The Ultimate Guide to PIR Insulation


PIR Insulation

In an age where energy efficiency and environmental consciousness are crucial, PIR (Polyisocyanurate) insulation stands out as the ultimate solution to meet the challenges of modern construction and design.  

In this guide, we’ll delve into the very depths of PIR insulation, and explore its properties, benefits, applications, installation methods and more. Whether you're a seasoned architect, a dedicated DIY enthusiast, or simply a curious individual eager to enhance your knowledge, this guide will equip you with everything you need to know about PIR insulation.  

An Introduction to PIR Insulation 

What is PIR insulation?  

PIR insulation is a highly efficient and advanced type of insulation material used to enhance the energy efficiency of buildings. It is a rigid foam insulation that is renowned for its exceptional thermal performance and versatility. If you’re wondering what does PIR stand for, PIR stands for Polyisocyanurate, which is a blend of isocyanate and polyol resin, that undergoes a chemical reaction to create a foam with a unique cellular structure. 

How does PIR Insulation work?  

PIR insulation works by effectively reducing the transfer of heat through a building's walls, roofs, floors, and other structural components. At the core of PIR insulation's functionality is its closed-cell structure. The foam is made up of numerous tiny, interconnected closed cells that contain air or other gases. This structure creates a barrier that impedes the movement of heat through the material. When heat tries to pass through PIR insulation, it encounters resistance due to the trapped air in the cells, which acts as a thermal insulator.  

Benefits and Properties of PIR Insulation 

What are the Key Benefits of PIR Insulation?  

PIR insulation offers many benefits that make it a popular choice for enhancing the energy efficiency and comfort of buildings. Some of the key advantages include: 

High Thermal Resistance:  

PIR insulation has a remarkable ability to resist heat flow, which means it can effectively keep indoor spaces warm in winter and cool in summer. This leads to reduced energy consumption for heating and cooling systems, contributing to lower energy bills and a smaller carbon footprint. 

Space Efficiency:  

Compared to some other insulation materials, PIR insulation requires less thickness to achieve the same level of thermal resistance. This is particularly advantageous when space constraints are a concern, as it allows for thinner insulation layers while maintaining efficiency. 


This insulation can be used in a wide range of applications, from residential homes and commercial buildings to cold storage facilities and industrial settings. It can be applied to walls, roofs, floors, and various other surfaces. 


PIR insulation is known for its durability and long lifespan. It doesn't degrade easily over time, ensuring that its insulation properties remain effective for many years. 

What about the Key Properties?  

PIR insulation has several distinctive properties that contribute to its effectiveness as an insulation material, with the key properties including:  

Closed Cell Structure:  

PIR insulation is characterised by its closed-cell foam structure. The closed cells trap air, reducing heat transfer and enhancing thermal insulation. 

High R-Value: 

The reason for its high thermal resistance, PIR insulation has a high R-value per inch of thickness. This makes it an efficient insulator even in the thinnest of applications.  

Low Thermal Conductivity: 

Indicating its ability to resist heat flow, PIR insulation has a low thermal conductivity which helps it to maintain stable indoor temperatures and reduce energy consumption.  

Moisture Resistance:  

The closed-cell structure of PIR insulation not only prevents heat transfer but also acts as a barrier against moisture infiltration. This characteristic helps prevent mould growth, maintain indoor air quality, and protect the building's structural integrity. 

Fire Performance:  

PIR insulation exhibits strong fire-resistant properties. It doesn't readily ignite, and it produces minimal smoke and toxic gases when exposed to flames. This can contribute to improved fire safety in buildings. 

Lightweight and Easy to Handle: 

The lightweight nature of this PIR material ensures ease of handling and manoeuvrability, which contributes towards safer installation practices.  

Applications of PIR Insulation  

PIR insulation's exceptional thermal efficiency and versatile properties make it an ideal choice for a variety of applications in both residential and commercial construction, including: 

Roof Insulation: 

PIR insulation is a popular choice for roof insulation due to its high R-value and moisture resistance. Installing PIR insulation in the roof space helps prevent heat loss through the roof, keeping interiors warmer in winter and cooler in summer. Its lightweight nature makes it well-suited for pitched and flat roofs, contributing to reduced energy consumption and improved indoor comfort. 

