Does Polystyrene Insulation Belong in a Green Building?

In an August 2009 feature article entitled, “Polystyrene Insulation: Does It Belong in a Green Building?,” Environmental Building News executive editor Alex Wilson says there’s enough health and environmental evidence to suggest that the answer is “No.” Wilson describes various problems with polystyrene insulation, including the hazards of a flame retardant used in it, and recommends that alternatives be used when doing so will not compromise a building’s energy performance.

“All insulation materials are green on one level,” Wilson points out, “because they play a huge role in reducing building energy consumption.” But polystyrene insulation may not be the best choice from a health and environmental standpoint. First, the plastic from which the insulation is made (polystyrene) is produced from some fairly toxic chemicals—benzene is a known human carcinogen, while styrene is considered an endocrine disruptor, asthma inducer, and possible carcinogen.

Second, all polystyrene building insulation—both extruded (XPS) and expanded (EPS)—contains the brominated flame retardant HBCD, which European agencies have labeled both a persistent organic pollutant and a persistent bioaccumulative toxin. Despite significant effort, industry has so far been unable to find a substitute flame retardant that will impart fire-resistant properties without adding toxicity risks.

“Polystyrene is the least green of common insulation materials,” Wilson writes in the article, which outlines several ways in which polystyrene insulation could be replaced with alternative materials or otherwise be made safer in building applications. In an accompanying editorial in the same issue, Environmental Building News argues that we should look for alternatives: “EBN recommends that use of polystyrene insulation made with HBCD should be avoided in buildings as long as doing so will not sacrifice energy performance or durability.”

One solution to the HBCD flame retardant concern would be for manufacturers to offer XPS and EPS for below-grade applications that do not contain any flame retardant. “A lot of people assume that all polystyrene insulation has to be flame-retardant-treated,” says Wilson, “but that’s not the case.” Because there is no risk of fire underground, building codes allow non-treated foam insulation to be used as long as there is at least one inch of concrete or masonry between the insulation and the building interior. “The challenge will be to convince manufacturers to offer products exclusively for below-grade installations,” according to Wilson.

Another option is to substitute safer insulation materials for XPS or EPS. The article addresses both above-grade and below-grade options. “Rigid mineral wool performs very well on exterior foundation walls, and it is being used beneath concrete slabs in Europe,” says Wilson. Spray polyurethane foam is also being used in Canada and the northern U.S. for these applications.

“Polystyrene Insulation: Does it Belong in a Green Building?” was published in the August 2009 issue of EBN. Access to the full article requires a membership in BuildingGreen.com, but key points can be found in Wilson’s blog on the topic.

* * *

BuildingGreen, LLC, founded in 1985, is the nation’s oldest company devoted to green building information. BuildingGreen’s flagship newsletter, Environmental Building News (EBN), has been serving the building industry with objective, timely, and useful information about green building since 1992. BuildingGreen’s other publications include the GreenSpec® Directory of green building products, GreenBuildingAdvisor.com, covering residential green building and remodeling, and LEEDuser.com, a new website for teams going through the LEED certification process. For information, visit www.BuildingGreen.com.

—30—