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Humid climate - Novel ideas for preventing mould in bathrooms??

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  1. #1
    Senior Member
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    Default Humid climate - Novel ideas for preventing mould in bathrooms??

    Guys I'm trying to brainstorm ideas - no matter how unusual - for preventing mould growth in our bathroom.

    We live in a very humid area. We have one bathroom containing a shower only on the lower level of our two-story home. It turns out the locals tend to give their bathrooms big windows and put them on the east or west side of their homes in order to expose them to direct sunlight, giving them a good daily drying-out. We made the mistake of putting ours on the south side of the house and the mould growth is insane. From day one we've always had a 150mm inline exhaust fan venting to the outside, which we switch on religiously (and leave running for a good 10-20 mins after showering) which hasn't stopped mould from growing all over the floor and wall tiles, and even on the painted fibro walls above the wall tiles.

    Any suggestions on what the heck we should do to help with this? I'm willing to consider fairly major changes/renovations if it will make a big difference. Relocating the bathroom to the east/west side of the home is one solution we are trying to avoid, however, as this will require MAJOR renos.

    A friend suggested constantly blowing hot, dry air down from the ceiling space via ducting into the bathroom. Not sure how effective this will be...and it will require some fiddly ducting efforts (though not impossible) as the bathroom is on the lower level of our 2 story home.

    Any other ideas??

  2. #2
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    I've found a big difference in having the fan installed directly over the shower.
    After 8 years in this place without a heat lamp, compared to the previous place we were in for 10, its a big difference as a starting point for consideration.

    Humid locations are an additional challenge. Lived on the Sunshine coast for 2 years and understand some of the issues you face with humidity as the main bedroom had mold build up in the wardrobe and behind the bed (the lower 150mm) around the skirts. I'm guessing 8 hours of 2 people breathing every night produced an increase in moisture and lack on ventilation in these areas allowed mold growth.

    Don't have a solution, but assume any increase in ventilation and light will improve the situation.
    Blowing warm dry air has only got to assist as well.....maybe that's your starting point to test the waters in deferring a major reno.
    Having wet bath towels drying out in the bathroom would increase the humidity.
    Painting with mold resistant paint can assist but it can only do so much before it too will fail without addressing the root cause of high humidity/moisture in that room

  3. #3
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    I live on the Sunshine Coast 700 metres from the beach.
    Bathroom on west side.
    I repainted the bathroom ceiling about 5 years ago.
    No sign of mould anywhere and all we have is the standard 1200 x 600 window always part open and a small tastic, and we always use the exhaust fan when showering
    Only when really cold do we use the heat lamps.
    However we do wipe down the shower area with an old towel every time after we have showered.

  4. #4
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    If you have a vent properly going to the outside and it is still moldy, I would try a couple of things. (Note, we live in the Tallebudgera Valley, Gold Coast, which gets a lot of rain and featured on the news as one of the flooded areas in February)

    1 Install infrared lamps and leave them on, with the fan going, for ten minutes after a shower. We do this and I find it works to dry the horizontal surfaces - but not the ceiling -, evaporating the moisture (only off the surfaces the infra red shines on mind you) so that the moisture is airborne and can be pumped out by the fan.

    2 Considering your vent and fan, hopefully not stating the obvious but if the mold is on the ceiling and upper walls, check for leaks in the venting as it goes through the roof-ceiling space - even a little leak would make a big difference. Also make sure your vent to the outside isn't next to an open window. Check the prevailing winds - are they assisting or hindering the vent. Maybe consider an on-roof vent if you haven't got one. And of course, as previously posted, placing the fan vent over the shower area makes a big difference IF your partner doesn't then complain about the draft and then refuse (or quietly 'forget') to put the fan on, so you are worse off than before (don't ask me how I know).

    3 This is a big one. Stop using standard alkaline bathroom cleaner. Bleach based cleaners might be effective in removing soap scum and mold (some say it just bleaches and half kills the mold) BUT the mild alkaline to neutral ph environment they leave after rinsing encourages mold to grow later. We get good results using straight cleaning vinegar in a spray bottle ($2,50 for 2l at Bun.. gs) for the everyday cleaning. Also use the citrus-based bathroom cleaners for hard cleaning (soap scum etc). You can spray straight cleaning vinegar on the shower walls and anywhere that gets wet (ceiling, walls) and it really seems to keep mold at bay, particularly if you add a little tea tree oil (only about 20 drops) to the sprayer, and it doesn't seem to effect the paint. After spraying the vinegar solution on the painted walls, let it dry on there to leave a low ph.

    4 Consider the air movement around and through the bathroom. How big is the window, is it left open through the day, is anything stopping free flow of dry air through it during the day. If there is a structural reason for low passive airflow that you cannot change, then a combination of the other strategies will be the go.

    5 Another idea (untested but I cannot see an issue) is to put a whirly-bird vent smack bang over the bathroom with a big-@@@@ vent in the bathroom ceiling. If I have this issue and all the above didn't work, that is what I would try. 24 hour cost-free venting should help.

  5. #5
    1K Club Member havabeer's Avatar
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    do you have windows or doors open while showering?

    i often find it weird people put large CFM moving exhaust fans in their bathrooms but close everything up (doors and windows) and expect the fan to still move that much air? if your asking a fan to move 300cfm through the gap underneath your door you're asking alot. also be aware the stated CFM written on most exhaust fan boxes are pretty much a lie. those numbers are absolute best case scenario's for the fan only... you slap an intake and exhaust grill on it and a few meters of air flow sapping foil ducting and you'd be lucky to get half of whats written on the box

    I'd echo dolphin and say use the double strength cleaning vinegar for cleaning (coles sells it), it will actually help KILL the mould.
    Remember if you don't sin, then Jesus died for nothing

  6. #6
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    Hi Rosey
    agree with Dolphin and Beer - but nothing beats sunlight and ventilation to "STOP" mould occurring in the first place. Once you have conditions where its growing - your always going to be fighting battles cleaning it/killing it. you really want to ensure the war doesnt start - and that means dry, light and airy. Windows open and doors open as much as possible. The other thing is moisture - the longer your shower goes for the more moisture in that room.
    When I was single bloke, I didn't much care for my privacy (only one in the house) and showered with window full open and door open, had maybe 10-15min long showers - never ever had any issues of mould on walls or ceiling. But my wife loves her hot water - takes about 40mins min, insists on window being shut - we constantly have lots of mould on ceiling - her fault.
    If renovating i would highly encourage floor to ceiling wall tiling for the entire bathroom area - this will at least keep mould off the walls - or at worst, make your walls super easy to clean.
    Good luck.

  7. #7
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    Thanks guys....I'm gonna try your suggestions!

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