PIR Insulation

Choosing the Right PIR Insulation Boards for Your Project

At County Building Supplies, we supply PIR insulation boards for professional builders, contractors, self-builders and DIY customers. Whether you're insulating walls, floors or roofs, choosing the correct insulation thickness and specification can help reduce heat loss, improve thermal efficiency and support the required building performance.

Our range includes Mannok Therm Foil Faced PIR Insulation Boards in 25mm, 50mm, 75mm and 100mm thicknesses, with standard board dimensions of 2400 x 1200mm.

What Are PIR Insulation Boards Used For?

PIR (polyisocyanurate) is a rigid foam insulation material commonly used in suitable wall, floor and roof constructions. It provides high thermal resistance relative to its thickness, making it useful where insulation space is limited.

Foil faced PIR boards have reflective facings that form part of the product's construction. Their suitability for a particular application depends on the board specification and the complete installation system.

Choosing PIR Insulation Thickness

The correct thickness depends on the building element, available space and required thermal performance.

• 25mm PIR boards: Suitable for certain applications where a thinner insulation layer is specified or space is restricted.
• 50mm PIR boards: Used in suitable wall, floor and roof insulation systems where the required performance can be achieved.
• 75mm PIR boards: Provide greater thermal resistance than thinner boards of the same material.
• 100mm PIR boards: Offer increased thermal resistance and may be specified for projects requiring higher insulation performance.

Thicker boards generally provide greater thermal resistance, but insulation thickness alone does not determine Building Regulations compliance. Always check the required U-value and the manufacturer's technical information.

PIR Insulation vs Mineral Wool

PIR and mineral wool are both widely used insulation materials, but they offer different characteristics.

PIR insulation is rigid and provides good thermal performance relative to its thickness. Mineral wool is commonly supplied in rolls or slabs and can offer thermal and acoustic benefits, alongside fire performance characteristics that vary by product.

The best choice depends on the construction type, thermal requirements, acoustic performance, fire safety specification and installation method.

Installing Foil Faced PIR Insulation Boards

Correct installation is important for achieving the intended thermal performance. PIR boards should be cut accurately and fitted according to the manufacturer's instructions, with appropriate treatment of joints, gaps and penetrations.

Depending on the construction, additional requirements may include vapour control, airtightness measures, suitable protective linings and ventilation.

Always follow the specified building system and relevant Building Regulations, particularly for fire safety and moisture management.

How Many PIR Insulation Boards Do You Need?

County's Mannok Therm PIR boards measure 2400 x 1200mm, providing a nominal coverage of 2.88m² per board.

To estimate quantities, multiply the length and width of the area to calculate its size in square metres, then divide by 2.88.

For example, an area measuring 6m x 4m covers 24m². Dividing by 2.88 gives approximately 8.34 boards, so you would need at least nine boards before allowing for cutting waste and installation details.

Need Advice?

Not sure which PIR insulation thickness or quantity you need? Visit your local County Building Supplies branch or contact our team for help with product information, quantities and availability.