How long do flexible heating ducts last in a roof space?

There is no single figure. Duct life depends on the quality of the original ducts, roof temperatures, whether they were supported properly and whether anything has been stored on or near them. Ducts that have sagged, torn or lost their insulation should be replaced whatever their age.

Can torn ducts just be taped up?

Tape can hold a small tear for a while, but it often lets go in the heat of a roof space. A duct with a long split, crushed sections or failed insulation is better replaced. Ask the installer which runs can be repaired and which need replacing.

Do I need new outlets when the ducts are replaced?

Not always. Outlets in good condition can often stay, but old ones may be cracked, rusted or the wrong size for new ducts. Moving an outlet to a better spot in the room is usually easiest while the ducts are being replaced.

Will new ducts make my heating cheaper to run?

Ducts that deliver more heat to the rooms can let the heater run for less time, but the result depends on how much heat the old ducts were losing and on the heater itself. An installer can point out leaks and damage during the inspection, though they cannot promise a set saving.

Is under-floor ductwork replaced the same way as roof ductwork?

The idea is the same, but access is different. Under-floor jobs depend on how much crawl space there is, whether the ground is damp and whether the ducts are buried in sub-floor dirt. Tell the installer if your outlets are in the floor so they can check access before quoting.

Ducted heating duct replacement in Traralgon

Ducted heating duct replacement in Traralgon means pulling out old flexible ducts from the roof space or under the floor and running new, insulated ducts of the right size from the heater to each outlet. People usually need it when far rooms never warm up, airflow at some outlets is weak, or an inspection finds ducts that are torn, crushed or disconnected. An independent local installer inspects the system and quotes the work; this site passes on your enquiry and has no part in the job.

Illustrative photo for Ducted heating duct replacement in Traralgon

What are the signs that ducts need replacing?

Ducts sit out of sight, so the first clue is usually in the rooms.

Weak airflow at the far outlets. The outlets nearest the heater blow hard, the ones at the end of the house barely move.
Rooms that never warm. The heater runs for hours on a cold night and one or two bedrooms stay cold.
The roof space gets warm. If heat is escaping from split or disconnected ducts, it heats the roof instead of the room.
Dust or a musty smell from the outlets. Torn ducts can draw in roof dust or insulation fibres.
Damage you can see from the manhole. Ducts lying flat, crushed under stored items, held together with tape, or with the outer sleeve and insulation hanging loose.
Rodent damage. Chewed ducts are common in older roofs.

In Traralgon, July nights average a low of 3.7 C going by Bureau of Meteorology records from the Latrobe Valley Airport station. On a night that cold, a leaking duct system means the heater runs longer and the house still feels cold.

What does a duct inspection involve?

Leave the roof space to the installer. Roof spaces have exposed wiring, fragile ceilings, loose insulation, and stepping between joists can put a foot through a ceiling. If you want to look, do it from the top of a ladder at the manhole with a torch, and take a photo without climbing in.

A careful installer will:

Run the heater and check airflow at each outlet
Go into the roof or under the floor and follow each duct from the heater to its outlet
Look for tears, kinks, crushed sections, loose joins and missing insulation
Check the duct sizes against the outlets they feed
Check the return air path and filter
Tell you whether a repair of one or two runs will do or the whole system needs replacing

They will not quote a whole-house replacement without going into the roof, and they will not reuse a duct they have not inspected.

Repair some runs or replace the lot?

Situation	Usual approach
One or two runs damaged, the rest in good condition	Replace those runs and reseal the joins
Many runs sagging or torn, insulation breaking down	Whole-house duct replacement
Ducts are fine but the heater is being replaced	Inspect and reuse if suitable, replace any poor runs
Moving from gas ducted to ducted reverse cycle	Check whether the duct sizes suit the new system; often some or all are replaced
Rooms added or layout changed	New runs and outlets for the new rooms, rebalance the rest

What should new ductwork include?

The Victorian Energy Upgrades consumer factsheet from Energy Victoria advises speaking to your installer to make sure new ducting is appropriately insulated and correctly sized for your heating and cooling needs. You can read it in the VEU space heating and cooling factsheet.

In a quote, look for:

The insulation level of the new ducts
Duct sizes for each run, matched to the room
New or reused outlets, and new or reused take-off fittings at the heater
How the ducts will be supported off the ceiling so they do not sag
Removal and disposal of the old ducts
A check of airflow at each outlet once the work is done

How is a whole-house duct replacement done?

The order of work is fairly standard, though every roof is different:

Plan. The installer records each outlet, the room it serves and the duct size it needs, and decides whether outlets move.
Protect the house. Drop sheets go down under the manhole and outlets, and the heater is switched off and isolated.
Strip out. Old ducts are cut free from the heater take-offs and outlets and taken out through the manhole.
Run new ducts. New insulated ducts are laid along the shortest practical path, hung or supported clear of the ceiling, with gentle bends rather than kinks.
Connect and seal. Each duct is fixed and sealed at the heater end and the outlet end.
Balance and test. With the heater running, airflow is checked at every outlet and adjusted so the far rooms get their share.
Clean up. Old ducts go to disposal and the roof access is closed.

Most homes stay liveable during the work, but there is no ducted heating while the old ducts are out.

What does ducted heating duct replacement cost?

The Melbourne guide range for whole-house ducted heating ductwork replacement, supplied and installed, is $2,000 to $6,300, and you can get a duct replacement price for your house to compare. That is a Melbourne metro guide figure including GST. A Latrobe Valley installer may quote differently, and the price depends on the number of outlets, the size of the house, how easy the roof or under-floor space is to work in, and whether the outlets are being moved. All the price bands on this site are listed together in the Traralgon heating and cooling cost guide.

Can old gas ducts be used for a ducted reverse cycle system?

Sometimes, but do not assume it. A ducted reverse cycle system also cools, and cooled air carries moisture, so duct insulation and sizing matter more. The airflow a reverse cycle indoor unit needs may differ from what an old gas furnace pushed through the same ducts.

The Energy Victoria reverse cycle air conditioner buyers guide tells buyers to have the installer confirm that any reused parts are fit for the new system and up to today’s standards. For ducts, that means a written statement on the quote naming which runs stay and why. The new system itself is covered on the ducted reverse cycle air conditioning page, and taking out the gas furnace is part of a gas to electric heating upgrade.

What if the heater is the problem, not the ducts?

Weak airflow can also come from a dirty filter, a failing fan or a heater fault. If the heater is gas, its servicing and safety checks are covered on the gas ducted heating page. A good installer checks the heater and the ducts together before recommending new ducts, so you are not paying to replace ducts when the fault is in the unit.

Who can do duct work?

Replacing flexible ducts that connect to the heater does not by itself involve refrigerant or gas lines, but it often happens alongside work that does. If the gas heater has to be unhooked from its gas supply or flue to reach the ducts, that part falls to a gasfitter on the Building and Plumbing Commission’s books. Work on a reverse cycle indoor unit needs a refrigerant handling licence. Moving or adding outlets near ceiling wiring may need an electrician. Ask the installer who will do each part, and check their licences on the registers listed on the about page.

Next step: describe the ducted system

To book a duct inspection enquiry, include:

The heater’s make and model, from the plate on the unit, and whether it is gas or reverse cycle
How many outlets the house has, and whether they are in the floor or ceiling
Which rooms are weak or cold
Roughly how old the ducts are, if you know
A photo taken from the roof access hole, only if you can take it safely from the ladder
Your suburb, and whether the roof space is easy to get into

An installer can then plan the inspection and tell you what a repair or a full replacement would involve.

Send a job enquiry