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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorgravelld
    • CommentTimeSep 26th 2017
     
    Modelling my retrofit. I am designing a warm roof over what is currently a cold loft. We have no plans on using the loft. Therefore should the loft be included in TFA, or not?

    What if we wanted to use it in the future and convert it to living space? I'm not going for certification, but what happens with Passivhaus when there's a change like this?

    (And also, is it silly to have a warm roof in this case? I'm doing it really just because it seems much easier to get the AT detailing right, otherwise there's a lot of timber to tape around, plus also the thermal bridging through the loft timbers).
  1.  
    Once the loft is inside the thermal envelope it's no longer a 'cold loft'. It's a good idea in my view. It wouldn't be included in the TFA because it's not part of the living space. If it were converted in the future, depending on the size, it would probably have an effect on the PHPP results and the calculations would have to be done again anyway.
    • CommentAuthorgravelld
    • CommentTimeSep 27th 2017 edited
     
    Ok, thanks. That whacks up the kWh/m2 but never mind!

    I'm interested as a side subject - if you have a certified Ph and make a change like this (making the loft liveable), is the certification invalid?
    •  
      CommentAuthordjh
    • CommentTimeSep 27th 2017
     
    As Peter says, the PHPP would have to be recalculated.
    • CommentAuthorgravelld
    • CommentTimeSep 27th 2017
     
    I get that...

    What I mean is, what is the certification status? Does someone come around and rip the plaque off the wall? ;-) I suppose the same thing could be asked for any old change to the house - add a satellite dish, drill through a wall and ACH spikes...
  2.  
    AFAIK the certification isn't checked after it's given. I could be wrong but it seems a bit of a mistake not to check especially in the UK where new owners always seem to want to 'put their stamp on a property'.
    •  
      CommentAuthordjh
    • CommentTimeSep 27th 2017
     
    It's like every other certificate in the world. It certifies a particular state at a particular time.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 27th 2017
     
    That's the narrow meaning of 'certificate' - the bit of paper.
    But on a broader meaning, some certificate schemes are regularly reviewed for renewal (or not) - others aren't. With such detailed and systematised info at the start, PH should be an easy one to review.
    •  
      CommentAuthordjh
    • CommentTimeSep 27th 2017
     
    Think what you're saying, Tom. Since you'd specifically be looking for changes, the initial information wouldn't be very helpful. Plus, who do you expect to pay for a review process?

    If significant changes are made to a building, then you just repeat the process. C.f. planning, building regs, EPC etc etc.
    • CommentAuthorgravelld
    • CommentTimeSep 27th 2017
     
    I think I can predict the answer but I'll ask anyway...

    Would a window in this loft, not covering part of the TFA but being a boundary of the thermal envelope, still have to be added to the Windows sheet? I assume so.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 27th 2017 edited
     
    Depends whether certification will be valued as relevant, desirable and credible into the future, having invested considerably in getting it in the first place.

    Posted By: djhwho do you expect to pay for a review process?
    Someone who values their certificate remaining in force, FWIW - if they don't care then they don't mind it lapsing.

    Posted By: djhSince you'd specifically be looking for changes, the initial information wouldn't be very helpful
    As a clearly organised baseline, changes would be unusually evident, compared to a less rigorously documented certification scheme.
    • CommentAuthorgravelld
    • CommentTimeSep 27th 2017
     
    It's not certified and it's not a passivhaus performance. More like AECB silver.
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