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    • CommentAuthorSimon Still
    • CommentTimeMay 3rd 2017 edited
     
    http://www.telegraph.co.uk/science/2017/05/02/energy-scandal-misleading-efficiency-claims-leading-huge-bills/

    My head has melted under the articles internal inconsistencies. Apparently the problem is 'building modelling professionals'
    • CommentAuthortony
    • CommentTimeMay 3rd 2017
     
    Such a poor article -- not worth reading
    • CommentAuthorDarylP
    • CommentTimeMay 3rd 2017
     
    'Planners' don't care about dwelling efficiency, do they? from home-owners to school...? typical Torygraph misleading nonsense :devil: no mention of the NCM for dwellings and non-dom (SAP and SBEM).
    Makes you think what is the behind-the-scenes reasoning for publishing such articles? :wink:
    •  
      CommentAuthorfostertom
    • CommentTimeMay 3rd 2017
     
    The first 6 paras, above the first 2 body pics (as it appears on my m/c anyway) is spot on - a real issue that we constantly highlight on GBF, apart from throwing in 'planners' (note the small p - so not denoting 'The Planners'?). Thereafter, what's the Bath Univ man saying?

    The problem is not 'building modelling' - it's the complete lack of same, instead reliance on prescriptive Building Regs compliance, OK weakly informed by SAP calcs which everyone knows are unrealistic.

    Is it the latter (and even worse rdSAP, for retrofits) that the Bath Univ man is aiming at? Anyone looked up David Coley lately, see what his research piece is really saying?
    •  
      CommentAuthordjh
    • CommentTimeMay 3rd 2017
     
    The university's summary of the research is at http://www.bath.ac.uk/research/news/2017/04/30/illiterate-modellers and includes a link to the actual paper at http://journals.sagepub.com/doi/pdf/10.1177/0143624416684641

    What they basically seem to be saying is that among many other factors that are already well-known, the competence of the building energy modellers is another factor that affects the accuracy of predictions.

    There appears to be confusion as to whether this is about commercial or domestic buildings. They actually measured dynamic simulation of a domestic retrofit, so not something that is normally performed as far as I am aware, and judged modellers competence by their judgments about this scenario.

    What does seem clear is that recently graduated modellers are better than those with longer experience. I would argue that what that means is that there needs to be a lot more post-completion monitoring of buildings both to check the accuracy of models and to provide feedback to the modellers so they stand some chance of improving their understanding.
    • CommentAuthorDarylP
    • CommentTimeMay 3rd 2017
     
    ...the 'performance gap' has been discussed years ago.
    IMO it results from buildings (both domestic and non-dom) not being built to spec, with corners cut, no effective on-site inspections, and building down to a price, rather than up to a standard.:cry:
    • CommentAuthorbarney
    • CommentTimeMay 3rd 2017
     
    All true DaryIP - however, there is no doubt in my mind that some of the model inputs become perverse just to get an SBEM certificate back out

    I have an example on my desk at the moment of a building circa 3000m2 that need an incredibly tight air envelope to provide a function as a shelter building under a chemotoxic plant release

    We want less than 1m3/m2/hr@50Pa of leakage (infiltration) to allow the filtered fan sets to maintain 40Pa building pressure internally (to prevent ingress of nasty stuff

    This is basically an office building without windows - so Part L considerations etc - perversely, the only way we can get it through Part L without excessive amounts of cooling is to tell the model that the leakage is actually 5m3/m2/hr@50Pa

    I can find many other examples that relate to domestic hot water zones etc that drive perverse design solutions that undoubtedly perform badly in practice but SBEN seems to like them.

