Humidity High in Sydney

Ozbfan on 25/05/2025 - 17:04
Last edited 25/05/2025 - 18:07 by 1 other user

I purchased a little Sensibo air quality meter a while ago and I’ve noticed it’s always very high humidity in my house (4bdr), at nighttime typically about 80-90% and the daytime minimum of at least 70%. Live in Southwest Sydney.

I’ve started hanging clothes outside but it’s not really making any difference. I read online that ideal humidity should be between 30 to 60% to prevent mould. I bought a high capacity dehumidifier but it uses about 800w and while it helps a room that it's in, it doesn’t do much for the whole house. I could potentially put the ducted Aircon on fan mode and have the dehumidifier on but that would use well over a kilowatt and I’d have to run it all day.

I looked at the outside humidity levels and there is only a slight difference to what I’m experiencing inside even if we left the doors open all day I don’t know if it would make much of a difference.

The only thing I could think of is to buy a whole house ducted dehumidifier and run it during peak solar for a few hours but they’re very expensive and they appear quite niche in Australia. Is everyone else in Sydney experiencing the same very high humidity levels perhaps the Sensibo made me aware of a problem that I didn’t know I had.

It’s easier to solve in summer as I can run the Aircon which obviously dehumidifies however when I run the reverse cycle in winter it actually makes the humidity worse because it heats the air which drops the relative humidity which sucks all the moisture out and then when I turn it off and the temperature goes back down, you end up with a higher relative humidity than when you started.

Home & Garden

Comments

  • jjjaar on 25/05/2025 - 17:22

    What type of house do you have? What is your insulation like?

    • Ozbfan on 25/05/2025 - 22:29

      A brick house, glass wool insulation in most of house.

      • jjjaar on 26/05/2025 - 00:53
        -3

        What’s the r value of the insulation in the ceiling, walls and subfloor (if you have subfloor)?

        Double brick? Brick veneer?

        Is there decent waterproofing between the external brick and internal walls?

        Have the bricks been covered with anything (render, plants) or painted?

        Bricks are porous and can hold a lot of moisture themselves. Painting/covering them if not done properly can trap that moisture inside the bricks, and therefore inside your home.

  • 7ekn00 on 25/05/2025 - 17:33
    +5

    I could potentially put the ducted Aircon on fan mode

    Most air-conditioners have a dehumidify mode, look to see if pressing the "Mode" button comes up with a waterdrop/teardrop icon (that's dehumidify mode) …

    https://ibreeze.com.au/blog/what-is-dry-mode-in-ac/

    • RogerLoger on 25/05/2025 - 19:30
      +2

      I asked my installer. Heating does not dehumidify (but humidity level will reduce as temperature rises). You need dooling mode to dehumidify. Dehumidify setting is a cooling mode. I have no idea what the difference is. Cooling and dehumidify seem to do nothing different in our Mitubishi ducted.

      • 7ekn00 on 25/05/2025 - 19:41
        -4

        It aint a cooling mode, read the fricken link :/

        Oh well, I don't care … it works fine here in Darwin during the wet to eliminate the mold and reduce humidity at a fraction of the power of cooling modes :P
        (yes, I tested the usage from solar inverter)

        • abcdefg5 on 25/05/2025 - 20:10
          +1

          You might want to come at this from first principles - an air conditioner needs to cool the air below the dew point to remove moisture. It just cools the room less because it runs the compressor intermittently.

          • 7ekn00 on 25/05/2025 - 20:43
            +1

            @abcdefg5: Same thing happens with a separate room unit :/

            Why buy a room one when you already have the same thing ducted in the house …

            • Ozbfan on 25/05/2025 - 22:19

              @7ekn00: They are two very different devices. Perhaps if you live in Darwin an air-conditioner on dry mode is good enough as it would be very hot and humid.

          • Ozbfan on 25/05/2025 - 22:18
            +2

            @abcdefg5: Correct dry mode is not a dehumidifier. It’s simply clever marketing which put’s the setpoint on the air-conditioner down just a couple of degrees from ambient.

            A dehumidifier obviously cools the air and then it heats up again, Evaporator and condenser.

        • theHMASfriendship on 25/05/2025 - 21:03

          Woah chill out, brussel sprout

      • JIMB0 on 25/05/2025 - 22:29
        +1

        Dehumidify setting is just cooling with the fan at a low speed.

        A dedicated dehumidifier will heat the air back up by running it through the condenser and it will actually be hotter than before it went through the unit..

