Building Defect in New House - Bathroom Exhaust Fan Not Vented outside

Ecivon on 02/09/2025 - 17:19
Last edited 03/09/2025 - 16:58

Hi everyone,

​I'm hoping to get some advice and hear about similar experiences regarding a building defect in my new house, which was completed last year in Victoria.

​I recently discovered that my bathroom exhaust fan (model MXFSS25W) is not connected to a duct to vent outside. Instead, it seems to be blowing humid air directly into the roof space( colorbond roof). I believe this is causing the fan's suction to be extremely weak and the bathroom gets very steamy after only a few minutes of showering.

I've tried contacting the builder's maintenance team about this, but they've been not much helpful so far, claiming the subcontractor is not responding.

​I've also done some research and found that this practice is a clear violation of the National Construction Code (NCC) and is considered a serious defect by the Victorian Building Authority (VBA). https://www.vba.vic.gov.au/news/news/2022/complaints-exhaust…

​Has anyone here dealt with a similar issue in a new build? I've already drafted an email to the builder, but I'd like to know what to expect.

​Any advice on the best way to handle this with the builder, or what steps to take, would be greatly appreciated.

​Thanks in advance.

Home & Garden

Comments

  • battler on 02/09/2025 - 17:26
    +2

    Is the roof space ventilated per the code?

    • Ecivon on 02/09/2025 - 17:51
      -4

      I got one whirly bird thats all I can see.

    • Dr Phil on 03/09/2025 - 12:27
      -8

      "​I recently discovered that my bathroom exhaust fan (model MXFSS25W) is not connected to a duct to vent outside. Instead, it seems to be blowing humid air directly into the roof space( coluorbond roof)"

      OMG! This is NOT a defect!

      This is NORMAL

      whats not normal is your spelling of "Colorbond"

      https://colorbond.com/

      • mrvaluepack on 03/09/2025 - 13:51
        +2

        It is if its a new energy efficient build with a sealed roof.

      • Ecivon on 03/09/2025 - 16:59

        Corrected thanks

  • mskeggs on 02/09/2025 - 17:29
    +6

    This was common in the old days, as the roof space had multiple vents.
    If your roof cavity does not have any vents, the rectification is to add ducting to an eave, or add some vents.
    My preference would be to use ducting to preserve maximum insulation.

    Probably not a big deal, and reasonably easy to correct in most cases.

    • Ecivon on 02/09/2025 - 17:53
      -4

      I got one whirly bird thats all I can see

    • Dr Phil on 03/09/2025 - 12:29
      -4

      Incorrect

      All roof spaces are naturally vented

  • JimmyF on 02/09/2025 - 17:57

    ​I recently discovered

    Cool, but when was the house built? As it will depend on when it was built for what was code at the time.

    • Ecivon on 02/09/2025 - 18:00
      +2

      Mine is built last year and the code was published in 2022

      • MrFrugalSpend on 03/09/2025 - 17:33

        It is not important when it was finished being built, the building code will apply from when the design undertaken and more specifically, when the building certifier was appointed. This could have locked in a version prior to the 2022 code, because they kept delaying the actual date the code took effect.

        There was a later transition date for new energy efficiency, condensation mitigation, and livable housing requirements which did not come into effect until 1 October 2023. If the certifier was appointed prior to then, the previous standard would apply.

        My house, my parents house, my in laws house, most I can think of are vented straight into the roof with no issues I'm aware of coming from it as the roof space is ventilated.
        That said, I would duct it out if doing a new build going forward and bought draft stoppers to retrofit from bunnings for sealing it up when it is off like this - https://www.ebay.com.au/itm/305897784714

  • Ecivon on 02/09/2025 - 17:59
    -1

    I just found my plan states as below

    The Energy Rating Inclusions on Page 3, item 5, require that "100% of Exhaust fans to be sealed"

    What is the correct interpretation of this statement?

    • GordonD on 02/09/2025 - 18:14
      +3

      I'm seeing two different definitions of a sealed ehaust fan.

      One is that the there's no leakage around the fan housing.

      The other is that it cuts off air flow so when it is not running heat can't get out or in through the fan.

