How to ensure there are no holes in my geometry? I have been given a geometry like the one in the picture but find that although it is a building, there appears to be holes in the façade...



Is there any way of making sure there are no holes (see below) in it apart from looking at it very carefully and making faces?
you can use the 3d print toolBox :


press Ctrl+Alt+U
go to Addons and enable 3d print toolBox and save the settings





in the 3D view switch to Edit mode and select your mesh 
use the Non-Manifold operator ( press T to show the tools panel )