PIR Insulation Panel — Lambda, Thickness and Fire

What it is

A rigid polyisocyanurate foam core bonded between two metal skins, supplied as a self-supporting sandwich panel for roofs and walls. The foam is closed-cell, which is why it insulates so well for its thickness.

Specification at a glance

Property	Typical specification
Core	Polyisocyanurate, closed cell
Thermal conductivity	Approximately 0.022 W/mK
Core density	38 — 45 kg/m³ typical
Panel thickness	30mm — 150mm
Skins	Pre-painted Galvalume, 0.45mm — 0.60mm
Standard	EN 14509 for the panel system
Fire class	Named EN 13501-1 class; core is combustible

Thickness against U-value

Indicative, before thermal bridging at fixings and joints:

Core thickness	Approximate U-value
40mm	~0.52 W/m²K
50mm	~0.42 W/m²K
80mm	~0.27 W/m²K
100mm	~0.21 W/m²K
150mm	~0.14 W/m²K

The ECBC 2017 target for the climate zone sets which row applies. On a single-storey industrial building the roof usually governs, because it takes the highest solar incidence of any surface.

Why it gets specified

Best thermal performance per millimetre of the common industrial insulations, so it wins wherever build-up depth is constrained or the U-value target is demanding.

Single-fix envelope. The panel is structure, insulation, weather line and finish in one operation, which compresses the programme against a built-up system.

Where projects go wrong

• Thickness chosen by habit rather than from the ECBC target for the climate zone.
• Fire class unstated. "PIR" is not a fire specification.
• Combustible core behind a combustible outer panel in a ventilated cavity — the assembly behind the worst facade fires.
• Joints and fixings ignored in the U-value. The installed assembly underperforms the datasheet, sometimes substantially.
• Panels stacked and handled carelessly. A crushed edge cannot be made weathertight afterwards.

Standards referenced

Opaque assembly U-value targets under ECBC 2017. Panel system requirements under EN 14509. Reaction-to-fire classification to EN 13501-1.