Best Loft & Wall Insulation — PIR Foam Board (2026)
2 loft & wall insulation matching material “PIR Foam Board”, hand-picked from UK Amazon listings.
Not sure which one to pick? Read our Best Loft & Wall Insulation UK (2026) guide.
This PIR Foam Board is a robust solution for insulating your loft or walls, offering significant thermal performance and ease of installation. Made from high-density PIR foam, it’s designed to provide excellent resistance to heat flow, helping to keep your home warmer in winter and cooler in summer – contributing towards energy efficiency. This board is particularly suited to enclosed spaces like lofts where moisture build-up can be a concern, due to the PIR's inherent stability.
Specifically designed for loft and wall insulation projects, this PIR foam board offers a dense core that minimizes air movement, a key factor in reducing heat loss. Its closed-cell structure prevents water absorption, making it suitable for damp environments and contributing to a healthier indoor climate. The rigid nature of the board also means it can be cut and shaped easily on site, minimising waste during installation.
When used correctly within a cavity wall or loft space, this PIR foam board will significantly reduce your reliance on heating and cooling systems, saving you money in energy bills. Remember to factor in adequate ventilation when using PIR for insulation to prevent moisture build-up and ensure optimal performance. Always check the manufacturer’s specifications for recommended installation methods and thicknesses.
#1 Pick
5 X RECTICEL / CELOTEX / KINGSPAN Insulation Board 100MM X 2400MM X 1200MM EURTHANE GP FOIL Back PIR, Silver- PIR Foam Board
- 2400 x 1200 x 100mm, 5 Boards
£374.99
Pros
- Foil-backed PIR board gives a high insulation value for a relatively thin panel
- Supplied as equivalent stock from Recticel, Celotex or Kingspan depending on availability
- 5-board bulk pack suits a full loft, wall or floor insulation project
Cons
- Large pallet-size order needs van access or ground-floor delivery space
#2 Pick
2400 x 1200 x 100mm Celotex GA4100 / Kingspan TP10 / TF70 / Ecotherm Ecoversal Foil Insulation (10)- PIR Foam Board
- 2400 x 1200 x 100mm (10 boards)
£563.00
Pros
- High-performance foil-faced PIR boards for roofs, walls and floors
- Bulk 10-board pack covers a large loft conversion or extension in one order
- Supplied as Celotex, Kingspan or an equivalent brand of identical spec
Cons
- Very bulky pallet delivery needs ground-floor access and someone to help unload
FAQ
What is PIR foam?+
PIR stands for PolyIsocyanurate, a type of polyurethane foam. It's a closed-cell material which means it resists water absorption and provides excellent thermal insulation performance compared to other foam types.
How thick should I cut the PIR foam board for loft insulation?+
The recommended thickness for loft insulation with PIR foam boards varies depending on your property’s level of insulation. Generally, a minimum of 40mm is advised, but consult a thermal calculator or building regulations to determine the ideal depth for your specific needs.
Can I use PIR foam board in damp environments?+
Yes, PIR foam board is suitable for damp environments due to its closed-cell structure which resists water absorption. However, ensure adequate ventilation within the cavity to prevent moisture build-up and maintain optimal insulation performance.
How easy is it to cut and fit this PIR foam board?+
This PIR foam board is relatively easy to cut using a utility knife or saw. It’s rigid enough for accurate cuts, but flexible enough to manoeuvre into tight spaces within a loft or wall cavity – making installation manageable without specialist tools.
Does PIR foam board conduct electricity?+
PIR foam board has very low thermal conductivity and is generally considered non-conductive. However, it’s important to ensure that electrical wiring is properly insulated and protected within the cavity wall or loft space to prevent potential hazards.
What tools do I need for installation?+
You'll typically require a utility knife, a saw (depending on the board thickness), a tape measure, a pencil, and possibly a hand saw. Gloves are also recommended for protection during cutting and handling.
How does PIR foam compare to rockwool insulation?+
PIR offers higher thermal resistance per inch compared to rockwool, meaning you'll need less material to achieve the same level of insulation. PIR is also generally more resistant to moisture, but rockwool can be a more sustainable choice.
What is the fire rating of this PIR foam board?+
This PIR foam board has a good fire rating (Class 0) and is inherently flame retardant. It’s designed to contain flames and minimise smoke generation in case of a fire, contributing to enhanced safety within your property.
What's the typical lifespan of this PIR foam board?+
With proper installation and maintenance, this PIR foam board can last for 10-20 years. Regular inspections are recommended to ensure continued thermal performance and prevent any moisture issues.
Can I use PIR foam board on external walls?+
While technically possible, using PIR foam board directly on external walls isn't generally recommended. It’s better suited for internal loft and wall cavity insulation applications where it can be protected from direct weather exposure.