Breathing New Life into Aging Manufacturing Facilities: A Strategic Path to HVAC Modernization, Reliability, and Decarbonization

Across the United States, thousands of manufacturing plants built in the mid-20th century continue to power today’s advanced industrial economy. Many of these facilities (well maintained, carefully operated, and central to their organizations’ core business) now face an unavoidable reality: their original heating, ventilating, and air conditioning (HVAC) systems have exceeded their useful life by decades. As manufacturers pursue aggressive sustainability goals, increase operational resilience, and compete for top-tier workforce talent, HVAC modernization is no longer optional. It is strategic.

To demonstrate this approach in practice, consider the following real-world case study: a 57-year-old manufacturing plant located in the center of the country, producing high-tech equipment for the construction industry. Although the building has been well maintained and remains fully operational, its HVAC systems (most of which date back to original construction) have reached a tipping point. The modernization approach developed for this facility offers a powerful model for how legacy plants can meet the next era of manufacturing demands.

The Hidden Costs of Aging Mechanical Infrastructure

For nearly six decades, the building’s mechanical systems have served this facility well. The infrastructure includes:

• Cooling towers rebuilt multiple times over their 57-year life

• 57-year-old air handling units with belt drive constant volume supply fans, filter racks, galvanized condensate drain pans, single wall galvanized casings with exposed foil faced thermal insulation, chilled water-cooling coils, indirect fired natural gas duct heaters, non-ducted outside air intake ducts; outside air is drawn in through the penthouses.

• Low-voltage electric controls that have become increasingly unreliable

• Chillers and pumps installed 14 years ago. They are functioning well but the chillers are reliant on a refrigerant scheduled to be no longer produced within the next six years

• Air handling units located in the rooftop penthouses showing visible and widespread mold growth

According to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) standards, these systems were nearly three times beyond their expected useful life of 20 years. Predictably, the Owner began experiencing an escalating set of issues, including: poor temperature and humidity control, equipment failures, and cooling towers in rapid decline. The mold contamination in the penthouses also posed significant health risks.

Beyond equipment failures, there was a larger strategic driver at play—the Owner’s corporate commitment to decarbonization. The existing system could not support that long-term sustainability vision, with fossil-fuel-based heating, aging equipment, and inefficient controls.

Balancing Feasibility, Cost, Sustainability, and Operational Continuity

When modernizing an aging manufacturing plant, the path forward is rarely straightforward. Any solution must balance capital investment, energy usage and costs, indoor air quality performance, system reliability, installation complexity, and—critically—how to minimize disruption to ongoing production.

Multiple HVAC upgrade concepts were rigorously evaluated, each offering benefits but falling short of the full project goals.
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‍Direct Replacement: Costly, Disruptive, and Misaligned with Sustainability Goals

Replacing the existing systems with like-for-like equipment would have been the most straightforward technically, but it failed two fundamental tests: It did not support the Owner's decarbonization strategy and it would not eliminate the mold issue within the existing penthouses.

The initial investment for this option was high, and the long-term impacts—notably ongoing fossil fuel usage—did not align with the future state of the organization.

‍Hybrid System Using Existing Chillers and New Hot Water Plant

Another approach evaluated was to leverage the 14-year-old chilled-water system and introduce a new hot-water heating loop using geothermal, electric resistance, or air-to-water heat pumps. This concept was ultimately rejected due to high initial cost and site land usage, lack of meaningful energy savings, significant costs and operational disruption, and the impending obsolescence of the existing chillers’ refrigerant and the condition of the existing cooling towers. Despite offering some modernization, this path lacked long-term value.
‍Heat Recovery-Based Systems

Heat recovery strategies are often effective in facilities with large volumes of exhausted conditioned air. However, in this plant, outside air enters through penthouses and is exhausted through multiple general and process systems. Introducing heat recovery would have increased infiltration, degraded temperature and humidity control, and delivered no measurable energy savings.

Each of these options illuminated the complexity of the decision—but also clarified what the system needed to achieve.

A Strategic Shift: Modernizing Through Packaged Rooftop Heat Pump Units

The chosen system embraced both modernization and decarbonization while respecting the operational rhythm of an active manufacturing environment.

The new solution included:

• Removal of the existing penthouses and replacement with packaged rooftop heat pump units that provide low ambient heating, economizers, direct expansion cooling and heating, and auxiliary resistance heat.
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• Integration of hot-gas reheat, variable-speed compressors, and variable-speed supply fans to enhance humidity control—a critical factor in both equipment performance and occupant comfort.
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• Adaptation of existing supply ductwork to minimize disruption and reduce cost.
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• Installation of a non-proprietary building management system (BMS) to improve reliability, transparency, and long-term maintainability.

This modernized HVAC strategy will transform the plant into a more sustainable, resilient, and controllable environment without requiring large-scale interior demolition or operational downtime.

Key Benefits: Why This System Works for a 21st Century Plant

The selected approach delivered tangible, immediate improvements and long-term value including:

• ‍Enhanced Temperature and Humidity Control
  
  Variable-speed compressors and hot-gas reheat allow the system to manage temperature and moisture levels—both essential to manufacturing consistency and to preventing mold recurrence.
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• Improved Reliability
  
  New equipment replaces failing infrastructure and eliminates the need for constant repair, freeing maintenance staff to focus on higher-value operations.
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• Alignment with Sustainability and Decarbonization Goals
  
  By eliminating natural gas heating and moving to high-efficiency electric systems, the facility dramatically reduced its carbon footprint.
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• ‍Better Indoor Air Quality
  
  Modern ventilation strategies and removal of mold-prone penthouses significantly improve IAQ for employees and protect product integrity.
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• ‍Moderate Initial Investment with Long-Term Operational Saving
  
  The chosen solution delivers a positive balance of first-cost practicality, energy efficiency, and reduced maintenance burdens.
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• ‍Minimal Disruption to Manufacturing
  
  A rooftop-based system allowed installation with minimal interference to production—an essential requirement for revenue continuity.
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• ‍Reasonable Delivery and Installation Timelines
  
  Manufacturers’ lead times and expected installation time lines align with the Owner’s project schedule, ensuring predictable execution.

A Roadmap for Success: Lessons from a Complex Modernization

Modernizing a 57-year-old manufacturing plant is not simply an engineering exercise—it is a strategic design initiative requiring collaboration, investigation, and rigorous decision-making. The following steps were critical to achieving a successful outcome:

1. Developing a thorough Owner’s Project Requirements (OPR) document to articulate performance, sustainability, and operational priorities.
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2. Understanding the manufacturing process in detail to avoid disruptions and protect production flow.
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3. Conducting extensive field verification to uncover hidden conditions and constraints.
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4. Performing a deep comparative study of potential systems, including benefits, drawbacks, costs, and long-term risks.
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5. Engaging in iterative reviews with the Owner to align the solution with both short-term needs and long-term strategy.
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6. Providing continuous communication throughout the design process to refine, validate, and optimize decisions.

The Bigger Picture: Why This Work Matters

Upgrading mechanical systems in legacy manufacturing buildings is one of the most critical—and complex—opportunities facing industry leaders today. The right HVAC modernization strategy delivers more than code compliance or energy reduction. It strengthens the resilience of a facility, improves employee well-being, enhances process quality, and supports the organization’s long-term vision for growth and sustainability.

Projects like this serve as a reminder: while the technical challenges are real, the rewards are even greater. When engineers, owners, and operations teams work together to reimagine outdated systems, they create buildings that are not only functional—but future-ready.

If you're ready to update your systems, reach out to the Progressive Companies team to start the conversation.

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