[Bldg-sim] Streamlining CAD-to-Building Simulation Workflows

Fri Sep 26 22:56:48 PDT 2025

Dear All,

Thank you for the thoughtful discussion. Many of the challenges you’ve
highlighted around preparing CAD/BIM files for simulation — such as
over-detailed drawings, unclear room boundaries, and manual input of loads
— resonate strongly with our experience as well.

In our own work, we’ve been exploring how the modeling and editing power of
CAD can be used to ease this process. Instead of simply cleaning up
geometry, we’ve experimented with generating walls, windows, and room tags
directly in CAD and attaching xdata that can carry simulation-relevant
information downstream. This metadata not only helps build structured 3D
models more easily but can also automate first-order calculations (e.g.,
estimating infiltration from external wall and window areas), which
otherwise often require manual effort.

The idea is not to replace simulation engines, but to harness CAD as a
strong pre-processor and reduce redundant steps. When the model moves into
tools like eQuest, gbXML, HAP, or Rhino, much of the groundwork is already
structured and simulation-ready.

I’d be interested to hear if others have tried embedding
simulation-friendly metadata at the CAD stage, and how you see the balance
between preparing models in CAD versus in the simulation tools themselves.

Regards
Gurneet Singh
Director

Environmental Design Solutions Pvt. Ltd.
D-1/25, Vasant Vihar, New Delhi 110057

[m] +91 9899240140    [t]  +91 11 4056 8633
gurneet at edsglobal.com | www.edsglobal.com

Achieving water resilience with LEED Zero Water – setting a new standard
for sustainable water management!

On Fri, Sep 26, 2025 at 2:34 PM Dennis Knight via Bldg-sim <
bldg-sim at lists.onebuilding.org> wrote:

