Closing the Loop: Managing Polystyrene on Building Sites

Polystyrene insulation is widely used in construction because it is lightweight – around 98% of it is air – durable, and highly effective at improving building performance, but how it is handled on site can ultimately decide its lifecycle beyond installation  

As New Zealand continues to adapt to the H1 energy efficiency requirements, insulation at slab stage is becoming an increasingly important part of designing warmer, more efficient homes.  

EXPOL modelling has shown that, when using the Calculation Method, insulation in the slab can provide opportunities to balance insulation levels elsewhere in the home while still meeting the required R-values. In some cases, modelling for a typical 180m² single-storey home has shown potential build cost savings of up to $4,400 by insulating the slab and reducing roof insulation from R6.6 to R3.3, the maximum reduction permitted under the Calculation Method.  

Because slab insulation is installed before the concrete is poured, it is also one of the few insulation elements that cannot be retrofitted later. Getting this stage right early in the build is critical for both compliance and long-term energy performance.  

However, the way polystyrene is handled on building sites plays an important role in ensuring it remains a responsible and sustainable building material.  

Simple practices that make a difference  

Managing polystyrene on site doesn’t need to be complicated. A few simple practices can significantly reduce waste and make recycling possible.  

Using EXPOL hot wire cutters rather than saws helps prevent small beads from spreading across a site. Storing insulation in a contained area and keeping it weighted down also helps stop pieces from blowing away.  

Equally important is keeping waste clean. Polystyrene offcuts that are free from dirt, tape, paint, or concrete can be easily recycled, whereas contaminated material often cannot.  

These steps not only support environmental responsibility but can also improve site efficiency and reduce cleanup time.  

Supporting builders on site  

To help builders manage polystyrene waste effectively, EXPOL supplies collection bags with product deliveries so installers can gather clean offcuts as they work.  

Builders or site managers can then arrange collection through the EXPOL Live App, which allows users to quickly book waste pickups and track collection requests.  

EXPOL also works with builders to minimise waste from the start by offering custom-cut products where required and coordinating deliveries, so insulation arrives when needed, rather than sitting exposed on site.  

Turning waste into new products  

Once collected, the material is returned to one of EXPOL’s seven manufacturing plants across New Zealand.  

Here the polystyrene is processed and recycled back into raw material, which is then reused in the manufacture of new EXPOL products. Around 75% of EXPOL products contain recycled content, and over 500 tonnes of polystyrene is recycled each year.  

Recycled polystyrene is also used to manufacture products such as EXPOL Underfloor Insulation, StyroDrain – a drainage board made entirely from recycled material, and QuickDrain.  

With the right handling on site and accessible recycling systems in place, polystyrene insulation can remain part of a circular building system, helping reduce waste while keeping valuable materials in use.