As part of broader efforts to achieve Net-Zero Buildings (NZBs) while meeting Indoor Air Quality (IAQ) standards, ERVs have become standard components in energy-efficient HVAC design. However, their performance is only as good as their maintenance — particularly the filters. This article addresses a vital yet often overlooked question: How often should ERV filters be cleaned or replaced?
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:
| Filter Type | Action | Notes |
| Washable filters (e.g., aluminum mesh or foam) | Clean with mild detergent and dry thoroughly | Inspect for damage or deterioration |
| Pleated or fiberglass filters (non-washable) | Replace | Use like-for-like rated filters |
| Carbon or HEPA filters | Replace | Follow Original Equipment Manufacturer (OEM) guidance strictly |
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
AS/NZS 3666.2:2011: Air-handling and Water Systems of Buildings – Microbial Control