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Black Mould on Windowless En-Suite Bathroom Ceiling and Venting into Loft Space

Postby stuartrobins » Mon Nov 09, 2015 1:53 pm

Hi, I have an en-suite with no windows. There is an extractor fan that vents into the loft space.

I am slowly getting back mould spots on the ceiling. My question is should the extractor be vented to the outside or is the loft space ok? If it is what can I do to stop the mould.


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Postby thedoctor » Mon Nov 09, 2015 6:28 pm

Hi Stuart

The main cause of black spot mould in this situation is lack of ventilation and air flow but if you don’t have any windows, it can be hard to achieve a decent amount of air flow to prevent condensation buildup and the resulting black mould.

It may be that you need a slightly more powerful extractor fan to remove more of the moist air.

In terms of venting in the loft space - it should really vent externally as all you are doing is pumping the hot, moist air into the loft void and this in turn can bring its own issues.

We do have a project on damp and condensation that may be of some more use to you:

Hope this helps!
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