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... on (major) thermal bridging and derating of surface constructions

asked 2020-12-11 04:06:28 -0600

updated 2022-06-12 08:36:42 -0600

We recently published an OpenStudio measure that automatically extracts major thermal bridges (e.g. slab edges, cantilevered balconies, corners, fenestration perimeters) from OpenStudio model geometry, and then thermally derates connected OpenStudio surface constructions (up to 70% in some cases), à la BETBG, ASHRAE RP1365, ISO 10211. This is a requirement in several Canadian energy codes (varies across provinces, municipalities), which can be quite time-consuming and error-prone. One can get the "Thermal Bridging and Derating" measure (or TBD) from BCL (or search "derating" or "rd2"), or by looking up "releases" under (which also holds more information on the measure, e.g. underlying concepts, planned enhancements).

TBD defines a standard JSON format for describing the major thermal bridges of a project using shared surface names as easily accessible identifiers. The TBD measure can generate a TBD JSON file holding the dozens or hundreds of major thermal bridges found in an OpenStudio Model. The exported JSON can be customized and (re)imported by the measure itself or in principle by other EnergyPlus-based software to perform construction derating prior to simulation. The exported JSON can also be used for other purposes such as costing, or other calculations.

We have 2 questions:

First, anyone else doing something similar (more on the practical side than academic work)? Curt Hepting ( first asked us the question - it would be nice to know (e.g. pooling resources).

Second, we are trying to come up with a list of software packages that already offer APIs like the OpenStudio SDK, and where there might be some interest in using the TBD JSON schema and methodology for construction derating from major thermal bridging, e.g.:

  • TRNSYS types/components
  • IDA ICE extensions
  • IES VE Python scripting

... any others? suggestions?

Thanks for your time, any follow-up responses and/or personal communications.

  • Denis Bourgeois (rd2)
  • Dan Macumber (automaticmagic)


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answered 2022-06-12 08:35:35 -0600

updated 2022-06-12 10:22:37 -0600

I'm closing this question (as "answered"), with an overview of some documentation + personal communications we've maintained since we first solicited feedback. IDA ICE seems to be the only other software solution that currently addresses these needs with similar thermal bridging/derating calculations. Others developers have this on their TO-DO list - they'll surely announce/deploy when they're ready! At some point, it would be beneficial to carry out intermodel comparisons to identify gaps vs commonalities. Merci!

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... being thorough/fair with available solutions out there: DesignBuilder has offered similar functionality for a number of years (> v5, 2019).

Denis Bourgeois's avatar Denis Bourgeois  ( 2022-11-02 13:29:46 -0600 )edit

... and so does ESP-r.

Denis Bourgeois's avatar Denis Bourgeois  ( 2022-12-15 13:41:52 -0600 )edit

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Asked: 2020-12-11 04:06:28 -0600

Seen: 460 times

Last updated: Jun 12 '22