The concrete is being used for the first time in the South Island. It was poured in the basement of the four-level building on 211 High St, which will house office, retail, and hospitality spaces.
The building is being developed by Anthony Leighs’ investment company, Portus. The sustainable concrete solution means the building’s overall embodied carbon will be lower and its carbon emissions will be significantly reduced, compared to traditional concrete and steel buildings, Leighs said.
"Concrete has a very high embodied carbon content, primarily due to the atmospheric release of CO2 during the manufacturing process but also because of the energy intensive process and the subsequent international transport to bring cement in from overseas.
"Using low carbon concrete will reduce the embodied carbon of our building by 537 tonnes of CO2 - more than half a million kilograms that would have been otherwise emitted into the atmosphere."
Leighs expects the building’s total embodied carbon to be about 80 per cent less than similar concrete or steel structures.
"The word sustainability means a lot of different things to different people.
"For Portus, we think there’s an absolute need to change the way things are done.
"We want to make sure that we don’t use more carbon than we need to. We take a long-term view so that we are doing the right thing for the future.
"For the buildings Portus is developing, we’re working hard to ensure they don’t have a lot of embodied carbon and that they are really energy efficient."
For instance, Leighs said 211 High St, the site of the historic Excelsior Hotel, is targeting a NABERS rating of at least five, which is a market leading performance.
He wants Portus to take a leadership role in efficient and sustainable buildings.
"Our expertise enables us to look at new building materials that are available internationally and understand how we can adapt them for New Zealand conditions and our building code.”
Allied Concrete national services manager Bob Officer said demand for low-carbon concrete is growing.
"The use of suitable substitute materials in correctly designed concrete mixes maintains or even improves the strength and durability of concrete, while reducing its carbon footprint," Officer said.
"With correct specification, it can be used in any building component where traditional concrete has been used previously."
