Plastics are under assault around the world – a byword for pollution and degradation. But what if they’re also essential to modern construction, where the manifest defects are the sustainability benefits?

The world has a problem with plastics. Taken together, all forms of plastics are the major solid pollutant in the world. Since 1950, we've made 9 billion tonnes of plastics, of which 7 billion tonnes have gone to waste. Land, oceans and air are being destroyed.

A huge insoluble problem, literally. We have microplastics in everything, including us. You would hope that such an environmental catastrophe, commensurate with carbon pollution, would bring about some action. But no.

At INC-5.2 (the inelegantly named ‘second part of the fifth session of the UN Intergovernmental Negotiating Committee to develop an international legally binding instrument on plastics) nothing was agreed. No resolution on protocols for raw materials, manufacture, use and recycling of plastics.

Plastics was the way of the future after WW2. Nylon (named to join design centres in NY and London*) was invented in 1935 and used widely from 1940, as plastics began their heyday, or rather hey-decades. Variations proliferated in the fifties, but by the late 60s the warnings in Rachel Carson’s Silent Spring were ringing out, and plastic technology fell into disrepute, if not ridicule.

In the 1967 movie The Graduate, Dustin Hoffman, as the titular character of Benjamin Braddock, is given advice by family friend Mr McGuire (played by Walter Brooke) to go into Plastics. Pulling Benjamin aside at his college graduation party, he says, "Plastics. There's a great future in plastics." An iconic line dripping with irony that resonates more strongly now.

And yet, as we face this environmental reckoning, I’m saying I like plastics.

Not because I was born in the plastics golden age of the fifties, or that I was literally weaned on plastics, or that my mum was a leading Tupperware seller (all true), but I like plastics for the very reason others don’t: it’s hard to destroy.

My guess is that some of those 2 billion tonnes that are not waste, that are not recycled, have ended up in buildings where they work in exactly the same way that plastic waste is problematic: they’re really, really long-lasting.

There are seven different kinds of plastics, and all of them appear in buildings, and all are useful. A case in point is Type 3 / PVC (polyvinyl chloride), used, amongst many things, for sewer and stormwater drainage. Long lengths of PVC pipes are far better than the terracotta or cast-iron pipes that preceded it. The use of solvent glue enabled plumbers to create far more elaborate drainage lines, previously unthinkable.

Although superior in carbon input and longevity to its predecessors, PVC has multiple issues in manufacturing pollution (all that chlorine) and disposal. Its carbon lifecycle is better, but it’s a ‘one-way’ thermoplastic, meaning all the offcuts and waste can’t be easily recycled.

Type 1 / PET (polyethylene terephthalate) and Type 2 / HDPE (high-density polyethylene) present a better option. Now used for water tanks and cold and hot water pipes, where jointing has been resolved; with some further design research could resolve jointing for drainage pipes to replace PVC. And it’s easily recycled, not downcycled.

Type 4 / LDPE (low-density polyethylene) comes as a flexible film, used for waterproofing and vapour barriers. As for others, these uses are intended to last the time of the building, not be replaced or upgraded. Likely never recycled.

Type 5 / PP (polypropylene): a solid plastic in furniture and hardware. And one that can be recycled more easily than types 3 and 4: it can be cleaned, melted into pellets, and reformed into new products like plant pots, building and automotive parts, and textiles.

Type 6 / PS (polystyrene): forms the basis of the SIPS (Structural Insulated Panels), and its development into many alternatives, including fire-rated types, is instructive in how plastics have developed beyond the 80s Esky.

Type 7 / other plastics, including Nylon, increasingly developed for textiles such as window coverings. Recycling can be challenging, using mechanical and chemical recycling methods; whilst recycled nylon offers a way to save energy and reduce waste, it is often more expensive than virgin nylon, and collection systems for post-consumer remain limited.

Plastics highlight one big issue of materials use in buildings. Many products we want to use (concrete, brick, steel, and particular plastics) have a very high carbon input and high pollution factors but have few if any alternatives for permanent installations. The very characteristic of longevity of those building materials (built on high carbon content) is that which makes them so valuable in building design. Plastic long-life is what I like and what makes it so valuable inside a building; it lasts 1000+ years.

Where I am frustrated is the diabolical problem of waste generated on building sites. The GBCA says 22% of material taken onto a building site is removed as waste, whether it be packaging, filler, offcuts or broken materials (bricks, timber, plasterboard, plaster, aluminium and, of course, plastics).

The past conundrum of one-way ‘direct to waste’ is being addressed by the ‘circular economy’ for 16% of those materials, but 6% is still waste, much of which is inevitably the reviled plastics. Look inside any site bin to see the problem.

The world has a problem with plastics. And so do I, despite how much I like using it. It’s complicated.

*A complete myth. It was named for ‘nyl-’, an arbitrary diminutive that Dupont engineers liked, and ‘-on’ as in Cotton and Rayon. But I still prefer the NY + Lon version.

Cross-Sections are Friday musings from Tone Wheeler, following on from Tone on Tuesday columns. Remember: amateurs draw plans, professionals draw sections; never at cross purposes.

Tone Wheeler

Let’s connect!