PIR Thermax Light Duty


Dow Thermax Light Duty thermal insulation sheathing is a non structural, rigid board consisting of a glass fibre reinforced Polyisocyanurate (PIR) foam core laminated between smooth, reflective aluminium foil facers on both sides. 

Dow Thermax Light Duty has a glas fibre reinforced PIR foam core, along with chemical modifications, contribute to improved fire performance and dimensional stability. The Thermax Light Duty PIR foam core will not melt, flow or drip when exposed to fire, instead it will form a strong char that prevents flame spread and further degradation to the core, unlike EPS (Expanded Polystyrene) which will spread the flame due to oxygen being held between the cells within the panel.

The EPS cells are also a thermoplastic, which tend to melt and shrink under intense heat.


Dow Thermax Light Duty Print/PDF

Dow Thermax Light Duty PIR Insulation 

Dow Thermax Light Duty PIR thermal insulation has bonded aluminium foil facers which serve as effective moisture vapour retarders. Dow Thermax Light Duty PIR thermal insulation can be installed exposed to the interior without a thermal barrier which offers a high insulating value


  • Thermax Light Duty PIR is designed as a thermal insulation and interior finish system for walls and ceilings in metal, wood post frame, and concrete or masonry buildings


  • Durable white acrylic-coated aluminum on one side, embossed aluminium on the other for light-impact areas.
  • It can be pressured-washed up to 6,894.7 kPa with a 15-degree or greater sprag tip


  • Dow Thermax Light Duty PIR thermal insulation is manufactured with a zero ozone depleting potential. The use of Thermax Light Duty PIR thermal insualtion helps reduce the carbon footprint of commercial buildings.

Specification Clause - Soffit

Dow Thermax™ Light Duty Soffit Board should be described in Specifications as:–

The soffit insulation supplied by Dynamic Composite Technologies shall be modified PIR (Polyisocynurate) Dow Thermax™ Light Duty Soffit Board ____mm thick CFC/HCFC–free, rigid modified PIR thermoset insulation core with autohesively bonded 35 micron embossed pure foil facings on both sides, conforming to AS fire tests, AS1530–3, AS3837 Group Classification 1, ISO 9705 Group 1 (ceilings only), FM 4880, manufactured to the highest standards under quality control systems approved to ASTM C1289-02 by Dow Insulation Limited and shall be applied in accordance with the instructions issued by them.  


Technical data
Product Name: Dow Thermax Light Duty 
Polyisocyanurate PIR rigid thermal insulation
Product Description: Dow Thermax Light Duty polyisocyanurate PIR rigid thermal insulation for an interior finish system for walls and ceilings in metal, wood post frames and concrete or masonry buildings.

Surface Finish:

Product Code:
Edge Treatment:
Nominal Thickness:
Compressive Strength:
Flexural Strength:
Water Absorption:
Water Vapour Permanence: 
Maximum use temperature: 
Light reflective, visual light spectrophotometer: 

1.25mil embossed white acrylic-coated 
aluminum on one side and 1.25mil embossed aluminum on the other.  
Thermax LD
Square Edge
13, 19, 25, 32, 38, 45, 51, 57, 64, 70 and 76 mm
1219 mm
2235 mm
172 kPa
379.21 kPa


Nominal Thickness to R-Value
Dow Thermax Light Duty PIR @ 24°C 
Nominal Thickness
Lambda/K Value/Thermal
R Value
13 0.022 0.6
19 0.022 0.9
25 0.022 1.2
32 0.022 1.5
38 0.022 1.7
45 0.022 2.0
51 0.022 2.3
57 0.022 2.6
64 0.022 2.9
70 0.022 3.2
76 0.022 3.5













PH: 1800 174 900 



Proctor Group Australia


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