Inverted Roofing Insulation

The table below shows the thickness of the Inverted Roof Insulation Boards required to achieve a specific target u-value. The calculations take into account a correction factor as specified in ETAG 031 to compensate for the short term cooling effect of cold rainwater reaching the waterproof layer. Calculations are based on an inverted roof construction of 150mm reinforced concrete deck, hot melt waterproofing, EPS inverted roof insulation, filter membrane, drainage factor ƒx = 0 and average rate of precipitation (P) ≤3.000 (mm/day).

To complete the Inverted Roof Insulation system a finish is required in order to prevent flotation, wind uplift and UV degradation. Several finishing options are available depending on the final use of the roof. Below are typical examples of the different options and the material build ups.

Gravel Ballast Finish – Cost effective and quick to install, this finish is mainly used on untrafficked roofs. The gravel ballast is placed directly over the Filter Membrane to cover the entire system with a minimum thickness of 50mm.

Paving Slab Finish – Provides a strong, durable and accessible surface making it an ideal finish for roof terraces and balconies. Paving stones are usually supported on adjustable bearing spacers to allow a completely flat area on sloping roofs.

As part of the Inverted Roofing Insulation System we offer a special Filter Membrane. This is a type LR Non-woven spunbonded polypropylene vapour permeable water reducing membrane. This is used as a filter layer and water control layer between the insulation and the roof finish (ballast or paving) within Inverted Roof systems. Some of the physical properties are shown below, full technical details are available on our website. * Takes into account 300mm overlap during installation.

Expanded Polystyrene is non-toxic, non-irritant and odorless, making it completley safe to handle. It can be cut on site using a fine tooth saw or a hot wire cutter.

Expanded Polystyrene is rot proof, Expanded Polystyrene is not affected by bacteria, moulds or fungi, and will not provide nutrient value for insects or vermin. Expanded Polystyrene does not lose any performance over time and will remain an effective insulation for the life of the building.

Expanded Polystyrene should be kept away from hydrocarbons, solvents and volatile substances, however, Expanded Polystyrene is compatible with most chemicals and materials found in common construction environments. For more information, a full list of chemical behaviours is available on our website. Expanded Polystyrene should not come into contact with any PVC cables. This is to avoid plasticizer migration which causes PVC cables to become brittle and fragile. Any PVC cables should be protected within a suitable conduit or with a suitable air gap

The boards are delivered to site in packs, wrapped in polythene. They must be protected from prolonged exposure to sunlight and UV-rays. Packs should be stored either under cover or protected with opaque light-coloured polythene sheeting. The products must be stored fully supported and flat on a firm, level base, to prevent bowing. Care should still be taken to ensure EPS doesnt come into contact with any source of ignition.

Expanded Polystyrene will achieve reaction to fire Euroclass F. However, the classification achieved when installing in a building will be considerably better. We also supply FRA grades which contain a Fire Retardant Additive and achieve reaction to fire Euroclass E.

Expanded Polystyrene does not contain HFC’s, CFC’s or HCFC’s. Expanded Polystyrene has a Global Warming Potential (GWP) of zero and a low O-Zone Depletion Potential (ODP). Our Expanded Polystyrene is 100% recyclable. For more information on our recycling policy, you can contact our office to find out more.