When insulating your home or commercial building, you face an important choice: glass wool or PIR insulation? Both materials have unique properties, but if you are looking for the best thermal performance, moisture resistance, and long service life, PIR is the clear winner.
Feature | Glass wool | PIR boards
Insulation performance | Moderate | Very high
Flexibility | Soft and flexible | Rigid and stiff
Water resistance | Can absorb moisture | Does not absorb moisture
Thickness needed for good insulation | Thicker required | Thinner possible
Installation | Can itch, but easy to cut | Rigid, but easy to cut
The main differences between glass wool and PIR
Choosing between different insulation materials can sometimes be overwhelming. That’s why we clearly outline the key differences between glass wool and PIR insulation below.
1. Thermal insulation
The insulation performance of a material is expressed by the lambda value (λ). The lower this value, the better the material insulates.
PIR insulation has a much lower lambda value than glass wool, meaning you can achieve the same insulation performance with a thinner layer of PIR compared to a thicker layer of glass wool. This is especially beneficial in limited spaces, such as roofs or walls.
2. Thickness and space saving
Because PIR has a higher insulation value, less thickness is required. This means you retain more usable space in your roof construction or walls without compromising insulation performance. With glass wool insulation, you often need a thicker layer, which can be impractical in some situations.
Are you working in a space where room is limited and thin insulation layers are required? Then PIR is likely the better choice.
3. Moisture resistance
PIR boards have a closed‑cell structure and are usually finished with a vapour‑tight facing. As a result, they are less sensitive to moisture absorption than glass wool, provided they are correctly installed within a well‑sealed and dry construction.
Glass wool can absorb moisture, which may reduce its insulation performance and, over time, increase the risk of mould growth in cases of poor ventilation or incorrect installation.
Important: no (standard) insulation material (including PIR) should be used in areas with direct and continuous moisture exposure.
4. Fire safety
Glass wool is virtually non‑combustible and is known for its excellent fire‑resistant properties. PIR also offers a good reaction to fire, especially when finished with an aluminium facing, as is the case with the insulation boards in our range.
5. Acoustic insulation
Acoustic insulation strongly depends on the application and the complete system build‑up. PIR insulation is primarily designed for thermal performance, but when combined with other materials it can contribute to adequate sound reduction.
For applications where sound absorption is crucial (such as partition walls in homes or offices), systems often incorporate additional acoustic insulation materials.
6. Ease of installation
PIR insulation is supplied in rigid boards that are easy to cut and install. Glass wool is often supplied in rolls or batts that must be cut to size and release fibres that can cause irritation. This makes PIR a more hygienic and practical choice for installers.
When should you choose PIR?
PIR insulation is the best choice if:
- You want a high insulation value with minimal thickness.
- You are looking for a vapour‑tight and moisture‑resistant solution.
- You need insulation for a flat roof or timber structure.
- You are looking for a durable solution with a long service life.
In addition, the high insulation performance of PIR minimises heat loss, directly resulting in lower energy bills and a more sustainable building. This makes PIR an efficient and future‑proof insulation choice.
When should you choose glass wool?
Glass wool can be a good option if:
- Sound insulation is a priority.
- You are looking for a budget‑friendly solution for dry, non‑humid areas.
- You plan to apply thick insulation layers in larger spaces.
Conclusion: PIR offers the best insulation performance
While glass wool offers good acoustic properties and can be cost‑effective, PIR provides superior insulation performance, moisture resistance, and durability.
Frequently asked questions
Which is better, glass wool or PIR boards?
PIR boards offer better thermal insulation and require less space, while glass wool performs better in acoustic insulation. For most applications where thermal performance and moisture resistance are important, PIR is the best choice.
Can PIR and glass wool be combined?
Yes, PIR and glass wool can be combined to benefit from both thermal and acoustic advantages. This is sometimes done in multi‑layer insulation systems.
Which insulation is the most effective?
Effectiveness depends on the application. PIR offers the best thermal performance at minimal thickness, while glass wool is effective for sound insulation.
Why not use PIR under a flat roof?
PIR is actually an excellent choice for flat roof insulation due to its high compressive strength and moisture resistance. With correct installation and proper roofing, there is no issue. PIR is also an excellent choice for pitched roofs.
What are the disadvantages of glass wool?
Glass wool has a higher lambda value, meaning greater thickness is required. It can also absorb moisture, reducing its insulation performance, and the fibres may cause irritation.
Contact Idelco
Would you like expert advice on which insulation best suits your project? The specialists at Idelco Insulation are happy to help you make the right choice. Contact us today via our website or request a quote directly.
With our high‑quality PIR insulation, you benefit from maximum performance and an energy‑efficient solution for your home or commercial building.
