Polystyrene foam or Styrofoam (tradename) has been most commonly used as an insulation material in the building industry for the last 30 years. But how safe is this material to use in close proximity to areas we work, live and play in? New reports suggest that in its current form its not that safe.

What is Polystyrene

Firstly what is polystyrene foam? There are two types of rigid foam, EPS and XPS. Expanded polystyrene (EPS) is a rigid and tough, closed-cell foam. It is usually white and made of pre-expanded polystyrene beads. Extruded polystyrene foam (XPS) consists of closed cells and is usually colored. EPS is more commonly used in building applications due to its better thermal resistance. Commonly available grades in New Zealand include S and H, but SL and VH are available also. For S grade the typical density is 16kg/m3 and for H grade 24kg/m3.

Production and Waste

Polystyrene foams are produced using blowing agents that form bubbles and expand the foam. In expanded polystyrene the blowing agents are usually hydrocarbons such as pentane, this may pose a flammability hazard during manufacturing or storage, however pentane has relatively mild environmental impact. Extruded polystyrene is usually made with hydro fluorocarbons which have global warming potentials of approximately 1000–1300 times that of carbon dioxide. All polystyrene foam insulation used in building insulation is treated with hexabromocyclododecane (HBCD), a persistent, bioaccumulative, and toxic fire retardant. Discarded polystyrene does not biodegrade for hundreds of years. Polystyrene can be recycled to foam insulation and things like planter boxes and toys.

Green Science Policy Institute

Fire Retardant

We don't want building materials to catch fire so it makes sense to add fire retardant to polystyrene which is combustible in its raw state. Also around much of the world the building code states a level of flammability for building materials. This is the reason all polystyrene foam insulation used in building insulation is treated with hexabromocyclododecane, (HBCD). This chemical was nominated for the first EU list of “Substances of Very High Concern” It can now be found in dust, sewage sludge, breast milk, body fluids, wildlife and the environment. About 90% of the use of HBCD is with polystyrene insulation, which is the probable source of the global contamination.

Ban on HBCD

As of the May 2013 HBCD may no longer be used in any product worldwide including polystyrene foam. This was decided by representatives from over 160 countries (including NZ) as part of the Stockholm convention. It is due to be phased out of Europe by 2015 and over the next six years for the rest of the world. Science Daily & Chemical Watch.

Moving forward

It is going to take time before the removal of HBCD trickles downs down the supply lines. Substitutes for the substance do exist, but HBCD users say more time is needed for their commercialization and are seeking authorization for certain uses in Europe. The future is uncertain in the US who is not part of the convention but they do recognise it as a risk. No fire retardant in polystyrene will mean in a lot of cases the surrounding materials will all need to be fire retardant to meet regulations.

Building Green

Alternative materials

Fortunately there are alternatives each with their pros and cons.

• Non-flame retardant EPS

• Mineral wool (stone and glass)

• Plastic foams: Polyurethane rigid foams (PUR) and polyisocyanurate

• (PIR)

• Wood fibreboards

• Cellulose

• Cork

• Hemp

• Aerogel

• Sheep's wool

• Perlite

Building with Polystyrene

From the information I have found there is no way I will be using any form of polystyrene in our house. I personally don't want to take the risk of the presence of HBCD in the polystyrene. I am likely to use either polyurethane (PUR) or polyisocyanurate (PIR) rigid foams for the application I want to use. These two options are usually a simple direct substitute for polystyrene with the benefit of much better thermal resistance.