This case study explores how integrated HVAC optimisation and renewable energy design can dramatically improve the energy performance and resilience of buildings in remote or energy-constrained locations. Using advanced simulation workflows in DesignBuilder, researchers evaluated different HVAC configurations for the Bundanon Art Gallery in Australia, comparing an existing ground-source heat pump system with an optimised hybrid solution combining VRF, VAV, and water-cooled chillers. The study demonstrates how system-level integration can reduce inefficiencies often hidden in conventional HVAC designs while maintaining strict indoor environmental conditions required for sensitive spaces such as galleries and museums. The optimised design achieved substantial reductions in annual energy use and HVAC electricity demand, while also supporting the transition toward near off-grid energy operation through renewable energy integration. By combining performance simulation, energy systems thinking, and climate-responsive design strategies, the project highlights how buildings can simultaneously achieve occupant comfort, operational efficiency, and long-term sustainability in a low-carbon future.