When we talk to builders and contractors about insulation choices, one question comes up repeatedly: which material delivers the best thermal performance per millimetre of thickness? The answer consistently points to PIR insulation boards, a solution that's become our go-to recommendation for projects where space is at a premium but performance cannot be compromised.
PIR (Polyisocyanurate) insulation boards represent a significant advancement in thermal efficiency. We've seen countless projects where traditional insulation materials simply couldn't achieve the required U-values within the available cavity depth. That's where PIR boards prove their worth, offering exceptional thermal resistance in remarkably thin profiles.
Understanding PIR Insulation Technology
PIR insulation boards are rigid foam panels created through a chemical reaction between polyol and isocyanate. The resulting closed-cell structure traps gas within tiny bubbles, creating an incredibly effective barrier against heat transfer. What sets PIR apart from other rigid foam insulations is its enhanced fire performance and superior thermal conductivity values.
We typically supply PIR boards with thermal conductivity values as low as 0.020 W/mK, significantly better than traditional materials like mineral wool (around 0.035 W/mK) or expanded polystyrene (approximately 0.030-0.040 W/mK). This means you can achieve the same insulation performance with substantially less thickness, freeing up valuable space in your build.
The boards we stock come with various facing materials depending on the application. Aluminium foil facings provide excellent vapour resistance and reflect radiant heat, whilst paper facings offer better compatibility with certain adhesives and renders. For specific applications, we also supply unfaced boards that can be customised on-site.
Where PIR Boards Excel in Construction
Cavity Wall Applications
In cavity wall construction, PIR boards work exceptionally well as partial fill insulation. We often recommend this approach for new builds where architects need to maximise internal space whilst meeting stringent thermal regulations. The boards can be mechanically fixed to the inner leaf, creating a continuous thermal barrier that virtually eliminates thermal bridging through wall ties.
Flat Roof Systems
For flat roof applications, PIR boards provide unmatched performance. We supply boards specifically designed for warm roof construction, where the insulation sits above the structural deck. The boards' excellent compressive strength means they can support roof coverings and foot traffic without degrading performance over time.
Floor Insulation
Ground floor applications benefit enormously from PIR boards, particularly in beam and block construction. The boards fit neatly between concrete beams, creating a continuous thermal barrier that eliminates cold bridging. We've measured significant improvements in floor surface temperatures when PIR boards replace traditional solutions.
Steel Frame Construction
Steel frame buildings present unique challenges due to thermal bridging through the structural elements. PIR boards can be installed as external sheathing, breaking the thermal bridge and dramatically improving overall building performance. We work with many steel frame specialists who rely on this approach to meet Building Regulations.
Installation Best Practices We Recommend
Cutting and Fitting
PIR boards cut cleanly with a sharp knife or fine-toothed saw. We always advise measuring twice and cutting once, as the rigid nature means mistakes are costly. For irregular shapes, create a template first using cardboard or thin plywood.
Fixing Methods
The fixing method depends entirely on the application. For masonry walls, we recommend mechanical fixings with low thermal conductivity washers. Adhesive fixing works well for internal applications where wind loads aren't a concern. Always ensure fixings don't compromise the board's integrity or create unnecessary thermal bridges.
Joint Treatment
Joints between boards require careful attention. We supply compatible tapes and sealants that maintain the thermal barrier across board edges. Staggered joints work better than continuous lines, distributing any thermal bridging across a wider area.
Vapour Control
PIR boards with foil facings provide good vapour resistance, but joints need sealing to maintain continuity. We stock specialist tapes that bond reliably to foil surfaces, creating an effective vapour control layer when properly applied.
Fire Performance
PIR insulation achieves excellent fire ratings, typically Class B or C under European classification systems. The material is thermoset, meaning it won't melt and drip like thermoplastic insulations. We've seen this characteristic prove crucial in commercial projects where fire performance is rigorously specified.
Moisture Resistance
The closed-cell structure means PIR boards absorb minimal moisture, maintaining their thermal performance even in demanding conditions. We've tested boards that have been exposed to high humidity environments for years, finding negligible performance degradation.
Dimensional Stability
PIR boards maintain their dimensions across wide temperature ranges. We stock boards that perform reliably from -50°C to +120°C, making them suitable for everything from cold storage facilities to industrial applications with elevated temperatures.
Durability
Well-installed PIR insulation lasts for decades without performance loss. We guarantee our boards for 25 years, reflecting our confidence in their long-term stability and effectiveness.
Specification Considerations
When specifying PIR boards, several factors need consideration. Thermal conductivity varies between manufacturers and products, so always check specific values rather than assuming. Thickness requirements depend on target U-values and other building elements' thermal performance.
Compatibility with other building materials matters significantly. PIR boards work well with most common construction materials, but always check manufacturer guidance for specific applications. Some renders and coatings require particular surface preparations.
Building regulations require specific performance levels, but these are minimum standards. We often recommend exceeding minimum requirements, as the additional cost is modest compared to the long-term benefits of superior thermal performance.
Making PIR Work for Your Project
We supply PIR boards across numerous applications because they consistently deliver results. The material's versatility means one product type can often serve multiple functions within a single project, simplifying procurement and installation logistics.
Cost considerations extend beyond initial material prices. PIR boards' superior performance means less thickness required, potentially reducing overall construction costs through thinner wall constructions or increased internal space. Installation speed is typically faster than alternative materials, reducing labour costs.
Ready to specify PIR insulation for your next project? We maintain comprehensive stocks of PIR boards in various thicknesses and facing options, ready for immediate delivery across the UK. Our technical team can provide specific guidance on product selection, installation methods, and performance calculations to ensure your project achieves its thermal performance targets efficiently and cost-effectively. Contact our specialists to discuss your requirements and access our full range of high-performance insulation solutions.