Thermal boundary definition ASHRAE vs DIN EN vs Simulation

Hi @mostapha,

I’d like to use the hbJSON model for different use cases, where it seems there are different definitions of the position of the boundary that has to taken into account for the surface calculations:

  1. Simulation (daylight and thermal-dynamic with IDA-ICE)
    In these cases the Inside surface is fine, guess thats the “Wall Finish” option.
    So we just need some translation to lisp-style IDA-ICE files :slight_smile:

  2. ASHRAE / energyplus
    not sure about that, but they seem to need the “Wall Center” option

  3. German (and i guess EU) energy demand calculation
    Therefore the outside of the construction (or the water-bearing layer) is required for the calculation of the thermal envelopes surface. Is there any chance to get this out of Revit? Maybe by using the border of the gross floor area as guideline?
    Then I’d try to translate the hbJSON to the E-CAD xml that most german buliding code software can use as an input

Hi, @heikow - I ended up recording a video. You can use the combination of the boundary location and alignment lines to do any combination of the logic that you want. For this example, I’m keeping the interior boundary location at the center of the wall but aligning the exterior walls to the outside of the wall.

Thank you, @asisnath for sharing the model.

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Hey @mostapha, how easy is it to do this on larger models?

For IES best practice is to draw all external wall lines to the external face of the wall. Would be good to understand if it gets challenging to do what you demonstrated in your video on a model that’s multi level and potentially >1000 spaces.

Hey @charliebrooker - Good question! The number of spaces doesn’t directly affect the amount of work in this particular case but the complexity of the facade can make it harder to draw the guidelines. That’s exactly why I mentioned using Area Plans as an option at the end of the video. Revit can generate Area Plans automatically and it is easier to create them for larger models. It hasn’t been a high priority to implement it as an option.