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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorShevek
    • CommentTimeNov 14th 2021 edited
     
    - Existing block of apartments (concrete frame, northern Portugal)
    - Bathroom is internal with no windows, ceiling is concrete slab with plaster finish
    - Building is badly insulated with draughty windows (apart from ours, which now has new windows)
    - Crappy little intermittent fan at high level in the wall (which is probably the main culprit)
    - There appears to be have been a mild but longstanding issue with (presumably) black mould

    I sprayed the ceiling with bleach when we moved in, which improved how it looked on the surface but also made some of the paint peel off and I've since scrapped it and there are still little spots of black in the plaster behind the paint.

    What's the long term solution?

    1. Remove all plaster, re-plaster and change fan unit to continuous extract?
    2. As above but add suspended ceiling with very carefully installed VCL?
    3. As item 2 but add larger d-MEV fan unit or even MVHR

    If we added a suspended ceiling, would spraying the concrete soffit with polyurethane foam (after removing plaster) help guard against mould or just provide it a hiding place and make it worse?
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    • CommentAuthortony
    • CommentTimeNov 14th 2021
     
    Clean the fan grille and make sure that it is extracting ideally fit a new Svara fan, these think for you and are programmable via an App.

    Anti mould paint would help

    Replastering won’t help , ventilation will, some heat might be needed too
  1.  
    I would expect spraying the ceiling with polyurethane foam, if a good thickness was applied, would solve the problem. Any insulation applied should be bonded to the ceiling otherwise air and therefore mould will get behind it.
    The real fix would be external insulation to the affected parts - but I guess this is not an option.
  2.  
    Is there any external wall or is the room all internal? ISTR you are not on the top floor?

    If it's internal, then insulation might not help much, unless there's some good reason why the ceiling should be thermally connected to the outside? Have you tried taking surface temperature measurements with an IR to see if the ceiling is much cooler than other surfaces in the room?

    Ventilation is the answer, and a better fan can be trialed cheaply while you are thinking about more drastic options. If there is any external wall then think about a single room MHRV (the kind with a spout that sticks out of the wall and includes extract and intake) - they are cheap and easy to install, though less quiet and effective than a full MHRV.
    • CommentAuthorShevek
    • CommentTimeNov 15th 2021
     
    Thanks guys. That fan looks like just the ticket, thanks Tony. Great idea to add some heating too; a heated towel rail would probably help a lot.

    Above us is another flat, so no chance of external insulation. It's just relatively cold because the whole building is badly insulated and draughty but I haven't actually measured it. Maybe it's not so cold.
    • CommentAuthorLF
    • CommentTimeNov 15th 2021
     
    A bluetooth temperature and humidity logger are about £10 or so for a pair. You can see trends on your phone and help optmise how long you need fan on for.
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