ThermalFlex™ Cavity

Flexible Reflective Insulation

ThermalFlex™ Cavity is a high performance reflective insulation, vapour barrier and radiant barrier. ThermalFlex™ Cavity is rated Extra Heavy Duty and is strong and durable, making it perfectly suited for use in cavity wall applications. ThermalFlex™ Cavity is ideal for use in residential homes, commercial buildings and domestic sheds.

ThermalFlex™ Cavity reduces thermal bridging and conductivity between building elements, along with providing high thermal performance as a radiant barrier and an effective alternative to conventional insulation.

Product Advantages

  • Insulation, Vapour Barrier & Radiant Barrier.
  • Extra Heavy Duty for strength & durability.
  • Low Flammability to suit bushfire-prone areas.
  • R0.11 flexible insulation to help prevent condensation.
  • Antiglare Coating for installation safety.


Premium wall wrap for brick cavities.

Blank one so all stay closed
Product Details
Product NameReflex Insulation ThermalFlex™ Cavity
Product Thickness4mm
Roll Size1350 mm x 22.25 m (30m2)
R Values
Declared Total System R-ValuesWinterSummer
Double Brick Wall
110mm clay brick walls, 20mm unventilated air space, ThermalFlex™ Cavity and 20mm unventilated air space.
Brick Veneer Wall
110mm clay brick, 35mm unventilated air gap, ThermalFlex™ Cavity, 90mm unventilated cavity, 10mm plasterboard
Product Testing

Material Properties and Classifications
ThermalFlex™ Cavity classifications in accordance with AS/NZS 4200.1:2017 and AS/NZS 4859.1:2018.


Flammability IndexAS 1530.2-1993Low ≤ 5
Material Thermal ResistanceASTMC518R0.11
Duty RatingAS/NZS 4200.1:2017Extra Heavy Duty
Vapour ControlASTM E96Class 2 Vapour Barrier
Vapour PermeanceASTM E96< 0.142 µg/N·s
Water ControlAS/NZS 4201.4:1994Water Barrier
Resistance to Dry DelaminationAS/NZS 4201.1:1994Pass
Resistance to Wet DelaminationAS/NZS 4201.2:1994Pass
Shrinkage (Repeated wetting & drying)AS/NZS 4201.3:1994≤ 0.5%
Emmitance ValueAS/NZS 4201.5:1994Anti-glare side: >0.05 to ≤0.15, Foil side: ≤0.05
Bushfire Attack Levels
ThermalFlex™ Cavity complies with AS 3959-2018 Construction of buildings in bushfire-prone areas for use in all BALs.
Specification Notes

When specifying, state the following:

Product Name: Reflex Insulation ThermalFlex™ Cavity

The insulation to be installed shall be Reflex Insulation ThermalFlex™ Cavity reflective flexible insulation, comprised of closed-cell core XPE foam with anti-glare foil facing on one side and plain foil facing on the other side. Product shall be installed in accordance with AS/NZS 4200.2 and the product must have the following properties:

Emittance Value: 0.06, 0.03
Emittance Classification: IR Semi-Reflective, IR Reflective
Material Value: R0.11
Vapour Control Classification: Class 2 Vapour Barrier, < 0.1429 µg/N·s
Water Control Classification: Water Barrier
Duty: Extra Heavy in accordance with AS/NZS 4200.1

Installation Instructions

ThermalFlex™ 4 Installation Instructions: Please select the following applications for detail:

  • Residential Brick Cavity Walls
  • Residential Walls