A heritage office building in North Sydney had a 400 kW chiller approaching end of life and a 290 kW gas boiler, with no outdoor plant space other than the pad the chiller stood on. Design Better replaced both with two 200 kW 4-pipe heat pumps in a seasonally staged programme, removing 100% of Scope 1 emissions and adding redundancy to both heating and cooling.
at a glance.
Client: Local Council
Building: Heritage office building, North Sydney
Plant removed: 400 kW chiller and 290 kW gas boiler
Plant installed: 2 × 200 kW 4-pipe (simultaneous heating and cooling) heat pumps
Outcome: 100% of Scope 1 emissions removed; redundancy on both heating and chilled water
Role: Concept, design and tender documentation, construction phase oversight
Year: 2026
the constraint.
Heritage listing ruled out new plant locations and visible changes to the building. The only external plant space was already occupied by the chiller, so there was nowhere to put heat pumps while the existing plant kept running.
what we did.
The replacement was staged around the seasons. The chiller will come out in winter, when cooling demand is lowest, and the heat pumps are to go onto its pad; chilled water will be commissioned over winter while the gas boiler stays in service for heating. In summer the boiler will be decommissioned and the heat pumps connected and commissioned on heating hot water through the shoulder period. The building will never be without heating or cooling, and no temporary plant was needed.
outcome.
One pair of heat pumps now does the work of two separate plants. Gas is gone, Scope 1 emissions are zero, and because either unit can carry heating or cooling, the building has redundancy it never had with a single chiller and a single boiler.
lesson.
Engage with heritage early. The approvals pathway, not the engineering, sets the programme on a listed building.
