ST. LOUIS, MO – Wiegmann Associates has completed a $132,000 HVAC upgrade at the St. Charles Old Post Office on Historic Main Street in St. Charles, which was converted into a state-of-the-art co-working technology incubator for digital startup businesses called OPO Startups. Wiegmann transformed outdated HVAC systems and installed automation controls in the 10,000-square-foot historic building. The general contractor was Droste & Sons Construction Company.

The existing antiquated HVAC system consisted of window air conditioners and outdated, inefficient air handlers in the attic, which resulted in inconsistent heating and cooling.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.

A major challenge of the project was to design an efficient, minimally intrusive system that did not significantly modify the architectural features or structures of the 100-year-old historical building. The team also 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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Media Contact Rachel Brown 
(314) 210-4419

St. Charles Old Post Office on Historic Main Street  

St. Charles Old Post Office on Historic Main Street  

St. Charles Old Post Office on Historic Main Street