PUR vs PIR: Which Is The Best Choice?

Rigid PUR (Polyurethane) and PIR (Polyisocyanurate) insulated panels are extremely strong, long-lasting, and thermally resistant insulation that suit the needs of a wide range of construction and building applications, if you are about to buy PUR or PIR insulated sandwich panels for your modern building, this comprehensive guide determine the differences between PUR and PIR based on various factors such as insulation performance, thermal resistance, composition, benefits, and cost, which help architects, builders, and contractors choose the best material that meet their requirements, while gaining a proper understanding about different types of PUR and PIR insulated panels. 




What Is The Difference Between PUR and PIR?

To make the best choice between PUR (Polyurethane) and PIR (Polyisocyanurate) insulated panels, it is very important to determine the differences between their composition, insulation value, and compressive strength:


PIR and PUR insulated panels


Polyurethane (PUR/PU) and Polyisocyanurate (PIR) are derived from polyurethane, and both are made from a reaction of polyol liquid and polymeric isocyanate or a mixture of MDI (Methylene Diphenyl Di-isocyanate), however, to create PIR, blowing agent is added to a mix of polyols, isocyanates, and other additives. The manufacturing process of Polyurethane (PUR) and Polyisocyanurate (PIR) results in rigid closed-cell structure foam which ensures thermal insulation, dimensional stability, fire resistance, and enhanced moisture resistance, thanks to their thermally resistant properties, chemical, and physical composition which makes them the best choice for a wide range of building applications including interior and exterior walls, partitions, roofs, floors, facades, and building envelopes. Below you will find more information about the composition of Polyurethane (PUR) and Polyisocyanurate (PIR):


Polyurethane (PUR)

Polyurethane (PUR, PU, or urethane) is a highly cross-linked polymer that forms a rigid molecular structure and refers to a class of polymers that contains two types of monomers, it is produced by reacting a polymeric isocyanate, mostly aromatic diisocyanates, toluene diisocyanate (TDI) and Methylene diphenyl diisocyanate (MDI)  with polyols, catalyst/tertiary amines, and organic chemicals such as DABCO (known as triethylenediamine or TEDA), DMDEE, or metallic soaps like dibutyltin dilaurate that are bonded by urethane linkages. The reaction between these properties results in a heat-curing thermosetting material that does not melt on heating.



Polyisocyanurate (PIR)

 Polyisocyanurate (PIR, Polyiso, or ISO), is a Thermosetting Polymer (or a Thermoset plastic) which contains similar starting material used in polyurethane (PUR) including isocyanate that reacts with polyether after catalyst action, except that the proportion of Methylene Diphenyl Diisocyanate (MDI)  is higher than PUR, while polyester-derived polyol is used in the reaction instead of polyether polyol, and the catalysts and additives are also different from those used in the production of PUR, this result in a chemical structure with complex polymeric structure. However, when compared to (PUR), the PIR (Polyisocyanurate) foam contains a high degree of aromaticity which forms the polyisocyanurate structure, provides higher thermal stability, and improves fire resistance; this makes them ideal for residential building insulation, industrial facilities, cold storage, chemical plants and oil refineries construction.

PIR panel


Insulation Value

 Generally, the R-value measures the thermal resistance of insulation material and its ability to resist the heat flow, however, higher R-values offer better insulation performance and greater insulating properties which increase thermal resistance, improve energy efficiency, and hence reduce heating and cooling costs. Polyurethane (PUR) R-value is typically R 5-7.1 per inch, while Polyisocyanurate (PIR) R-value ranges between R 7 and 7.2 per inch. However, when compared to PUR, PIR has a higher insulation R-value and low thermal conductivity, therefore, PIR insulation is one of the most thermally efficient insulation materials which provides superior insulation performance while it reduces effectively heat loss more than other insulations with similar thickness, this insulation qualities makes the PIR sandwich panels the first choice for builders and homeowners.


Compressive strength

PUR and PIR structural panels have become the best choice for lightweight construction and building applications that require compressive strength of 150-400 kPa, polyurethane foam (PUR) is essentially made of closed-cell structure and hard polyurethane foam, thanks to the rigid insulation, which allows PUR to resist compressive strength and ensure a high mechanical performances for various building envelopes including industrial zones, warehouses, showrooms, garages, workshops, cold rooms and agricultural halls, besides this, PUR insulation can withstand exceptional mechanical loads while it can ensure excellent dimensional stability. Also, PIR sandwich panels are made from a tough, durable, and low-weight PIR insulation core which is nestled between two sheets of galvanized steel sheet, pre-coated galvanized steel (PPGI/PPGL), aluminum alloy skin layers, stainless steel facings, FRP/fiberglass sheets, plywood boards, etc.