      • jetblack on 26/05/2025 - 08:31
        +2

        Heating does not dehumidify (but humidity level will reduce as temperature rises)

        Humidity is a measure of how saturated the air is compared to how much it could potentially hold.

        If you increase the temperature, your "relative" humidity may drop, but the amount of moisture in the air will increase (or at best, stay the same).

        • RogerLoger on 26/05/2025 - 08:37

          That's correct.

      • Jolakot on 26/05/2025 - 15:54

        You need dooling mode to dehumidify

        Would a Labrador suffice, or do I need to obtain a Mastiff?

  • apsilon on 25/05/2025 - 17:42
    +8

    We've just had a large amount of rain, humidity will be higher while things dry back to a more usual level.

  • Euphemistic on 25/05/2025 - 18:06
    +1

    Its been pretty wet for a couple of months. Humidity is likely high due to that. If it ever stops raining itl dry out a bit.

  • freefall101 on 25/05/2025 - 18:43

    Buying a heatpump dryer would make more sense than buying a dehumidifier. Added benefit that it drains the water off (instead of adding it into the air in your house).

  • suti1 on 25/05/2025 - 20:12

    if you are concerned about dehumidifier/air con running costs get solar panels

    • Ozbfan on 25/05/2025 - 22:21

      I do I have 6.6 kW and an average day in winter generates 9 kWh power. Air-conditioner uses 4 1/2 kW for the first few hours while it’s ramping up. The numbers don’t add up, I could buy another solar system but I’m still back to having a small dehumidifier.

  • snivy on 25/05/2025 - 20:20

    Where did you hang your clothes before?

    Yes, opening the windows/doors and letting the air circulate would help with the mould, but you didn't indicate you have problems with that though. Make sure you also let the sunlight into the house as well.

    • Ozbfan on 25/05/2025 - 22:23

      I used to hang them up inside, but I’ve been hanging up outside now to try and fix the humidity problem but it makes no noticeable difference on the Sensibo. I suspect the problem is the house leaks air. The humidity inside is a function of what the humidity is outside.

  • outlander on 25/05/2025 - 20:22
    +1

    Yep, Sydney is terrible for humidity. I came up from melbourne and it almost killed me.

    If you want to deal with high humidity in a place were the outside weather is always humid, you need to isolate any sources of moisture from the rest of the house (ie your bathrooms, your laundry), seal up the building as best you can and then use one of two ways:
    1) Refrigerant based dehumidification
    2) Dessicant based dehumidification.

    Both are expensive, but it gets cheaper after a while of running as everything dries out.

    Cheapest way would probably be to use a desicant during the night, and then transport the saturated dissicant outside and boil off the moisture using cheap solarpower. But you'd spend a few hundred just on the desiccant alone and it would be quite annoying to carry it back and forth

    • Ozbfan on 25/05/2025 - 22:24

      Yeah that’s right. The other thing is the compressor dehumidifiers are extremely noisy and really only run it when I’m not here or or in a room with the door close a long way from where I am.

  • dtc on 25/05/2025 - 21:03
    +1

    So having lived in very humid places like HK and Singapore, most of the time (apart from cranking up the air con) they put boxes of dehumidifying crystals around the place (especially in wardrobes, near windows if there is condensation). You can’t do the whole house but you can protect the expensive stuff like clothes (and shoes)

    In Sydney it will not usually be super humid overnight so you can open windows for a while as well

    • Ozbfan on 25/05/2025 - 22:26
      -1

      No it’s normally the other way round. If you look at any Sydney humidity chart during the day it’s obviously not as humid because the sun’s out and the temperature is hotter but overnight it’s normally 85 or 90% outside.

      • dtc on 26/05/2025 - 08:50
        +2

        no, thats relative humidity. Not absolute (physical) humidity.

  • mskeggs on 25/05/2025 - 21:22

    Do you have mould, or are you just worried it might appear?
    When you read online about ideal humidity, it is some guy in in the Midwest where the humidity falls to 6% in winter and they are most concerned about chapped lips

    Open the windows on a nice day and dry your clothes outside.

    • Ozbfan on 25/05/2025 - 22:25

      Perhaps, this is a very valid point you raise, only minor mould in shower around sink etc. Maybe the standard is a bit over the top

      • RogerLoger on 26/05/2025 - 08:36

        I have a storage area under the carport. When we first experienced wet weather, it was foggy. A 20l dehumidifier set full, with a separate humidistat set to 60% fixed the problem. No rusting tools, no mould damaged cloth. This post is only so you know 60% seems to protect things.

