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A heat recovery ventilator is a small fan unit that runs two air streams past each other through a core: stale air on its way out of the house, fresh air on its way in. The core lets heat cross between them without the two streams mixing, so the incoming air arrives already close to indoor temperature. An energy recovery ventilator does the same with heat and also transfers a share of the moisture, which is the difference that decides which one suits an Australian address.

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These units exist because of a change in how Australian houses are built rather than because of a change in the weather. A house that has been deliberately sealed, with a well-detailed envelope and few uncontrolled gaps, stops ventilating itself the way a draughty weatherboard did. That is good for comfort and running cost and bad for indoor air and condensation, and mechanical ventilation with recovery is the designed answer. Fitting one to a leaky house is putting a good system in series with a large hole.

So the sensible sequence is envelope first, ventilation second. Recovery ventilation is normally specified during a new build, a deep retrofit or a major renovation, when the ducting can be routed properly and the envelope is being addressed at the same time. It is a design decision with an installer attached, not an appliance you add on a weekend, and the quality of the duct layout matters at least as much as the unit you buy.

Heat recovery or energy recovery: what Australian humidity decides

In the cooler south, the problem in winter is that ventilation throws away heat you have paid for, and the house often has too much internal moisture rather than too little. A heat recovery unit is the straightforward answer there: recover the warmth, let the moisture leave with the exhaust air. Melbourne, Hobart, Canberra and the southern tablelands are the classic case.

In the humid subtropics and the tropics the calculation reverses. For much of the year the outdoor air is not only hotter than the indoor air but considerably wetter, and a ventilator that recovers heat alone will happily import that moisture into an air-conditioned house, undoing work the air conditioner has just done. Energy recovery, which transfers a proportion of the moisture as well as the heat, is what makes ventilation sustainable in Brisbane, Darwin and the Queensland coast.

In the temperate and dry inland zones the answer depends more on the building than on the postcode, and it is reasonable to ask the designer to show their reasoning. Either way, the unit is chosen against the climate and the house, and anyone quoting the same model from Hobart to Cairns is selling a box rather than designing a system.

The forms recovery ventilation takes in an Australian house

  • A centralised ducted unit in the roof space, drawing stale air from wet rooms and delivering fresh air to bedrooms and living areas through its own duct network.
  • A compact unit serving part of a house, common in an apartment or a self-contained extension where a full ducted layout is impractical.
  • Single-room or through-wall units that alternate direction or run in pairs, used where running ducts is impossible and where one or two rooms carry the problem.
  • A balanced supply and extract arrangement, which is what recovery requires, as distinct from a simple positive pressure roof ventilator that pushes roof space air into the house without recovering anything.
  • Systems with a summer bypass, which route air around the core when recovering heat would work against you, which matters in a climate with hot days and cool nights.
  • Systems with filtration on the supply side, which is what makes recovery ventilation attractive in a smoke or pollen prone area as well as a cold one.

How a recovery ventilation system should be specified and installed

Almost every disappointing recovery ventilation system in Australia was installed by someone who treated it as an appliance. It is a distribution system, and the parts that determine whether it works are the parts nobody sees.

  • An assessment of the envelope first, because recovery has nothing to recover in a house where air is entering through every architrave.
  • Airflow rates set room by room, with extract in kitchens, bathrooms and laundries and supply in bedrooms and living areas, so the house has a deliberate air path rather than a fan in a box.
  • Duct runs designed for the shortest practical path, with smooth ducting and sweeping bends, since every tight turn costs airflow and adds noise.
  • Intake and discharge terminals placed well apart and away from anything that pollutes, including the driveway, the rubbish bins, a flue and the neighbour's outdoor unit.
  • The unit itself accessible for filter changes, which in an Australian roof space means near the manhole rather than at the far gable.
  • Condensate drainage from the unit taken to a legitimate discharge point, because a recovery core produces water and a roof space is a poor place to leave it.
  • Commissioning with measured airflows at each terminal, balanced supply against extract, and the results recorded so the system can be checked again later.

