Does all Inverted Roof Insulation achieve the same U-value at a given thickness?

In the past this may well have been the case. There were fewer manufacturers, using similar blowing agents and much less challenging U-value targets.

However, environmental pressures led to a required change in blowing agent technology from CFC’s and HCFC’s to Recycled CO2, which although greener and cleaner led to higher lambda values and consequently greater thickness required to achieve the same U-values as before.

Pressure continued, with ETAG 031 and other regulatory legislation leading to the assessment of the effects of rainwater cooling and freeze thaw cycles. The industry began looking at design lambdas which addressed these issues and through new technologies such as the introduction of water reducing layers, the lamination of thinner more thermally efficient boards, the introduction of infrared blockers and the addition of new constituents such as graphite manufactures, over time, achieved thinner solutions.

Which leads us to the latest and perhaps greatest innovation in Extruded Polystyrene (XPS) technology to date. Ravago, have launched RAVATHERM XPS X 300 SL ULTRA. Developed to deliver improved thermal performance and therefore significantly thinner solutions. With specific board sizes manufactured to achieve given U-values in the most efficient way, Ravago have moved away from the arbitrary thicknesses of the past.

So what does that mean to our original question: Does all Inverted Roof Insulation still achieve the same U-value at a given thickness?

If we look at 0.15 W/m2K as the most commonly specified U-value for inverted flat roofs, RAVATHERM XPS X 300 SL ULTRA achieves this target in only 175mm, 30mm thinner than Ravago’s own previously best solution (RAVATHERM XPS X 300 SL) and almost 50mm thinner than most other XPS Solutions and at 0.1 W/m2 K RAVATHERM XPS X 300 SL ULTRA is only 260mm (2x130mm), 60mm thinner than most alternative XPS solutions and up to 95mm thinner than most EPS (Expanded Polystyrene) Solutions.

Then the answer is now emphatically NO!

With a design lambda of 0.028 W/mK and U-value targeted thicknesses, Ravago’s new RAVATHERM XPS X 300 SL ULTRA has radically changed how we look at product comparisons. We can no longer make price comparisons based on cost £/m3, we now need to look more closely at price £/m2 of any product to achieve any given U-value!