Air Filters for Homes Undergoing Open-Plan Wall Removal

Open-plan renovations can change more than the look and feel of a home. When a wall comes out, the return-air pathway, pressure balance and dust load can all shift in ways that affect how the heating and cooling system moves air through the space.

If the system is reopened without checking those changes, filters may load up faster, grilles can become ineffective, and airflow may not return the way it did before the works started. For homeowners, renovators and mechanical contractors, the key is to treat the filter and return-air setup as part of the renovation, not an afterthought.

Why wall removal changes return-air paths

In a typical home, return air is drawn back to the unit through a fairly predictable path: through hallways, door gaps, transfer grilles or dedicated return ducts. Once a wall is removed, that pathway can change in subtle but important ways.

A new open-plan layout may:

• •remove a corridor that previously acted as a return-air route
• •change how air moves around the ceiling space and through doorways
• •expose the return grille to a different dust source, such as a kitchen or work zone
• •alter room pressure patterns so supply air and return air are no longer balanced as expected

This matters because the filter is only one part of the system. If the return side now draws from a different area, the system can see more construction dust, plaster dust, timber dust or general renovation debris than before.

What this means for the filter

A filter that was suitable before the renovation may still be the right fit afterwards, but the actual operating conditions may be different. That is why it is worth checking the filter housing, grille locations and any duct modifications before the system is switched back on.

If the return path has changed significantly, a mechanical services engineer or the building owner should confirm the site requirements, including any relevant considerations under AS 1668.2:2024.

What to inspect before reopening the system

Before turning the HVAC system back on after wall removal, look at the whole air path, not just the visible filter.

Check the return-air grille locations

Confirm that return grilles are still positioned where they can draw air effectively from the new layout. A wall removal may leave a grille in an awkward position, or create a new open area that bypasses the intended return route.

Look for:

• •blocked or partially blocked return grilles
• •grilles left too close to ongoing dust sources
• •trimmed plasterboard, timber offcuts or dust buildup around openings
• •gaps or temporary coverings left from the renovation

Check the filter condition and fit

If the system remained in service during the works, inspect the filter before restarting. Construction dust can load a filter quickly, and a clogged filter can restrict airflow.

A proper check should include:

• •correct filter size and orientation
• •clean seating surfaces and intact seals
• •no warping, crushing or bypass gaps around the frame
• •no visible damage from construction dust or debris

If you need a replacement and are unsure of the dimensions, see how to measure an air filter before ordering.

Check the ductwork and return plenum

Wall removal often means more than a cosmetic change. Trades may have shifted framing, widened openings or opened up spaces around ducts. That can affect where air leaks in or where debris enters.

Look for:

• •accidental openings into wall cavities or ceiling spaces
• •disconnected flexible duct
• •damaged insulation around return runs
• •dust accumulation inside the return plenum

If there is significant contamination, filter servicing or commercial filter servicing may be appropriate depending on the system type and access.

Choosing the right filter after the renovation

The best filter choice depends on the system design, the level of dust expected, and the pressure drop the fan can handle. Open-plan renovations can change both the airflow demand and the type of particles entering the return side.

Match the filter to the equipment

Do not assume that a higher resistance filter is always better. The system needs enough airflow to work properly, and the filter must suit the fan, housing and return grille arrangement.

When selecting a replacement, consider:

• •the filter dimensions and frame style
• •the required media type for the unit
• •whether the system uses standard panel filters, pleated filters or a special format
• •whether the housing can accept a higher-efficiency option without affecting airflow beyond the equipment’s intended range

If the standard size no longer suits the changed layout, custom air filters may be the practical option.

Keep ratings in context

Different rating systems are used for filters, and they do not convert directly. MERV, EN 779 and ISO 16890 are not interchangeable on a simple one-to-one basis. In Australia, G3/G4/F5-F9 are still commonly referenced as EN 779 classes, even though ISO 16890 is now widely used.

If you are comparing products after a renovation, compare like with like and use the system manufacturer’s guidance rather than assuming that one label automatically equals another.

When washable filters may suit the job

Some filters are designed to be washable, but not all are. If you are considering a washable product for a home undergoing renovation, check the product instructions carefully and confirm that the filter type is suitable for the application and cleaning method.

Before restarting: a practical checklist

Once the wall removal is complete and the area is cleaned, go through a final system check before reopening the HVAC.

A sensible pre-start check includes:

• •removing protective coverings from grilles and registers
• •vacuuming dust from accessible return areas
• •inspecting the filter and replacing it if it is visibly loaded or damaged
• •checking that seals, clips and frames are secure
• •confirming that temporary renovation works have not altered the intended air path
• •monitoring pressure drop where gauges are fitted
• •following the filter and equipment manufacturer instructions for restart and maintenance

If gauges are installed, pressure drop is one of the most useful indicators that the filter is becoming restricted. In homes with heavy renovation dust, it is worth keeping a closer eye on the system during the first period of operation after the works finish.

Watch for bypass and leakage

A filter can only capture air that passes through it. If there is a gap around the frame, a loose door or a poor seal at the housing, some air may bypass the filter altogether.

That is why it helps to inspect:

• •the frame seating surface
• •gasket condition, if fitted
• •access door latches and fasteners
• •any new openings created during the renovation

Working with the right supplier during a renovation

For open-plan changes, it is often faster to confirm the filter size, media type and housing details before the system is restarted. That helps avoid delays if the original filter no longer fits the modified return arrangement or if the new layout needs a different configuration.

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, established 2009. We can supply standard filters or make the right filter for the system once the post-renovation layout is confirmed.

If you are unsure what the new return-air path means for your system, take a measured approach: inspect the ductwork, confirm the grille locations, check the filter condition, and speak with the mechanical services engineer or building owner where needed.

For help with the right size or replacement setup, call 07 3800 3448 or request a quote. You can also view our products or contact us if you need to discuss the renovation details first.