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Warm Roof Insulation

Warm roof insulation boards deliver continuous thermal performance by positioning insulation above or between the rafters, reducing cold bridging and improving energy efficiency in your roof space. This method is well suited to loft conversions, attic rooms, and room-in-roof applications where insulation needs to follow the roofline rather than the ceiling. Our range of Polyiso boards meets current Irish Building Regulations Part L requirements for pitched roof construction.

Our Warm Roof Insulation Range

We stock high-performance Polyiso (PIR) boards designed for pitched roof rafter-fit applications.

  • Polyiso pitched roof rafter-fit boards - rigid PIR boards in 100mm thickness (and other sizes) engineered to cut and fit between rafters, enabling lower U-values in a single layer compared to traditional mineral wool solutions.
  • Foil-faced finish - integrated foil facing provides a vapour control function and reflective surface, reducing the need for a separate vapour control layer in some assemblies.
  • Compatible with breathable membranes - designed to work alongside roofing underlays and breathable membranes for a compliant, condensation-controlled roof assembly.

For a complete thermal strategy, explore our full Insulation Materials range, including complementary products like Air Tightness Insulation to achieve optimal airtightness in your build.

When specifying rafter insulation, consider the rafter depth available, the required U-value for your project, and whether a single-layer or two-layer approach is needed. For very deep rafters, combining a between-rafter board with an under-rafter layer can achieve higher performance while avoiding the need for a ventilation gap above the insulation.

Why Choose McMahons for Your Roof Insulation?

With over 190 years serving Ireland's construction industry, our team understands the technical demands of compliant roof assemblies. We carry boards in multiple thicknesses, with expert staff on hand to help you calculate quantities and specify the right product for your U-value targets. Ready to streamline your insulation orders? Set up a McMahons trade account for faster purchasing and access to trade pricing on all your building material needs.