Central ventilation systems in multifamily buildings are a vital building system with significant implications for energy, sustainability and occupant health and safety. In this session, we compare and contrast the building stock in Boston and NYC and explore a variety of techniques for restoring and improving these systems. We consider how to evaluate candidates and how to structure the project from commissioning back through design to achieve results based on optimizing energy savings, complying with finance-related and building owner requirements, and how to get these things to just plain work. We build on lessons learned from 10 years’ experience and offer practical recommendations for designing and constructing both new and retrofit systems.