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THE CONDUIT BLOG

Equipment Blog | Controls Blog
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7 -10 Minute Read Time

AIR LEAKAGE: UNDERSTANDING ITS IMPACT ON AIRSIDE PERFORMANCE

Every air handling unit is the result of hundreds of design decisions. 

Fan selection.
Coil selection.
Cabinet construction.
Damper performance.
Controls integration.
Service access.

Each decision influences the performance of the others.

The challenge is that buildings don’t operate one component at a time—they operate as complete airside systems. Understanding how those individual design decisions affect overall system performance is fundamental to effective airside optimization. 

vision-cac-cah-indoor-air-handler

Air leakage is one of the clearest examples of why systems perspective matters.  It’s often viewed as a specification buried within an equipment submittal: a cabinet leakage rating, a damper leakage class, or a performance percentage reported during testing. In reality, leakage can influence airflow, building pressure, ventilation, humidity control, controls performance, and energy consumption throughout the life of the system. 

The amount of leakage matters, but so does where it occurs and how it affects overall system performance. 

The sections that follow examine where air leakage occurs, how it influences overall system performance, and how a systems-thinking approach helps engineers evaluate its impact within the complete airside system. 

Why Air Leakage Is Difficult to Diagnose

Unlike a failed fan or a clogged filter, air leakage rarely presents itself as a single, obvious problem. Instead, it often appears as a collection of symptoms that seem unrelated—or point to the wrong cause. 

A building may struggle to maintain positive pressure. Outdoor air percentages may drift. Space humidity becomes difficult to control. Occupants report comfort complaints even though the equipment appears to be operating normally. 

Because these issues span multiple disciplines, each team may verify that its portion of the system is functioning as intended. The mechanical contractor confirms equipment operation. The controls contractor verifies the sequence of operation. TAB confirms airflow. Commissioning validates system functionality. 

As a result, air leakage can remain hidden even when individual components appear to be operating as designed. 

Air leakage isn’t simply an equipment specification. It’s a system-performance consideration because its effects can extend well beyond the location of the leak. 

To understand those impacts, it helps to first understand where air leakage commonly occurs. 

Where Air Leakage Occurs

Not all air leakage has the same impact. Two systems may have similar leakage rates but experience very different operating consequences depending on where the leakage occurs and the pressure conditions within the air handling unit. 

Figure 1 highlights the most common leakage paths found within an air handling unit and connected ductwork. Cabinet seams, access doors, dampers, pipe penetrations, field-assembled sections, and duct transitions all have the potential to become unintended leakage paths. While manufacturers evaluate cabinet leakage using standards such as AHRI 1350 and damper leakage using AMCA 500-D, these ratings represent controlled laboratory conditions. Installation quality, commissioning, maintenance, and operating conditions all influence how the system performs in the field. 

Cabinet leakage is only one source. Dampers, ductwork, access doors, and field installation details can all influence overall airside performance and should be considered as part of the complete system. 

air leakage

Why Location Matters

The location of a leak often matters as much as the amount of air leaking. 

Leaks on the negative-pressure side of the fan allow unconditioned air to enter the system, increasing the amount of air that must be heated, cooled, filtered, humidified, or dehumidified. Leaks on the positive-pressure side allow conditioned air to escape before it reaches the occupied space, reducing delivered airflow and affecting ventilation and building pressure. 

Rather than evaluating leakage by specification alone, it should be considered how leakage paths influence the performance of the entire airside system. 

Looking Beyond the Specification

The effects of air leakage extend beyond the air handling unit itself. Depending on where leakage occurs and how the system operates, it can influence multiple aspects of HVAC performance.

  • Energy Performance – Air that enters or escapes the system must often be heated, cooled, filtered, or dehumidified, increasing fan energy and conditioning loads.
  • Ventilation & Building Pressure – Leakage can make outdoor-air quantities and building pressure more difficult to maintain, particularly in facilities with strict pressurization requirements.
  • Humidity Control – Unintended airflow can alter latent loads, contributing to humidity drift, condensation, excessive reheat, or dehumidification challenges.
  • Controls Performance – Control sequences are developed based on expected airflow. When leakage changes how air moves through the system, achieving the intended operating conditions becomes more difficult.
  • Long-Term Operation – Leakage can contribute to recurring comfort complaints, additional troubleshooting, and increased maintenance throughout the life of the building.
 
