PROBLEM:
Revit shadows are based on "what you see". If you create a plan or section that cuts the building the sun can see into the building and casts shadows.
SOLUTION:
This is a workaround. Future versions of Revit (hopefully) will make this redundant.
Duplicate your view.
Turn the Shadow off in the Duplicate view.
Create a sheet.
Place the view with a Shadow on the sheet.
Place the view without the Shadow on the sheet, directly over the building with the shadow.
If you have Revit 2014-2015, you can crop the view in the specific shape of the building without the shadow so it traces the outside edge of the building.
The building without a shadow will sit on top of the building with a shadow, masking out the building elements with the plan with no shadow. The shadow on the site, which does not have anything on top of it because the building without a shadow was cropped down, will still show the shadow.
In short: Overlap two views... one with shadow and one without, only leaving the "shadow" plan exposed around the building perimeter.