Use less and less HVAC "stuff", it's that simple. OK, how you may ask....?
By learning all about where the heating and cooling loads come from in a building (building physics) and beating up architects to make them use much higher performance envelope designs, glass and wall specifications, and use exterior shading, double skin facades, etc. to reduce the loads, then reduce the loads, then reduce the loads (clear yet?).
Energy efficient (and sustainable HVAC) buildings must rely on more passive, low-tech solutions to reduce life-cycle costs, reduce maintenance requirements, reduce energy consumption, reduce "consumables" (filters, chemical treatment, replacement parts and components, etc.)
Durability of systems and building components is a big issue - sustainable long-life building systems and finishes need to be used. No more "25 year lifespan then tear it down" buildings - design a building so it can be used for many uses and occupancies during it's life.
Learn how to apply low level air supply systems like 100% DOAS Displacement Ventilation systems that basically remove about half of the room cooling loads via the stratified air layer and the physics of the low level air supply compared to fully mixed overhead air delivery systems.