Vray sun problem

[annamole]

 

Hi I have problem with vray. I want to enlighten the scene on the roof of my building. I've used the vray sun. But it doesn't look properly. As you can see I have something grey on the sky and it ruins my renders. I've tried everything to make it better. I've deleted the light and put it again. But everytime is the same. Maybe you know some other way to enlight this scene except using vray sun or how to use another enviroment map with this light. Please help me.