      If you look at the VBA document you cited, it is allowable to vent the fan into the roof space if the roof space is ventilated. But it must be ventilated according to the rules.

    • JimmyF on 02/09/2025 - 18:57
      +3

      Exhaust fans to be sealed

      Means they have a draft stopper fitted.

      • MrFrugalSpend on 03/09/2025 - 17:35

        this is an easy thing to retrofit for almost no money - like $40 on amazon

    • foolsgold on 03/09/2025 - 11:48
      +5

      dont know why your getting negged. It's hard to definitively know which version of NCC your house was built in without seeing the actual permit documents. I'd say it's likely to need to be exhausted to atmosphere, ie via a duct would be best practice.

      New regs require it to be ducted to outside. If your house was finished last year, its likely NCC2019 but theres a chance it could be older NCC2016. For instance I have one project that STARTED (ie not finished) this month that is NCC2019, and one more thats due to start November thats NCC2019 too. And within NCC2019 there are different volumes and revisions.

      Older regs allowed for bathroom vents to vent into a roof space if it was adequately ventilated or wasn't sarked.
      Anyway, its not a huge deal, most builds prior to 2015 ducted to a roof space, and heaps were installed without self closing dampers. The only one that i'd be upset is if your rangehood exhausts into your roof cavity, again very common, I just find it dirty. And I'd say if they didnt exhaust your fans out they probably didn't do the rangehood either.

      To others commenting about energy loss, yes its true, from an energy rating point of view, any ceiling penetration including recessed downlights, recessed smoke alarms, fans etc reduce your energy efficiency so these should be addressed too if your going to get anal about the fan

      • mskeggs on 03/09/2025 - 14:35

        Good info, thanks.

      • MrFrugalSpend on 03/09/2025 - 17:35

        Yes - These new codes always transition in slowly so as to not impact designs and contracts that are already underway.

        Plus the new energy efficiency, condensation mitigation, and liveable housing requirements transitioned in later - 1 October 2023. So if the certifier was appointed before then, even if the permit was not yet issued, the old standard could apply.

        Was it this provision that made it mandatory for Class 1 builds or was there one in 2015 you mentioned? I do commercial mainly Class 5 and 7 so not my forte.

    • foolsgold on 03/09/2025 - 11:51
      +1

      What energy rating did your house achieve? That could give you a clue a to what revision of the code it was complied under. If its below 7 stars its like NCC2019 or older.

  • MrHyde on 02/09/2025 - 18:56

    We had our house renovated in 2020 and the builders did the same - bathroom exhaust went into the roof space. They said that it was as per code since there was sufficient ventilation in the roof and they showed us the house plans which did not have any ducts shown in them.

    Since we realised this early enough, we requested changes to the plans and had ducts put in ventilating to the outside. No issues with the builder making the changes.

  • Hybroid on 02/09/2025 - 19:03

    All new builds are like this unfortunately. Just vents into void or roof space and not exhausted outside.

    • ricadam on 03/09/2025 - 09:39
      +1

      Mine (settlement Feb '25 from a major volume builder) is exhausetd outside.

    • Domingo on 04/09/2025 - 01:56

      Mine, build completed 2022, has exhaust fans that are vented to outside

  • MS Paint on 02/09/2025 - 19:20
    +6

    Non compliant

  • AndyC1 on 02/09/2025 - 19:59
    -2

    Call your lawyer and ask them.

  • joka on 02/09/2025 - 21:55
    +7

    I’m exhausted

    • JIMB0 on 03/09/2025 - 08:16
      -1

      Better than being tyred.

    • bdl on 03/09/2025 - 09:29

      now you're just blowing hot air

    • altomic on 04/09/2025 - 06:51

      You’re just venting

  • BeeseChurger on 02/09/2025 - 22:01
    +1

    Guys this is non compliant

  • Duckie2hh on 02/09/2025 - 22:10
    +2

    exhaust fan from bathrooms do not need to vent to outdoor. Mine is the same OP.

    • waade395 on 02/09/2025 - 22:16
      -4

      Section 10.8.2 of the NCC disagrees with you

      • Duckie2hh on 03/09/2025 - 08:18
        -1

        Last time I checked, roof spaces are not air tight….

