Can anyone help me to solve mould/moisture issue (maybe install ceiling vent)

I have a house in brisbane logan central, very close to logan shopping center.

I have a problem with mould inside house, I guarantee that no leaking from roof, gutter is also clean.

But my tenants complained that there is always mould inside the house, walls and ceilings, house is in NOT BAD condition, no leaking.

worst room is bathroom, window is always open, ceiling fan is working, no leaking, but still get mould.

only thing we can think of is condensation, Any specialist here to solve this problem?

bedrooms on dark side (no sunshine) always have mould on ceilings and walls, but there is window in each room.
kitchen and laundry on sunny side are ok, no mould.

roof is low, metal sheet roof, flat, not much room/space inside roof, so no manhole.
And there is NO insulation inside roof (between ceiling and roof), and NO insulation inside walls.
there are a few whirlybird, no vent inside each room now.

I plan to install ceiling vent for each bedroom (3 bedrooms), but it is old house and fiber ceiling sheet.

house is low set, on stumps.

Anyone can shed some light on how to solve this issue.

thanks a lot Jeff

 

Is there ‘Anti con’ roof blanket installed under the roof (e.g. from a roll - batts with fiberglass on one side and foil on the other)? This should stop condensation getting onto the ceiling when installed correctly.

Put a stronger fan in the bathroom - ensure it is vented outside and that there is a source of air getting into the room (window or vent in the door). Link it to the light and have it ‘run on’ for a few minutes after the light is switched off.

Also, how is the mould being cleaned? Bleach is not a permanent solution and you could be seeing the results of this. Use the ‘3 buckets’ vinegar method from Choice (google it).

How good is the range hood extractor? Remember moist air from cooking, breathing, showering will travel to the coldest part of a house and land on the coldest parts - then condensate and create mould.

You could try installing a dehumidifier in one of the worst rooms and see if that makes a difference.

Is aircon being run a lot? How about heating?

 

You've given us a great rundown of the situation, but unfortunately mould can be very complex. Once it takes hold, often it's impossible to get completely out AND do you know if the tenants are properly ventilating the house at all times?

Have you had any mould inspectors attend? They'll check moisture levels, mould growth patterns, ventilation, light and any other factors that could be causing the mould in order to solve the problem.