> Thank All,
> I have used ConstructDXF with some success when the 2D drawings are clean,
> as suggested. However, if I’ve got a really clean “stick” drawing, its
> about as easy just to use the IES geometry tools to draw the spaces from
> scratch. The process I use to get clean floor plans quickly is use a 2D CAD
> drawing, turn off all the layers I want to keep (walls, doors, windows,
> space names), then select everything else and delete it, then turn the
> layers I turned off, save as DXF, then use ConstructDXF or simply sketch
> the plan using the attached DXF. This workflow works fairly well.
>
>
> M. Dennis Knight, P.E., FASHRAE
> Founder & Principal
> *W*hole *B*uilding *S*ystems, LLC
> P.O. Box 1845
> Mt. Pleasant, SC 29465
> Phone: 843-437-3647
> Email: dknight at wholebuildingsystems.com
> Website: www.wholebuildingsystems.com
>
>
>
> On Thu, Sep 25, 2025 at 10:37 PM Karen Walkerman via Bldg-sim <
> bldg-sim at lists.onebuilding.org> wrote:
>
>> The approach we take in EP3 (https://ep3.solutions), is similar to
>> Chris's description of creating "watertight" 2D CAD drawings. 2D floorplans
>> are created, and then walls are extruded up to intersect with flat or
>> pitched roofs.
>>
>> If you already have clean CAD drawings, you can translate them to EP3
>> floors with one click.
>>
>> In EP3, instead of grouping 3D surfaces by space or zone, we maintain the
>> 2D floorplans, and have exterior walls, interior walls, and roof surfaces.
>> The major advantage is that changes to floorplans can be made in the 2D
>> floorplans at any phase of the project.  Adjacent zone geometry, walls, and
>> intersections with complex roof shapes happen automatically. This makes it
>> much easier to adapt and update building geometry as a project moves from
>> SD through to construction.
>>
>> While EP3 is primarily uses EnergyPlus as a simulation engine, we can
>> also create eQuest geometry, constructions, schedules and internal loads.
>>
>> Best,
>>
>> Karen
>>
>> On Thu, Sep 25, 2025, 22:51 Chris Yates via Bldg-sim <
>> bldg-sim at lists.onebuilding.org> wrote:
>>
>>> Hi Gurneet,
>>>
>>>
>>>
>>> There are many formats and geometry paradigms (E+ has several ways of
>>> defining geometry). Some paradigms are based on simple collections of 3d
>>> polylines, whilst others are a bit more “parametric” and therefore
>>> predicated on some limitations (such as a single planar nGon defining the
>>> floor).
>>>
>>>
>>>
>>> *IES*
>>>
>>> Commercially, I can only speak of how I hack geometry into my tool of
>>> choice – IES VE. I’ve not found gbXML or IFC import very reliable to import
>>> into IES. However, there’s a function called constructDXF that is very good
>>> at extruding 2D cad plans into a 3d model. The cad plans have to be
>>> super-clean, but I don’t mind this because I’m very happy working in CAD.
>>> You need to create a stick drawing presenting watertight zones. Each zone
>>> has a line of Dtext in the middle representing the zone name. It’s a bit
>>> archaic and it’s generally not what they teach you on the training course!
>>> I think constructDXF has been part of the software for almost 30 years!
>>>
>>>
>>>
>>> I believe the underlying geometry paradigm is 3d polylines. A “gem”
>>> (geometry) file can be exported out of IES in ascii text format. The format
>>> of this is definitely 3d polys.
>>>
>>>
>>>
>>> *IDA ICE*
>>>
>>> I also have some experience with IDA ICE. This tends to do a fairly
>>> decent job of importing IFC files, as long as the zones are valid (good
>>> luck with your architect). The zone definition appears to be more on the
>>> “parametric” side with IDA – a typical zone is prismatic but features such
>>> as a clipped roof can be applied. Max Tillberg at Equa has worked on a
>>> number of workflows to get geometry into IDA apart from using IFC. From
>>> what I understand, he’s had a degree of success using Rhino, Revit,
>>> Speckle, and even the open-source tool, Blender.
>>>
>>>
>>>
>>> I hope that this helps.
>>>
>>>
>>>
>>> Kind regards
>>>
>>>
>>>
>>> Chris
>>>
>>>
>>>
>>> *From:* Bldg-sim <bldg-sim-bounces at lists.onebuilding.org> *On Behalf Of
>>> *Gurneet Singh via Bldg-sim
>>> *Sent:* 25 September 2025 10:15
>>> *To:* bldg-sim <bldg-sim at lists.onebuilding.org>
>>> *Subject:* [Bldg-sim] Streamlining CAD-to-Building Simulation Workflows
>>>
>>>
>>>
>>> Hi all,
>>>
>>> We’ve been exploring ways to reduce manual effort in transferring
>>> geometry from CAD into building simulation formats like eQuest, gbXML, and
>>> others. In our recent work, we developed a plugin that facilitates this
>>> process by converting CAD lines directly into multiple simulation-ready
>>> formats (eQuest, GBXML, HAP, Rhino), aiming to save time and minimize
>>> errors.
>>>
>>> I’d be very interested in feedback from this group on workflow
>>> improvements or challenges you’ve encountered when moving from CAD to
>>> simulation formats—especially regarding geometry accuracy and
>>> interoperability.
>>>
>>> Best regards,
>>>
>>> Gurneet Singh
>>>
>>> Director
>>>
>>>
>>>
>>> Environmental Design Solutions Pvt. Ltd.
>>>
>>> D-1/25,
>>> <https://www.google.com/maps/search/D-1%2F25,+Vasant+Vihar,+New+Delhi+110057?entry=gmail&source=g>
>>>
>>> <https://www.google.com/maps/search/D-1%2F25,+%C2%A0+Vasant+Vihar,+New+Delhi+110057?entry=gmail&source=g>Vasant
>>> Vihar, New Delhi 110057
>>> <https://www.google.com/maps/search/D-1%2F25,+Vasant+Vihar,+New+Delhi+110057?entry=gmail&source=g>
>>>
>>>
>>>
>>> [m] +91 9899240140    [t]  +91 11 4056 8633
>>>
>>> gurneet at edsglobal.com | www.edsglobal.com
>>>
>>> Achieving water resilience with LEED Zero Water – setting a new standard
>>> for sustainable water management!
>>> _______________________________________________
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