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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.

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    • CommentAuthorgyrogear
    • CommentTimeJan 26th 2020
    Mainland cousin says:

    "Multi-unit dwelling, owner-occupier: I have a problem siting a bathroom extractor fan -- it can't be in the outside wall or in the window, as they are both over the bath, which isn't allowed. The only alternative is a ceiling-mounted one, which routes through the loft space, and vents in the eaves soffit. However, venting to eaves soffit is a NOK as water vapour could be drawn back into the loft. Also not my loft (even if I do have access to it...). Can't afford the angst of cutting a hole in the soffit viz. neighbour's ratting and hassle from managing agents etc.

    Whence flash of inspiration: I have a condensing tumble dryer, which manages to condense the soup from my washing without releasing any moist air into my hall. Putting two and two together, I wondered about buying a condenser to install in the loft, to receive a duct from a bathroom extractor fan. I ended up deciding that it would be worth making one, to see if it works (don't see why it wouldn't!).

    So I have bought two 2nd-hand drier condenser units off of ear-bay...

    These will need hacking around somewhat, then mount one atop the other, inside a cabinet with a fan pulling air through the fins.

    I have ordered an 80mm 240v fan, but think I might need two. Then the unit would be plumbed in so that the condensate drains down through the wall and into the waste pipe in the kitchen.

    Sort-of replacement for a commercial dehumidifier, but « somewhat far cheaper... »

    Project guidance appreciated".

    via gg.
    • CommentAuthortony
    • CommentTimeJan 26th 2020
    Try to use all the heat that it generates and keep this inside your home at least in the colder months.

    Humidity monitoring is going to be essential and if this can control the fan, well and good, if not then a humidistat.
    • CommentAuthorgyrogear
    • CommentTimeJan 26th 2020
    Aha, thanks for that, Tony !

    So his cabinet needs to be inside his heated volume, and not up in the loft.

    Thanks for the feedback !

    • CommentAuthorgoodevans
    • CommentTimeJan 26th 2020 edited
    Or, alternatively, buy a zone 1 extractor fan that can be located above the bath.
    • CommentTimeJan 27th 2020
    Posted By: gyrogearMainland cousin

    Sorry, where is 'mainland'? What regs are applicable? In particular, given the regs make some statements about what type of extractor is not permitted, do they say anything about what is required?
    • CommentAuthorCWatters
    • CommentTimeJan 27th 2020 edited
    "Multi-unit dwelling, owner-occupier: I have a problem siting a bathroom extractor fan -- it can't be in the outside wall or in the window, as they are both over the bath, which isn't allowed.</blockquote>

    Is this in England...

    The bath is zone 0, the area above the bath upto 2.25m is zone 1, above that zone 2.

    In zone 1 you can have electrical appliances as long as they are rated IPx4 or greater. Must also be RCD protected.

    Manrose make IP rated wall mounted fans. I think window fans are harder to find because of double glazing.
    GG, the airflow through a bathroom fan is about 1m3 every minute, each m3 contains about 20g of water vapour when saturated. So that's lots of grammes of water to condense every minute.

    Gut feeling is that a tumble dryer doesn't condense that much water that fast. So the extracted air would still be quite damp when it is discharged into the loft. Maybe your cousin could recycle the air back into the bathroom, then run the fan for a period after showering, so the air gets gradually drier, after several passes through the condenser?

    Few other thoughts
    -mains electric and water and bathrooms don't mix well, could he use SELV as GE suggests

    -damp and lofts don't mix well either, the managing agent is quite correct

    - the regs are different in the Scottish and English mainlands and islands, but both have requirements about electrical safety and avoidance of damp decay

    - tumble dryer condensers don't recover heat, they dump it into the outgoing air stream (to dry the clothes more) - re-siting the box will not help this

    - extractor fans have an important function the morning after curry night

    Your cousin should consider a MHRV fan professionally installed and ducted through the loft to a soffit or tile vent
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