Why Traditional HVAC Systems Fail to Control Humidity

Humidity control is one of the most misunderstood challenges in industrial and commercial buildings. Many facilities assume that if an HVAC system is properly sized for temperature, humidity will “take care of itself.” In reality, temperature control and humidity control are related, but not the same thing.

Temperature Control Is Not Humidity Control

Conventional HVAC systems are designed first and foremost to manage sensible heat—that is, air temperature. Moisture removal (latent heat) is essentially a secondary function.

In a typical cooling cycle, air passes over a cold evaporator coil. If the coil surface temperature is below the air’s dew point, moisture condenses and drains away. This process works reasonably well when cooling loads are high and outdoor conditions are hot and humid.

The problem is that industrial facilities rarely operate under “ideal” conditions for coil-based dehumidification.

The Key Limitation

HVAC systems can only remove moisture when they are actively cooling. When sensible loads drop but latent loads remain, humidity control suffers.

The Sensible–Latent Load Mismatch

Many industrial environments have low or variable sensible loads but high latent loads. Examples include:

• Food and beverage processing

• Pharmaceutical manufacturing

• Cold storage and refrigerated spaces

• Warehouses with frequent door openings

• Facilities with washdown processes

• Indoor pools or water treatment plants

In these spaces, moisture enters the building through:

• Ventilation air

• Infiltration from doors and loading docks

• Process-related evaporation

• Occupants and equipment

When the HVAC system cycles off because the space temperature is satisfied, moisture removal stops—even though humidity continues to rise.

This is the classic sensible–latent imbalance, and it is the primary reason traditional HVAC systems fail at humidity control.

Overcooling and Reheat: An Inefficient Workaround

One common attempt to solve humidity issues with conventional HVAC is overcooling followed by reheat.

Here’s how it works:

1. The air is cooled well below the space temperature to remove enough moisture.

2. The air is then reheated to avoid overcooling the space.

While this method can reduce humidity, it introduces several problems:

• High energy consumption (cooling and heating at the same time)

• Increased mechanical complexity

• Higher operating costs

• Reduced sustainability and efficiency metrics

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In many regions, energy codes and corporate sustainability goals actively discourage or prohibit this approach.

Coil Limitations in Industrial Environments

Even when HVAC systems are designed to dehumidify, cooling coils themselves impose physical limitations.

Coil Temperature Constraints

To remove moisture, coil surfaces must operate below the air’s dew point. However:

• Extremely cold coils increase the risk of freezing

• Low airflow rates reduce heat transfer efficiency

• Frost buildup further degrades performance

Part-Load Conditions

Most facilities operate at part load the majority of the time. At part load:

• Compressors cycle off more frequently

• Coil temperatures rise

• Moisture removal becomes inconsistent

The result is wide humidity swings that are unacceptable for many industrial processes.

Ventilation Air: The Hidden Moisture Load

Ventilation air is one of the largest sources of moisture in commercial and industrial buildings—especially in humid climates.

Outdoor air often enters the system at:

• High humidity ratios

• High dew points

• Conditions far above acceptable indoor moisture levels

Cooling-based HVAC systems must lower this air below its dew point to remove moisture. When outdoor humidity is extreme, this becomes impractical or inefficient.

In contrast, desiccant dehumidifiers are designed specifically to handle high moisture loads, regardless of temperature.

Why Desiccant Dehumidification Works Where HVAC Fails

Desiccant dehumidifiers remove moisture through adsorption, not condensation. A hygroscopic material (the desiccant) attracts and holds water vapor directly from the air.

This fundamental difference creates several advantages.

Independent Control of Temperature and Humidity

Desiccant systems decouple latent and sensible control. Moisture can be removed:

• Without overcooling the air

• Without relying on low coil temperatures

• Across a wide range of operating conditions

This allows engineers to design systems that precisely meet humidity requirements while allowing HVAC systems to focus on temperature.

Low Dew Point Capability

Many industrial processes require very low dew points—often well below what cooling coils can achieve economically. Desiccant systems can consistently deliver:

• Low humidity ratios

• Stable dew points

• Year-round performance

Reliable Performance at Part Load

Unlike HVAC systems, desiccant dehumidifiers do not rely on compressor cycling to remove moisture. They provide:

• Continuous moisture removal

• Stable humidity control

• Predictable performance during light load conditions

Industrial Risks of Poor Humidity Control

For engineers and facility managers, the consequences of uncontrolled humidity are not theoretical—they’re operational and financial.

Common issues include:

• Corrosion of equipment and infrastructure

• Mold and microbial growth

• Product spoilage or contamination

• Condensation on ceilings, ductwork, and piping

• Slippery floors and safety hazards

• Regulatory compliance failures

Sales teams often find that customers are already experiencing these problems—they just don’t realize humidity is the root cause.

A Complementary, Not Competitive, Solution

It’s important to note that desiccant dehumidifiers are not a replacement for HVAC systems. Instead, they complement traditional HVAC by addressing what HVAC was never optimized to do.

A well-designed system often includes:

• HVAC equipment sized for sensible cooling

• Desiccant dehumidification sized for latent load

• Improved energy efficiency

• Better process control

• Longer equipment life

For engineers, this approach offers better system stability and design flexibility. For sales professionals, it provides a clear, technically sound value proposition.

Conclusion

Traditional HVAC systems fail to control humidity not because they are poorly designed—but because they were never designed to prioritize latent load control in demanding industrial environments.

When humidity matters—and in many industrial spaces it absolutely does—cooling-based systems alone are not enough. Desiccant dehumidification provides the independent, reliable, and energy-efficient moisture control that modern facilities require.

Understanding this distinction empowers engineers to design better systems and enables sales professionals to have more informed, credible conversations with customers. In the end, controlling humidity isn’t about adding more cooling—it’s about using the right technology for the job.