A panel on polymers

Materials World magazine
28 Jan 2020

The role of plastics in construction is discussed in this roundtable of industry experts.

Waste, recycling, challenges and solutions

NH: Plastics are used in a range of applications from windows, doors and flooring, to pipes, insulation and roofing, and there are various initiatives that exist to drive down waste. The VinylPlus voluntary commitment aims to recycle 800,000 tonnes (t) of PVC in Europe by 2020. The VinylPlus product label is also helping companies promote their contributions to sustainability.

Expanded polystyrene (EPS) is another example. There are many different applications for this 100% recyclable and lightweight material. Insulation is incorporated into walls and roofs and does not degenerate through moisture, rotting, mould, UV exposure or compaction by vibration. EPS is being recycled by businesses globally with developed collection infrastructures to support recycling efforts. The recyclate can also be used in new products including picnic benches, hangers, picture frames and sometimes for insulation in new housing.

AS: There are many uses of plastic in construction materials where it is the best option for that product or component, and we should avoid knee-jerk reactions in encouraging every sector to move away from plastics. Decisions on product switching or substitution should be based on the required function for the material and a move to lower embodied carbon products – both must be integral for us to responsibly specify our products.

That being said, there is one primary source of plastic that ends up as waste in construction sites and that is plastic packaging and wraps. This is a waste that should be targeted in the sector and requires purchasers of materials to exercise their buying power to challenge their supply chain to find alternatives to the single-use packaging problem. Reusable alternatives exist and have been used on multiple sites. However, it tends to only be on high-profile projects or those that have high environmental performance requirements.

The construction sector is not particularly motivated to either find solutions to plastic waste it creates or be the solution for other sectors. There are, however, examples of where plastic recovery into other products is possible, such as recycled plastic decking boards and park benches, but these have had limited uptake thus far. There is also MacRebur, which takes plastic waste from other sectors and turns it into bitumen replacement for roads.

Packaging is the main source of plastic waste that should be addressed in the short term, as this typically makes up to 25% of a mixed waste skip content by area. In the long term, all plastic products are likely to become a problem for the sector eventually and end up in landfill, as there is rarely a separate plastic waste skip on construction sites. In order to prevent this from occurring, there needs to be increased focus on whole-life considerations when specifying materials, and increased responsibility on the manufacturers for the end-of-life destinations and increased segregation of the materials to improve recovery.

BD: Enhancing the durability and quality of plastic products are the most effective ways to drive down plastic waste. This is a constant target in such a competitive market. When products eventually reach the end of their useful life, the aim should be to valorise the waste as well as possible – recycling where possible, and energy recovery if recycling is not eco-efficient. The largest plastic applications in construction are pipes, insulation, window profiles, cables and flooring, of which many are made out of PVC. There is currently a voluntary commitment to boost recycling of PVC products.

The polystyrene insulation materials sector is also investing in recycling technologies. Today, many used EPS fish boxes are being recycled into extruded polystyrene (XPS) insulation materials. The EPS value chain has already come together to invest in a new recycling technology designed to upcycle used polystyrene insulation foam back into new insulation materials with the removal and subsequent destruction of the persistent organic pollutants flame retardant hexabromocyclododecane, or HBCD.

SC: The question of plastic waste in the construction sector was discussed at the Healthy Buildings Expo in 2019 with a wide range of industry experts and academics. The organistion has since formed a plastics working group to help us work through the complexities of how we can use less plastic and switch away, while avoiding any unintended consequences.

Plastics are ubiquitous in buildings, however, alternatives to products are available. One of our plastic working group members, Accord Housing, has launched a zero-plastic development, intending to complete 12 plastic-free houses in 2021 with the CHARM project. Aluminium rainwater goods will have a maintenance-free lifecycle of 100 years and if the aluminium is smelted using renewable energy, such as in Norway, the embodied carbon is broadly similar to plastic, with a product that has a much longer lifecycle. In addition, companies such as Mace have launched initiatives like the Time to Act campaign.

We need to make the distinction between packaging and single-use plastics and plastics that are contained in products, which will have a much longer lifespan. We also need to ensure the quality of information presented to the industry is better too. For example, in our research into the impact of uPVC windows and doors, we have been unable to ascertain the actual recycling rates – which we believe to be very low (3-20%).

Benefits of plastics and innovation

BD: Cables are very important in building and construction. Cable insulation is almost exclusively made from plastics and it would be difficult to replace this with other materials. There are alternatives for pipes and window frames, but plastics are used because they have specific advantages such as easier installation and fewer leaks in the case of pipes, better insulation and lower maintenance in the case of window frames.

NH: Plastics aid the move from sites to factories for modular construction. For example, a house can be built in five days using lego-style bricks – they are fire resistant and 30% cheaper than conventional bricks. In terms of innovation and new materials, a range of polymeric composites and glass reinforced materials is continually being developed and utilised.

While traditionally made from asphalt, recycled plastic roads are stronger and cheaper. Successful trials in Scotland, Cumbria and the West Country have already taken place, and researchers from Bath University have also found a way to reuse waste plastic in concrete. 10% of the sand in concrete can be replaced with plastic which could save over 800 million tonnes of sand.

Future plastics use and smart construction

BD: Smart construction is expected to use more modular elements produced and pre-assembled in factories, and brought to the construction site just before being installed. This will reduce costs further, speed up construction and provide better working conditions and plastic materials well-suited for such smart production.

AS: The emerging movement to tackle our plastic ‘addiction’ in society has yet to permeate the construction sector in a significant way. The age of intelligent buildings must be embraced to help us overcome this malaise and we must use our digital technologies to approach the problem in a similar way to how we have tackled asbestos.

Now I’m not saying plastic is in the same hazardous league as asbestos, but the approach taken by the built environment industry to focus on a material type of interest i.e. asbestos, shows that the sector can be mobilised – with a little help from legislation – to make the appropriate decisions. The approach to asbestos has been hampered over the years due to a lack of building information in a useful format. This will not be the case if we embrace the digital capabilities of our new intelligent buildings and models.

We can know exactly what is in our buildings – who made it, where it is, what condition it is in, what are the optimum maintenance requirements to maximise its lifespan, and what the best ways to reuse it or recover it for use in other products are. We just need to be motivated to use the tools in this way.

SC: We do not advocate a plastic-free built environment future. However, we believe that wherever possible, the use of plastic products in construction should be confined to specialist, high-value, low-volume application areas such as binders, seals, tapes, gaskets and services. Basically, where the use of plastics can significantly enhance the overall performance of the building and where alternatives are not readily available.