Editing Polystyrene (section)

====EPS in building construction====
Sheets of EPS are commonly packaged as [[rigid panel]]s (common in Europe is a size of 100&nbsp;cm x 50&nbsp;cm, usually depending on an intended type of connection and glue techniques, it is, in fact, 99.5&nbsp;cm x 49.5&nbsp;cm or 98&nbsp;cm x 48&nbsp;cm; less common is 120 x 60&nbsp;cm; size {{cvt|4|by|8|ft}} or {{cvt|2|by|8|ft}} in the United States). Common thicknesses are from 10&nbsp;mm to 500&nbsp;mm. Many customizations, additives, and thin additional external layers on one or both sides are often added to help with various properties. An example of this is  [[ThermaSAVE|lamination with cement board]] to form a [[structural insulated panel]].

[[Thermal conductivity]] is measured according to EN 12667. Typical values range from 0.032 to 0.038&nbsp;W/(m⋅K) depending on the density of the EPS board. The value of 0.038&nbsp;W/(m⋅K) was obtained at 15&nbsp;kg/m<sup>3</sup> while the value of 0.032&nbsp;W/(m⋅K) was obtained at 40&nbsp;kg/m<sup>3</sup> according to the datasheet of K-710 from StyroChem Finland. Adding fillers (graphites, aluminum, or carbons) has recently allowed the thermal conductivity of EPS to reach around 0.030–0.034&nbsp;W/(m⋅K) (as low as 0.029&nbsp;W/(m⋅K)) and as such has a grey/black color which distinguishes it from standard EPS. Several EPS producers have produced a variety of these increased thermal resistance EPS usage for this product in the UK and EU.

Water vapor [[diffusion resistance]] (''μ'') of EPS is around 30–70.

ICC-ES ([[International Code Council]] Evaluation Service) requires EPS boards used in building construction meet ASTM C578 requirements. One of these requirements is that the [[limiting oxygen index]] of EPS as measured by ASTM D2863 be greater than 24 volume %. Typical EPS has an oxygen index of around 18 volume %; thus, a flame retardant is added to styrene or polystyrene during the formation of EPS.

The boards containing a flame retardant when tested in a tunnel using test method UL 723 or ASTM E84 will have a flame spread index of less than 25 and a smoke-developed index of less than 450. ICC-ES requires the use of a 15-minute thermal barrier when EPS boards are used inside of a building.

According to the EPS-IA ICF organization, the typical density of EPS used for insulated concrete forms ([[expanded polystyrene concrete]]) is {{convert|1.35|to|1.80|lb/ft3|kg/m3}}. This is either Type II or Type IX EPS according to ASTM C578. EPS blocks or boards used in building construction are commonly cut using hot wires.<ref>''[http://www.ceresana.com/en/insight/products/plastics/expandable-polystyrene/ Expandable Polystyrene]'', Insight database from Ceresana Research</ref>