What Is The Thermal Conductivity of PUR and PIR?

PUR and PIR sandwich panels offer an excellent thermal conductivity/lambda (λ) value which ranges for PUR from 0.025 to 0.035 W/mK and PIR between 0.022 and 0.027 W/mK, also, RPURFs  (Rigid Polyurethane Foams) provides an R-value of 7.0 8.0 per inch of thickness, while PIR (Polyisocyanurate) foams an R-Value of 6.0 per inch of thickness, due to the low conductivity blowing gases trapped in their closed porous structures and their physical and mechanical properties, PUR/PIR insulated sandwich panels deliver proven thermal performance that meets the most demanding insulation requirements for contemporary architecture and modern construction. Also, when compared with other conventional insulating materials, PUR/PIR insulation can dramatically reduce the load on heating and cooling systems which helps maintain consistent temperatures in winter and summer, improve the energy efficiency of buildings while minimizing the emissions of CO2 and protecting the environment.


PUR vs PIR – Reaction and Resistance To Fire

Polyisocyanurate (PIR) offers better fire performance when compared to Polyurethane (PUR), thanks to the non-combustible material and fire retardant properties which offer high resistance to flames while it generates less smoke when exposed to fire. However, PIR is preferred for building insulation applications where fire safety is an essential requirement, unlike PUR foam which has limited fire resistibility and emits less smoke during real fire events, PIR foam does not melt or drip when exposed to fire, this slows the spread of flames and reduces the smoke emitted from the fire when compared to PUR panels. PIR sandwich panels are FM Approved to FM 4470 for fire performance (rated as Class 1 roof) and pass FM 4450 fire tests for Class 1 Insulated Steel Deck, and ANSI UL 1256  roof deck construction, whereas, PU sandwich panel is rated according to the fire classification of building materials B1, B2 and B3:

Fire Resistance


Class B: Combustible materials

Class B1: Flame Retardant

Class B2: Normal Flammability

Class B3: Easily Flammable


PUR vs PIR – Water Resistance

Rigid polyurethane foam (PUR) is a waterproof building material that does not allow water to flow through the building envelope, nor absorb water, vapour, or humidity, given its closed cell structure, low vapor permeability, and low capillary absorption rate, polyurethane offers high resistance to external factors such as adverse weather conditions such as heavy rain, wind, snow, frost, hail, hurricanes, extreme temperature, and climatic changes. Likewise, PUR sandwich panels are watertight structural components; each unit is bonded to strong metal sheets and coated with anti-corrosive finish paint. Similarly, Polyisocyanurate (PIR) is inherently water resistant; thanks to the hydrophobic nature of the polyiso core and aluminium-faced panel which provide superior water resistance compared to other rigid foam insulation. PUR and PIR sandwich panels are demonstrated to be water-resistant, this makes PUR and PIR ideal for various applications including masonry cavity walls, exterior walls, building envelopes, foundations, floors, and roofs. 


PUR vs PIR – Moisture Resistance

Generally, Polyisocyanurate (PIR) foam is highly resistant to moisture and water penetration than Polyurethane (PUR), also, PIR sandwich panels are made of high-strength steel sheets, which are sealed to prevent water from infiltrating the PIR foam core and moisture intrusion, this makes PIR more resilient and preferred for wet and humid environments, as well as areas where buildings are exposed to moisture and humidity, also, given their closed-cell foam, inert and non-biological resistant properties, PUR and PIR insulation can withstand microorganisms and biological aggression, water leaks and vapor, and hence can provide high thermal performance and ensure structural integrity to building envelopes such as interior and exterior walls, walls partitions, roofs, facades, and structures.


PUR vs PIR – Acoustic Insulation 

Closed-cell rigid polyurethane (PUR) and polyisocyanurate (PIR) are designed and manufactured to form a strong barrier within a building’s interior and exterior environment against the impacts of acoustic atmospheres, thanks to the sound-absorbing insulation material which ensures excellent sound-absorption of sound waves, airborne sounds and noise pollution in modern residential, commercial, and industrial buildings, this makes PUR and PIR sandwich panels ideal for soundproofing walls, roofs, ceilings, floors, building disclosures, building envelopes, doors and windows. Also, despite the lightweight PUR and PIR insulation cores, acoustic sandwich panels and sound absorbing panels can effectively reduce the noise level of machinery in production plants, while ensuring maximum comfort, and wellness for building applications that require a high level of acoustics comfort such as marine ship, cruise ship, naval vessel, yacht, fishing boat, aerospace, and automotive applications. 


