St. Charles Old Post Office: St. Charles, MO


Client: OPO Startups, Randy Schilling
Project: Historic renovation, HVAC and controls upgrade
General Contractor: Al Droste & Sons Construction Company
Floor Area: 
10,000 sf
Construction Schedule: Six months




HVAC Engineer of Record
HVAC Contractor
HVAC Controls Engineer and Contractor


The historic St. Charles Post Office had an antiquated system of window air conditioners and old, inefficient air handlers in the attic.

We designed a new HVAC system with 11 independent zones for more flexible controls and enhanced comfort. The system minimized energy and first costs while creating a comfortable working environment for occupants.

A major challenge was to design an efficient system that did not detract from the architectural features of the historical building. We also took steps to ensure that the 100-year-old structure would support the 25-ton VVT system.

The result was an aesthetically pleasing design that retained many of the historical HVAC features, which required creative design concepts such as new electric baseboard heaters concealed behind original Victorian-era cast iron radiators.