Wall Insulation: 

In wall applications, PIR insulation provides excellent thermal resistance without adding significant thickness to the wall structure. Whether it's for new construction or retrofit projects, PIR insulation helps create well-insulated walls that minimise heat transfer, leading to enhanced energy efficiency and reduced heating and cooling costs. 

Floor Insulation: 

PIR insulation offers an effective solution for insulating floors, particularly those above unheated or open spaces. It prevents heat loss through the floor, ensuring a more even temperature distribution throughout the building and preventing cold spots. PIR insulation's lightweight nature makes it suitable for suspended floors and underfloor heating systems. 

Cavity Wall Insulation:  

Cavity wall insulation involves filling the gap between the inner and outer layers of a cavity wall with insulation material. PIR insulation's compactness and thermal efficiency make it a suitable choice for cavity wall applications. It effectively reduces heat transfer, improving energy efficiency and helping to maintain comfortable indoor temperatures. 

Attic and Loft Insulation: 

Uninsulated or poorly insulated attics and lofts can be major sources of heat loss. PIR insulation is a prime candidate for attic and loft insulation due to its high R-value and lightweight nature. By installing PIR insulation between and over the rafters or joists, homeowners can create a thermal barrier that prevents heat from escaping and contributes to reduced energy bills. 

External Wall Insulation (EWI) Systems  

External Wall Insulation (EWI) systems involve applying insulation to the exterior of a building's walls. PIR insulation is well-suited for EWI systems due to its compactness and ability to deliver significant thermal resistance with minimal thickness. EWI with PIR insulation not only enhances energy efficiency but also provides a fresh appearance to the building's exterior. 

How to Install PIR Insulation: 

Proper installation of Polyisocyanurate (PIR) insulation is crucial to maximising its thermal performance and achieving optimal energy efficiency in buildings. Let's delve into some essential methods and techniques for successfully installing PIR insulation: 

1. Preparation and Safety Measures:  

Before beginning any insulation installation, it's important to ensure proper safety precautions are in place. Use appropriate personal protective equipment (PPE) such as gloves, eye protection, and respiratory masks. Clear the work area of obstacles and debris, and follow safety guidelines when working at heights or using tools. 

2. Cutting and Fitting PIR Boards:  

PIR insulation boards are often supplied in standard sizes that may need to be cut to fit the specific dimensions of the installation area. Use a straightedge and a sharp utility knife to cut the boards accurately. Ensure a snug fit by measuring and cutting carefully around obstacles such as pipes, vents, and electrical outlets. 

3. Securing PIR Insulation:  

Securely fasten PIR insulation boards in place using appropriate methods. Common options include adhesive bonding, mechanical fixings, or a combination of both. Follow manufacturer guidelines for adhesive application and fastener placement to ensure a secure and uniform installation. 

4. Vapour Barriers and Air Sealing:  

In humid climates, using a vapor barrier in conjunction with PIR insulation can help prevent moisture infiltration and condensation. A vapour barrier should be placed on the warm side of the insulation to prevent moisture from reaching the cold surface and causing damage. Additionally, pay attention to air sealing by sealing gaps and penetrations to prevent air leakage, which can compromise insulation performance. 

5. Properly Insulating Joints and Gaps:  

Insulation joints and gaps must be carefully sealed to avoid thermal bridging and heat loss. Use compatible sealants or adhesives to seal joints between insulation boards and around openings. This prevents air infiltration and maintains the continuity of the insulation layer. 

Comparing PIR Insulation to Other Insulation Types 

When considering insulation options for your building project, it's essential to evaluate how different types of insulation materials stack up against each other. Let’s compare PIR Insulation to a few other types...  

PIR vs. Polyurethane (PUR) Insulation:  

Both PIR and PUR insulations are derived from similar materials, but PIR has a higher level of fire resistance and improved dimensional stability. PIR insulation also offers slightly better thermal performance due to its higher R-value per inch of thickness. However, PUR insulation can be less expensive, making it a budget-friendly choice for projects with specific requirements. 

PIR vs. Expanded Polystyrene (EPS) Insulation:  

EPS insulation is known for its cost-effectiveness and lightweight nature, but PIR insulation often surpasses it in terms of thermal performance. PIR insulation offers higher R-values and better moisture resistance, making it suitable for a wider range of applications, especially where energy efficiency is a top priority. 

