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EshaTherm PIR OSB Comp is a rigid polyisocyanurate (PIR) foam insulation and OSB composite for use in new build and refurbishment projects. EshaTherm PIR OSB Comp is a rigid polyisocyanurate (PIR) foam core faced with an exterior grade FSC Certified Grade 3 OSB and an aluminium foil backing. The PIR foam core is temperature tolerant and withstands the application of hot bitumen to the surface temperature of 240°C.


Covered by British Board of Agrément (BBA) certificate number 07/4487.

General information
Specification data
Product Reference

EshaTherm PIR OSB Comp


99–159 mm in 10 mm increments. Consult manufacturer's literature for typical U-values.

Standard product features

Product characteristics:

  • Appearance top side: FSC certified grade 3 OSB.
  • Core: Polyisocyanurate (PIR) foam.
  • Appearance bottom side: Aluminium foil.

Size (w x l):

1200 x 2400 mm.


Typical weight of a 120 mm thick PIR + 9 mm OSB is 28 kg.

Product Options

Technical data:

  • Ozone depleteion potential: Zero.
  • Global warming potential: 3.
  • BRE Green Guide rating: A.

Compressive strength:

Typical compressive strength for the foam exceeds 140 kPa when tested to BS EN 826: Thermal Insulating Products for Building Applications – Determination of compressive behaviour.


PIR foam has a typical density of 31 kg/m³.


The product is stable, rot proof and durable and will remain effective as an insulation system at least as long as that of the waterproof covering. Durability depends on the method of application, the supporting structure and conditions of use. The insulation core and facings resist attack by mould and microbial growth, and do not provide any food value to vermin.

Moisture tolerance:

Exterior grade OSB Grade 3 has inherent moisture resistant qualities.

Resistance to solvents (foam):

EshaTherm PIR OSB Comp resists attack from dilute alkalis and acids, mineral oil and petrol. The foam is not resistant to ketonic solvents. Damaged boards should not be used.

Thermal conductivity:

The low emissivity of the reflective foil can cut radiation heat transfer across an adjoining air-space:

  • The thermal conductivity (λ value) of the foam is 0.022 W/mK.
  • The thermal conductivity (λ value) of the OSB is 0.14 W/mK.
  • Thermal resistances of the range within given constructions are shown in the manufacturer's literature.

Water vapour resistance:

Foil facings have a high water vapour resistance and will, therefore, provide significant resistance to water vapour transmission. This will minimise both surface and interstitial condensation. The necessity for the inclusion of a water vapour control layer in the roof construction should be assessed in accordance with BS EN 6229 code of practice for flat roofs with continuously supported coverings. Consideration should also be given to BS EN 5250 code of practice for control of condensation in buildings.


PIR foam is CFC/ HCFC free and has a zero ozone depletion potential (ODP) with a global warming potential (GWP) of 3, less than the target value of 5. It has a BRE Green Guide rating of A. EshaTherm PIR OSB Comp is manufactured from FSC (Forest Stewardship Council) certified OSB Grade 3.


  • Achieves BS EN 476-7: Class 1 rating for surface spread of flame.
  • Finished with three layer built-up felt and chippings, the roof will attain an FAA rating when tested to BS EN 476: External Fire Exposure Test.
  • Further details on the fire performance may be obtained from Radmat Technical Services.

Roof loading:

Depending on the chosen waterproofing system, EshaTherm PIR OSB Comp is suitable for use on roof decks that are subject to limited maintenance foot traffic. Walkways should be provided on roofs requiring regular pedestrian access. The roof should be boarded out with protective boarding whenever site work is to take place after the roof board has been laid and the roof made watertight.

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