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Thermal Insulation - Thermal R-Values

Polystyrene Thermal Insulation R-Values,
Specification & Technical Guide

What you should learn from this guide is that there are many products that can achieve the same thing.


In this guide we will show you how to compare different insulation products and options from a thermal insulation and costing perspective. 


Our technical experts are always ready to assist you in any way we can.  So speak to us if you need advice. 

Polystyrene Thermal Insulation (R-Values)

Thermal insulation values and calculations are critical when designing, specifying and buying insulation products. 


Extruded Polystyrene Insulation (SANBOARD)  & Expanded Polystyrene insulation (PolyBoard) products have different insulation values and costs so here we will try to give you the tools and tables to compare the different products. 


Thermal Insulation


Thermal K-values, not to be confused with Thermal R-Values are simply shorthand for the thermal conductivity of specific materials.

Extruded Polystyrene


Extruded Polystyrene insulation products like SANBOARD have a K-Value of 0.024. 

Expanded Polystyrene

Expanded Polystyrene insulation like PolyFloor, PolyWall & PolyRoof have a K-Value of 0.035

Polystyrene R-Value Calculations

Thermal R-Values are calculated the dividing the thickness of the material (in meters) by the K-Value of the material. So effectively, by changing the thickness of different insulation products you can achieve the same Thermal R-Value required.

Polystyrene Thermal R-Values By Thickness (mm)


(Extruded Polystyrene Ceilings & Boards)

30mm - 1.000

40mm - 1.333

50mm - 1.667

60mm - 2.000

70mm - 2.333

80mm - 2.667

90mm - 3.000

100mm - 3.333

110mm - 3.666

120mm - 4.000

150mm - 5.000

PolyFloor, PolyWall & PolyRoof

(Expanded Polystyrene)

30mm - 0.857

35mm - 1.000

40mm - 1.143

50mm - 1.429

60mm - 1.714

70mm - 2.000

80mm - 2.286

90mm - 2.571

100mm - 2.857

110mm - 3.143

120mm - 3.429

150mm - 4.286

Costing Extruded  & Expanded Polystyrene Insulation Options

If you know the insulation values required you can now compare the costs of the Expanded Polystyrene & Extruded Polystyrene Thicknesses to achieve that thermal value. 

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