Find the answers to our most frequently asked questions

Information & Enquiries
0161 672 7387

What is PUR or PIR insulation?

Rigid polyurethane (PUR) and polyisocyanurate (PIR) insulation products are highly effective, lightweight and easy to handle. Their excellent thermal conductivity and high strength to weight ratio, combined with great manufacturing versatility provides a wide range of products.  As a result, PIR and PUR insulation products are the natural choice for most construction thermal insulation applications.



Rigid PUR insulation products are made by reacting a liquid polyol with a liquid polymeric isocyanate known as MDI in the presence of a blowing agent and other additives.  The mixed components then react exothermally to form a rigid thermosetting polymer.  Since the blowing agent evaporates during this reaction a rigid closed cell low density insulation product is created. Excellent insulation performance is achieved because the gas trapped within the closed cell structure has a very low thermal conductivity and there is minimal heat conduction through the solid cell walls due to the low density.  Approximately 97% of the volume of the foam is trapped gas.

Rigid PIR differs from PUR in that it is produced with a slight variation in the chemical components.  The resultant PIR insulation products exhibit increased fire performance and reduced combustibility and higher working temperature limits compared to PUR and when incorporated into building products, can meet some of the most demanding industry requirements.


Where can I buy PIR insulation boards?

PIR/PUR boards are available from most large builders merchants. Many will be stocked under their trade names from some of our member companies.

How can homes with solid walls be insulated?

There are several ways in which homes can be refurbished to the highest insulation standards. PIR and PUR products are able to achieve best practice in almost all insulation applications including externally on solid walls and internally.

How effective is PUR in terms of flood resilience?

In a report published jointly by DEFRA, DCLG and the Environment Agency “Improving the flood performance of new buildings” rigid PUR foam is shown to be the best performing when installed into cavity walls. The report states “Cavity insulation should preferably incorporate rigid closed cell materials as these retain integrity and have low moisture take-up. Other common types, such as mineral fibre batts, are not generally recommended as they can remain wet several months after exposure to flood water which slows down the wall drying process. Blown-in insulation can slump due to excessive moisture uptake, and some types can retain high levels of moisture for long periods of time (under natural drying conditions).” The results of the report are based on laboratory findings and classify wall components as good, medium or poor with regard to:

  • water penetration – the leakage (rate and volume) through the entire wall thickness (note that this is different from “water absorption”)
  • drying ability – the capability to regain its original surface moisture condition (assessed by the average drying rate and the time taken to reach the original value)
  • retention of pre-flood dimensions, integrity – the lack of deformation or change in form or appearance of the wall panel.

PUR foam gained a Good rating for retention of pre-flood dimensions, integrity and a Medium rating for water penetration and drying ability with all other insulants having a Poor rating.

Closed cell insulation is also recommended when installing floor insulation in order to minimise the impact of flood water.

To see a complete copy of the report click here.

Is PUR insulation suitable for cavity wall insulation?

Yes, PUR can be used as insulation for either partial-fill cavities or fully-filling cavities. For many years PUR injected into cavity walls has been used not only as a highly efficient insulant but also as a means of stabilising masonry cavity walls where wall ties have corroded or failed. It has also been used by many local authorities and housing associations for stabilising and insulating high rise buildings.