Thermal Conductivity and Resistance in Different Cores of Isopanels

Thermal Conductivity and Resistance in Different Cores of Isopanels

In this blog, we explore the thermal properties of each insulating core available for our Isopanels: expanded polystyrene (EPS), rock mineral wool (Rockwool), polyisocyanurate (PIR) core and phenolic foam core.

Note that Structural thermal performance of the panel varies with the thickness of the core material. All the thermal resistance values below are based on panels with a core thickness of 100mm, and these values will increase with the core thickness.

Expanded polystyrene (EPS)

EPS is extensively used in sandwich panel insulation and other building applications due to its excellent energy-efficiency, thickness and length versatility, low-cost installation and cost-effective long-term maintenance.

At a glance, EPS has an excellent thermal conductivity lower than 0,1 (approx. 0,03) and a thermal resistance of R 2,7 per 100mm. An EPS core is generally more advantageous as an option than pricier PIR and phenolic foam applications, for example. In addition, fire-retardant EPS provides good fire resistance comparable with other core materials.


PIR offers a competitive R value that increases proportionally with the thickness of the product. It provides a high level of fire resistance because of its chemical cross-linked polymers structure. PIR is not pliable after burning, withstanding higher temperatures.

PIR has a thermal conductivity of approx. 0,02 and a higher thermal resistance than EPS of approximatively R 4 per 100mm. However, research shows that the overall thermal resistance of PIR may reduce in time, despite an initial thermo-efficient advantage over EPS.

Specifiers who include Isowall in their design brief can be confident that they have chosen the most extensively tested and proven panel system in the marketplace. All enquiries will be dealt with by our experienced and friendly staff who will give you prompt and courteous service.

Phenolic foam

Phenolic foam is a rigid thermal insulation foam, with excellent outstanding thermal performance thanks to its high R-value insulation. It also possesses a great combination of strength, weight and ease of application.

Phenolic foam has a comparative thermal conductivity value of 0,02 with PIR and EPS, and a high thermal resistance R value of 2,7 per 100mm of thickness recommended for superior fire resistance.

Rockwool (rock mineral wool)

Rock mineral wool provides superior thermal and acoustic properties and high compressive strength, with a significant advantage in fire safety. The core material is non-combustible and resistant to temperatures in excess of 1000 C.

Our Isopanels use Rockwool Conrock Q5 as the panel core, made of basalt, a volcanic stone. Rockwool has a low Thermal conductivity of 0,02 and a superior thermal resistance R value of 2.5 per 100mm that increases with thickness.

Isowall manufactures and distributes Insulated Sandwich Panels as Isopanels. Various facing materials, cores and finishes are available, depending on the application required. Click here to find out more.

Isowall is the supplier of choice within Africa for Insulated Sandwich Panel, EPS and EPP products. Contact us for more information.


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