Visualizing Thermal Transfer Data in AutoCAD Architecture

This example focuses on a presentation technique that architects could use to clearly communicate their decision in the choice of building envelope composition. The wall object in AutoCAD Architecture (formerly ADT) can convey a vast amount of information, both automatically generated and user added, but in respect to physical properties and the way those can be visualized does not provide for any analytical depiction. Yes, we can add an array of information to individual wall layers, and if we get really adventurous we can use ACA's powerful and mature API to access those wall sub components and through material definitions assign values like thermal conductivity and embedded carbon footprint, but this would be a topic for a different post.

Click to see DWF model

What I tried to accomplish here is to visualize the thermal transfer data within this particular wall/window detail with a help of a really amazing free analytical tool the Steady State Heat Transfer, Therm 5.2. To achieve this I have modeled a fairly accurate window sill condition in AutoCAD Architecture, by using custom end caps and strategically placed Mass Element objects.

After cutting the section through this assembly and detailing it by using the Detail Component Manager , this drawing was exported to a DXF file for the purpose of bringing it in as the background into THERM 5.2. In this application, that is available from LBNL, the appropriate materials and boundary conditions were, so to speak, "painted" over the imported CAD underlay. This means that for every polygon that represents a different material in section we have to assign the appropriate material definition, and for those polygons / materials that are exposed either to the exterior or to the interior we need to assign the set of boundary conditions. In order to do the meaningful approximation, adiabatic boundary conditions are assigned where the top and bottom section cuts occur.

It is worth mentioning that even though THERM 5.2 comes with an extensive material library, you will still have to do your due diligence in order to define some of the missing construction materials, if approximation is not an option.

The pseudo IC thermal images can be exported into an image editor of your choice and applied as the bitmap within a ACAD/ACA material that will be mapped onto a Region object generated from 2D section object. After a few tweaks in respect to mapping of the newly created material thermal image is assigned as the diffuse map and its inverted B&W image as the opacity map. Enabled live section of this model has been exported as the DWF file for an easy share with anyone that is interested in the thermal performance of a building's envelope on any given project.

In this example even though the analytical data does not reside within BIM compliant model, we can use the very same model as a link to the external data and more effectively communicate or justify the design intent.