Some of the major projects he had been involved in - in Glasgow in Scotland, Hastings in England and Bendigo in Australia, had been successful precisely because they had retained their heritage buildings, he said.
He is heavily involved in the Christchurch rebuild, and says one of the most difficult things about that project was that in the earthquake and ensuing demolitions, a lot of heritage was lost.
"It's impossible to replace it. Your opera house is unique and both buildings should be saved. Demolishing them would be a disaster."
On the development of plans for Civic Square, Mr Lunday urged the IWP to "be bold". He said buildings in the square needed to have "multiple faces" on to the surrounding streets, to encourage people to use them but he urged patience.
"Don't risk the long-term success for the sake of a couple of months. Once you've made the right decisions, you can claw that time back during the process."