31 recommended ECM and O&M projects for the U.S. Capitol Building were developed through the process of a Level 3 Energy Audit, where the building energy usage was compared to metered energy data in a complete energy model. Estimated cost to implement the recommended projects was $10.5 million with an associated savings of $3.2 million annually. Two-thirds of the construction cost and annual savings were attributed to the building-wide replacement of the pneumatic HVAC controls with Direct Digital Controls (DDC), which includes replacing the controls on air handling units, reheat coils, and space (zone) temperature sensors. High energy use in the building was correlated to the older controls that created a large degree of simultaneous heating and cooling. Significant HVAC system energy savings opportunities were also associated with resetting cooling coil discharge temperatures to minimize reheat energy use and improve control of exhaust fans.

Of the 31 recommended ECMs, many also involved lighting retrofits and controls. Approximately 50% of the lighting savings were realized from the conversion of inefficient lighting, such as incandescent, to more efficient lighting, such as LED. Another 40% of the lighting savings were associated with the use of occupancy sensors that turn lighting fixtures off when not needed. The remaining lighting savings come from reducing the wattage in over-illuminated spaces with more efficient fluorescent lamps and ballasts.