Plastic foams for thermal insulation have been available for more than 70 years. Extruded polystyrene (XPS) was introduced in 1943, followed by expanded polystyrene (EPS) in 1950, and polyisocyanurate (polyiso) in 1954.
The April 2015 issue featured an article entitled “Selecting Polystyrene Foam Where Moisture Exposure Occurs.” The public relations manager at the EPS Industry Alliance wrote to the magazine, wanting to comment on what he called “several inaccuracies and omissions” he felt slanted the piece in favor of extruded polystyrene (XPS) at the expense of expanded polystyrene (EPS).
The purpose of building insulation is to reduce heating and cooling energy consumption, contribute to durability, and provide comfort for occupants. However, there are numerous locations where significant exposure to moisture—which severely affects a material’s thermal performance—occurs, such as in protected membrane roofs, vegetative assemblies, below grade, and frost-protected shallow foundations (FPSFs).
The December 2013 issue of The Construction Specifier included the article, “Out of Sight, Not Out of Mind,” by Ram Mayilvahanan. The feature focused on expanded polystyrene (EPS) and included reference to a particular industry study. In response to the piece, we recently received the following e-mail from John Ferraro, executive director of the Extruded Polystyrene Foam Association (XPSA):