Application
Why Leakage Matters
Commercial OfficesEnergy efficiency, occupant comfort, and maintaining outdoor-air ventilation.
HealthcareMaintaining pressure relationships, ventilation requirements, and humidity control in critical spaces.
LaboratoriesSupporting directional airflow and pressurization required for occupant safety and process integrity.
EducationProviding consistent ventilation, occupant comfort, and efficient operation across varying occupancy schedules.
Industrial & ManufacturingMaintaining process conditions, ventilation effectiveness, and building pressure where operations are sensitive to airflow.
Rather than asking, “How much air is leaking?” ask, “How does that leakage affect the way the system operates?” 

Design Insight

Equipment specifications describe individual performance characteristics. Successful airside design depends on how those characteristics work together. 

Engineering Tradeoffs: Balancing Leakage and Pressure Drop

Air leakage and pressure drop are separate performance characteristics, but they are often evaluated together during equipment and damper selection. 

Air leakage is airflow passing through or around a component where it is not intended. 

Pressure drop is the resistance imposed on the intended airflow as it moves through a component. 

Design decisions such as casing construction, seals, damper blades, transitions, and other airside components may influence both characteristics. However, a low-leakage product is not inherently a high-pressure-drop product, nor is a low-pressure-drop product inherently leaky. Each characteristic should be evaluated independently using standardized performance data. 

This distinction is reflected in industry standards. AMCA 500-D provides separate test methods for damper leakage and pressure drop, while AHRI 1350/1351 separately evaluates AHU casing leakage and other mechanical performance characteristics. 

 

Why the Energy Comparison Matters 

Although air leakage and pressure drop are evaluated independently, they influence energy consumption in different ways. 

Pressure-Drop Energy 

Pressure drop affects all of the intended airflow moving through the system whenever the fan operates. Even a modest increase in pressure drop can increase fan energy because the fan must overcome that additional resistance across the system’s full design airflow for every operating hour. 

Leakage Energy 

The energy associated with air leakage depends on several factors, including: 

  • How much air leaks 
  • The pressure difference across the leakage path 
  • When the leakage occurs 
  • Whether the air is outdoor, return, exhaust, or conditioned supply air 
  • Whether the fan must move additional air to maintain required airflow 
  • The heating, cooling, and humidity load associated with that air 
 

Depending on the application, air leakage may result in: 

  • Additional fan energy to move replacement airflow 
  • Heating or cooling energy to condition unwanted air 
  • Latent energy associated with humidification or dehumidification 
  • Changes in ventilation performance, economizer operation, or building pressurization
 

Effective airside optimization requires considering both leakage and pressure drop together rather than attempting to minimize either characteristic in isolation. 

A good example is damper selection. In the Southwest, economizers can provide significant hours of free cooling because of cool nighttime temperatures and large daily temperature swings. Capturing those energy savings depends on more than simply opening the outdoor air damper. Low-leakage dampers help maintain intended airflow, building pressurization, and ventilation performance, while pressure drop directly affects fan energy consumption. Focusing on only one characteristic can improve one aspect of system performance while negatively affecting another. 

KEY TAKEAWAY

The lowest leakage rate is not always the best solution.

The right balance delivers the best overall system performance.

Engineering Considerations

While every project has different priorities, a few design principles can help ensure air leakage is evaluated as part of the complete airside system—not simply as an equipment specification. 

Coordinate Controls with Mechanical Design 

Mechanical and controls design should work together to achieve the intended system performance. Economizer sequences, building pressurization strategies, and airflow control all rely on components operating as expected. Even well-designed sequences cannot overcome mechanical limitations such as excessive leakage or improperly selected dampers. 

Consider the Application 

The appropriate leakage performance depends on the building, occupancy, and operating requirements. A healthcare isolation room, research laboratory, and commercial office may all justify different design decisions based on their ventilation, pressurization, and humidity requirements. 

Verification and Troubleshooting

Even the best design should be easy to verify. Providing access for inspection, testing, balancing, and commissioning makes it easier to confirm that the system is performing as intended—not just during startup, but throughout its operating life. 

