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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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    • CommentAuthorgravelld
    • CommentTimeAug 30th 2017
    What are "typical" ACH rates for air permeability in the UK stock?

    For example, there are various numbers mentioned for m3/m2*hour @ 50Pa:

    20 - real bad
    12 - once saw this called "average" - I'm sceptical
    10 - regs
    3 - worth installing MVHR
    1 - good job

    The reason this is useful, I think, is that I don't think you can easily convert from the above m3/m2*hour figures for ACH.
    • CommentAuthortony
    • CommentTimeAug 30th 2017
    Typically above 10 if you want to genaralise, very difficult to find many below 1 except on here.

    I don't agree that MVHR is only worth installing below 3

    10 is maximum allowed, not regs, the worst that regs will allow.

    Then we could start talking about leaking into the house, does this mean into the rooms, inside the thermal envelope, into voids within the house like floor void, svp pipe box, behind dry linings or what?
    • CommentTimeAug 30th 2017
    You probably won't find many ACH numbers for UK stock since the legislation uses m³/m²/hr. Apart from people using PHPP that has 0.6 for PH, 1.0 for EnerPHit & PHI Low Energy


    • CommentAuthorgravelld
    • CommentTimeAug 30th 2017
    Yeah it's for PHPP I'm asking. I'm just trying to model my current house to learn about the tool before I start design work, so want something in the right ballpark.
    Based on relatively out of date academic papers for the UK, averaged over a large number of homes in the UK:
    1. Solid masonry 11 ach @ 50 pa, Cavity masonry 14 ach, timber frame 8 ach, SIPs 7 ach
    2. by age: 1900- 12, 1900-1920 10, 1920-1960 15, 1960-1980 14, 1980+ 10
    3. number of storeys seems to make no difference
    • CommentAuthorgravelld
    • CommentTimeAug 31st 2017
    Superb, thanks.
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