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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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    • CommentAuthorJeremy S
    • CommentTimeDec 16th 2021 edited
     
    Hi,
    Regarding the intake and exhaust 150mm galvanised spiral metal duct for MVHR:

    I understand that the metal duct is usually insulated with foil-faced mineral wool.
    And, in the light of GreenPaddy's comment in Is loft insulation sufficient to insulate MVHR ducting? , I know to provide a vapour-barrier.
    ... these do need a vapour IMpermeable (polythene) wrap around them whilst 
    inside the thermal envelope, as regular glasswool will allow moisture through,
    to condense on the duct surface in winter.

    So, is there any reason not to use sheep's wool insulation rather than mineral wool?

    Also, taking account of GreenPaddy's follow-up comment
     ... they should have the same Uvalue of insulation around them again as per your house external envelope

    does the exhaust need to be as heavily insulated as the intake?
    •  
      CommentAuthordjh
    • CommentTimeDec 16th 2021 edited
     
    Posted By: Jeremy Sis there any reason not to use sheep's wool insulation rather than mineral wool?
    Not as long as you're happy with sheeps wool in general, AFAIK. edit: the mineral wool products come pre-prepared for such use, so they're a bit easier.

    Posted By: Jeremy Sdoes the exhaust need to be as heavily insulated as the intake?
    Yes, they should both be at approximately the same temperature if the MVHR is working. i.e. outdoor temperature.
    • CommentAuthorJeremy S
    • CommentTimeDec 16th 2021
     
    Thanks djh

    We have some leftover sheep's wool, and some leftover vapour barrier, so this seems like a good use for them. :smile:
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