        If you want to know how I use it, the humidistat ensures the unit only switches on when necessary, so the fan doesn't run constantly.

        The unit used: https://www.amazon.com.au/Inkbird-Controller-Conditioner-Deh…

        There are two sockets. One would take a plug for humidifier, the other take the dehumidifier. Why would anyone want that? Someone who raises orchids in a hothouse might want to hold humidity within a narrow range of tolerance.

      • wobblydrow on 28/05/2025 - 09:24

        Mould around sinks and showers has little to do with humidity as such. Even in dry climates this may occur. The reason is two fold. One is soap and detergents that remain on the surface (especially in a shower) provide a nutrient source for mould, and secondly, constant moisture of spilled water is the ideal breeding ground for mould spores. Hence why a shower cubicle tends to be the worse area as can be wet for extended periods and lots of chemicals on surface.

        Yes in general high humidity atmosphere makes this more prevalent in a whole house, but specifically in a bathroom its just as much to do with the nutrient source and enclosed areas.

        If this is the only area you have an issue, keep the surfaces well wiped down and shower door open until dry to allow airflow and drying will assist

  • Subere on 25/05/2025 - 22:20
    +1

    West Sydney just had 100mm of rain. Of course there's moisture in the air still.

    Am I the only one that when they hear humidity they think of Red Heat and Arnie saying "no moisture"

  • Protractor on 25/05/2025 - 23:08
    -1

    Look at your postcode location on Weatherzone and select the humidity as an option on the forecasts, that graph up per 7 or 10 day forecast. You will notice humidity spikes on a regular rise and fal over 24 hours. It's called climate. Not sure you can isolate that humidity outside very selectively with any tech, but it's your $$$.
    Go for a walk and smell the roses. It's winter in a mega rainfall period.You aren't becoming a mushroom.

    But if it makes you feel better to worry about it>

  • MS Paint on 26/05/2025 - 08:24

    Huge rain event hovering over coastal nsw for a while and op wonders why it's humid? FFS.

    • Protractor on 26/05/2025 - 15:59

      You and your facts!

  • SydneyHer on 26/05/2025 - 08:49

    I live in Sydney as well and in the green area with humidity. Some areas in Sydney have pockets of high humidity. I measure humidity in my apartment. 80-90% is not normal and is too high. I have hay fever and humidity makes it worse so I'm careful in choosing accommodation, for example I avoid south facing bedroom. Run aircon on fan or dry setting and perhaps consider moving. P s. My clothes dry on the line till 75-70 % dryness and I finish them in a dryer

  • LFO on 26/05/2025 - 12:45

    Been there, done that.

    If the outside is warm and very humid, tropic humid, then your house will be.

    Focus on keeping "dry" a room or two. Only.

    Typically for Sydney the weather will change and all will improve. Long weather forecast says so.

    It is virtually impo$$ible to have a full house/residence at low humidity when outside is high humidity.

    • LFO on 28/05/2025 - 20:35

      Just on time:

      Here in Gold Coast we had about an average of 70-80% humidity for the last 4 months.

      Yesterday it dropped to 43% thanks to strong dry Westerly winds.

      The weather is the Master.

  • knasty on 26/05/2025 - 16:34

    In winter we run the reverse cycle air cons on drying cycle for an hour in the bedrooms while no one is there; does a pretty good job and costs next to nothing as the solar has kicked in by then. Leave the cupboard doors open too so they don't become stuffy. We also use Damp-Rid moisture absorbers on every window sill to absorb some of the vapour that condenses on the inside of the windows. These are minor fixes but may help a little.

  • alexdagr8 on 26/05/2025 - 17:54
    -2

    I am really sorry to hear that you live in Sydney.
    Best of luck

  • rumblytangara on 26/05/2025 - 19:24

    at nighttime typically about 80-90% and the daytime minimum of at least 70%. Live in Southwest Sydney

    Totally normal for my neck of the woods in Sydney. Especially as it's been wet outside lately.

    I have a dehumidifier, but don't bother to use it. I just make sure there's a cross breeze some of the time. Running a dehumidifier only works for smaller sealed spaces, not for an entire house or even an apartment.

  • Drakesy on 26/05/2025 - 20:30

    Its sydney

    It comes with the location

    Sure there's "optimal" humidity levels but unless you're a hypochondriac i wouldn't bother.

    You're not going to dissolve. If you want somewhere drier move further south

  • bashar20 on 27/05/2025 - 07:22

    Get a decent dehumidifier

  • R4 on 27/05/2025 - 09:56
    -2

    Another reason not to live in New Shanghai ( the city previously known as Sydney).

