What PIR is
PIR (polyisocyanurate) is a rigid closed-cell foam. The roof boards we use, termPIR AL, are faced on both sides with multilayer aluminium foil, which protects the core and stabilises its thermal performance.
Manufacturer data: core density 30 kg/m³; declared λD = 0.022 W/(m·K) for 20–250 mm; compressive strength at 10 % deformation ≥ 150 kPa (30–139 mm) and ≥ 140 kPa (140–250 mm); tensile strength perpendicular to faces TR80 (up to 130 mm), TR40 (thicker); long-term water absorption WL(T)2 ≤ 2 %.
How thick?
Thickness follows the U-value required by the building’s energy design. The tool below gives an indicative thickness from the manufacturer’s table — the designer sets the final figure.
Roof U-value: U = 1 / (Rsi + ΣR + Rse). The tool uses the manufacturer’s declared RD per thickness (not λ/d), Rsi = 0.10 and Rse = 0.04 m²·K/W (EN ISO 6946, upward heat flow). Mechanical fastener corrections, thermal bridges and tapered falls are not included — the result is indicative.
Edge profiles
FIT
Square edges. In two-layer build-ups the joints are staggered.
LAP
Rebated edge — boards overlap so no through-joint remains.
TAG
Tongue and groove — a tight single-layer joint.
Boards with profiled edges are 2–4 % smaller in cover size. Standard sizes 600×1200 and 1200×2400 mm.
Installation
Boards are laid tightly butted on a stable substrate, in one or more layers with staggered joints, and fixed mechanically, bonded or held down depending on the substrate and waterproofing. They are protected from weather during installation, and fasteners must not pull through. PIR boards are not load-bearing.
Fire: termPIR AL reaction to fire class E (50–250 mm). In the manufacturer’s tested build-ups with PVC on trapezoidal steel, timber or concrete — BROOF(t1). Protan SE’s BROOF(t2) classification on PIR in the SINTEF approval applies only to the tested Kingspan TR26 board. The fire strategy decides for each building.
