Insulation Values and Methods

What is an R-Value?

R-value is a term predominantly used in the building industry to describe the insulation properties of certain building insulation materials. Its use is limited to situations where thermal insulation is achieved by retarding the flow of heat through the material itself rather than reflecting radiant heat away. The higher the R-value, the greater the insulation.

R-value is a measure of apparent thermal conductivity, and thus describes the rate that heat energy is transferred through a material or assembly, regardless of its original source.

Although R-Values offer a useful means of comparing the performance of different products, other factors need to be considered in maintaining thermal comfort.

What is Thermal Mass?

Materials such as concrete have poor thermal resistance (R-value typically less than 1), but work well for thermal mass applications because of their high specific heat. Such materials are able to slowly store or release, relatively large quantities of heat compared to other materials.

Thermal mass should not be confused with insulation. Materials used for insulation typically have much lower thermal conductivity than materials used for thermal mass and generally do not have a high capacity to store heat. They can reduce unwanted heat transfer but are not significant sources of heat in themselves. Often a combination of good insulation and thermal mass is used to achieve an optimum solution.

What is a Thermal Bridge

A thermal bridge is created when materials that are poor insulators come in contact, or penetrate through a good insulation barrier allowing heat to flow through the path created. Insulation around a bridge is of little help in preventing heat loss or gain.

Surface moisture due to condensation can occur on the surface where the thermal bridge occurs.

EPS is a thermal break, when used as a wall cladding it will insulate the walls trapping the exterior air temperature out & the inside air temperature inside the house. EPS as a wall cladding has the insulation in the best place possible – the outside of the building which ultimately makes the framing far more stable as it doesn’t have to endure constant temperature fluctuations reducing potential for movement in the wall structure.

Examples of thermal bridging

  • Concrete balconies that extend the floor slab through the building envelope
  • Nails that are used to fix a Insulated Wall Cladding
  • Timber/Metal Battens that are used to seperate a Insulated Wall Cladding
  • Timber framing used to construct a house
  • Single Glazed Windows
  • Certain types of alumium joinery

1.5.4 Material R-Values

40mm S-Grade Expanded Polystyrene – 1.06
50mm S-Grade Expanded Polystyrene – 1.32
60mm S-Grade Expanded Polystyrene – 1.58
80mm S-Grade Expanded Polystyrene – 2.11
100mm S-Grade Expanded Polystyrene – 2.64

40mm H-Grade Expanded Polystyrene – 1.11
50mm H-Grade Expanded Polystyrene – 1.39
60mm H-Grade Expanded Polystyrene – 1.67
80mm H-Grade Expanded Polystyrene – 2.22
100mm H-Grade Expanded Polystyrene – 2.78

40mm VH-Grade Expanded Polystyrene – 1.18
50mm VH-Grade Expanded Polystyrene – 1.47
60mm VH-Grade Expanded Polystyrene – 1.76
80mm VH-Grade Expanded Polystyrene – 2.35
100mm VH-Grade Expanded Polystyrene – 2.94

40mm Graphex – 1.25
50mm Graphex – 1.56
60mm Graphex – 1.87
80mm Graphex – 2.50
100mm Graphex – 3.12

50mm XTherm Blue – 1.65
50mm XTherm Gold/PIR – 2.34
75mm XTherm Gold/PIR – 3.50
100mm XTherm Gold/PIR – 4.67
150mm XTherm Gold/PIR – 7.01

Timber Framing 90 x 45 wall construction with studs at 600 centres (incl Plasterboard and Building Wrap) – 0.35

50mm Integra AAC Panels – 0.331
75mm Integra AAC Panels – 0.497

10mm Duratherm – 0.303
20mm Duratherm – 0.606
33mm Duratherm – 1.0

20mm Cavity – 45% reduction in the R-Value from the Cavity outwards (sourced from NZS 4214:2006)


Timber Frame with a cavity and 40mm EPS

40mm H-Grade EPS – 1.11
Timber Framing – 0.35
Cavity Derates EPS by 45% – multiply by EPS by .55

Total R-Value = 0.96

Masonry Block with 50mm XPS

Masonry Block – 0.33
50mm XTherm – 1.65

Total R-Value = 1.98