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    • CommentAuthorharper16
    • CommentTimeSep 4th 2013
     
    The company I work for are looking to buy some thermal bridge modelling software to more accurately model building fabric (improve SAP modelling accuracy).
    Does any one use thermal bridging modelling and if so, what can you recommend?
    •  
      CommentAuthorfostertom
    • CommentTimeSep 4th 2013
     
    LBNL Therm is free, competent, and is the one everyone uses, but it's clunky.
    WUFI 2D and Delphin also do it along with their prime function which is moisture modeling. Haven't tried them so don't know if any better.
    Psi-Therm is a new one - discussion on http://www.aecb.net/forum/index.php/topic,3875.0.html . 3D Psi-Therm is pricey, but far less than Ansys, the only 3D alternative.
    • CommentAuthorSigaldry
    • CommentTimeSep 4th 2013
     
    The main ones competent modellers seem to use for modelling junctions for SAP are:

    BISCO (for 2D)/ TRISCO (for 3D). http://www.physibel.be/index.htm - Not used, but heard good things (although a little pricier)

    HEAT 2 (for 2D) & HEAT 3 (for 3D) - http://www.buildingphysics.com/ not a bad bit of software once you get the hang of it - downside is it doesn't handle complex sloping elements too well, but a lot cheaper than TRISCO/BISCO.

    STRAND 7 http://www.strand7.com/ (Probably overspecced for most users as it can do more - heard it's a bit pricey, but don't know for sure).

    LBNL Therm http://windows.lbl.gov/software/therm/52/therm_52.html (because the old version is free) - but a little trickier to get the results you want out and set up properly.

    There may well be others, but the modellers I know around the industry (and there don't seem to be a lot of us) use one of or a combination of the above.

    There's not a great deal of training available. BRE did run some training, but haven't in the last 2 years! http://www.bre.co.uk/eventdetails.jsp?id=5342 Their training was using BISCO/TRISCO I believe.

    I trained with STROMA back in March 2011 and it was a pretty good course - not sure if they are still running it, but it's on their website: http://www.stroma.com/certification/training/energy-assessment/thermal-modelling. They trained use of HEAT software and you can buy via them (was about £1600 + VAT I think).


    AECB were running introduction courses - introducing users to modelling with Therm http://www.aecb.net/products-page/carbonlite-training/thermal-bridging/

    It's a tricky subject to become competent in and I would very much recommend getting some training/guidance and successfully completing a modelling portfolio via a trainer before using any software in anger as it were...

    There is talk of a future accredited thermal modeller scheme being set up at some point.
  1.  
    we use physibel trisco, which is hugely expensive (but very powerful) and needs a lot of training and practice as it's UI is irritatingly counter intuitive. it will however model anything and everything if you can persuade it to :) i think there's a demo which i would highly recommend messing with for a bit before thinking about buying (EDIT: I got training from GCAL on a day rate consulting basis, also not cheap, AFAIK there's no other option though)

    i also got phone spammed by autodesk regarding their new Sim 360 software which apparently can do similar but via a more autocad like interface, which sounds like it might be a winner. they also offer a pay as you go license model, with cloud processing, so depending on your intended usage that might be worth a look?
    •  
      CommentAuthorfostertom
    • CommentTimeSep 4th 2013 edited
     
    Posted By: SigaldryAECB were running introduction courses - introducing users to modelling with Therm http://www.aecb.net/products-page/carbonlite-training/thermal-bridging/
    Still doing it - I'm doing a 'refresher' at their next in Bristol on Fri 13 Sept £249 + VAT, because my borrowed laptop broke down first time! Courses run by excellent Peter Warm Associates of Plymouth.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 4th 2013 edited
     
    Posted By: fostertompricey, but far less than Ansys, the only 3D alternative
    I may have meant Trisco or Bisco - out of my league, anyway! Or is it Trynsys?

    Psi-Therm looks v interesting - anyone?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 4th 2013 edited
     
    As thermal modelling is only finite element analysis then you may be able to use LISA
    http://lisafea.com/

    I have a copy (its free) but never got around to using it.
    I think that SolidWorks does thermal modelling as well.

    Just had a quick play with LISA, the latest free download is so much better and easier to use than the last version. It has online tutorials as well now. 2D very easy, now just got to have a crack at the 3D.
    If anyone learned AutoCad in the old DOS days, nothing will come as a shock when drawing up your shapes. The rest if us have to put out thinking caps on and get a pencil and paper out to keep track of the coordinates, edges, surfaces and node. That is just good practice anyway.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 5th 2013 edited
     
    Had a quick play with LISA this morning and dead easy.

