Frequently asked questions about PIR insulation
Find answers to common questions about PIR insulation boards, thermal performance, applications, moisture resistance and installation.
What is PIR insulation?
Polyisocyanurate, commonly known as PIR, is a rigid foam insulation material used to improve the thermal performance of floors, walls and roofs.
PIR insulation boards typically feature a lightweight, closed-cell core with facings designed for particular applications, such as aluminium foil or glass tissue.
What are the main benefits of PIR insulation boards?
PIR insulation offers low thermal conductivity, allowing high levels of thermal performance to be achieved with comparatively slim insulation thicknesses.
The boards are lightweight and suitable for many construction applications. When correctly specified and installed, PIR can help reduce heat loss, improve energy efficiency and support compliance with project U-value requirements.
Where can PIR insulation be used?
Depending on the product and facing, PIR insulation boards can be used in various applications including:
- Solid and suspended ground floors
- Masonry cavity walls
- Timber-frame walls
- Pitched roofs and loft conversions
- Warm flat roofs
- Panel systems and offsite construction
Always check the individual product documentation and certification to confirm that a board is suitable for the intended application.
What thermal performance does PIR insulation provide?
Most PIR insulation products have a relatively low declared thermal conductivity, commonly around 0.021 to 0.022 W/mK. This means PIR can often achieve the required thermal resistance using a thinner layer than many alternative insulation materials.
The thickness of PIR insulation required will depend on the target U-value and the overall construction build-up.
Is foil-faced PIR insulation a vapour barrier?
The aluminium foil facing used on many PIR boards provides high resistance to moisture vapour, but the boards do not automatically form a complete vapour control layer.
For the foil facing of the PIR insulation to contribute effectively to air and vapour control, the boards should be tightly butted to form a continuous layer, with all joints sealed using a suitable airtight tape.
The required vapour-control strategy should always be established for the complete construction.
Does PIR insulation need an air gap?
Whether an air gap is required will depend on the construction type, the position of the insulation and the product being used.
Please refer to the SOPREMA Handy Guide, product-specific installation guide or BBA certificate for details of the requirements for each application.
Can PIR insulation get wet?
PIR insulation has limited moisture absorption, and foil-faced boards offer good resistance to moisture vapour. However, PIR should not be installed where it will remain in prolonged contact with water.
Water exposure can affect thermal performance and may damage the bond between the insulation core and its facing. Boards should be stored, installed and protected in accordance with the manufacturer’s instructions.
How long does PIR insulation last?
When correctly specified, installed and protected within the building envelope, PIR insulation can continue performing for the design life of the building.
Please refer to the relevant product technical documentation and independent certification, such as the applicable BBA certificate, for further information.
How do I choose the correct PIR insulation board?
The correct PIR board depends on the intended application, required thermal performance, board thickness, compressive strength, facing and compatibility with the rest of the construction.
Boards that appear similar may have different intended uses or supporting certification. Review the product datasheet, Declaration of Performance and relevant third-party certification before specifying or installing a product.
Need help selecting PIR insulation?
Contact SOPREMA’s technical team for support with product selection, thermal performance, specification and project documentation.