How to unify BEM & BIM models for (simple) house retrofit projects

Dear community,

I am looking for references/ressources on a specific topic. Maybe some of you will kindly point me to relevant informations/articles/githubs or share their thoughts on my case ??

I am working on a simplified tool/workflow for designing relevant energy retrofit scenarios for houses, here in France. I am thinking on leveraging LDBT to do this and bring more fine-graine insights than what is done at the moment on this market segment (very basic I must say, based on simplistic regulations).

It must stay super simple in term of modeling time & complexity to achieve a reasonable billing price (around 1000€ / 1 day per study). Because of the market segment (individuals).

Thus, I am planning to rely on a kind of parametric definition of a house (several templates, one for each topology).

Still, I would like to unify the 3D Building Modeling (wich account for element thickness) and the Building Energy Modeling (where thickness is not represented).

A certain level of 3D modeling is requiered to provide minimal yet impactfull vizualization capabilities for the clients. IFC standard might be a good fit here with several libraries to rely on for model rendering.

A “binded” geometrical model suitable for BEM. Relying on HBJON might be a good fit here too.

  1. How would you approch this two requirements ?

  2. Can you point me to valuable ressources that review in depth the conceptual & technical difficulties of any BIM <> BEM process regarding the question of “element thickness” ?

  3. Any thoughts on this project would be really appreciate !

Hi @lionpeloux ,

Have you tried the Pollination Revit plugin yet?

I realize that I’m doing some shameless self-promotion by bringing it up but you’ll see from the testimonials there that our Pollination plugins are currently the only way we know of for going from BIM > BEM that gets you a clean/usable model and is faster than re-tracing the geometry from scratch in the BEM interface. In all other cases, including routes with gbXML and internal tools developed within offices, the result is just too messy and difficult to repair that it is more economical to re-trace the geometry in the BEM interface.

Part of the reason for this is because of how we built the HBJSON schema, which underlies all of the Pollination plugins and, of course, LBT Grasshopper. In that sense, a good fraction of credit is due to McNeel for making us aware of important geometry practices (like using tolerance), which we built into HBJSON. The other half of the reason why our plugins are fast is that we added a lot of commands like alignment, auto-removing short segments, etc. which help you get rid of the “thickness” that you mention.

But what you are asking for here is not a trivial thing to solve. I know it took a lot of work on our part to make the Pollination plugins as reliable as they are. But it still boggles my mind that we have had both CAD and BEM software for almost 4 decades now and yet people are telling us that we are the first to offer a semi-automated path between them that is better than re-tracing geometry manually.