Think Beyond Startup

Air leakage performance isn’t determined on the day the equipment is installed. Maintenance, adjustments, component replacement, and years of operation can all influence how the system performs over time. Designing with long-term operation in mind helps preserve performance throughout the building’s lifecycle. 

From Design Intent to Field Verification

When system performance doesn’t match the design intent, air leakage is often overlooked because its effects appear elsewhere. Building pressure may fluctuate, ventilation rates may drift, humidity may become difficult to control, or the BAS may require repeated adjustment—even though the root cause lies outside the control sequence. 

A systematic approach can help determine whether unintended leakage is contributing to the problem. 

Follow the Pressure

Begin by understanding the pressure zones within the air distribution system. Leaks on the negative-pressure side allow unconditioned air to enter the system, while leaks on the positive-pressure side allow conditioned air to escape before it reaches the occupied space. Knowing where the system is under positive or negative pressure helps narrow the search and connect observed symptoms to potential leakage paths. 

Verify the Mechanical System

Before adjusting control sequences, confirm that the mechanical system is operating as intended. Inspect cabinet seams, access doors, duct connections, and penetrations for visible leakage. For dampers, verify blade position, actuator travel, linkage adjustment, end stops, and seals. 

Remember, a BAS command of 0% confirms what the controller requested—it doesn’t confirm that the damper is fully closed. 

Confirm System Performance

Verification methods should match the application and the suspected leakage path. Smoke pencils, ultrasonic leak detection, airflow measurements, and TAB testing can all help identify suspected leakage or confirm system performance. 

When a more quantitative evaluation is required, ASHRAE Standard 215 provides a standardized method for measuring and reporting leakage airflow in operating HVAC air distribution systems, giving engineers a consistent approach for evaluating field performance. 

Whether using field observations or standardized testing, the objective remains the same: determine how unintended air leakage influences the performance of the complete airside system. 

Safety Note: Any smoke or fog testing should be coordinated with the equipment manufacturer, facility personnel, and fire alarm team before testing begins. 

Field Reminder

A closed command confirms what the controls requested—not necessarily what the damper did. 

Verifying mechanical movement is just as important as verifying the sequence of operation.  

Conclusion

Air leakage is often reduced to a cabinet rating or damper specification, but its influence extends well beyond a single published value. Its impact depends on where leakage occurs, how the system operates, and how it interacts with airflow, ventilation, controls, humidity, and building pressure. 

Evaluating air leakage therefore requires more than comparing specifications. It requires understanding how individual design decisions work together to influence the performance of the complete airside system—from equipment selection and installation through commissioning and long-term operation. 

The goal isn’t simply to specify the lowest leakage rate. It’s to design an airside system in which every component works together to deliver reliable, efficient, and predictable performance. 

Continue the Conversation

Air leakage is only one part of successful airside design. Download our Damper Challenges & Sequence Guide to explore how damper leakage, control sequences, ventilation strategies, and building pressurization work together to influence overall system performance.
Download
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The information presented in this article is intended to support engineering discussions and should be used in conjunction with applicable project requirements, manufacturer recommendations, and the latest editions of relevant industry standards. 

References 

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Humidity Control Technology Selection Guide

A practical reference to help match humidity control technologies with the right application, performance requirements, and operating conditions.

Selecting the right humidity control technology starts with understanding the application—not the equipment. Required dew point, ventilation rates, moisture loads, available utilities, and energy goals all influence the best solution.

This guide provides a high-level comparison of common humidification and dehumidification technologies. Use the interactive graphics below to explore each technology’s typical operating range, applications, advantages, and limitations.

What's Your Goal?

Remove Moisture or Add Moisture?

