Why XPS insulation is a must for inverted roofs

XPS insulation inverted roof


Inverted roofs require some extra care and attention in terms of sealing, connections and finishing, among other things. Moreover, XPS is the ideal insulation type for inverted roofs. This article explains why that is.

The insulation layer in an inverted roof

With an inverted roof, the insulation layer is installed on top of the waterproofing material. An external insulation system like this involves the risk of water getting trapped underneath the insulation material. ROOF 115, a waterproof and vapor-permeable geotextile, ensures that the rainwater runs off and is directed to the outlet locations. Given that the insulation is inverted, the water absorption performance is critical. Being a closed-cell product, XPS is ideal for this type of application.

Inverted roof insulation requirements

Inverted roof insulation must be able to take a beating. Because the roof is subject to the effects of sun, rain and wind, the material must …

  • absorb only a limited amount of water
  • not be affected by the freeze-thaw cycle
  • have a high heat resistance
  • have a high compressive strength
  • have great dimensional stability to withstand moisture and temperature fluctuations

XPS for proven performance on inverted roofs

The above properties point to just one conclusion: XPS meets all the conditions for use on an inverted roof. It has a closed cell structure and therefore offers many advantages. It is not only moisture-proof, but also resistant to mould. XPS boards are lightweight, easy to apply and have a very high compressive strength, making them easy to cut. At SOPREMA, we specifically recommend using XPS SL boards for inverted roofs. For roofs with a high load, such as rooftop car parks, we produce XPS 500 and XPS 700.

Combine your XPS insulation with ROOF 115, made of non-woven polypropylene. This product ensures rainwater run-off is directed to the outlet points. ROOF 115 is a critical layer in ensuring that the insulation performs according to the U-value calculation when calculated according to the latest industry guidance.

SOPREMA’s XPS insulation boards are 100% recyclable and are made using climate-friendly CO2 technology. The BREEAM independent certification ensures that specifiers can score BREEAM points as a result of specifying EFYOS XPS insulation. XPS is also approved by the Green Guide to Specification.

Do you have any questions about XPS insulation for inverted roofs? Please don’t hesitate to contact our waterproofing and insulation experts.