Which is better: EPS or PIR insulation?
If you are looking for insulation material, you may be facing the dilemma: EPS or PIR? The choice between expanded polystyrene (EPS) and polyisocyanurate (PIR) has a major impact on insulation performance, cost, and application. In this article, we compare both materials so you can make the best choice for your project.
EPS vs. PIR: comparison table
Feature | EPS | PIR
Insulation performance (λ‑value) | 0.031 – 0.038 W/mK | 0.022 W/mK
Thickness for the same insulation value | Thicker | Thinner
Compressive strength | Moderate | High
Moisture resistance | Limited | Excellent
Fire resistance | Moderate | High
Applications | Walls, floors, roofs | Walls, floors, roofs
What are EPS and PIR?
EPS stands for expanded polystyrene, also known as styrofoam. Expanded polystyrene consists of small fused polystyrene beads filled with air.
PIR stands for polyisocyanurate, a rigid plastic foam used as insulation material. It is a development of PUR (polyurethane) and has improved properties such as higher fire safety, better moisture resistance, and a higher insulation value.
Insulation performance and thickness
EPS: has a lower insulation value (λ 0.031 – 0.038 W/mK), meaning a thicker insulation layer is required to achieve the same performance as PIR.
PIR: has a higher insulation value (λ 0.022 W/mK), meaning a thinner insulation layer is sufficient for the same thermal performance.
If you want to guarantee good thermal insulation, PIR is an excellent option. PIR insulation has a significantly lower lambda value than EPS insulation. This means you can achieve the same insulating performance with a thinner PIR board than with a thicker EPS board. This is especially advantageous in renovations or façade insulation, where space is often limited.
In addition, the thinner PIR insulation layer allows you to retain more usable space in your home or building. This can be particularly important when insulating interior walls, where every centimetre counts.
Moreover, the high insulation value of PIR minimises heat loss, which directly results in lower energy bills and a more sustainable home. This makes PIR an efficient and future‑proof insulation choice.
Moisture resistance and durability
Some insulation materials, such as EPS, have an open cell structure, making them more sensitive to moisture absorption. Prolonged exposure to moisture can reduce the insulation value of EPS, increasing the risk of mould growth or structural damage.
PIR insulation has a closed cell structure, meaning it absorbs less moisture than open‑cell insulation materials. Note, however, that PIR is not waterproof and should not be directly exposed to wet conditions. For applications such as flat roofs or cavity walls, proper sealing, vapour barriers, and water‑resistant layers are essential to maintain long‑term performance.
Compressive strength and applications
EPS: has moderate compressive strength, making it less suitable for applications with heavy loads.
PIR: has high compressive strength, allowing it to retain its shape and insulating properties even under heavy loads.
EPS insulation is typically used in applications where compressive strength is less critical, such as standard façade or roof insulation. The material is relatively light and easy to process, but less suitable where high loads occur.
PIR boards, on the other hand, are extremely pressure‑resistant and maintain their shape and insulation performance even under heavy loads. This high compressive strength makes them ideal for applications such as flat roofs, floors, and industrial constructions where mechanical strength is required.
Conclusion: PIR offers an excellent combination of thermal insulation and structural strength, contributing to a longer service life of the construction.
Fire safety
PIR insulation has higher fire resistance than EPS. This is because PIR ignites less easily and emits fewer harmful substances in the event of a fire. This contributes to a safer indoor environment and better protection of structures.
An important aspect of PIR is that it is self‑extinguishing. This means flame spread is slowed down, providing additional time to take action in the event of a fire.
Frequently asked questions
1. Which insulation is most suitable for renovations with limited space?
PIR insulation is the best choice, as it offers a high insulation value with minimal thickness.
2. Which insulation minimises thermal bridges the most?
PIR insulation has a closed cell structure, allowing better fit and reduced thermal bridging.
3. Which insulation shrinks the least over time?
PIR insulation boards retain their shape better than EPS, resulting in a longer lifespan.
4. Which insulation performs better with underfloor heating?
PIR insulation offers excellent thermal performance and heat resistance, making it the best choice for underfloor heating.
5. What can PIR be used for?
PIR is used for:
- Roof insulation – ideal for flat and pitched roofs due to high insulation value and moisture resistance
- Wall insulation – suitable for interior walls, façades, and cavity walls
- Floor insulation – often used under floors to minimise heat loss
- Concrete insulation – applicable in concrete structures to prevent thermal bridges
- Plasterboard systems – PIR can be combined with gypsum boards for efficient wall insulation with a clean finish
- Agriculture – suitable for stables and sheds to maintain a stable temperature
PIR: Idelco’s choice
Although EPS is a cost‑effective and widely used insulation solution, PIR offers a higher insulation value, better fire safety, and excellent moisture resistance. Especially for applications where a thin yet high‑performance insulation layer is required, PIR clearly comes out on top.
Would you like to learn more about the possibilities of PIR insulation?
