New windows, better insulation and careful sealing can make an older home more comfortable, but they also create a reason to review how fresh air enters. Heat recovery ventilation is one option for providing planned air exchange while reducing some of the heating or cooling energy otherwise lost with outgoing air.
It is not an air conditioner, a universal mould treatment or a product every renovation needs. A useful retrofit begins with a ventilation assessment: how the home is occupied, where moisture is generated, how airtight the finished building will be and whether practical routes exist for the equipment.
For more detail on this part of the project, see Moving an Air Conditioner During Renovation: Reuse or Replace?.
For Australian homeowners, the main choices include a central system serving multiple rooms and decentralised units serving selected areas. Compare the complete design, maintenance and installation implications before choosing a model from its advertised heat-recovery percentage.
Understand what heat recovery ventilation does
In a typical balanced heat recovery arrangement, outgoing indoor air and incoming outdoor air pass through a heat-exchange process. Heat transfers between the streams while the system provides controlled ventilation. The exact operation depends on the product and system design.
The Australian Government’s Your Home ventilation guidance describes heat recovery ventilation as a way to temper incoming fresh air using energy from outgoing air. It also emphasises expert design and commissioning. Those two points are central to a retrofit: the benefit belongs to the installed system, not simply the equipment box.
The system does not eliminate the need for heating or cooling. Nor should a household assume it removes every pollutant. Filtration capability varies by product, filter and operating condition, and maintenance affects performance. Ask the supplier to state what the selected system is intended to achieve.
Begin with a ventilation problem you can describe
Write down why the system is being considered. Bedrooms may feel stale when windows remain closed, or the renovation may substantially improve airtightness. Noise outside might make open-window ventilation impractical. Each situation leads to a slightly different brief.
Moisture problems need separate diagnosis. A roof leak, plumbing leak or damp subfloor cannot be solved simply by installing a ventilation product. If condensation is present, the assessment should consider moisture sources, surface temperatures, building details and existing extraction.
Keep those issues within the wider sustainable renovation plan. Ventilation works alongside the building fabric and household use, so selecting it independently can miss the cause of the original problem.
Measure where the information will change the design
A ventilation professional may recommend measurements or a building assessment to clarify the problem. Ask what each test will establish and how it will influence the proposal. A collection of readings is useful only when someone interprets them in the context of the house.
Airtightness is an input, not a complete diagnosis
A blower door result can help characterise building leakage, but it does not by itself prove that every room receives adequate fresh air during normal use. It also does not identify all moisture sources. Use the result alongside the ventilation and occupancy assessment.
The guide to blower door testing before and after renovation explains what that test can reveal and what it cannot.
Compare central and decentralised retrofit arrangements
Central systems
A central system commonly uses a main unit with ductwork serving selected supply and extract locations. The design must provide suitable air paths between rooms, practical external intake and exhaust positions and access for filters and servicing.
This can suit a renovation with accessible roof space or planned service zones. It becomes more complicated where finished floors, shallow cavities or structural elements prevent sensible duct routes. Ask for a layout drawing showing the equipment and all significant routes before accepting a quotation.
The central unit’s service location matters. A filter that can only be reached by climbing into a difficult roof cavity may not be maintained consistently. Ask the installer to demonstrate the proposed maintenance access in terms an ordinary homeowner can understand.
Decentralised systems
Decentralised units can reduce the need for a whole-house duct network, but they still require suitable locations, wall penetrations and a coordinated operating strategy. Fanco’s Australian heat recovery range, for example, includes decentralised products and arrangements for linking multiple units.
Ask how the proposed units work together and which rooms they serve. A product intended for a selected room should not be described as a complete whole-house solution without a design showing how the remaining spaces receive ventilation.
Wall thickness, external appearance, internal noise and access to filters all need assessment. In apartments or attached housing, penetrations may also involve common property or rated construction. Obtain the necessary professional and property approvals before ordering equipment.
Map supply, extraction and transfer paths
A room list is not enough. The designer should show where air enters, where it leaves and how it moves between the relevant spaces. Bedroom doors, acoustic seals and newly enclosed rooms can affect those paths.
Ask for the design to reflect normal occupancy. A system that relies on all internal doors being open may not suit a household that closes bedrooms overnight. Any transfer arrangement needs to coordinate with acoustic expectations and applicable building requirements.
Kitchen and bathroom extraction should be considered explicitly. Do not assume an existing rangehood can be connected to a heat recovery system or that every intermittent exhaust fan becomes unnecessary. The designer must follow the selected system’s requirements and coordinate separate extraction where appropriate.
- Which rooms receive outdoor air?
- Which rooms have extraction points?
- How does air move when internal doors close?
- Which existing exhaust systems remain?
- Where are outdoor intake and discharge points located?
- How will normal and boosted operation be controlled?
Choose external locations carefully
The outdoor-air intake should be assessed for nearby contamination sources, weather exposure and the surrounding building arrangement. Exhaust outlets, vehicle areas and other services can influence the location. Product instructions and applicable requirements must guide the final separation and detailing.
Do not accept a location simply because it produces the shortest duct run. A short route may create an awkward external appearance, exposure to a pollutant source or a maintenance problem. Ask the designer to compare feasible positions on the actual elevations.
