
What are U-values, R-values and Lambda Values?
Lambda, R-values, U-values, Thermal Conductivity and Thermal Resistance simplified in one article
There are lots of important factors to consider when installing a flat roof, from thickness of materials to making the most of your budget. We can offer a number of insulation solutions to meet the requirements of your specific project.
Our Flat Roof Insulation Solutions
Material | Advantages | Products |
|---|---|---|
Vacuum Insulation Panels (VIPs) | Suited to applications where there may be a requirement for both low U-values and the thinnest possible roof build-up Problem solver for where a lack of construction depth or space is an issue Optimum performance with a declared thermal conductivity of just 0.007 W/mK Design service for your specific roof For use with most fully adhered single-ply waterproofing membranes |
Page updated 8/1/2025
Our Flat Roof Insulation Solutions
PIR | High performance insulation - thermal conductivities as low as 0.022 W/mK Fully compatible with most mechanically fixed single-ply waterproofing systems Compatible with most green roof systems Installation technique is ideal for fast track building programmes Easy to handle and install compared to some other commonly used insulants | Thermaroof TR26 - for use with mechanically fixed single-ply waterproofing Thermaroof TR27 - for use with fully adhered single-ply, partially bonded built-up felt, mastic asphalt and cold liquid applied waterproofing |
Rigid Extruded Polystyrene (XPS) | Ideal for car park decks High compressive strength withstands vehicle loads Easy to handle and install compared to some other commonly used insulants |
Rock mineral fibre | A1 Euroclass Fully compatible with most mechanically fixed single-ply waterproofing systems |
Easily compare how the use of different materials, or thicknesses of materials, can impact the overall thermal performance of a building. This helps to ensure you specify and install the right insulation thickness and set clear construction targets.





Thermaroof TR26
Flat roof insulation for mechanically fixed systemsThermaroof TR27
Flat roof insulation for adhered systemsKingspan GreenGuard
Rigid extruded polystyrene (XPS) insulationOPTIM-R Roofing System
Optimum performance flat roof insulation for where space is limitedThermaroof TR26
Flat roof insulation for mechanically fixed systemsThermaroof TR27
Flat roof insulation for adhered systemsKingspan GreenGuard
Rigid extruded polystyrene (XPS) insulation