You can eventually add a far away flat object with the same shape of your home that will project its shadow exactly above your home.
This is not exactly the same thing as having a real ceiling, but will come very close.
If your home is rectangular you can use a simple box. If the home has a complex shape it would be easier to create a floor on a new level following the underlaying perimeter and then move it in the proper location. This location depends on the latitude set on the compass and the hour of the day. Although it can be calculated using math, I think that a try and error approach works as well.
Here an example:
The same using a ceiling at 75 meters above the ground and shifted toward the sun:
If you use a ceiling you could find very hard to place the camera at the right place, in this case the Pan3dView plugin can help you because it allow to place the camera below the selected level elevation.