    So, would I agree that a fresh young modeller can get close to how a building really would perform - yes - but you need an old and experienced one to defeat good practice to get it through Part L

    Regards

    Barney
    •  
      CommentAuthordjh
    • CommentTimeMay 3rd 2017
     
    Yes, everybody agrees that there is a performance gap and that there are many reasons for it. What this research claims is that in addition to all the reasons that have been discussed for years there is another one, namely the incompetence of many building modellers.
    •  
      CommentAuthordjh
    • CommentTimeMay 3rd 2017
     
    Posted By: barneyWe want less than 1m3/m2/hr@50Pa of leakage (infiltration) to allow the filtered fan sets to maintain 40Pa building pressure internally (to prevent ingress of nasty stuff

    This is basically an office building without windows - so Part L considerations etc - perversely, the only way we can get it through Part L without excessive amounts of cooling is to tell the model that the leakage is actually 5m3/m2/hr@50Pa

    Would you mind explaining that a bit more?

    For one thing, I'm just surprised that the change in airtightness affects the cooling requirements so much?

    But also, are you saying that the model is so inaccurate (to the point that it is totally unfit for purpose) and that the actual cooling required wil be sensible with the very airtight building whilst the model predicts it will not? Is the model designed for use at these levels of airtightness? (and previously tested and/or certified as such?)
    • CommentAuthorbarney
    • CommentTimeMay 3rd 2017
     
    Certainly

    We have a sealed box we want to keep nasty stuff out of, to protect occupants

    We also have no windows to stop any effects of blast

    Every litre of air that the occupants need is treated through HEPA filters and other active filters that can grab the particularly toxic external atmosphere

    So, we need enough air to meet occupant demands - about 10l/s per person - we also have to keep the building at 40Pa above external ambient pressure - so the latter dominates the airflow requirements - particularly as we "leak air" via the access lobbies to prevent ingress of "stuff"

    The more the building leaks, the more air we have to supply (at great cost) - so we have a pretty airtight building - our dynamic simulation shows that to be the case - as it also shows the cooling demands with full occupancy and the design day external condition (it's a UK location, so not that onerous but higher than the design summer year or test reference year at the location) - the cooling demands are modest given that it's fabric and internal gains - no windows

    When we switch the model to Part L compliance mode however, it's an epic fail - so we have examined every relevant aspect of this - cooling efficiency, fan efficiency etc - and the only variable left is the building airtightness - if we allow it to drop from target as I indicated the model moves closer to Part L compliance - clearly it's actually expecting infiltration to provide some sensible cooling

    The model is a fully certified product approved by DCLG for Level 5 SBEM outputs

    So, we are perfectly happy that the Dsim is telling us accurately what will actually happen - we've proved it several times by a variety of methods including a % of longhand calcs undertaken by some pretty competent engineers - but the algorithms embedded in the Part L compliance part of the software throw a wobbly and tell us it's a fail - until we make it more leaky

    You probably aren't as surprised as us that the leakage influences the cooling so much (in Part L world) - in the Dsim proper, it has the exact opposite effect as we predicted - more airtight, less cooling demand (build tight, ventilate right)

    I think the other effect going on is the actual air flow rates versus BR compliance air flow rates (we are at about 3 times that required for "occupancy" )

    Keep in mind this is just an office building (albeit with a bigger than normal data room) - the Part L output is definitely being unduly influenced by the "tight" building - so for compliance we need to let the building leak much more - which we do for the Part L BRUKL document - the actual design is much more airtight - we just don't tell BC that (yet)

    So - my comment that some modelling for "compliance" will give perverse results compared to reality

    More generally, there is a whole load of crap input into models to get through Part L that will never, ever be achieved on site

    regards

    Barney
    • CommentAuthortony
    • CommentTimeMay 3rd 2017
     
    Wow, thanks, great to see how others see things.

    I like build tight, build to perform better than design.

    A model can only ever be a model, hopefully it can model the real world. I would like the real world to perform. As intended by the regulations and designers.

    Very interested to see the planners being talked about, they are involved and badly need to improve.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 3rd 2017 edited
     
    Posted By: tonyVery interested to see the planners being talked about, they are involved and badly need to improve
    You mean The Planners, rather that just someone planning a scheme (e.g. Architect/Manager/Modeller)?