        • waade395 on 03/09/2025 - 12:59

          It isn't based on your opinion. The fact your fan doesn't vent externally doesn't mean it's compliant to current standards.

          The 2022 NCC word for word is:
          "Exhaust from a kitchen, kitchen range hood, bathroom, sanitary compartment or laundry must discharge directly or via a shaft or duct to outdoor air."

          The 2019 NCC which the VBA article OP linked references, allowed for exhaust fans to discharge to a ventilated roof space. That is no longer the case.

      • Penguin30 on 03/09/2025 - 16:48
        -1

        If you read it, it does not.

        All you need is a window of a certain size for the room.

        An exhaust fan while good and I would put one in isn't even required.

        As it is installed better to have a duct but not required at all.

        No duct is not a defect.

        • waade395 on 03/09/2025 - 17:31

          Quote me the clause you've apparently read to arrive at the conclusion ducting isn't required.

          Because agreed, an exhaust fan isn't required but if one is installed:

          "An exhaust fan or other means of mechanical ventilation may be used to ventilate a sanitary compartment, laundry, kitchen or bathroom, or where mechanical ventilation is provided in accordance with 10.6.3(b), provided contaminated air exhausts comply with 10.8.2."

          And per my comment above, section 10.8.2. reads…

          "Exhaust from a kitchen, kitchen range hood, bathroom, sanitary compartment or laundry must discharge directly or via a shaft or duct to outdoor air."

          The 2019 NCC which the VBA article OP linked references, allowed for exhaust fans to discharge to a ventilated roof space. That is no longer the case.

          • Penguin30 on 03/09/2025 - 23:53

            @waade395: Read part (5) then click the link.

            You are only looking at the requirements of an exhaust fan not of the actual code as a whole.

            If you have a window that is sufficient you don't need a fan at all. In turn the venting of said fain is not required.

            If you have a room with no ventilation ie window.

            You do need a fan capable of venting to the outside.

            Check 10.6.2

            Ventilation requirements.

            As you quoted " exhaust fans may be used" part c
            The top ventilation requirement is a window. Part a

            Window is usually the primary ventilation for most bathrooms and will void the need of an exhaust fan at all. So if there is a window in the bathrooms which I doubt there is not one they don't really need to have it vented to outside. As the window is the primary ventilation used.

            • waade395 on 04/09/2025 - 01:14

              @Penguin30: You're conflating the intent of two different requirements. 10.6 relates to managing ventilation of a space, this talks about windows.

              10.8 relates to condensation management of exhaust systems if one is installed. This does not care whether a window exists.

              "they don't really need to have it vented to outside". Cool opinion, it is not what's written in the code. The intent is that you cannot vent moist air into the roof space.

              If you need it spelled out even clearer, what you're stating was explicitly permitted in NCC 2019 3.8.7. This statement is now removed in NCC 2022:
              "Exhaust from a bathroom, sanitary compartment, or laundry must be discharged—

              (i)
              directly or via a shaft or duct to outdoor air; or

              (ii)
              to a roof space that is ventilated in accordance with 3.8.7.4."

              I literally just successfully held a builder accountable to this. They tried quoting venting externally as an upgrade but acknowledged it is included standard as part of NCC compliance.

    • mrvaluepack on 03/09/2025 - 13:54
      +1

      New energy efficient builds have sealed roofs and need vents to outside. Your house is probably old, pre-2020 build.

      • Duckie2hh on 03/09/2025 - 15:52

        yep

        • waade395 on 03/09/2025 - 17:32

          congrats, your anecdotal experience doesn't apply lol

  • ForkSnorter on 03/09/2025 - 07:16
    -4

    Not a big deal. A lot of houses are like this. I keep the door open when I shower. Bathroom window is open too.

    If you don't like it, get them (or someone) to put a vent in.

    The reality is, even with a properly vented fan, you will still get a steamy bathroom if you have a long, hot shower.

    after only a few minutes of showering

    How long do you want to be showering for? Many minutes?

  • MartinESQ on 03/09/2025 - 07:45
    +3

    It’s your builders responsibility to fix. The fact that that their subcontractor isn’t responding isn’t your problem.

