EPIC (Engineered Panels in Construction)

When it comes to optimising energy efficiency and thermal performance in buildings, insulation plays a pivotal role. Among the many options available, Polyisocyanurate (PIR) insulated panels stand out. It is one of the most versatile forms of insulation, known for its high thermal and moisture resistance and ease of use. PIR insulated panels are also one of the most widely used cladding systems for roofs and walls, being used on the majority of modern industrial commercial buildings. As the building industry shifts towards sustainability targets and energy-efficient builds, it is easy to see why PIR is gaining popularity as it helps to achieve higher levels of thermal performance more easily than other traditional insulation materials.

How does the thermal performance of PIR work?

PIR is created by combining isocyanates, polyols and a blowing agent such as pentane, that produces a foam which then hardens and sets rapidly, forming an airtight, closed cell barrier. PIR insulated panels contain this material as an insulating core that autohesively adheres to steel facings during the curing process under heat, further contributing to the strength and rigidity of the material. The result is a rigid thermoset insulation that will form a carbonaceous char when exposed to naked flame or significant heat flux and then self-extinguish once the source of the fire is removed. Read PIR the facts Part 1 to find out more about fire performance. The blowing agent, which is trapped inside the closed cell structure also plays a fundamental role in providing thermal insulation to the panels.

Open Cell vs Closed Cell

PIR insulation being a closed-cell structure has advantages over open-cell structures in insulating effectively. Closed-cell insulation features fully enclosed and isolated cells whereas open-cell insulation, as the name suggests, has interconnected cells that allow air and moisture to pass through. Other insulation materials such as glass wool or rock mineral fibre are fibrous in nature, and have much lower moisture resistance. Glass wool tends to have much lower density while rock fibre when used in panels is much higher than PIR. The performance of fibrous insulation is dependent on its ability to trap air between the fibres which means it also has a higher thermal conductivity, allowing heat to pass through more easily. They can be more vulnerable to issues such as compression and moisture ingress.

Although lightweight, closed-cell PIR insulation is rigid and resistant to both air movement and moisture ingress, which makes it ideal for use on buildings that are exposed to extreme weather conditions such as heavy rain/snowfall and strong winds. Due to their strength and rigidity, PIR insulated panels also help to maintain structural integrity, and retain their thermal properties throughout their lifetime.

Key Metrics

To truly understand the thermal performance of PIR, it is helpful to compare the key metrics to see how PIR compares with other insulation materials:

Lambda Value:

The Lambda value, also known as the ‘K-value’, measures a product’s thermal conductivity, meaning how easily heat passes through a material. The lower the Lambda value, the better the insulation. It is assessed by passing heat through a specific thickness of material and measuring the temperature difference, and is expressed in units of watts per metre Kelvin W/mK. Here are some indicative values of different insulation materials that are commonly used in insulated panels:

U-Value:

Used to measure thermal transmittance, a U-Value is a sum of the layers that make up an entire building element. For example, a roof, wall, window, door or floor. It measures how much heat transfers through a given area of material from a warm space to a cold space in the building, and vice versa.  U-Values can be affected by several factors, such as the type, thickness and density of the insulation material, the presence of air gaps or thermal bridges, and the surface properties of the material.

U-Values are expressed as W/m²K, meaning watts per square metre kelvin. The lower the U-Value, the better the insulation. So, for example, a wall panel with a U-Value of 0.022 W/m²K means that for every square metre of the wall, 0.022 watts of heat will pass through for every degree kelvin difference in temperature on either side of the panel. A building’s U-Value is extremely important as there are minimum levels that should be reached according to Building Regulations/Standards.

R-Value:

The R-Value measures the thermal resistance of insulation against the conductive flow of heat. This is calculated by dividing a material’s thickness by its lambda value to show how well it resists heat transfer at a specific thickness. Unlike Lambda, the higher the R-value, the better the insulation. It is expressed in square metres Kelvin per watt as m²K/W. R-value can be added up for different layers of materials to get the total R-value of the structure, however, U-values are more frequently used in the UK.

Why choose PIR insulated panels?

Metal-faced PIR insulated panels are a smart investment for those seeking high-performance insulation for their building envelopes. They provide an excellent balance of thermal efficiency, moisture resistance, and durability.

In addition to thermal performance, EPIC-member PIR panels are specified for many other reasons, including:

• Lightweight, slim construction
• Ease and speed of installation
• Design flexibility

• Factory in-built quality
• Excellent air and weathertightness
• Single component reduces on site waste and carbon footprint
• Proven fire performance

As a trade association, EPIC works closely with its members to ensure their expertise benefits the industry. This includes the creation of guides for construction professionals, informing Government consultations and documents, and working with other industry bodies. If you would like more information, please submit a question through the contact form or email us at info@epic.uk.com.