What goes wrong with recovery ventilation in Australian roof spaces

  • Unbalanced airflow, which turns a balanced system into a pressurising or depressurising one and can interfere with flued appliances elsewhere in the house.
  • Flexible duct left kinked, crushed under a truss or run in long sagging loops, which quietly removes most of the design airflow.
  • Filters never changed, because the unit was installed where nobody can reach it, which is the most common reason a system underperforms after a few years.
  • Intake positioned where it draws exhaust from a flue, a clothes dryer vent or a nearby outdoor unit.
  • Condensate allowed to discharge into the roof space or onto the ceiling, which produces exactly the damage the system was meant to prevent.
  • A summer bypass that was never enabled or was set incorrectly, so the system imports heat on the afternoons you most want it not to.
  • Noise carried along the ducts from the unit to a bedroom, which is what makes households switch systems off and leave them off.

Balance, flued appliances and negative pressure

Any mechanical ventilation changes the pressure inside a house, and that matters wherever there is a flued combustion appliance. Energy Safe Victoria explains that appliances such as bathroom exhaust fans can lower the air pressure inside a room and create a negative pressure environment, and that airflow through a flue may then become restricted or even reversed, with the flame producing high levels of carbon monoxide if the supply of fresh air to the burner is interrupted.

A recovery ventilator is meant to be balanced, so in principle it does not depressurise the house the way a large extract fan does. In practice it is only balanced if someone measured it, and it shares the house with rangehoods, bathroom fans and clothes dryers that are not balanced at all. If the house has an open-flued gas heater, a gas hot water unit indoors or a solid fuel heater, the ventilation designer needs to know before the system is specified, and the gasfitter needs to know before the next service, since Energy Safe Victoria states that gasfitters are required to test during installation and servicing to ensure heaters do not spill combustion products and that exhaust fans do not affect the heater.

Keeping a recovery ventilator working

  • Change or clean the filters at the interval in the manual, and more often in a smoke season or near a busy road, since a blocked filter starves the system and strains the fan.
  • Clean the core itself at the manufacturer's interval, because dust that gets past a filter collects in the narrow passages where the heat exchange happens.
  • Check the intake and discharge grilles outside for insect nests, cobwebs and vegetation each year.
  • Confirm the condensate drain is still flowing, particularly after a long dry spell when a trap can evaporate.
  • Listen for a change in noise, which is usually the first sign of an unbalanced fan or a partly blocked duct.
  • Keep the commissioning airflow figures, so a technician has a baseline rather than a guess if performance is ever questioned.

What moves a recovery ventilation quote, and how LokalMatch fits in

The drivers are the number of rooms being served, whether the roof space allows a sensible duct layout, the length and complexity of the runs, whether filtration and a summer bypass are included, and whether commissioning with measured airflows is part of the price. A system quoted for a new build where ducts can be run before the ceiling goes on is a different job from the same system retrofitted through an existing roof space above a plaster ceiling.

LokalMatch is where the job starts, not where it ends. Describe the house, whether it is a new build, a renovation or a retrofit, the roof space access, any flued gas appliances and your postcode, and ventilation and mechanical services businesses covering your area contact you directly; those businesses pay LokalMatch for the requests they receive. LokalMatch does not do the work, does not set or quote prices and does not vet, rank or recommend anyone, so ask for the room-by-room airflow design and the commissioning figures in writing.

HRV & ERV Systems: frequently asked questions

Do I need heat recovery ventilation in an ordinary Australian house?

Most existing Australian houses leak enough air that a recovery ventilator has little to recover, and the money is better spent on the envelope and on targeted extraction in wet rooms. Recovery ventilation earns its place in a house that has been deliberately sealed, in a new build designed that way, or in a deep retrofit where the envelope is being addressed at the same time. Ask any installer to justify it against the house you actually have.

What is the difference between an HRV and an ERV?