PUR vs PIR – Durability

Polyisocyanurate sandwich panels (PIR) can last for 20 years under normal wear and tear, due to the inert insulating material and closed-cell PIR properties, PIR insulated panels can resist rot, and decay and deliver high-performance insulation values throughout the lifetime of the building. Whereas, polyurethane rigid foam (PUR) has an average lifetime of 50 years or more, given its cellular structure closed-cell structure and rigid insulation foam, PUR composite panels can maintain their thermal resistance for a long period while they withstand aggressive climates and impacts of environmental factors such as moisture ingress, fungi, bacteria, molds, humidity, or air movement or other microorganisms.


PUR vs PIR – Features

PUR and PIR sandwich panels are highly versatile in applications, and come in endless appearances, finishes and colors that suit the functional and aesthetics requirements of homeowners and construction professionals, some of the common features of PUR/PIR insulated sandwich panels include:

Orientation: horizontal and vertical orientation

Profile Options: embossed, non-embossed, micro-rib, mini micro-rib, mini-wave, Shadowline, etc


PUR vs PIR – Cost

Polyurethane (PUR) is generally less expensive than Polyisocyanurate (PIR), this is due to the high cost of the PIR production process which is more complex and involves additional raw material, processes, and chemicals, this impacts the price of the final PUR and PIR sandwich panel. However, despite the high price of Polyisocyanurate (PIR) insulated panels, they offer a great thermal value which reduces energy consumption and decreases the cost of cooling and heating for the long term.   


PUR vs PIR – Sustainability

PUR/PIR sandwich panels have become the top choice for low-energy buildings and sustainable architecture which require superior insulation performance for low-rise structures and high-rise buildings, and at the same time it ensure energy efficiency, cut CO2 emissions, and significantly reduce greenhouse gas emissions. Besides, Polyurethane (PUR) and Polyisocyanurate (PIR) sandwich panels are recyclable and reusable, the recycling involves melting the metal skin-layers while PUR/PIR are recycled using several methods such as mechanical recycling, and chemical recycling by glycolysis or incineration with energy recovery, this reduces waste and ends up landfills and makes the environment more sustainable.



Which Type of Insulation To Choose For Your Building Applications: PUR or PIR? 

Nowadays, PUR (Polyurethane) and PIR (Polyisocyanurate) insulation are both preferred for different types of building and construction applications including timber/metal framed buildings or masonry applications, whether you are an architect, contractor, or real estate developers, you can choose from a large selection of PUR/PIR sandwich panels that includes the following:

 PUR/PIR wall insulation, cavity insulation, external and internal cavity walls, timber or steel frame walls, foil faced, plasterboard or cement particle board.

PUR/PIR insulated metal panels (IMPs) or PUR/PIR insulation board with core sandwiched between two metal facings (Galvanized steel sheets, Aluminum or Stainless steel facings).

PUR / PIR insulated metal panels


PUR/PIR insulation bonded to plasterboard or cement particle board for solid masonry walls or timber frame lining applications. 

PUR/PIR Roof insulation, pitched/flat roofs, warm roofs, insulated roof decking (Plywood or chipboard roof boards).

PUR/PIR Architectural facades insulation and floor insulation.

PUR/PIR Cold storage insulation, cold room panels, refrigeration panels, freezer panels, and duct panels.

PUR/ PIR insulation bonded to plywood, OSB board, or coated with mineral glass

PUR/PIR sandwich panels are available in various sizes, thicknesses, strengths, and facings material.

PUR/PIR insulation comes in standard and custom-made boards and can also be engineered and customized for specific applications.



In conclusion, making the best choice starts with understanding the difference between PUR and PIR, this depends mainly on a wide range of factors including thermal conductivity, strength-to-weight ratio, soundproofing, applications, materials, features, and cost, this allows architects, builders, and contractors to construct modern steel buildings and structures that help to build owners achieve high insulation performance, energy efficiency, and comfort, while it meets the highest industry standards and responds to the exact requirements of local building regulations in your region.

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