PIR Insulation Boards

What we supply

• General-purpose PIR boards2400 × 1200 mm foil-faced boards for floors, walls and roofs.
• Cavity wall boardsBoards sized for partial-fill cavity insulation.
• Flat roof boardsBoards for warm flat roof build-ups.
• Thermal laminate boardsPIR bonded to plasterboard.
• Foil tape and fixingsTo seal joints and fix boards.

Sizes and specifications

Standard	BS EN 13165
Sheet size	2400 × 1200 mm
Thicknesses	25 to 150 mm
Thermal conductivity	Typically around 0.022 W/mK (check the maker's declared value)

Sizes and standards are typical for the UK market; exact figures depend on the manufacturer and are confirmed on your quote.

Common uses

• Under floor screeds and slabs
• Between and under rafters
• Warm flat roofs
• Cavity and internal wall insulation

Choosing PIR insulation boards

Thickness for the U-value

The thickness you need depends on the U-value the building regulations require and the rest of the build-up. Manufacturers publish U-value tables; your designer or building control will confirm.

Fire considerations

PIR is a combustible product. Building regulations restrict combustible materials in some situations, such as external walls of taller buildings; check what applies.

Sealing joints

Tape the joints with foil tape so the foil layer works as a continuous vapour control layer where the design relies on it.

Building regulations differ across the UK. In England, building work is checked against the Approved Documents, for example Part A for structure and Part L for energy efficiency, through your council's building control team or a registered building control approver. Wales has its own Approved Documents, including its own Part L for energy efficiency, and building control is handled by the local authority or a registered approver. In Scotland most building work needs a building warrant from the local authority, assessed against the Building Standards Technical Handbooks. In Northern Ireland building work follows the Building Regulations (Northern Ireland), with guidance in the Technical Booklets, and applications go to the council's building control team.

How it arrives on site

Boards are light but bulky; they travel in wrapped packs and should be stored flat and dry. We agree the drop point and offload method when we price your order. Read more about how delivery works.

How much do you need?

Insulating 20 m² of rafters, floor or wall takes 8 boards of 2400 × 1200 mm including offcuts. The thickness depends on the U-value you need, so check it before you order. Try the insulation calculator

PIR Insulation Boards: questions

How thick should PIR insulation be?

It depends on where it goes and the U-value required. Pitched roofs often need 100 mm or more between and under rafters; floors and walls vary. Use the maker's U-value tables or ask your designer.

Is PIR better than mineral wool?

PIR insulates more per millimetre, so it suits tight spaces. Mineral wool is non-combustible, cheaper per square metre and better for sound.

How many PIR boards do I need?

Divide the area by 2.88 m² (one 2400 × 1200 board) and add about 5 to 10 percent for cutting.

Can PIR be used in external walls?

In some situations, but building regulations restrict combustible insulation in external walls of certain buildings. Check the rules for your building.

What is the foil for?

The foil facing reflects heat, protects the foam and, when joints are taped, can act as a vapour control layer.