Shadows in Rendered view - foggy appearance

Hello,

we are trying too get more shadow into our images by the use of Sun and an Environment map also used for the Skylight emittance. Adjusting the colour of the shadows in the display mode settings to a darker colour also brings out more of the white fog on the ceiling. Is there a way we could get rid of this white, apparently shadow, emittance?

Kind regards,
Nils