When you attempt to import a DAE file created in AutoCAD into LumenRT, all of the elements within the file have its material type set to "Glass" instead of "Standard". This gives the object an overall shiny and reflective look you may not want.
The cause for this issue lies in the Autodesk software you are using. Autodesk does not export the transparency value of the object in a way that LumenRT can correctly display. Basically, the COLLADA standard (which is the standard for DAE files) says that with respect to transparency, 1=opaque and 0=transparent, while it is the opposite for LumenRT. To fix this, open the DAE file at hand in notepad and use notepads' find/replace utility to change:
Saving and opening in LumenRT will show that the object's elements all now have material type set to "Standard".