The San Francisco Museum of Modern Art uses an innovative HVAC system that the authors say could become a new standard for museums and similar applications. Key elements of the innovative design include dual fan/dual duct variable air volume distribution systems with air economizers and centralized humidity control using direct evaporative humidifiers. The system is much more energy efficient and less expensive than traditional constant volume systems with zonal humidity control, yet it provides the same tight humidity and temperature control required in museums.