Tuesday, December 22, 2009

Bentley Hevacomp and Revit Interoperbilty

In my previous post I mentioned interoperability issues the gbxml import to Bentley Hevacomp. In this post I plan to show examples, specifically of taking a model from Revit into Hevacomp.

The example shown below comes from a university studio project where students had to take existing buildings and re-design them to perform better. Students working with non-residential buildings had to evaluate their schemes against ASHRAE 90.1 (to be honest not all of the models came through cleanly), before modifying the designs for better performance.

The original office building modeled in Revit was fairly basic which helped with a clean export from Revit into several programs including Ecotect, IES, Green Building Studio, and Design Builder.

Gbxml to Ecotect

Gbxml to Hevacomp

The export from Revit to Hevacomp had some obvious problems, but because Hevacomp is ahead of the field in BIM and LEED (see previous post) I really wanted to make this connection work. After having failed with the gbxml path I tried an IFC model exchange between Revit and Bentley Architecture, which came through clean but it only got me half of the way there.

Having translated the model from Revit to Bently Architecture using IFC I didn't have an energy model, but I had all of the building components which could be used to export a gbxml from Bently Architecture into Hevacomp. I found that this exchange worked out much better than the direct Revit to Hevacomp path, and now that I had the model in Hevacomp I could quickly evaluate the design against AHSRAE 90.1 standards and determine how many LEED energy points the design could earn.

Using the IFC exchange I was also able to cleanly take the Revit model into Archicad where it could be used with Graphisoft EcoDesigner, but this really belongs to a separate post when I can get around to it.

Now that we had BIM models which we used to run energy, daylighting, and solar analysis (not shown), the students then modified their designs for better performance. For this particular project the strategies used included daylighting, stack ventilation, a sun space (removed from energy model here), and solar electricity generation.

The energy model from the modified design didn't have any problems between Revit and other analysis programs (not shown) but absolutely failed when I attempted to import it into Hevacomp. In fact the import into Hevacomp brought the building roofs with nothing else.

As with the first model I tried an IFC exchange between Revit to Bently Architecture where the model came in fairly cleanly.

However, now when I tried to export a gbxml of the new model from Bentley Architecture into Hevacomp, the top part of the model never came.

This roofless model is much better than what we got from a direct Revit to Hevacomp exchange, however it's still not acceptable for analysis. I attempted to troubleshoot what went wrong this second time but ultimately gave up without an answer. I was hoping for success but came away with a sad ending after a promising start to the story. Hopefully this description sheds some light on how important interoperability is and why I am critical of software that doesn't communicate well outside of its own family of tools.

During the next semester of class we will continue exploring multiple paths from BIM to analysis software, and will hopefully be able to settle on a consistent set of tools which work well together.