How green is polystyrene?
[Much of the information from this post is adapted from Environmental Building News.]
When it comes to buildings, "green" and "energy efficient" are often used synonymously. There are, if you ask me, a number of problems with conflating these two term, at least one of which will, hopefully, become clear in this discussion of foamed polystyrene insulation.
Insulation is a key component of temperature regulation in buildings and the most common type of insulation out there [at least in North America] is foamed polystyrene. It comes in two forms: Expanded Polystyrene [EPS] and Extruded Polystyrene [XPS]. EPS is slightly less expensive, but at R-5/in. XPS has a better thermal performance. XPS also has excellent moisture resistance and high compressive strength; it is consistent, relatively cheap, and easily available, making it very popular for use in insulating walls, roofs, and exterior foundations.
So what's the problem?
Both XPS and EPS contain a chemical additive [and flame retardant] called brominated flame retardant hexabromocyclododecane [HBCD or HBCDD in Europe.] According to the European Chemicals Agency, this chemical is "of very high concern" because of possible toxicity and classification as a "bioaccumulative." Additionally, as we all know by now, Styrofoam isn't biodegradable. If you don't think this is a big deal, maybe it's because you don't know about the "Great Pacific Garbage Patch," the 3 million ton mass of plastic waste floating somewhere between California and Hawai'i.
Basically, XPS and EPS are Styrofoam that's been coated with a toxic flame retardant called HBCD. The negative health impacts of HBCD are still being debated but contenders include: neurodevelopmental problems, negative impacts on the functioning of the liver, thyroid, and reproductive systems, and status as the ultimate [chemical] evil: carcinogen.
If that's not enough to make you worry, how about this: Polystyrene [a polymerized form of styrene] is made by combining ethylene [which comes from natural gas or petroleum] and benzene [made from petroleum] to form ethylbenzene, which is then dehydrogenated to make styrene, releasing benzene [a known human carcinogen] and toluene [a developmental toxicant] as byproducts. There's also significant evidence linking Styrene to Asthma incidence and endocrine disruption. Yum!
So, you get the idea, right? EPS and XPS are, admittedly, extremely efficient insulating materials, produced by combing petroleum with toxic materials - contributing to buildings that are energy efficient, but not necessarily healthy, and highlighting the problem with judging "greenness" on functionality alone.