Should EPS foam be given a clean bill of health in green building?

It's perhaps the best of the plastic foam insulations, but it is still a solid fossil fuel.

The best way to have our buildings use less energy is to insulate them really well. But for a long time, I have also been writing about the problems of insulating with plastic foam, even writing that Polystyrene insulation doesn't belong in green building.

There were a number of reasons, including the fact that they are full of dangerous fire retardants, that the blowing agents were serious greenhouse gases, and that they were made from fossil fuels. That's why I have often written that it is better to build foam free.

But it is hard to be totally doctrinaire about this, and to a degree it can depend on the foam. Perhaps the most benign foam is expanded polystyrene (EPS), the white stuff that coffee cups are made of. The beads are made with steam, which are compressed together with heat so there are no greenhouse gas emissions there. The manufacturers are switching over to a less toxic flame retardant, PolyFR, "a butadiene styrene brominated copolymer."

floating foam foundationLloyd Alter/ floating foam foundation/CC BY 2.0

A lot of architects and designers like the stuff and suggest that the benefits outweigh the problems. You certainly can do interesting things with it, like the Legalett people have. And recently, Simon McGuinness, an Irish Passive House architect, came up with some other interesting reasons to use EPS.


There is no argument with this; there are many valuable and necessary plastics that are made from fossil fuels.


This is true; we have to stop burning fossil fuels to cut carbon emissions.


Yes, but there are still a few problems.

fractional distillationFractional distillation of oil/via

Perhaps the biggest one is that only a really small portion of what comes out of the ground as crude oil is used for making plastics. What are they going to do with the rest? Pump it back into the ground? And if demand collapses, and the price of the stuff drops way below the price of production, who is going to pay to drill, pump, and refine? Perhaps Saudi Arabia might own the the world supply of EPS then, because it gets its oil out of the ground at the lowest cost. That will be fun.

Then, there is still the question of the components that Polystyrene is made of. Its main component is styrene, which, according to How Products are Made, is "derived from petroleum or natural gas and formed by a reaction between ethylene (C 2 H 4 ) and benzene (C 6 H 6 ); benzene is produced from coal or synthesized from petroleum.... The beads of polystyrene produced by suspension polymerization are tiny and hard. To make them expand, special blowing agents are used, including propane, pentane, methylene chloride, and the chlorofluorocarbons. [and steam]

Benzene is a known and recognized carcinogen; Styrene is a possible carcinogen and endocrine disruptor. Once it is turned into expanded polystyrene, these are all bound up and safe, unless it catches fire, in which case it turns into carbon monoxide and "a complex mixture of polycyclic aromatic hydrocarbons (PAHs) from alkyl benzenes to benzoperylene. Over 90 different compounds were identified in combustion effluents from polystyrene."

There are still good reasons to consider using EPS, and it is 98 percent air. There are not a lot of options for foundations that are as affordable or effective. It is invaluable in retrofitting old buildings, of which we have thousands. It is no surprise that it is beloved by Passivhaus architects; you can wrap a building up in a thick layer of it from top to bottom.

But it is still a solid fossil fuel, and it is not going to save the oil and gas industry.

Tags: Green Building | Insulation | passive house

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