"Ath had a hugely engaging personality - he was smart, funny, generous and sometimes outrageous. He had a huge impact on Wellington, on New Zealand architecture and on his profession, and he had friends all across the country, and all around the world."
Sir Ian was a former president of the Institute of Architects and a recipient of the institute's gold medal for career achievement.
Less than a month ago, his knighthood was announced in the New Year's Honours.
Ms Pennington said the Civic Square service would be an opportunity for some of the people who knew Sir Ian best to talk about his career, and for people from all walks of life to pay their respects to the memory of an accomplished architect and larger-than-life personality.
"The Institute of Architects would like to thank the many groups and individuals who have offered their support for the memorial service. In particular, we'd like to thank Wellington City Council for its help in staging the service."
It was expected that displays featuring Sir Ian's projects would be set up in the City Gallery and Wellington Library to accompany the memorial service, Ms Pennington said.
"It's most appropriate that Sir Ian should be remembered in the heart of the city, in the square which he helped design, and in the library which was one of his most notable buildings."
Other significant Wellington buildings designed by Sir Ian Athfield and his practice included First Church of Christ Scientist, Telecom House, Massey University Te Ara Hiko College of Creative Arts, the new Dowse Art Gallery, and his own house, which he built over the course of four decades.
The redeveloped Wellington waterfront was another Athfield project, as were the new apartments on the former Overseas Passenger Terminal.