    If so, how on earth should they be involved? Sure they're required to support allegedly 'sustainable' development and individual buildings, but surely get crossed wires when trying to micro-manage ways and means to that (a la Merton BC).

    That's what Building Regs are for, and how govts should enforce the technicalities of building.

    If Dun Laoghaire mandates PH https://passivehouseplus.ie/news/government/dublin-local-authority-makes-passive-house-mandatory-in-historic-vote , surely that's not to be enforced by the Planning system, but by Building Regs?
    • CommentAuthortony
    • CommentTimeMay 3rd 2017
     
    No, one of the good thing about CSH was that it started at the planning stage, design can preclude options for low energy use.

    Building regs or PH can't close the door after the horse has bolted. e.g. too much glass etc
    •  
      CommentAuthorfostertom
    • CommentTimeMay 3rd 2017
     
    Yeah but I'd hate Planning Officers to try and enforce that - horses for courses. If all Applicants knew that after Planning they'd have to jump thro the hoop of e.g. PH standard, like in Dun Laoghaire, then they'd get the 'too much glass' etc (esp compact floor plan/envellope) sorted before making a Planning Application that they'd be sure to get refused at Bldg Regs.

    You're saying that Planning system should enforce what Bldg Regs isn't written to do, and doesn't enforce properly anyway.
    • CommentAuthortony
    • CommentTimeMay 4th 2017
     
    No, I am pleading the case for giving consideration to reducing energy use at the design stage because once the design is done it is often difficult or impossible to do it then. Simplest example is dormer windows but it influences everything.
    • CommentAuthorgravelld
    • CommentTimeMay 4th 2017
     
    The trouble with that Tony is that I don't think hair shirt attitudes will get us anywhere, and the British love a dormer, and an open fireplace, and bi-folds, and... and...

    Best to work out how to design best performance in, so long as the requirements are "reasonable". And there's the battle-line.
    • CommentAuthorEd Davies
    • CommentTimeMay 4th 2017
     
    Posted By: gravelldThe trouble with that Tony is that I don't think hair shirt attitudes will get us anywhere, and the British love a dormer, and an open fireplace, and bi-folds, and... and...
    And it's OK to kill off people in the third world to get those, of course, particularly as they won't be affected for a few decades.
    • CommentAuthorgravelld
    • CommentTimeMay 4th 2017
     
    I've been re-watching the Adam Curtis documentaries The Century of the Self over the past few nights. I highly recommend it as an insight to the motives of the "demos" especially the compromises the Clinton and Blair government had to enact to at least make some progressive change.
    •  
      CommentAuthordjh
    • CommentTimeMay 4th 2017
     
    Posted By: barneyThe model is a fully certified product approved by DCLG for Level 5 SBEM outputs

    It sounds like the Part L mode of the model is simply wrong and should never have been approved (which wouldn't surprise me in the least) but maybe there is something else going on. Without looking at the model itself, it's difficult to form an opinion.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 4th 2017
     
    Posted By: Ed DaviesAnd it's OK to kill off people in the third world to get those, of course, particularly as they won't be affected for a few decades.
    This is the quality of trenchant truth that some of us were backing J Corbin to speak - no such luck, sadly.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 4th 2017
     
    Posted By: gravelldthe compromises the Clinton and Blair government had to enact to at least make some progressive change
    I think it's finally become clear with H Clinton, if not Obama, that this is the strategy that we're supposed to believe -
    a token few hard-won progressive measures excuse the blatant main theme of failure to stand up against big-money,
    the latter presented as 'we did our best but were defeated'.
    • CommentAuthorgravelld
    • CommentTimeMay 5th 2017
     
    Yes but you wouldn't have even got the free token measures if they hadn't been elected.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 5th 2017
     
    Better to see the naked ugly truth with Trump, than dream through another round of the sophisticated neutering-machine that Democratic rule has become.
    Trump is dismantling all of Obama's token measures anyway - net neutrality, Standing Rock, now Obamacare, next Bradley Manning?
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