    Modelled a beam, of 10 long, 0.25 high and 0.2 wide and made of solid oak.
    Made one end 8°C, the rest 20°C. Set the time up for 24 hours at 15 minute intervals and let rip with the solver.
    First image is the initial state, the second is after 25 minutes, no change after that.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 5th 2013
     
    Did you enter a figure for thermal resistance? Can you place an adiabatic boundary? Looks competent in your screenshots - def worth a look.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 5th 2013 edited
     
    Yes, well conductance, density and SHC. Then you specify the boundary conditions, any convection or radiation if you so wish, initial conditions. You can subtract and add nodes, join nodes (say a beam and a wall), look at surface or solids, put in time dependant temp files etc. Does mean you have to make up your own list of material and weather properties, that is easy though (what pencil and paper is for).
    Once you have done all that you can export the numeric data and create a condensation risk analysis if you wish from the weather data and node temperatures, that is very simple as long as you have the data.

    And better than all that, if you can be bothered you can load it with structural parameters as well. I have an idea that using the fluid parameters you can do acoustic modelling.

    It is a vast improvement over version 7xx which I could not get the hang of.

    Just noticed that you can import STEP and IGES files, think that some CAD packages allow you to export in those formats. My version of TurboCad can (17.1)
    •  
      CommentAuthorfostertom
    • CommentTimeSep 5th 2013
     
    Therm is not time dependant - just works out the steady-state - so doesn't need density and SHC data.

    I'm thinking heat storage into uninsulated ground, creating a very wide-volume model. i had no idea that such software was so available, and adaptable, for application to that seemingly insoluble question.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 5th 2013
     
    Posted By: fostertomI'm thinking heat storage into uninsulated ground,
    Should be fairly straightforward, just need to get some material and weather data.
    Posted By: fostertomTherm is not time dependant
    LISA does both and more, lots more, some of it I don't understand yet. Trouble is I would need a real project to work on rather than an imaginary one.
    Posted By: fostertomfor application to that seemingly insoluble question.
    I was chatting to a Dr. in the building science bit of the university yesterday about this very issue. We both laughed about it.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 5th 2013
     
    Yeah but it does work - several successful buildings in NW US climates comparable to ours. I've heard the prima facie simpistic basic physics/geometry reasons why it can't work, but there must be more to it.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 5th 2013
     
    Posted By: fostertomNW US climates comparable to ours
    Where?
    •  
      CommentAuthorfostertom
    • CommentTimeSep 5th 2013
     
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 5th 2013
     
    Is that the one that is south of us and with no internal temperature data?

    I am pretty sure we could build a house near Nantes in France that needs virtually no extra heating if we put large enough fridge and freezer into it and a couple of old tellys.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 5th 2013 edited
     
    Posted By: SteamyTeaIs that the one that is south of us and with no internal temperature data?
    Eh? is what what?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2013
     
    Right, forgetting about the comment about the house in Rockford, WA that we have commented on before and back to playing with LISA.

    Drew up a crude earth thermal store, 5m by 5m by 5m, 1m diameter hole down the middle.
    Set the overall temp at 0°C earth thermal store temp at 8°C and the 'hole' temp at 25°C and ran the model to simulate 24 hours at the half hour level (you can just add different temps to all the base figures if you want to use real numbers).
    The cube heats up to about 12°C overall.
    Using a SHC of 0.8 and a density of 2.5, that gives you a store of about 226kJ or 62 kWh but, and this is the important but, it is at 12°C or 10°C below a usable temperature.
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2013
     
    Did the same at 40°C for the hole temp and this is what happens
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2013
     
    Bit more playing about and I am sure a really good picture of what is happening could be created.
    Now who wants to part with cash for that.:wink:
    •  
      CommentAuthorfostertom
    • CommentTimeSep 6th 2013
     
    'overall temp 0C' - that's temp of what? 'earth thermal store temp 8C' - that's its starting temp? Is there any heat loss from perimeters, or just a closed system?

    24hr is surely nowhere near long enough for equilibriation - no way should the entire earth cube show a uniform temp after 24hrs - 2.5 months more like. Once equilibriated, how could the entire cube fail to reach the 25C maintained temp of the hole, if there's no perimeter loss in this model?
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2013 edited
     
    Just about to upload a video.

    I made a bit of an error, actually set the earth temp at 8°C and the starting temp for the earth store at 8°C as well.
    So the starting conditions are 8°C with a constant 40°C going into the hole in the middle.
    The model runs for 96 time units, subdivided into 5 units, so may have made an error there as I am not too sure how the software works out time from the units for the material (it is unit less but if you keep the right magnitude it should sort itself out, all in the documents).

    Hopefully this is the video.

    http://youtu.be/PiFcP0HekkQ

    Edit
    Link changed as it seems that my old file store now wants to download software to play it.
  2.  
    If I've read the second model right the suggestion is that the peripheral surface of the area being modelled cools to subzero ... clearly not would happen if the periphery was bounded by insulation?
    I take it from this then that the model is somehow assuming that the "total heat" in the area must remain constant, so if you heat up the core, the periphery cools down.
    I may well have missed something as this is way out of my zone of expertise .....
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 6th 2013
     
    I am not sure I did it right, is the first time I have played with it.
    Think I may have made a skin rather than a solid.