PIR vs. Extruded Polystyrene (XPS) Insulation:  

XPS insulation shares some similarities with PIR insulation, such as moisture resistance and high compressive strength. However, PIR insulation typically offers a higher R-value per inch and can be more efficient in terms of thermal performance. XPS insulation can be used in specific applications where higher compressive strength is required. 

PIR vs. Mineral Wool Insulation:  

Mineral wool insulation, including both rock wool and fiberglass, provides good fire resistance and sound absorption. PIR insulation, on the other hand, offers superior thermal resistance and moisture resistance. Depending on the application, mineral wool insulation might be favoured for its fire safety features, while PIR insulation shines in terms of energy efficiency. 

PIR vs. Fibreglass Insulation:  

Fibreglass insulation is a well-known and budget-friendly option. While it provides effective thermal insulation, PIR insulation outperforms fibreglass in terms of higher R-values, moisture resistance, and better overall energy efficiency. PIR insulation's closed-cell structure also contributes to reduced air infiltration. 

How to Select the Right Thickness and R-Value for Your Project 

Choosing the appropriate thickness and R-value for insulation is a critical step in ensuring optimal thermal performance and energy efficiency in buildings. Here’s how to do it the right way.  

Understanding R-value and Thermal Performance:  

The R-value of insulation measures its thermal resistance—the ability to impede heat transfer. A higher R-value indicates better insulation effectiveness. It's important to choose an insulation material with an R-value suitable for your climate zone and the specific application. For example, colder climates typically require higher R-values to combat greater temperature differentials. 

Factors Influencing Insulation Thickness:  

Several factors influence the selection of insulation thickness, including: 

  • Climate and Location: Colder climates necessitate thicker insulation to prevent heat loss, while warmer climates require less insulation for heat gain prevention. 
  • Building Type: Residential, commercial, or industrial buildings have different insulation needs based on their usage and structural design. 
  • Heating and Cooling Systems: The efficiency of your heating and cooling systems impacts the required insulation thickness. Well-insulated buildings reduce the load on HVAC systems. 
  • Budget and Space Constraints: Balancing insulation performance with budget limitations and available space is crucial. 
  • Environmental Goals: For those aiming for higher energy efficiency or green building certifications, thicker insulation might be necessary. 

Calculating Required Insulation Thickness:  

Calculating the optimal insulation thickness involves considering the desired R-value, the thermal characteristics of the insulation material, and the specific climate conditions. Online calculators and software tools can aid in determining the required insulation thickness based on these variables. 

Meeting Building Code Requirements:  

Local building codes often stipulate minimum R-values for different building components based on the climate zone. Adhering to these requirements ensures compliance and helps achieve energy-efficient structures. However, aiming for insulation levels beyond the minimum code can lead to superior energy performance and long-term cost savings. 

Cost Considerations and Return on Investment 

Making informed decisions about insulation materials involves weighing upfront costs against long-term savings, as well as considering the return on investment (ROI) associated with energy efficiency improvements. Here's a breakdown of key factors to consider: 

Upfront Costs vs. Long-Term Savings:  

While it's true that some high-performance insulation materials, including PIR insulation, might have higher upfront costs compared to other options, it's essential to view this expense in the context of long-term savings. Energy-efficient insulation leads to reduced energy consumption for heating and cooling, resulting in lower utility bills over the years. The initial investment can pay off through substantial savings in the long run. 

Assessing Energy Efficiency Improvements: 

Energy-efficient insulation like PIR can significantly improve a building's energy performance. By reducing heat loss or gain, it helps maintain consistent indoor temperatures, decreases the load on heating and cooling systems, and minimizes energy waste. Conducting an energy audit before and after insulation installation can quantify the energy savings achieved, providing tangible evidence of the insulation's effectiveness. 

