After several days or modeling I decided to render building I am working on. Mantra is rendering model with smooth normals (term borrowed from other apps). Searching this forum I find out that would be best to use Vertex node to fix that, with Cusp Normal option.
And this work to some extent, what I am facing now are some black polygons in render, I tried to use Reverse node but that does not help. What would be my next step?

Here is screenshot of what I get in render.
http://screencast.com/t/uK3vIxDB [screencast.com]

As usual I found answer 5 sec after I post question.
This is what was causing problem for me all a along. Just turn it off.
http://screencast.com/t/y1MoeK3poId [screencast.com]