State of Illinois Capitol, West Wing

Springfield, Illinois

Henneman Engineering was selected to lead the entire design team for the historic preservation and restoration of the west wing of the Illinois State Capitol, including the historical preservation and restoration design architects, Vinci-Hamp Architects. This is the first State Capitol to be awarded LEED Gold Certification.

The Illinois Capitol building, originally designed by Alfred Piquenard, was constructed from 1877 to 1888 and is listed on the National Register of Historic Places. The interior architecture of the west wing was restored back to its Period of Significance, which was determined to be 1868-1908. In the 1970s several mezzanines were added between floors to create additional office space; these mezzanines were removed in order to restore the original 25-foot ceilings and the ceremonial nature of these offices.  Currently, spaces in the West Wing are utilized by the Senate, containing office space on Floors 1, 2, 3 and 4 for the representatives and their assistants.

A major consideration during the renovation included reducing energy consumption by improving overall comfort and indoor air quality by way of designing new HVAC systems. Four new air-handling units were installed in the attic above the fourth floor. A new mechanical room was built above an 8-inch-deep welded steel pan that will prevent any future leaks from damaging the historic finishes below.  

In addition, each office has independent temperature control, with both supply VAV and return VAV, in order to ensure proper building pressurization control. Energy consumption was decreased through the use of energy recovery units that reclaim the heating or cooling energy in exhaust (from restrooms) and use it to preheat/precool incoming indoor air. With large windows measuring 5-feet-by-20-feet tall, Henneman Engineering integrated hot water fin-tube radiation to counter the conduction heat loss through exterior windows.

Henneman performed the mechanical, electrical, plumbing, and information technology design engineering on this award-winning LEED Gold Certified project.

This project received numerous design awards including the following:

Illinois AIA, Crombie Taylor Award for Historic Preservation, Special Recognition, 2014

Landmarks Illinois Richard H. Driehaus Foundation Preservation Awards, Project of the Year for Restoration, 2014

AIA Chicago, Devine Detail Award for the copper-clad mahogany entry doors, 2014

National American Institute of Architects, National Honor Award for Interior Architecture, 2014