    Point I was rally making is that there is perfectly good free software that can model transient heat transfers and one that is fairly easy to use, unlike the previous offering that was just horrible.

    Just got to find a crack for it to get around the 1300 node limit :wink:
    •  
      CommentAuthorfostertom
    • CommentTimeSep 6th 2013
     
    Posted By: MikeRumneyassuming that the "total heat" in the area must remain constant
    you mean 'in the volume'? So as the inner ring heats up the rest must cool?!
    Posted By: MikeRumneyclearly not would happen if the periphery was bounded by insulation?
    Wouldn't happen under any circumstances. I assume the perimeter surface of the model is adiabatic - no heat transfer across it - or is everything outside assumed to remain at 8C? Or at 0C in the first model?
  3.  
    <blockquote><cite>Posted By: SteamyTea</cite>I am not sure I did it right, is the first time I have played with it.
    Think I may have made a skin rather than a solid.

    Point I was rally making is that there is perfectly good free software that can model transient heat transfers and one that is fairly easy to use, unlike the previous offering that was just horrible.

    Just got to find a crack for it to get around the 1300 node limit<img title=":wink:" alt=":wink:" src="/forum114/extensions/Vanillacons/smilies/standard/wink.gif"></img></blockquote>

    Sorry Steamy, wasn't knocking your tests etc, just trying to get my head round why the outer "skin" cooled.
    I think I'll be sticking with the "wait and see what actually happens" duffers class :wink:
  4.  
    <blockquote><cite>Posted By: fostertom</cite><blockquote><cite>Posted By: MikeRumney</cite>assuming that the "total heat" in the area must remain constant</blockquote>you mean 'in the volume'? So as the inner ring heats up the rest must cool?!<blockquote><cite>Posted By: MikeRumney</cite>clearly not would happen if the periphery was bounded by insulation?</blockquote>Wouldn't happen under any circumstances. I assume the perimeter surface of the model is adiabatic - no heat transfer across it - or is everything outside assumed to remain at 8C? Or at 0C in the first model?</blockquote>

    Quite ... so Steamy + software not there yet, but see above ... If I've understood other threads correctly Steamy's not convinced about AGS so I was probably assuming he was making a point, as opposed to giving us a demo ......
    •  
      CommentAuthorSteamyTea
    • CommentTimeSep 7th 2013
     
    Too right I am not convinced of the benefits of passive thermal stores other than over a very short time period (4 or 5 hours) in the UK, active is a different matter. I am willing to be shown different.
    The main problems I have with it as the huge areas needed to collect the energy, the small volume needed to store it, the weather, the expenditure, the high levels of insulation needed to store it, just not a practical solution when even a bit of badly designed PV or ST can give you much greater benefits.
    Take a 20 tonne slab that you allow to vary by up to 5°C that will be about 20 kWh, or a days worth of heating for a small house.
    20 kWh of gas will cost about £1.2, electric about £3.6.
    Now even is a mid 1980's house you only need to heat for about 4 months of the year, so that will be about £144 (gas) to £432 (electric) a year.
    Taking normal hot water usage of about 70 litres of of water a day per person, that is about 3 kWh. Or about 1.1 MW a year per person, so about £200 on gas for 3 people, £600 on electric.
    So tackle the water with proven technology and then improve the building, mainly the air losses after. No need to dig deep holes, line with a couple of feet of insulation, run pipes, fit valves and controllers and then connect it to a large ST collector.
    Much easier and simpler tried and tested methods.
    Not as much fun as a DIY approach to it I agree, and would give it a go myself if I could (what I did my BSc dissertation it after all), but I have never seen any decent data for a UK installation that can be used to compare a house with and without an AGS.
    Sorry if that sounds harsh, but if it worked then we would all have them, why would a plumber bother with getting tested and insured to fit gas when he could fit a solar collector to a tank and heat a house that way.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 7th 2013
     
    You've most creatively dived in to start modelling interseasonal storage into 'infinite' uninsulated ground - so why revert to disputing small super-insulated tanks or chunks of concrete? Quite right the latter is non-starter.

    Remind me - was your BSc about uninsulated ground, or insulated tank?
  5.  
    Posted By: fostertom Psi-Therm is a new one - discussion on http://www.aecb.net/forum/index.php/topic,3875.0.html . 3D Psi-Therm is pricey, but far less than Ansys, the only 3D alternative.
    I know Andy Lundberg from http://www.passivate.ie/ quite well, he has a no nonsense approach and is well regarded in the industry, he translated the Psi-Therm programme from German. We also plan to add a new page to the PHPP software to allow for a full integrated Solar Roof in Passive Houses.
   
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