Penetrations also need proper weatherproofing and coordination with cladding or roofing. Assign responsibility for those details in the contract. A ventilation installer and a builder should not each assume the other is sealing the building envelope.
Consider climate and moisture behaviour
Australian climates place different demands on ventilation. Outdoor air may be cool and dry, hot and humid, or change substantially through the year. The system selection should respond to those conditions and the way the house is heated or cooled.
Ask the designer to explain whether the proposal uses heat recovery only or a product with moisture-transfer characteristics, and why that choice suits the location. Avoid assuming that similar acronyms describe identical performance. The exact product and design are what matter.
Controls such as bypass modes may be relevant, but their value depends on how the system operates under local conditions. Ask for an ordinary seasonal explanation: what happens on a mild evening, a cold morning and a humid summer day?
Natural ventilation can remain useful when conditions are favourable. The guide to cross-ventilation in renovated homes helps identify where operable windows and planned mechanical ventilation can complement each other.
Compare noise at the intended operating setting
A quietest-setting specification can be misleading if the system must operate faster to deliver the designed airflow. Request relevant sound information at the normal and boost conditions proposed for your home.
Noise can reach rooms through the unit, ductwork, grilles or the building structure. Ask how the design addresses bedrooms and quiet work areas. A central unit hidden above a bedroom ceiling may deserve a different location or acoustic treatment.
For decentralised units, consider the proximity to the bed and how the sound changes through the operating cycle. If a display is available, listen to the exact model at useful settings. A catalogue description such as “whisper quiet” is not a substitute for a considered room design.
Make filter maintenance practical
Ask which filters are supplied, what they are intended to capture and how often inspection or replacement is recommended for the actual environment. Dust, pollen and other local conditions can influence the maintenance routine.
Confirm the replacement part numbers, availability and cost. A low purchase price is less attractive if filters are difficult to obtain or replacement requires a service visit the household did not expect. Check whether cleaning is permitted for the selected filter rather than assuming all filters can be washed.
Have the installer demonstrate access before final sign-off. The household should know how to identify the correct filter and which tasks remain the responsibility of a service professional. Record the routine with the rest of the home’s maintenance information.
Build a complete retrofit budget
The main unit price is only one component. Allow for design, ductwork or wall penetrations, electrical work, controls, external grilles, weatherproofing, acoustic measures, commissioning and making good. Difficult access can materially change the installed total.
For illustration only, a central retrofit budget might allow AUD $4,000–$7,000 including GST for equipment and controls, AUD $3,000–$6,000 for distribution and installation, and AUD $1,500–$3,000 for electrical work, penetrations and repairs. The combined illustrative allowance is AUD $8,500–$16,000.
These are invented planning ranges, not current Australian market prices. They exclude major structural alterations, hazardous-material work and unusual access. A smaller decentralised arrangement may have a different scope and should be quoted for the actual rooms served rather than compared as though it provides the same coverage.
Use a structured quotation comparison to make the coverage and exclusions clear. Ask each supplier to identify design airflow assumptions, maintenance access and commissioning deliverables.
Keep savings claims separate from comfort claims
A heat-recovery percentage describes a particular aspect of product performance under stated conditions. It is not the percentage by which the household’s total energy bill will fall. Fan electricity, building leakage, climate and the previous ventilation method all influence the eventual result.
For an illustrative operating-cost calculation, a system averaging 40 watts over 24 hours uses 0.96 kWh. At an assumed electricity rate of AUD $0.35 per kWh including GST, that electricity costs about AUD $0.34 per day. This does not include filter replacement or quantify recovered heating and cooling energy.
Ask a supplier making a payback claim to show the comparison scenario. Replacing open-window ventilation during cold weather differs from adding ventilation to rooms that were previously underventilated. The latter may improve comfort and air exchange without reducing the bill.
Coordinate installation with the renovation programme
Resolve routes while ceilings or walls are accessible and before joinery occupies the proposed equipment space. Protect installed ducts and components from construction dust. The builder and ventilation installer should agree when the system may be operated during finishing work.
If the renovation also changes heating or cooling, coordinate the systems but do not assume they share compatible ductwork. The guide to air conditioning duct replacement explains why retained distribution needs assessment rather than automatic reuse.
Allow time for commissioning after the building is sufficiently complete. The installer should check the intended operation, explain controls and provide the relevant measurements and settings. A system connected to power has not necessarily been commissioned as designed.
Agree how changes will be handled
Renovations often reveal an obstructed cavity or an unexpected beam after work begins. Ask the installer to obtain approval before changing a designed route or relocating a room outlet. A seemingly minor alteration can affect access, noise or distribution. Keep the revised drawing with the commissioning record so future servicing is based on the installed system, rather than an early concept plan.
If the project is staged, identify which rooms are served initially and what further work is required for later coverage. Do not describe an incomplete first stage as whole-house ventilation. The handover instructions should match the stage actually installed and occupied.
Choose the proposal you can maintain and understand
Before accepting a quote, ask the designer to show the air path, maintenance access and seasonal operating strategy on a single set of drawings. Confirm who will handle service calls and how replacement filters are obtained.
Heat recovery ventilation is most useful when it responds to a clear need and fits the building. A well-designed, accessible system can support a more comfortable renovation; an oversized promise attached to an inaccessible product is much less valuable.