The US Capitol is an 843,600 SF, 4-story building with approximately 49 air handling units (AHUs) within the building. The majority of these units are over 50 years old and have exceeded their useful operating life. Summer Consultants designed the full replacement of four aging air handling units.

The new AHUs are variable air volume (VAV) systems serving VAV terminal units with heating coils for individual temperature control. Existing duct and piping systems were reused with modifications for the new terminal units. Each unit has additional capacity to allow humidifiers to help preserve the historic materials and artwork. Clean steam generators supply chemical-free steam for humidification. Direct digital control systems were integrated with the Architect of the Capitol’s Building Automation System Network.

The project was phased as construction could not disrupt congressional activities. System outages were limited to congressional recesses, and temporary units were used while the permanent units were being replaced.