Insulating Concrete Formwork (ICF) is a kind of formwork system that is left in place to become part of the building. In New Zealand, ICF block systems are widely available and are being used more and more frequently in both commercial and residential construction.
The forms are typically made of polystyrene filled in with a reinforced concrete core, providing all the structural capacity of the wall along with great insulation. They’re also light and fast to build with, reducing cost and effort right from the start.
According to Concrete NZ, the other main advantages of ICF systems are that the blocks have a long life expectancy, are extremely strong once filled, and it’s relatively easy for services to be concealed in the polystyrene layer. This helps when services are being retrofitted later as well, saving on waste and labour. Blocks can be cut to any shape, enabling a wide range of uses including multi-storey developments.
They can also be a more sustainable option. A study commissioned by the Portland Cement Association concluded that homes built with ICF exterior walls offer heating and cooling cost reductions of up to 50 percent when measured against comparable wood-frame houses, reducing energy use over the lifetime of the building. They typically carry an insulation (R) rating of more than 3.7, which is almost twice what’s required in New Zealand.
The biggest downside is the challenge of recycling the expanded polystyrene if there’s waste to be disposed of, as disposal options are limited in some areas. Mitre 10 offers polystyrene recycling for non-commercial use at selected stores through a partnership with EXPOL, and we’re currently working on a trade solution. Meanwhile,
Green Business HQ has a list of businesses who offer commercial expanded polystyrene recycling services throughout New Zealand.
There are also products designed to minimise waste, for those who are looking for greener options. For example, ECO-Block products recycle any polystyrene waste during the manufacturing process, adding it back into the product.
QuickSet uses 100% recycled plastic in its click-together stirrups and bases that brace the formwork.
Altogether, for ease of construction, longevity and longer-term sustainability, ICF is well worth considering for any new build. Just make sure you check with your supplier that their ICF has an appraisal for New Zealand requirements before ordering, as not all products do.
