Grocon has unveiled plans to refurbish the heritage listed Legion House in central Sydney as a carbon neutral building, designed to be disconnected from the mains electricity grid.

Legion House, which dates from 1902, is part of the 161 Castlereagh Street project, where a premium office tower is currently being developed and built by Grocon for tenants ANZ and Freehills.

Grocon CEO Daniel Grollo said it was planned the refurbished Legion House would be one of the most sustainable buildings in the world.

“Following on from Pixel in Melbourne, which is currently the greenest building in Australia as rated by the Green Building Council, Grocon is keen to take the next step,” he said.

“In an Australian first for a CBD office building, we plan to disconnect Legion House from the mains electricity grid, with the surplus power created to be supplied to the 161 office tower.”

Legion House will be the new corporate head office for Grocon in Sydney from 2013.

Mr Grollo said: “We have been working with sustainability consultants Umow Lai and architects FJMT on this project, as well as with investment partner GPT Wholesale Office Fund (GWOF) and long term tenant, the St James Ethics Centre,” he said.

The work will also include an extension incorporating two new office floors designed in consultation with heritage architects, Weir and Phillips. The internal lift and stair will be relocated to the exterior of the building, creating a new visually interesting laneway entry.

A key feature of the proposal is that the St James Ethics Centre will be provided with a modern 6 Star Green Star open plan office, which Grocon and GWOF plan to fund.

Mr Grollo said the building of the new Legion House would utilise “green” construction materials and methods, including sustainable bamboo and timber elements.

“Water saving initiatives including air cooled chillers and vacuum toilets will be included and the building will be water-balanced.

“We are keen to future proof this project to deal with what will become an increasingly carbon constrained economy. We will create the on-site renewable power for the building through biomass gasification technology.”

Mr Grollo said this type of technology was well known overseas but had not been used before in Australia.

GPT CEO and Managing Director Michael Cameron said Legion House marked the next sustainable GPT investment to appear on the Sydney skyline, joining iconic buildings such as the MLC Centre, a 1978 5 Star NABERS Energy rated tower, through to the 6 Star Green Star workplace6, which features tri-generation and a black water treatment plant.

“Legion House will set a new benchmark for the creation of sustainable city precincts,” he said.