Upgrading Filters in Older Strata Buildings Without Changing the Whole HVAC System

Older strata buildings often still have serviceable HVAC plant, but the original filter arrangement may no longer suit how the building is used today. If the system is working, a full plant replacement is not always the first move. In many cases, a smarter filter upgrade can improve fit, airflow and particle capture while keeping the existing system in place.

For strata managers, building owners and contractors, the key is to match the filter to the equipment, the available space and the operating conditions. A filter that is too restrictive, too loose or the wrong size for the frame can create more problems than it solves. The good news is that there are practical upgrade paths for older apartment blocks, from better panel filters to custom-made replacements and improved servicing routines.

Start with the existing filter arrangement

Before changing filter type or grade, look closely at what is already installed. In older buildings, the original setup may have changed over time through piecemeal maintenance, equipment modifications or temporary fixes. A proper assessment should confirm the filter dimensions, frame style, holding hardware and how the filter sits in the cabinet or return air path.

Useful checks include:

• •Measure the filter face size and depth accurately, rather than relying on nominal labels alone
• •Check whether the frame is square, bent or worn
• •Look for bypass gaps where air can pass around the filter instead of through it
• •Note the direction of airflow and any space limits in the plant room or ceiling void
• •Inspect for visible dust loading, damaged media or collapsed frames

If you are unsure how to record the size, how to measure an air filter is a useful starting point. For older sites, measurements matter because even a small mismatch can lead to poor sealing and inconsistent performance.

Improve fit before chasing a higher rating

A common mistake in ageing strata buildings is focusing only on the filter media grade while overlooking fit. A well-sealed moderate-grade filter will often perform better in practice than a higher-grade filter that leaks around the edges.

For older plant, practical fit upgrades may include:

• •Replacing worn disposable panels with correctly sized panels that seat properly in the frame
• •Using deeper filters where the housing allows, to increase media area and reduce stress on the system
• •Adding better sealing surfaces or gaskets to reduce bypass leakage
• •Converting loose or improvised installations into proper framed filter assemblies
• •Using custom air filters when standard sizes do not suit the cabinet or access opening

This is particularly relevant in strata buildings where original equipment was installed decades ago and replacement parts are no longer standard. In these situations, custom manufacture can be the cleanest way to restore proper fit without changing the whole HVAC system.

Choose a filter grade that suits the system, not just the wish list

Older systems can usually accept some improvement in filtration, but the right choice depends on fan capability, housing space and the actual service conditions on site. A filter upgrade should support the system, not overload it.

In practical terms, consider whether the existing arrangement is best served by:

• •A better quality coarse or pre-filter to catch larger dust and protect downstream components
• •A medium filter for improved particle capture where the system can handle it
• •A staged arrangement using a pre-filter plus a finer final filter, where the cabinet allows it

Some older buildings still use EN 779 style descriptions such as G3, G4 or F5 to F9, while other projects refer to ISO 16890. These rating systems do not convert directly, so it is better to select the filter based on the system requirements and the manufacturer data rather than trying to force a one-to-one comparison.

If the building has specific ventilation requirements, confirm site needs with the mechanical services engineer or building owner, and consider AS 1668.2:2024 where relevant to the installation. That is especially important when changing filter resistance, airflow paths or the overall ventilation arrangement.

When a standard filter is not enough

Many older strata buildings were built around standard panel sizes, but not every plant room still matches the original drawings. Damaged frames, modified housings and non-standard access panels can make off-the-shelf filters hard to fit properly.

This is where purpose-made options are often the most practical solution. Custom manufacture can help when you need:

• •Non-standard dimensions
• •Special frame depths or materials
• •Improved sealing around the edge
• •Replacement filters for obsolete equipment
• •A filter built to suit a restricted access cabinet

Older apartment blocks often benefit from custom work because it restores a clean fit without forcing mechanical changes that may be costly or disruptive. If the cabinet is serviceable, it is usually worth solving the filter interface first.

For building teams that need regular support, filter servicing and commercial filter servicing can also help keep installations tidy and easier to maintain.

Don’t overlook maintenance access and pressure drop

Upgrading the filter is only part of the job. In ageing buildings, the easiest way to create ongoing issues is to install a better filter that cannot be checked or changed safely. Access matters, especially where filters are tucked into tight ceiling voids or small plant rooms.

Good planning should account for:

• •Safe access for maintenance staff or contractors
• •Space to remove and replace filters without tearing media or bending frames
• •Clear labelling of filter sizes and orientation
• •Pressure drop monitoring where gauges are fitted
• •Inspection frequency based on the system, site conditions and dust load

Rather than using a fixed replacement timetable, follow the filter and equipment manufacturer instructions and watch how the system behaves in service. If the pressure drop climbs faster than expected, that can point to a filter that is loading quickly, a dirty intake path or an issue with the installation itself.

It is also worth checking whether some filters are designed to be washable. If so, follow the product instructions carefully, because washability is a property of specific products rather than a general feature of all filters.

Practical upgrade paths for ageing strata buildings

If you are deciding how to improve an older building without replacing the whole HVAC system, the most useful approach is usually staged and practical.

Common upgrade paths include:

• •Replacing poorly fitting legacy filters with correctly sized equivalents
• •Adding a pre-filter to help protect the final filter and reduce rapid loading
• •Moving to a deeper or better-sealed frame where space allows
• •Ordering custom filters for obsolete or irregular housings
• •Reviewing the installation with the mechanical services engineer before changing to a different filter grade

This approach is often less disruptive than major plant replacement and can be implemented in a way that suits strata budgets and access constraints. It also gives contractors a clearer maintenance path, because the filter can be specified to match the real condition of the equipment rather than the original assumptions from decades ago.

Getting the right filter for the building

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, and we work with strata managers, building owners and contractors who need practical filter solutions for older systems. We can supply standard options or make filters to suit unusual sizes, frames and plant room constraints.

If you are planning an upgrade and want help matching the filter to the building, call 07 3800 3448 or request a quote. You can also view our products or contact us to discuss the options for your site.