    Go back to your contract and enforce the provisions about maintenance.

    You might want to get someone like https://www.suretyproperty.com.au/ to do a post handover inspection and find out anything else the builder might have not done correctly.

    We had the same issue with fans not ducted externally.

  • jellykingdom on 03/09/2025 - 08:56
    +1

    I don't recall whether the ducting is or isn't required.

    However…

    I doubt the fan's lack of suction is related to venting into the roof space. Its probably just undersized for the room size. Have a google and find one of those Air Change calculators, then check the CFM rating of the fan.

    • Nebargains on 04/09/2025 - 08:55

      Was thinking the same thing, I have an older house, probably built in the 70s and both bathrooms just vent into the roof space and neither room gets steamy with the fan on. I would say the fan is just undersized for the room.

  • Bignudge on 03/09/2025 - 09:51

    Same thing with my house built in the 80s. Bathroom exhaust fan pulls air straight into the roof cavity. I've since blocked it off and just installed another exhaust fan at the window. Works great!

  • mrvaluepack on 03/09/2025 - 13:56

    Looking at the majority of comments here, a lot of people are still living in pre-2020 built houses which do not have sealed roofs. Please get yourselves up-to-date, most new builds now have sealed roofs and require a vent to outside.

    • mskeggs on 03/09/2025 - 18:22
      +6

      Incredible that people persist in living in pre-2020 build houses!

      • Muppet Detector on 03/09/2025 - 19:47

        Homeless numbers are increasing though.

        • tenpercent on 03/09/2025 - 20:05
          -1

          Homeless numbers are increasing though

          Yes they are. At the fastest rate on record.

          There's an extreme shortage of dwellings in this country primarily due to the record breaking mass immigration we've seen since Albo became PM (although it was already bad under the previous LNP and the previous previous Labor governments too) and terrible planning and education policies for decades. We're literally full.

          Every new immigrant family arriving in Australia is indirectly or directly pushing a family already here into homelessness or over-crowded shared accommodation.

          • Muppet Detector on 03/09/2025 - 20:20

            @tenpercent: Don't stress. These things have a way of sorting themselves out eventually.

            People are coming.
            People are leaving.
            More people are dying than the
            People being born.
            People will start to move further inland.

            Before too long, another disaster will thin the herd a bit more too.

            Just keep cool. In time, things will sort themselves out and we will all be fine.

  • StingyBritches on 03/09/2025 - 16:07

    A genuine, curious question:

    By “sealed roof” do you mean Colorbond, not tiles?
    Or, would a sarked, tiled roof be classed as ‘sealed’?

    • wiltonson on 03/09/2025 - 17:09

      I'm confused and curious for an answer too, I have colorbond roof build in 2008 but my exhaust fans are ducted to outdoor ceiling

    • mrvaluepack on 03/09/2025 - 17:13
      +1

      Yes sarking and insulation would be considered 'sealing' the roof space and not allowing it to breathe/ventilate naturally.

  • Ecivon on 03/09/2025 - 17:08
    +1

    It looks like this has been, and still is, a very common practice in Australia, but it's neither ideal nor practical for the building or its insulation. Unfortunately, my building contract was under the NCC 2019 standards. I simply didn't expect that having no ductwork in the roof cavity would be considered safe and fine here, which is completely different from where I grew up.

    Thanks for those some helpful comments anyway guys!

  • ScottEh on 03/09/2025 - 17:29

    Is there sufficient new air coming into the bathroom? If doors and windows are closed when showering, it may be hindering exhaust performance.

  • OkWing99 on 03/09/2025 - 17:39

    Old house = Not a problem.
    New build = A problem.

    Reason: This rule was changed very recently. If you have an old house and it's vented to roof, it's ok. If it's a new build, it should be vented outside (either through the roof, or side.)
    Raise it with the builder. Not a major issue, might take a couple of hours of work to vent to outside with a kit (single story).

    Don't think it's intentional. Because the rule was changed recently, the tradie who did it may not be aware.

    • CalmLemons on 03/09/2025 - 21:57

      Depends if the build started/or was designed? before the NCC set in.

