Common Problems in Commercial HVAC Ductwork (And How to Resolve Them Effectively)
A guide for business owners, property managers, and facility supervisors across Ontario.
At LG Mechanical, we service commercial and industrial buildings across Ontario. From warehouses to offices to retail environments, we’ve identified a consistent set of problems that plague commercial ductwork — and in many cases, they’re preventable.
Below, we outline the most common ductwork issues, how they impact performance, and what proactive steps you can take to prevent costly disruptions.
1. Improper Duct Installation
Poor duct design or installation is often the root of many HVAC inefficiencies. Whether it’s incorrect sizing or poor routing, these mistakes can severely restrict airflow and compromise comfort.
Problems caused by poor installation include:
- Undersized or oversized ducts leading to airflow imbalance
- Excessive bends and long runs that reduce system efficiency
- Inadequate return air pathways causing pressure issues
- Non-compliance with local building and energy codes
Solution:
Ensure duct systems are installed by licensed sheet metal professionals using accurate load calculations and layout planning tools. Properly engineered ductwork supports long-term HVAC performance.
2. Leaky or Unsealed Ductwork
Air leakage is one of the most common and costly ductwork problems. In large commercial spaces, even minor leaks can result in substantial energy losses over time.
Signs of air leaks include:
- Inconsistent air pressure between zones
- Unexplained increases in energy bills
- Visible gaps or poorly connected duct joints
- Whistling or hissing noises from duct seams
Solution:
Conduct professional duct leakage testing to pinpoint weak points. Use commercial-grade sealants and insulation to secure joints and prevent conditioned air from escaping.
3. Damaged or Corroded Duct Sections
Ducts located in unconditioned spaces or exposed to moisture and chemicals can corrode or collapse, disrupting airflow and reducing system reliability.
Common causes of duct damage:
- Humid environments leading to rust
- Physical impact or poor support causing dents
- Lack of insulation resulting in condensation buildup
- Age-related wear in older buildings
Solution:
Inspect vulnerable duct runs regularly. Replace damaged sections promptly and apply insulation in high-risk areas to prevent corrosion and prolong lifespan.
4. Dust, Debris, and Contaminant Buildup
Commercial ducts can accumulate large volumes of debris over time, especially in buildings with high foot traffic, machinery, or recent renovations.
- Risks associated with duct buildup:
- Reduced airflow and system efficiency
- Accelerated filter clogging and fan strain
- Spread of dust, allergens, or mould spores
- Declining indoor air quality
Solution:
Implement a scheduled duct cleaning program — especially in sensitive environments like healthcare, food service, or education. Cleaner ducts ensure cleaner air and more reliable HVAC operation.
5. Uneven Temperature Distribution
When certain areas of a building are always too warm or too cold, it’s often a ductwork issue. Inconsistent airflow impacts occupant comfort and productivity.
Causes of uneven temperatures:
- Poor duct balancing
- Blockages or collapsed duct sections
- Incorrect zoning or duct sizing
- Leaky or uninsulated supply runs
Solution:
Perform a professional airflow audit and rebalance the system. Modify duct design or zoning as needed to ensure even distribution across all occupied areas.
6. Noisy Duct Systems
While all HVAC systems produce some sound, loud or irregular noises can indicate an underlying duct problem that requires attention.
Common duct-related noise sources:
- Loose fittings causing rattling or vibration
- High static pressure creating whistling sounds
- Thermal expansion or contraction causing “popping”
- Airflow turbulence from poor design
Solution:
Inspect for structural issues, secure all components, and consider acoustic insulation where appropriate. Addressing noise improves both system health and tenant satisfaction.
7. Inadequate Duct Insulation
Ducts that run through unconditioned spaces and lack proper insulation contribute to thermal losses — especially during Ontario’s extreme weather seasons.
Consequences of poor insulation:
- Loss of heating or cooling before reaching occupied areas
- Condensation forming on ducts, risking water damage
- Increased HVAC runtime and energy costs
- Potential for mould growth in ceilings or walls
Solution:
Upgrade to high-efficiency duct insulation and verify that all penetrations and joints are sealed. This ensures energy efficiency and protects the building envelope.
8. Inefficient Duct Layouts
Older buildings or those with poorly designed renovations often have duct layouts that no longer match usage patterns or building zones.
Inefficiencies caused by poor layout:
- Long, winding duct runs with high resistance
- Over- or under-supplied areas
- Inadequate return air placement
- Difficulty integrating new HVAC equipment
Solution:
Have your system reviewed by a mechanical engineer or licensed HVAC contractor. A layout redesign with updated zoning can significantly reduce energy use and improve comfort.
9. Visual Inspections Are Not Enough
While visual inspections can detect surface-level damage or leaks, they won’t identify internal or hidden issues that are common in complex commercial duct systems.
What basic inspections often miss:
- Internal obstructions or debris
- Small leaks in hard-to-reach areas
- Airflow imbalances between branches
- Hidden corrosion or insulation failure
Solution:
Use advanced diagnostic tools like borescopes, pressure monitors, and flow hoods. Combine visual assessments with airflow testing for a complete system analysis.
10. Lack of Preventive Maintenance
Ductwork, like any component of your HVAC system, requires regular maintenance to ensure long-term efficiency and reliability.
What happens without regular maintenance:
- System breakdowns and unplanned downtime
- Increased energy usage and operating costs
- Reduced equipment lifespan
- Poor indoor air quality and comfort complaints
Solution:
Establish a biannual HVAC maintenance plan. This should include duct inspection, cleaning, seal integrity checks, and airflow testing to detect issues early and keep your system performing at its best.
Final Thoughts
Ductwork may not be visible to occupants, but it directly influences comfort, energy efficiency, and operating costs in every commercial facility. Investing in proactive ductwork inspection, maintenance, and upgrades can help reduce service disruptions, support sustainability goals, and protect your bottom line.
At LG Mechanical, we provide comprehensive commercial ductwork services throughout Ontario. Our Red Seal-certified technicians bring expertise in diagnostics, repair, retrofitting, and maintenance — delivering results that align with both operational and energy-efficiency targets.