DX Cooling

Typical Dew Point Range:
55-50°F

Best For:

  • Offices
  • Schools
  • General Commercial Buildings

Advantages:

  • Lowest first cost
  • Familiar technology

Limitations:

  • Limited humidity control at part load

Products:

DX + Hot Gas Reheat

Typical Dew Point Range:
50-43°F

Best For:

  • Schools
  • Healthcare
  • Fitness centers
  • High ventilation applications

Advantages:

  • Improved humidity control
  • Reduced overcooling

Products:

Chilled Water

Typical Dew Point Range:
52-42°F

Best For:

  • Large Commercial Buildings
  • Healthcare
  • Higher Performance Facilities

Advantages:

  • Excellent humidity control
  • Ideal for central plant applications
  • Supports a wide range of cooling capacities

Products:

Liquid Desiccant

Typical Dew Point Range:
45–32°F

Best For:

  • Natatoriums
  • Dedicated dehumidification systems
  • High outdoor air applications

Advantages:

  • Removes moisture independently of sensible cooling
  • Maintains low dew points under varying load conditions
  • Ideal for applications with high latent loads

Products:

Solid Desiccant

Typical Dew Point Range:
40–0°F

Best For:

  • Laboratories
  • Pharmaceutical facilities
  • Industrial process applications

Advantages:

  • Achieves ultra-low dew points
  • Ideal for high latent load applications
  • Reliable performance in demanding industrial environments

Products:

Multi-Stage Desiccant

Typical Dew Point Range:
0°F to -150°F dew point

Best For:

  • Ultra-low dew point applications
  • Processes requiring moisture levels beyond conventional desiccant systems

Common Applications:

  • Lithium battery manufacturing
  • Semiconductor production
  • Aerospace manufacturing
  • Research laboratories
  • Specialty dry rooms
  • Highly controlled industrial processes

Advantages:

  • Achieves extremely low dew points
  • Designed for process-critical moisture control
  • Maintains ultra-dry environments for sensitive manufacturing

Limitations:

  • Specialized system design and application
  • Higher first cost and operating complexity
  • Typically not used for commercial comfort HVAC applications

Products:

Selection Starts With…

Before selecting equipment, define:

  1. Target dew point or humidity level
  2. Application requirements
  3. Available utilities (steam, chilled water, water quality)
  4. Operating priorities (first cost, energy, maintenance, control accuracy)

 

Once these design criteria are established, use the technology guides above and below to compare solutions.

Adiabatic

Typical Capacity:
Medium to High

Typical Humidification Method:
Evaporative (non-steam)

Best For:

  • Energy-efficient humidification
  • Facilities with evaporative cooling benefits

Common Applications:

  • Office buildings
  • Schools
  • Warehouses
  • Manufacturing facilities

Advantages:

  • Very low energy consumption
  • Provides evaporative cooling while humidifying
  • Lower operating costs than steam systems

Limitations:

  • Requires high-quality treated water
  • Cooling effect may not be desirable year-round
  • Greater water management requirements

Products:

Direct Steam Injection

Typical Capacity:
High

Typical Humidification Method:
Boiler steam

Best For:

  • Facilities with central boiler steam
  • Large commercial and institutional buildings

Common Applications:

  • Hospitals
  • Universities
  • Industrial facilities
  • Central utility plants

Advantages:

  • Fast response to changing humidity loads
  • High-capacity humidification
  • Simple when clean steam is readily available

Limitations:

  • Requires a boiler steam source
  • Steam quality must be appropriate for the application
  • Not practical where central steam is unavailable

Products:

Isothermal

Typical Capacity:
Low to High

Typical Humidification Method:
Self-generated steam

Best For:

  • Precise humidity control
  • Applications requiring stable room conditions

Common Applications:

  • Healthcare
  • Museums and archives
  • Laboratories
  • Commercial buildings

Advantages:

  • Precise humidity control
  • No cooling effect on the air stream
  • Available in electric, gas, and steam-to-steam configurations

Limitations:

  • Higher energy use than adiabatic systems
  • Requires a steam generation source
  • Operating costs depend on utility rates

Products:

Key Selection Factors

Start with the Application

Different building types have very different humidity requirements.

Define the Target Dew Point

Dew point—not just relative humidity—determines which technologies are capable of meeting the design conditions.

Understand the Latent Load

Outdoor air, occupancy, and process loads often drive equipment selection more than sensible cooling.

Consider Available Utilities

Steam availability, chilled water, and water quality can eliminate or favor certain technologies.

Evaluate Energy & Operating Costs

The lowest first cost is not always the lowest life-cycle cost.