Factors Affecting ROI: Several factors influence the return on investment from insulation upgrades: 

  • Energy Prices: Higher energy prices increase the potential for cost savings, making energy-efficient upgrades more financially appealing. 
  • Climate and Usage: Cold climates experience greater heating demands, which can lead to faster payback periods. Similarly, buildings with continuous usage benefit more from insulation improvements. 
  • Insulation Type and R-value: Higher-performing insulation materials like PIR yield greater energy savings, leading to improved ROI over time.
  • Installation Quality: Proper installation ensures insulation functions optimally. Poorly installed insulation can compromise expected energy savings. 
  • Building Size: Larger buildings stand to gain more from insulation improvements due to the increased volume of conditioned space. 
  • Utility Rebates and Incentives: Many regions offer rebates or incentives for energy-efficient upgrades, reducing upfront costs and improving ROI. 
  • Property Value: Improved energy efficiency can enhance property value, contributing to overall ROI. 
  • Length of Ownership: The longer you own the property, the more time you have to recoup your initial investment through energy savings. 


PIR insulation stands as a testament to human innovation, offering a solution that not only enhances thermal performance but also addresses the challenges of moisture resistance, fire safety, ease of installation, and more. From roofs to walls, floors to attics, PIR insulation is an excellent choice for use across various structures, contributing to reduced energy consumption, lower utility bills, and more sustainable living environments.  

The journey through this guide has equipped you with the knowledge needed to make informed decisions about PIR insulation. By embracing this insulation powerhouse, you're not only elevating the energy efficiency of your buildings but also playing a part in shaping a more sustainable future. 


What is PIR insulation board 

PIR insulation board is a high-performance type of rigid foam insulation widely used in construction to enhance energy efficiency and thermal insulation. PIR insulation boards are composed of a foam material created through a chemical reaction between isocyanate and polyol resin. This reaction forms a closed-cell structure, which gives PIR insulation its unique properties. 

Is PIR insulation flammable 

PIR insulation is designed to be inherently fire-proof. It contains fire-resistant additives that make them significantly less prone to ignition and combustion. In the event of a fire, PIR insulation produces minimal smoke and toxic gases, contributing to improved fire safety. 

How to cut PIR insulation 

To cut Polyisocyanurate (PIR) insulation, follow these steps: 

  • Gather Supplies: You'll need a straightedge, a utility knife with a sharp blade, a measuring tape, and safety equipment like gloves and eye protection. 
  • Measure and Mark: Measure the required dimensions on the PIR insulation board. Use a straightedge to create a straight cutting line across the board.
  • Score the Board: Place the straightedge along the cutting line and firmly press the utility knife along the edge to score the surface. Make multiple passes if needed to create a deep score. 
  • Snap the Board: Once the score is deep enough, gently bend the board along the scoreline. The PIR insulation should snap along the line, leaving a clean edge. 
  • Complete the Cut: If the board doesn't snap completely, use the utility knife to cut through the remaining insulation along the scored line. 
  • Trimming and Shaping: For more precise cuts or to fit around obstacles, use the utility knife to carefully trim or shape the PIR insulation as needed. 

PLEASE NOTE: It is important consult a professional before starting your project.  

Can PIR insulation get wet 

Yes - its closed-cell structure acts as a natural barrier against water infiltration. While PIR insulation is not completely waterproof, it is less prone to absorbing water compared to other insulation materials like fiberglass or cellulose. 

How much PIR insulation do I need 

The amount of PIR insulation you need depends on factors such as the area to be insulated, desired R-value, and local building codes. To determine the quantity: 

  • Calculate Area: Measure the length and width of the space to be insulated (e.g., a wall, attic, or roof). 
  • Determine Thickness and R-value: Research the recommended R-value for your climate zone and insulation type. Divide the desired R-value by the R-value per inch of PIR insulation to calculate the required thickness. 
  • Calculate Volume: Multiply the area by the required thickness to get the volume of insulation needed. 
  • Factor in Waste: Consider potential wastage due to cutting and fitting. Adding around 10% extra material is a common approach.
  • Consult Experts: For accurate calculations and to account for specific considerations, consult insulation professionals or use online calculators provided by manufacturers. 

Is PIR insulation sustainable 

PIR insulation is considered relatively sustainable due to its energy efficiency, durability, recyclability, reduced carbon footprint, and potential for contributing to green building certifications. 

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DISCLAIMER: The contents of this guide are intended for information purposes only. Insulation king shall not be liable, answerable or accountable for any loss or damage resulting from the advice given

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