A heat recovery ventilator transfers heat between the outgoing and incoming air streams. An energy recovery ventilator transfers heat and also a proportion of the moisture. In a cool southern climate where you want indoor moisture to leave, heat recovery is usually the right choice. In humid subtropical and tropical Australia, where outdoor air is often much wetter than the air inside an air-conditioned house, energy recovery stops ventilation importing that moisture.

Is a positive pressure roof ventilator the same thing?

No. A positive pressure unit takes air from the roof space, filters it and pushes it into the house, which is a different concept with a different purpose. It does not recover heat, and the quality of what it delivers depends on the condition of your roof space. Recovery ventilation is a balanced supply and extract system drawing fresh air from outside. They are sometimes sold in the same conversation, so ask which one is being quoted.

Will a recovery ventilator make my house cold in winter or hot in summer?

Not if it is specified properly. The point of the core is that incoming air arrives close to indoor temperature rather than at outdoor temperature. In summer, a unit with a bypass can route air around the core on cool evenings so the house can purge heat. What does make a house uncomfortable is an unbalanced or badly ducted system delivering cold air straight at a bed, which is a design and commissioning failure rather than a property of the technology.

Can recovery ventilation help with bushfire smoke or pollen?

It can, because the supply air passes through a filter before it enters the house, and because a house with a designed ventilation path is a house you can keep shut. How much it helps depends on the filter grade fitted, how well the rest of the envelope is sealed, and whether the system is set to reduce or stop outdoor intake when the air outside is very poor. Ask the installer what the unit can do on a heavy smoke day, and check that the filter type is one you can readily buy.

Do I still need bathroom and kitchen exhaust fans?

Usually yes, and a good design uses them deliberately rather than pretending the recovery system replaces them. Cooking and showering produce bursts of moisture and odour that a continuous low-rate ventilation system is not sized for, and rangehood extraction in particular is its own requirement. The important thing is that the designer knows what else is extracting from the house, so the whole arrangement stays balanced and any flued appliance stays safe.

Sources

  1. Energy Safe Victoria: Open-flued gas space heaters, frequently asked questions

Written by the LokalMatch editorial team. Last reviewed 22 September 2026. How we write and check our guides

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What affects the cost of HRV or ERV

Prices depend on the details of your project. We only publish price ranges when they’re backed by real LokalMatch quote data or reliable sources. Until then, here’s what usually changes the price:

  • Type of system and fuel source
  • Size and efficiency of the equipment
  • Condition of the existing ductwork and venting
  • Electrical or gas line changes
  • Access to the furnace room, attic or outdoor unit location
  • Removal and disposal of the old equipment
  • Emergency or after-hours service

How to compare HVAC contractors before you hire

  • Hire a technician who is licensed for heating, cooling and gas work in your area.
  • For a new system, ask for a load calculation for your home rather than a size based on the old unit.
  • Get written quotes that list the equipment, ductwork changes, removal of the old unit and any electrical work.
  • Ask how they handle service calls and repairs after installation, including in the middle of winter.
  • Compare the full scope of each quote, not only the equipment on it.

Questions to ask HVAC contractors before you hire

  • Are you licensed for this type of heating, cooling or gas work in my area?
  • How did you decide what size of system my home needs?
  • Does this installation need a permit, and will you take care of it?
  • What does the manufacturer's warranty cover, and what does your labour warranty cover?
  • Will you need to change the ductwork, venting or electrical to make this work?
  • Do you offer maintenance plans, and what do they include?
  • How quickly can you respond if the system stops working?

When to call a pro for HRV or ERV

  • If you smell gas, leave the home and call your gas utility's emergency line from outside.
  • If a carbon monoxide alarm goes off, get everyone outside and call emergency services.
  • No heat in cold weather, or a furnace that keeps shutting off
  • Unusual noises, burning smells or a big jump in energy use

HRV or ERV permits and local rules

Some HRV or ERV work needs a permit or has to meet local bylaws. Rules vary by municipality, so ask your pro whether a permit is needed and who will apply for it — and check with your city or town if you’re unsure.

Permits and licensing

Seasonal maintenance

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