Roofboards – Flat Roofs

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PIR insulation board are the most commonly used insulation product in flat roof applications.  As a result of their excellent thermal performance, PIR roofboards offer one of the thinnest methods of achieving the current U-value requirements of Building Regulations and Technical Standards.

PIR insulation products offer excellent dimensional stability and good compressive strength whilst being much lighter and easy to handle.

The insulation has the ability to withstand foot-traffic; this is an essential characteristic, especially when used in modern flat roofs waterproofed with single-ply membranes. Unlike PIR insulation products, some insulation materials can depress under foot-traffic creating dips in the roof where water can collect (known as water-ponding). When water-ponding occurs the design life of the roof can be seriously compromised as a result of thermal stress, alkaline formation and mould growth.

PIR insulation products are available with a wide range of facings. The choice of facing is dependent on the application i.e. a glass reinforced perforated cellulose facing would be used for an insulation board being employed in a partially bonded built-up felt application.

Benefits of PIR/PUR Insulation Products for Flat Roof Applications:

  • Maintains thermal performance for lifetime of the building
  • Resistant to moisture ingress
  • Lightweight and non-fibrous insulation
  • Excellent dimensional stability
  • Good compressive strength and resistance to foot-traffic

Manufacturers’ products will offer different benefits depending on the application. For full details users should refer to the manufacturer’s third party certification.

IMA has a number of publications relating to the use of PIR insulation boards in flat roof applications which can be found here.

Increasingly, PhotoVoltaic (PV) systems are installed on buildings in order to help meet energy saving and greenhouse gas emission reduction targets as well as to reduce fuel bills for occupants.  A recent study from PU Europe (available here) demonstrated that the performance of a tested FM approved roof with PIR insulation and a combustible waterproofing membrane compared well with a similar roof with mineral wool insulation.