Hey Gang,
Just wanted to give an update as I have been working through this problem for some time.
Softplan while exporting to Sketchup does not always properly place the normal of the face. Each exported mesh is created with a face that is meant to be seen and one that isn't. Some items are flat planes and thus will always have a visible face that won't be rendered.
For the most part Sketchup does not have an issue with this particular problem because sketch up (like softplan) can take a flat face and apply the texture to both sides. Many rendering programs don't like this as they usually don't render the hidden face. Thus why your glass in blender looks funny, it is visible only from one side and not the other as it is created in softplan as a single plane without any depth.
I've found some success by simply being careful as to what symbols and walls I export from softplan as a means to keep the flipped faces to a minimum. I'm also working on a couple different workflows to correct the issues I am running into. If anyone is interested send me a PM and I'll send over some details.
The fix from softplan would be to give items like glass in windows or gutters some depth (IE two sides) but at the cost of more mesh when rendering.
A slightly off topic gripe, I would love when exporting out of softplan to sketchup to get a better list and hierarchy of the items being rendered. The DWG01-001 nomenclature is not helpful in identifying what items belong to what groups. Even if all the walls were grouped together under a wall heading, then electrical, then symbols any required processing would be made much much easier. Currently I don't have the patience to go through the 600 components being exported and change all the names.