Openings appearing as transparent ghost

[Anonymous]

I've looked in MVO, Renovation Filter, and Object settings, but still appear as transparent opaque. Ideas?

[Anonymous]

RESULT: The Transparency box was checked under 3D Styles.

Thanks for the responses and advice. I've looked at Graphisoft's explanation:

Check this to produce transparent views of elements that have the appropriate Surfaces setting when generating a shaded view. Below, the same glass wall appears with Transparency Off and On.

Follow up question is this:
I tried several different surfaces (ones that showed up with a window opening), before unchecking the transparency box, but still it showed up as transparent. Where/how do I control the "appropriate Surfaces settings" of the door's transparency?