Plan for Serviceability

Maintenance access, water treatment, and component replacement should be considered early in design.

Need Help Selecting the Right Solution?

Humidity control isn't one-size-fits-all. Our engineering team can help evaluate: design dew point, moisture loads, ventilation requirements, humidification and dehumidification, strategies, and product selection.
Contact the Varitec Team Below
]]> https://varitecsolutions.com/humidity-control-technology-selection-guide/feed/ 0 R-32 and the Future of VRV Systems: What Facilities Teams & Service Contractors Need to Know https://varitecsolutions.com/a2l-readiness-guide/ Thu, 23 Oct 2025 23:17:40 +0000 https://varitecsolutions.com/?p=3365

THE CONDUIT BLOG

R-32 and the Future of VRV Systems:

What Facilities Teams & Service Contractors Need to Know

The refrigerant transition is not new — it’s already underway. As of January 1, 2025, most commercial equipment began phasing out R-410A in favor of lower-GWP refrigerants.

The next major step is approaching:
VRV systems will transition to R-32 beginning January 1, 2026.

For facility teams and service contractors already supporting VRV, this shift brings meaningful benefits — not additional complexity.

Why R-32 for VRV? A Practical, Future-Ready Choice

R-32 aligns with both regulatory requirements and long-term building performance priorities. It provides higher efficiency, lower environmental impact, and more stable servicing characteristics than the alternatives.

Unlike some refrigerant transitions of the past, this one isn’t about navigating new installation practices or maintenance headaches — it’s about adopting a refrigerant that works with existing VRV field practices.

Key Advantages of R-32 in VRV Systems

1. Single-Component Refrigerant (No Blend Shift)

R-32 is not a blend — which means:

  • No glide

  • No component separation during leaks

  • No remixing or rebalancing during service

  • Stable performance over the life of the system

This is a major differentiator from R-454B, which can change composition if leakage occurs.

2. Non-Proprietary = Lower Cost and Wide Availability

R-32 is widely manufactured and is not proprietary to any single OEM.
This supports:

  • Lower refrigerant cost per pound

  • Broader channel availability

  • Reduced long-term replacement risk

For facilities planning 20–30 year HVAC horizons, this matters.

3. Lower Refrigerant Charge Requirements

Compared to R-454B, R-32 requires less total refrigerant charge for equivalent system capacity — reducing:

  • Material cost

  • Stored volume

  • Transport and recovery time

Lower charge = lower total lifecycle cost of ownership.

4. Familiar Installation & Service Practices

Most VRV service procedures stay the same:

  • Same refrigerant piping design and brazing practices

  • Similar operating pressures

  • Evacuation and commissioning remain unchanged

The only update: ensure gauges, recovery pumps, and leak detectors are rated for A2L refrigerants.
Most modern R-410A tools already qualify.

5. Built-In Safety & Code Compliance

Daikin VRV systems integrate required A2L safeguards when charge thresholds apply, including:

  • Refrigerant leak detection

  • Automated shutoff logic

  • UL 60335-2-40 & ASHRAE 15-2022 compliant control strategies

Safety is engineered into the system, not added externally.

Preparing Your Team for the VRV R-32 Transition

While certification is not required, we strongly recommend A2L handling training for service personnel. Trusted resources include:

  • Daikin HVAC Learning Campus

  • ACCA A2L Safe Handling

  • NATE Refrigerant Transition Exams

 

For additional technical guidance, we recommend:
www.R32Reasons.com

Download the A2L Readiness Kit

We’ve put together a concise resource package for facilities & service teams:

✅ A2L Safety & Service Checklist
✅ Tool Readiness Reference
✅ VRV R-32 Transition Key Points
✅ Recommended Training Links

Final Thoughts

The industry is not preparing for refrigerant change — it is continuing it.
With most system categories already transitioned in 2025, VRV moves to R-32 in 2026 as the next step.

R-32 supports:

  • Lower lifecycle cost

  • Greater servicing stability

  • Stronger sustainability alignment

  • And a clearer long-term equipment roadmap

For facilities teams maintaining VRV systems today, the future is both familiar and improved.

Request More Information and Download Your A2L Readiness Guide

Fill out the form below to request more information and/or get the link to download the guide.
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