Polyisocyanurate
Polyisocyanurate (PIR or Polyiso) foam insulation is known for its high thermal resistance as well as fire resistance compared to other foam insulants. Its behaviour under fire conditions has though recently come under great scrutiny since the role of Celotex RS5000 PIR insulation in the Grenfell tragedy in London UK in 2017. It has commonly for many years been used in commercial roofing systems, wall insulation, cladding systems in many modern buildings and as a component in structural insulated panels (SIPs). It ia also commonly used for industrial and commercial pipe insulation, laminated to aluminum foil and used for fabrication of pre-insulated duct that is used for heating, ventilation and air conditioning systems.
The core materials of PIR are similar to those used in polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. The resulting chemical structure is significantly different, forming isocyanurate groups which the polyols link together, giving it a complex polymeric structure.
This structure means that PIR was generally accepted as performing significantly better than PUR against fire, previously thought to have excellent fire behaviour from being tested to high standards, the Grenfell tragedy bought much of this into question. Shortly after the fire on June 23 2017, the Police confirmed that small-scale fire tests had been carried out and Detective Superintendent Fiona McCormack commented "The insulation was more flammable than the cladding. Testss how the insulation samples combusted soon after the test started."
[edit] Related articles on Designing Buildings
- Acrylic.
- An in-depth look at Environmental Product Declarations EPDs.
- Celotex RS5000 PIR insulation.
- Composites.
- ETFE.
- Fire behaviour of expanded polystyrene.
- Forever Chemicals.
- Glass reinforced plastic.
- Grenfell Tower fire.
- Insulation.
- LPCB certification and Kingspan.
- Loss Prevention Standard.
- Packaging.
- Plastic.
- Polyethylene.
- Polyurethane (PUR).
- Polystyrene.
- Persistent organic pollutants (POP)
- Phenolic foam insulation.
- Polyurethane spray foam in structurally insulated panels and composite structures..
- Sandwich panel.
- Specifying insulation for inverted roofs.
- Thermal insulation for buildings.
- Transparent insulation materials.
- Types of insulation.
- Types of plastic in construction.
- What do design professionals need to know about U-value calculation conventions?
Featured articles and news
Design and construction industry podcasts
Professional development, practice, the pandemic, platforms and podcasts. Have we missed anything?
C20 Society; Buildings at Risk List 2025
10 more buildings published with updates on the past decade of buildings featured.
Boiler Upgrade Scheme and certifications consultation
Summary of government consultation, closing 11 June 2025.
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
From project managers to rising stars, sustainability pioneers and more.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.