ST. LOUIS, MO – Wiegmann Associates won a Contracting Business Design/Build award for their work on the St. Charles Old Post Office historic renovation. The HVAC upgrade was part of a project to convert the St. Charles Old Post Office located on Historic Main Street in St. Charles into OPO Startups, a state-of-the-art co-working technology incubator for digital startup businesses. Wiegmann transformed the outdated HVAC systems of the historic, 10,000-squre-foot building and installed automation controls. The general contractor was Al Droste & Sons Construction Company.

“We are proud to be honored for this unique historic renovation project,” said Steve Pearce, Vice President of Business Development for Wiegmann Associates. “This project challenged us to design a state-of-the-art efficient HVAC system while retaining the architectural features and core structure of this classic 100-year-old historical building.”

The Contracting Business Design/Build Awards honor the finest examples of commercial Design/Build HVAC mechanical systems installations across the U.S. The key element evaluated was the HVAC contractor’s ability to take a leading role in providing the ultimate in HVAC comfort and system performance for the benefit of the customer.

The St. Charles Old Post Office’s existing antiquated HVAC system consisted of window air conditioners and outdated, inefficient air handlers in the attic, which resulted in inconsistent heating and cooling. The new Wiegmann-designed system features 11 variable air volume zones for improved flexibility in controls and individual comfort levels throughout the space.

The team was challenged to fit and conceal new, significantly larger HVAC equipment and ductwork into small spaces without knocking down walls. The final design actually retained many of the historical HVAC features. For example, new electric baseboard heaters were concealed behind existing Victorian-era cast-iron radiators.

Wiegmann Associates is a St. Louis-based mechanical contractor serving the commercial, industrial and institutional markets, and a national leader in design/build HVAC projects. Since 1995, Wiegmann Associates has engineered and installed innovative, energy-saving and cost-efficient HVAC solutions and automation controls for clients in a wide range of industries. Wiegmann also provides 24-hour preventative maintenance programs and service in the St. Louis region. For more information, visit or call (636) 940-1056.

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St. Charles Old Post Office 

St. Charles Old Post Office