25mm Unilin Thin-R PIR Insulation Board

Unilin Insulation (formerly Xtratherm)

25mm Unilin Thin-R PIR Insulation Board (2400mm x 1200mm x 25mm) is an ultra-thin rigid polyisocyanurate foam board with foil facing, engineered for multi-purpose thermal applications. This high-performance insulation delivers a certified thermal conductivity of just 0.022 W/mK and suits pitched roofs, cavity walls, suspended floors, and timber or steel-framed construction.

About

The 25mm Thin-R PIR board excels in pitched roof applications—whether ventilated, hybrid, or warm roof designs—delivering superior U-values without compromising internal space. Roof insulation is critical to reducing heat loss through the building envelope, and this product minimises thermal bridging whilst maintaining excellent performance. Suitable for pitched roofs, cavity walls, and floor systems, the board combines lightweight handling with straightforward installation. It resists moisture, offers fire protection, and carries minimal environmental impact.

Product Details

Thickness: 25mm

Length: 2400mm

Width: 1200mm

Available Thicknesses: 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 60mm, 65mm, 70mm, 75mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 165mm

Maximum Board Weight: 0.45 kg/m²

Thermal Resistance: 1.14 m²K/W

Thermal Conductivity: 0.022 W/mK

Compressive Strength: >150 kPa

Water Vapour Resistivity: >100 MNs/gm

Density (Foam Core): 30–32 kg/m³

Surface Spread of Flame: Class 1

Reaction to Fire: E

Finish: Aluminium foil facings

Applications: Roofs, walls, floors, timber and steel frame

ETA Notification: Yes

Features: Versatile | High-performance | Rigid

Warm roof construction offers an effective solution for insulating complex roof designs. Positioning insulation above—or above and between—roof timbers maintains the structural envelope at internal temperatures, reducing thermal stress and condensation risk.

Store the 25mm PIR board on a clean, flat surface away from ground contact and under weatherproof cover. Polythene wrapping alone does not provide adequate outdoor protection. Protect the insulation during storage and on-site. The boards cut easily with a sharp knife or fine-toothed saw.

Key Facts

1. Achieves A+ rating under the BRE Green Guide
2. Certified lambda value of 0.022 W/mK
3. Minimises intrusion into living space
4. Reduces condensation risk
5. Low emissivity foil facings
6. Lightweight and simple to fit
7. Minimised thermal bridging
8. Suitable for ventilated, warm, and hybrid roofs

Browse our full Unilin stock and filter by thickness or coverage. For product suitability advice or bulk quotations, contact us on +4402038839057, email sales@insulationbee, or use Live Chat for the lowest UK insulation prices.