These figures highlight the pressing need to improve the efficiency of HVAC systems as part of broader efforts to reduce carbon footprint and operating costs. One effective strategy is the retrofitting of existing systems with Energy Recovery Ventilators (ERVs). This approach not only supports achieving Net-Zero Buildings (NZBs) but also delivers long-term benefits in system performance, indoor air quality, and energy savings.

Understanding HVAC Retrofitting

HVAC retrofitting involves upgrading or modifying existing systems to improve energy efficiency, operational reliability, or capacity without the need for complete replacement. This process is often undertaken to modernize older systems, enhance functionality, and align with current energy efficiency standards and environmental regulations.

The Role of ERVs in Reducing Energy Consumption and Improving Indoor Air Quality

Energy Recovery Ventilators (ERVs) function by capturing heat (and sometimes moisture) from exhausted indoor air and transferring it to incoming fresh air. This energy exchange process reduces the thermal load on HVAC systems by preconditioning outdoor air before it enters the system. Depending on system design and operating conditions, ERVs can recover between 40% to 80% of the energy that would otherwise be lost through ventilation.

This improvement in efficiency directly contributes to lower heating and cooling demands, helping to reduce operational energy costs and associated carbon emissions. In addition to energy savings, ERVs support improved indoor air quality by providing a continuous flow of filtered outdoor air while exhausting stale indoor air. This combination of energy recovery and ventilation makes ERVs a valuable component in optimising building performance and supporting sustainability objectives.

Why Retrofitting ERVs Is a Practical Choice for Existing Buildings

Unlike complete HVAC system replacements—which are costly and disruptive—retrofitting ERVs offers a more cost-effective and strategic solution that delivers measurable benefits:

• Energy Efficiency and Cost Savings: By recovering energy from exhaust air, ERVs reduce the amount of energy required for heating and cooling ventilation air, leading to significant energy savings. This translates to lower utility bills and operational costs over time.
• Enhanced Indoor Air Quality: ERVs facilitate continuous ventilation, removing stale indoor air and replacing it with fresh outdoor air. This process effectively reduces indoor pollutants, contributing to a healthier indoor environment
• Extended Equipment Lifespan: By reducing the workload on HVAC systems, ERVs can extend the lifespan of existing equipment, delaying the need for costly replacements.
• Regulatory Compliance and Sustainability Goals: Integrating ERVs aligns with regulatory standards and sustainability certifications, such as those outlined by ASHRAE and LEED. This not only ensures compliance but also demonstrates a commitment to environmental responsibility.
• Reduced Carbon Emissions: Lower energy use directly translates to lower GHG emissions, helping buildings align with Australia’s decarbonization goals.

Retrofitting ERVs into existing HVAC systems is a strategic move toward energy efficiency and sustainability. It addresses the pressing issue of high energy consumption in the HVAC sector — particularly in Australia, where these systems significantly contribute to greenhouse gas emissions. By reducing energy consumption, improving indoor air quality, and extending HVAC system lifespan, ERVs present a compelling solution for building owners and facility managers seeking to reduce their operational costs and carbon footprints. As the demand for sustainable building practices continues to grow, retrofitting ERVs into existing HVAC systems stands out as a practical, impactful step forward—one that pays off in energy savings, occupant well-being, and climate resilience.

References

www.energy.gov.au/publications/hvac-factsheet-energy-breakdown

www.airah.org.au/Common/Uploaded%20files/Advocacy/2024/AIRAH%20Pre-Budget%20Submission%202024.pdf

www.energy.gov/eere/buildings/hvac-retrofit

www.ashrae.org/technical-resources/energy-recovery

The Role of Filters in an ERV System

Filters in an ERV — located at both the fresh air and return air inlets — trap dust, pollen, pollutants and other airborne particles before they reach the energy recovery core. Of all ERV components, filters are the most prone to degradation and have the most immediate impact when neglected.

When filters become clogged, static pressure rises and airflow drops, forcing the fan motors to work harder. The results? Higher energy bills, poorer indoor air quality, and increased wear and tear. In more severe cases, fine dust can bypass the filters entirely and accumulate on the energy recovery core.

This dust build-up acts like an insulating blanket over the core’s surfaces, drastically reducing the heat (and moisture, in enthalpy cores) transfer efficiency. Over time, this not only cancels out the ERV’s intended benefits, but also risks permanent damage to the core, leading to costly replacements. Moreover, if the ERV is connected to ducted heating or cooling systems, the unfiltered dust may also enter other HVAC components, affecting coils and fans.

Hence, regular filter maintenance is not just a good practice — it’s essential to sustain the ERV’s intended benefits: improved IAQ, reduced energy use, longer system lifespan, and lower carbon emissions.

Recommended Frequency for Cleaning or Replacement

Filter maintenance intervals depend on several variables, including the building type, environmental conditions, and system usage. However, several industry standards and organisations offer practical benchmarks:

 General Recommendation

• Inspect filters every 3 months
• Clean or replace filters every 3–6 months, depending on air quality or environmental condition

➤ Residential Settings

• ASHRAE Standard 180-2018 recommends filters should be inspected quarterly. For homes in dusty or high-pollen areas (e.g. rural NSW, parts of WA), replacement or cleaning every 2–3 months is advised

➤ Commercial & Industrial Settings

• NCC and AS/NZS 3666.2:2011 require regular filter inspection and cleaning of air-handling system filters as part of microbial and air quality control measures.

For systems operating in high-occupancy buildings (e.g. offices, hospitals, schools), monthly inspections and filter cleaning/replacements every 2–3 months are often necessary.

➤ Construction Sites or Workshops

In environments with high airborne particulate levels (e.g. factories or manufacturing plants), filter cleaning or replacementshould be performed monthly to prevent performance decline and health risks.

Signs That ERV Filters Require Attention

Beyond schedule-based maintenance, here are practical signs that ERV filters may be due for cleaning or replacement:

• Noticeable reduction in airflow or changes in room pressure
• Audible strain from fans (higher pitch or louder operation)
• Increased energy consumption
• Dust deposits around supply grilles
• Air smells stale, musty, or dusty
• Visual inspection shows filter discoloration or deformation
• System controller displays a pressure warning (if equipped with differential pressure sensors)

Cleaning vs Replacing Filters

Filter type determines maintenance action:

ERV systems are designed to deliver long-term energy efficiency, cost savings, and improved indoor air quality — but these benefits can be compromised quickly by neglected filters. Filter degradation leads to diminished heat recovery, system strain, and potentially costly repairs.

In any setting — whether residential, commercial, or industrial — filter maintenance is not optional; it is an essential component of ERV best practice. By adhering to regular inspection and servicing schedules, building owners, contractors, and facility managers can protect their investment and maintain healthy, efficient indoor environments.

References

ASHRAE Standard 180-2018: Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems

AS/NZS 3666.2:2011: Air-handling and Water Systems of Buildings – Microbial Control