-Toxic: Wood fibre is generally free from harmful chemicals, contributing to healthier indoor air quality.
  • Fire Resistance: Though not as fire-resistant as mineral wool, wood fibre boards are often treated with fire retardants to improve their fire performance.


  • Pest Attraction: If not treated, wood fibre can be susceptible to pests such as termites or rodents.
  • Potential for Mould Growth: While its ability to manage moisture is generally a benefit if exposed to sustained, high levels of moisture without proper ventilation, there’s a potential risk of mould.
  • Weight: Compared to synthetic foams, wood fibre is heavier, which might have implications for transportation, handling, and installation.
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