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Last edited 13 Nov 2017
Fire behaviour of expanded polystyrene
EPS has many benefits to offer the construction industry including its super lightweight composition, sustainability credentials and of course its excellent thermal performance. These unique properties make it the ideal insulation product for many buildings, but what about its fire safety credentials?
Classification of EPS:
- Fire Rated EPS = Euroclass E
- Standard EPS = Euroclass F
The CPD requires a performance based approach for the whole building or the building elements i.e. walls, floors or roofs. To meet this requirement manufacturers can declare the reaction to fire classification as part of a full system or building element. This classification can be added to the product label just outside the CE marking box.
The main properties to determine the Euroclass for a specific product is its non-combustibility, ignitability, flame spread, calorific value as well as the development of smoke and burning droplets. Depending on the outcome of the various properties, the product is assigned a fire classification as shown below.
External Wall Insulation system designers typically carry out independent fire tests on complete wall elements with EPS insulation and declare the reaction to fire typically as Euroclass B-s1, d0. This certification satisfies current building regulations and is a good rating which is comparable to other similar insulation materials used in whole building elements.
 Design considerations:
 Covering material:
- Render on an external wall insulation system.
- Concrete screed on a floor.
- Plasterboard on a wall or ceiling.
Correct construction details are important in preventing the spread of fire. Suitable fire breaks should be designed into any building at floor levels and at compartment walls. Whilst the design of these details is vital, the quality of installation is equally as important.
1 - FRA EPS EWI Board
2 - Typical Fire Rated Fixing
3 - Non-Combustible Fire Barrier
4 - Typical render finish
Most floors will be covered with a structural topping which is classed as non combustible.
1 - Non-Combustible Screed
2 - EPS Flooring
3 - Non-Combustible Concrete
Only specify fire retardant EPS insulation manufactured in accordance with: BS EN 13163 : 2012+A1:2015 Thermal insulation products for buildings - Factory made expanded polystyrene (EPS) products and BS EN 13501-1:2007+A1:2009 Fire classification of construction products and building elements.
Fire retardant EPS when exposed to ignition energy behaves by shrinking away from the heat. When it is ignited by the heat source, it will self-extinguish if the heat source is removed therefore not readily supporting fire.
When designing a building, fire safety is one of the key requirements but the reaction to fire behaviour of naked EPS insulation is misleading since it is the covering material which determines the building element fire behaviour. The EPS is only affected by fire after this covering material fails by which time the whole building or compartment is unlikely to be saved from total loss.
 Related articles on Designing Buildings Wiki
- Celotex insulation.
- Eps recycling.
- EPS Geofill Civil Engineering - Case Study.
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