Auckland Council is recladding its high-rise headquarters in the central city with aluminium composite panels - a building material linked to the Grenfell Tower fire disaster in London.
The Alucobond PLUS panels being used on the 31-storey tower conform to the New Zealand Building Code and fire safety standards.
However, the panels are more combustible than an alternative product, Alucobond A2, which is classified as 98 per cent non-combustible in some countries. Alucobond A2 is a requirement for use in certain European countries like Germany.
The lightweight aluminium composite panels(ACPs) are being installed to replace heavy granite slabs as part of $31 million of cladding repairs on the 26-year-old building.
Auckland councillor Chris Darby said he was a little concerned that council chose the lesser of the two Alucobond products to reclad its Albert St headquarters.
Senior council finance and property manager Kevin Ramsay said the council and its contractors had followed the requirements of the building code, which defined ACPs as a finish on buildings with the ability not to spread flames and by the amount of smoke production and heat released.
Alucobond PLUS passed various tests and was in the best classification for building materials, he said.
Ramsay said Alucobond PLUS was selected because installation on the Albert St building is a rain screen arrangements over concrete facade panels, ranging from 120mm to 1200mm thick. The vertical concrete panels were well separated from each other and make up 28 per cent of the building facade, he said.
ACPs are made from two sheets of thin aluminium bound to a core of insulating material.
According to a guide on their use from the Ministry of Business, Innovation & Employment(MBIE), "ACPs are combustible" and range from 100 per polyethylene (plastic) cores that are readily combustible and melt at relatively low temperatures to products with a core of mineral fibre, which are less combustible or have limited combustibility.
Alucobond PLUS has a mineral filled polymer core. Alucobond A2 has a mineral filled core with polymer adhesives.
Jan Gouws, whose Auckland-based company Kaneba imports Alucobond panels, said Alucobond PLUS is used widely in New Zealand for commercial and residential buildings.
He said Alucobond A2 was rarely used because customers consider it "too expensive" at about $25sq m more than about $80sq m for Alucobond PLUS.
"Alucobond PLUS meets the requirements of the New Zealand Building Code when used as part of a properly designed cladding system. Spread of flame is one of the NZBC criteria when selecting the appropriate version of Alucobond," Gouws said.
The council did not say it was installing ACPs on its headquarters when it held a press conference last Friday about the safety of Auckland buildings.
Alucobond PLUS meets the requirements of the New Zealand Building Code when used as part of a properly designed cladding system
A council spokesman told the media it had found two buildings clad with a flammable plastic core similar to that used on Grenfell Tower. The buildings are being reclad for weathertightness issues, rather than fire safety concerns. Council is looking into the cladding on 90 high-rise buildings in the wake of the London fire, the spokesman said.
Ramsay said the recent talk about ACPs in Auckland had focused on existing buildings. The installation of the new cladding had only started in the recent weeks and was being done in accordance with the building code, he said.
New Zealand Fire Service fire risk management national adviser Peter Gallagher said the fire service does not comment on individual building products or the testing of products.
The independent testing authority was BRANZ and MBIE approved products based on BRANZ assessments, he said.
Data from the World Fire Statistics Centre shows New Zealand has 8.3 fire deaths per million people, slightly higher than 7.6 for the United Kingdom and much higher than Australia (4.7). Switzerland has the lowest death rate (2) and Finland the highest (18).