Alternatives to PIR Insulation

PIR (polyisocyanurate) insulation is widely used because of its high thermal resistance per unit thickness. However, it is manufactured from fossil-derived chemistry, its production is energy-intensive, and end-of-life options are limited - it cannot be easily recycled or composted.

As the construction industry moves toward net-zero carbon targets, specifiers are increasingly looking at the full lifecycle impact of insulation choices, not just installed performance. This does not mean PIR is always the wrong choice - but it is worth understanding the alternatives.

Wood fibre boards and batts offer a bio-based alternative with good thermal performance and excellent breathability. The material stores carbon, supports vapour-permeable wall assemblies, and can be recycled or composted at end of life.

Thermal conductivity typically ranges from 0.038 to 0.043 W/mK, meaning thicker build-ups are needed compared to PIR (0.022 W/mK). However, wood fibre also provides useful thermal mass, helping to regulate internal temperatures in summer.

Cork insulation is harvested from the bark of cork oak trees - a process that does not harm the tree, which regenerates its bark every 9 years. Expanded cork boards are manufactured using the natural resins in the cork itself, with no synthetic binders needed.

Cork provides good thermal performance (around 0.040 W/mK), is naturally water-resistant, rot-proof, and has excellent acoustic properties. It is also one of the most genuinely circular insulation materials available - it can be reused or composted indefinitely.

Cellulose insulation is made from recycled newspaper treated with mineral salts for fire and pest resistance. It is typically blown into cavities or applied as a wet spray, making it excellent for filling irregular spaces in retrofit projects.

With a thermal conductivity of around 0.035–0.040 W/mK, cellulose performs well and has very low embodied carbon - much of its energy content was already spent in the original paper manufacturing. It also has a high recycled content, typically 80% or more.

Sheep wool is a natural fibre insulation with excellent moisture-buffering properties. It can absorb and release moisture without losing thermal performance - a significant advantage in older buildings where moisture management is critical.

Products like Thermafleece and Black Mountain use UK-sourced wool, supporting local agricultural supply chains. Thermal conductivity is typically around 0.035–0.040 W/mK.

There is no single best alternative - the right choice depends on your project constraints. Consider these factors when comparing options.