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Duratherm OS is a polyurethane foam used for thermal insulation and stabilization. It can be used in new buildings and retrofit properties as stabilization for pitch/ flat roofs and loft conversions. The product is spray applied leaving a seamless rigid foam layer of approximately 25 mm. Extra layers are then applied to meet the required thickness. It is an HCFC and CFC free, two component, 1:1 ratio, rigid foam system which when processed through suitable spray machinery (Graco, Gusmer, Glas-Craft) will produce a rigid foam of approximate density 40 kg/m³ with exceptionally good compressive strength. Service temperature range -15 to 70°C. When tested to BS 476-7 the foam achieves a Class 1 surface spread of flame.


  • Retrofit insulation/ stabilization for pitched/ flat roofs.
  • New build insulation.
  • Loft conversions.
  • Commercial buildings.

Duratherm OS can be used to upgrade the thermal performance of roofs, floors or walls of any property, to meet current building regulations. Standard Duratherm OS should not be used on substrates below 5°C.

Standard product features

Technical properties:

  • Core density (to BS 4370): 38–42 kg/m³.
  • Compressive strength (to BS 4370): Parallel to rise, 220 kPa.
  • Closed cell content (to ASTM D2856, minimum): 88%.
  • Thermal conductivity, aged <80 mm (to BS EN 12667): 0.028 W/mK.
  • Thermal conductivity, aged 80–120 mm (to BS EN 12667): 0.026 W/mK.
  • Thermal conductivity, aged >120 mm (to BS EN 12667): 0.025 W/mK.
  • Water vapour permeability 80–100 mm, 38°C, 88% RH (to BS 4370): 7.16 ng/Pa/m².
  • Dimensional stability (to BS 4370), 1 day at -15°C: -0.53% volume.
  • Dimensional stability (to BS 4370), 1 day at 80°C: 0.75% volume.
  • Dimensional stability (to BS 4370), 1 day at 100°C: 0.93% volume.

Burning tests:

  • Extent of burn (BS 4735-74): 3.6 mm.
  • Surface spread of flame (to BS 476): Class 1.

Ozone depletion potential (ODP):


Product specification

An important note about specifying



Isothane Ltd


+44 (0)1254 872555

Product reference

Duratherm OS

Manufacturer details

Newhouse Road,
Huncoat Business Park,
Lancashire, BB5 6NT
Tel +44 (0)1254 872555
Fax +44 (0)1254 871522
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