  • moneyhungry on 03/09/2025 - 19:11

    I could smell non-compliant works.

  • Holm81 on 03/09/2025 - 19:25

    I had a house and land package built in 2022 and before final payment, had a professional come over. He gave me a detailed report on all the things that were wrong, the worst being exhaust vents going straight onto roof. Not as bad as recent ones on tiktok of some walls being made of foam.
    The report stated "Exhaust Fans Not Vented.
    Information: On inspection of the roof void, it was observed that the exhaust fans do not exhaust directly to the outside of the building, which is required by the NCC if sarking has been fitted, as it has in this home."
    The worst I had seen was my friend's granny flat. Their kitchen exhaust went into what seemed like a cupboard above. There was no filter box.

    Also check the front door is adequately sealed. There was a huge gap and I didn't push to fix. That was the other non-complaint thing. When the wind blew in winter, no amount of heating helped with such a gap, plus cockaroach came in through that gap.

  • genus on 03/09/2025 - 21:20

    It may well be non-compliant with some bureaucrat's code but codes only work if that fan is in use. Consider how much faster mould will grow if you do duct it and then move in with a tribe who keep forgetting to turn the fan on during their hour long shower sessions. I'd rather have it vent direct into a roof space whether it's fully sealed or not. At least you get a bit of natural ventilation this way.

  • CalmLemons on 03/09/2025 - 21:56

    We're sort of in a transition, even though the new codes are in.

    For every single house 2010 and before it was fine to have the exhaust fan blowing directly into the roof cavity, literally 99% of the houses in australia have done this.

    You will be fine.

    Even if your roof space is designed to be 'airtight', I assure you, it isn't.

    Unless you spent $1.5m on the building alone and it is a passive house.

  • 91rs on 03/09/2025 - 22:04

    Had this issue with a builder, had 3 bathroom exhaust fans that were not vented externally (as per the code or documents we had been provided at the time), and one for the range hood that was just thrown on top of some insulation.
    I just kept on the builder about it, had other issues, not all rectified sadly as they just stopped responding and never did the final warranty walk through etc, went to the VIC Domestic Building Dispute Resolution Victoria (DBDRV) which was just a waste of my time as they have absolutely zero power, I spent so much time preparing for the meeting and all the builder has to do is either not turn up or just say that they will not be doing something about each item on your dispute list and then thats it.
    Another useless VIC govt department, the whole state needs a bloody overhaul its shocking.

  • Herbs on 03/09/2025 - 22:55

    This issue annoyed me about my house too, though with 2 bathrooms. I purchased and installed new fans, ducting and an external vent gravity grill to solve the problem. Wasn't difficult or costly, and no additional wiring was required as the new fan plugged into the existing power outlet.

  • psdillon on 04/09/2025 - 08:07

    If that's your only problem in a recently built house, you're definitely winning by a long shot!

  • Hangryuman on 04/09/2025 - 08:40

    'I believe this is causing the fan's suction to be extremely weak and the bathroom gets very steamy after only a few minutes of showering'

    I've seen a lot of poorly ventilated bathrooms in strata unit complexes, with all kinds of failed/wrong installations. Poor suction often results when the fan cannot draw from or into a closed space

    Warm moist air condenses on cold surfaces, e.g. when you turn on the hot shower in a cold wall bathroom. I'm guessing steam (like clouds in the sky) results when warm moist air mixes with or rises to a layer of colder air.

    The problem in cold winter when you are wet and naked in a bathroom is the wind-chill factor - any breeze from a strong, effective fan can make you shiver with the cold

    The classic problem I've seen in units is young tenants never open the windows in winter because they don't want to pay more for heating, resulting in condensation running down the inside surface of external glass windows, and mould even growing on ceilings

    I've seen one place complaining of mould, where I walked in and it felt like a steam room - they were boiling a saucepan of water on the stove to try to warm the place up, and the bedrooms had condensation dripping off the ceiling, so to try to prevent it dripping on their face while they slept, they had stuck paper all over the ceiling, which was now black with mould - the worst I've ever seen. When I told them they needed to open the window to allow the moist air to go out, they said they were trying to save on heating costs. D'Oh!

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