  • ricadam on 27/05/2025 - 10:38

    If its consistantly like that and not just after a bunch of rain that you've just had. I'd be looking to ensure that you don't have a build up of moisutre in the walls and ceilings. Could be an underlying mold problem.

    Hard to tell now given all the recent rain.

  • luffyex2010 on 27/05/2025 - 11:40

    Open all your windows during the day, close them before the temp drops and buy cheap $25 dehumidifiers from bunnings for every room/area and on them on timer until the next morning.

  • cookietime on 27/05/2025 - 13:00

    I would highly recommend getting a good dehumidifier. Make sure that it's capacity matches or exceeds your house's size. Don't bother with those cheap dehumidifier for small rooms. Their compressors aren't powerful enough.

    My in laws also live in South west Sydney. Their poorly insulated house was unbearable until we got a dehumidifier for them.

    I also run a dehumidifier almost all year round. It makes the house so much more comfortable, and warmer during winter. We have a Delonghi Tasciugo in the hallway and it's perfect for us.

    • Ozbfan on 27/05/2025 - 17:12

      Where would you buy big ones from? The house is 180 m². I’m struggling to find that many ducted solutions.
      Do you have a drain in your hallway as I imagine it would generate a lot of water.

      I think we might have the other problem. We have a lot of insulation and I find the garage which has a roller door which leaks like a sieve is a lot less humid.

      I guess just the water generated from using sinks and showering creates a lot of water vapourIn the air.

      • rumblytangara on 27/05/2025 - 23:36
        +1

        A single standalone unit is going to do sweet FA for a 180sqm house. You need more than one.

      • cookietime on 28/05/2025 - 20:18

        We empty the tank whenever it is full. About once a day if the humidity is high so it's not much work at all.

        We got the big one from the good guys but pretty much any stores, including Amazon, sell them so just shop around for the best price.

        Is your house on a single level? Get one to try out first, then if you feel like it's better to have one at each end of the house then get another one. Our house is about the same size as yours and the hallway connects all the rooms so one dehumidifier is enough.

        • rumblytangara on 28/05/2025 - 20:32

          Have you used a hygrometer to confirm that the entire house is dry?

          When I had an apartment half the size, we would use two (16 and 20L) units.

          This was overseas in a warm and wet environment, but with sealed windows and doors.

          We currently have a single 20L unit for a larger apartment, and it's not powerful enough meaningfully shift humidity readings throughout. You need to seal off about half the apartment for it to do much.

  • Hangryuman on 27/05/2025 - 21:05

    Apart from 'I’ve started hanging clothes outside but it’s not really making any difference', I haven't seen any problem to be solved.

    How do you know the meter is accurate ? I have 4 temperature & humidity meters in our living area and they can all show different readings - now 19, 20, 22, 23C and 39, 43, 45, 60% humidity. Pick one to rely on.

    Problems to start thinking about include rotting carpets and mould causing kids respiratory problems (most people aren't affected). I'm not seeing that here.

    Creating a drama out of a new meter reading looks to me like tail wagging the dog …

    And after weeks of heavy rain and flooding, saying 'the air is humid' sounds a little bit … duh! … or should I say 'D'Oh!' - https://youtu.be/cnaeIAEp2pU

    • Ozbfan on 27/05/2025 - 21:50
      -1

      No Einstein, or should I say Homer, the humidity’s been 80% for over a year, confirmed by the dehumidifier.

      If your readings are all over the place, maybe it’s not the air that’s confused.

      Stick to quoting cartoons, it’s clearly your level.

    • rumblytangara on 28/05/2025 - 20:34

      How do you know the meter is accurate ? I have 4 temperature & humidity meters in our living area and they can all show different readings - now 19, 20, 22, 23C and 39, 43, 45, 60% humidity. Pick one to rely on.

      Your equipment is busted, or you have weird localised microclimates all over your place. Maybe some are upstairs and some are downstairs?

      I have 4-5 meters (Uni-T and Xiaomi) scattered about randomly, and they all read within 2% RH and 1 degree C of each other. They'll only read different if I'm drying clothes in one room, or if they're in the room that's poorly insulated compared to the rest of the place.

      • Protractor on 28/05/2025 - 20:47

        It's called catastrophising.

  • Protractor on 27/05/2025 - 21:10

    *Creating a drama out of a new meter reading looks to me like tail wagging the dog *

    Yes sirree

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