Our store is closed until 20th August due to ongoing upgrade works. We apologise for any inconvenience and invite our customers to come back for the new and improved shopping experience.

Insulation Cart Team – offering unbeatable prices on building insulation online.

Special offers

100mm Isover CWS 32 Cavity Wall Insulation Batts 1200x455 (pack of 6)

100mm Isover CWS 32 Cavity Wall Insulation Batts 1200x455 (pack of 6)

CWS 32 are silicone impregnated glass mineral wool slabs providing high levels of thermal insulation in masonry cavity walls. CWS 32 is designed to fully fill the cavity between two masonry leaves in external walls. Thermal Conductivity - 0.032 W/mK.

Price: £ 34.15
(£40.98 inc VAT)

100mm Rockwool Rollbatt Insulation Roll pre-cut 1200x5500mm (6.60m2)

100mm Rockwool Rollbatt Insulation Roll pre-cut 1200x5500mm (6.60m2)

Rockwool Rollbatt provides effective, medium density thermal insulation in loft spaces and suspended ceilings, reducing energy consumption and preventing fuel bills in all building types from going through the roof.

Price: £ 38.49
(£46.19 inc VAT)

65mm Knauf DriTherm 37 Standard Cavity Wall Insulation Slabs 1200x455 (pack of 10)

65mm Knauf DriTherm 37 Standard Cavity Wall Insulation Slabs 1200x455 (pack of 10)

DriTherm 37 Cavity Slabs are for the thermal insulation of masonry cavity external walls, either partially filling or fully filling the cavity. Thermal conductivity - 0.037 W/mK

Price: £ 25.00
(£30.00 inc VAT)

InsulationCart.com - Knowledge Centre

Knowledge Centre > About Products > PIR (polyisocyanurate) Boards

PIR (polyisocyanurate) Boards


PIR insulation is essentially an improvement of a previously used polyurethane boards (PUR) offering greater structural strength, increased heat stability and therefore better thermal performance (low thermal conductivity). The thermal conductivity of PIR insulation ranges from 0.021 to 0.029 W/mK making it easy to achieve compliance with the technical requirements of Part L of the Building Regulations and not compromising on space consumption.

The manufacturing process of PIR thermal insulation involves blending together two primary chemicals and other materials to form a rigid foam product. The heat generated during the reaction enable gases to evaporate and become trapped within cells delivering premium thermal performance characteristics.

PIR insulation boards are manufactured via a continuous production process combining PIR foam between two layers of facer.

The facers of the products will differ depending on the end use application and can be distinguished as:

  • PIR with foil facers – providing vapour barrier and insulation in one application and used for insulating pitched roof constructions, external walls, terraces, floors and ceilings (Celotex TB4000, Celotex GA4000, Celotex XR4000)
  • PIR bonded to 12.5mm plasterboard – a 3in1 product which allows the user to install thermal insulation, vapour barrier and dry lining in one operation significantly reducing installation time, this product can be used for thermal insulation of walls or pitched roof under rafters (Celotex PL4000)
  • PIR faced with mineral glass tissue - perfect solution for the thermal upgrade of external solid walls, the glass tissue facer provides direct render solution with no requirement for separate render boards or batten systems and is particularly suited for refurbishment projects (Celotex SW3000)
  • PIR with bitumen polypropylene fleece facers – perfect solution for built-up flat roofing applications including hot applied bituminous, mastic asphalting and torch-on systems (Celotex TC3000, Kingspan TR24)
  • PIR with coated glass tissue facings – provides quick and easy method of achieving effective thermal insulation in flat roof applications including hot applied bituminous, mastic asphalt and fully adhered single-ply membrane (Celotex EL3000)

This unique manufacturing process makes PIR one of the most thermally efficient and cost effective insulation solution in the UK construction industry.

Advantages of insulating with PIR (polyisocyanurate) boards:


  • PIR insulation products exhibit increased fire performance and reduced combustibility offering higher working temperature limits compared to PUR and when incorporated into building products, can meet some of the most demanding fire performance requirements.
  • PIR boards can be used for insulating virtually any setting. They work very well as over rafter insulation in pitched roof constructions but their use is not limited to roof applications. PIR insulation boards can be used for insulating external walls - also from the inside of the building. They are recommended for insulating flat roofs, terraces, foundations and ceilings.


  • Thanks to its outstanding thermal performance PIR insulation allows the user to install thinner profile (than in case of Polystyrene or Mineral Wool) of the boards to achieve specified by the Building Regulations U-Values and therefore PIR insulation will become a perfect solution for the projects in which reducing space consumption is a main concern.
  • One of the important factors to be taken into consideration when planning a selection of any modern insulation is water absorption – the ability of the product to resist water uptake when exposed to moisture.


Unlike mineral wool where thermal performance can be significantly compromised and reduced when exposed to moisture, PIR insulation with its closed cell structure is unaffected by the effects of moisture and therefore can be stored and installed during humid conditions. Those hydrophobic qualities of PIR allow the product to retain its integrity and thermal performance over time.

  • PIR insulation is characterised with increased inherent structural strength which allows the product to be used widely in the construction sector. Strong, rigid composition of the core prevents the product from sagging over time ensuring it retains its thermal characteristics. In addition PIR boards can withstand light foot traffic or loading which is an important consideration in flooring and flat roofing applications.


  • Another advantage of PIR boards is their lightweight structure which allows the product to be easily handled and transported during installation. Based on 100mm product, PIR is over 10% lighter than phenolic insulation.
  • PIR insulation boards do not absorb moisture, do not sag or be permeated by air. The user can be confident of consistent performance of the product which will typically last the full lifetime of the building. There is also no requirement for additional maintenance or treatment to the PIR boards during this time.