Open to closed Meshes


I know this has been asked before.
But I haven`t found a good solution to the probelm, if there even is one.

I need to convert the open meshes to closed meshes so that i can
calculate volumes of the buildings.

Is there a way to rebuild the meshes. It doesn`t have to be very precisely.

Thank you

Open Mesh to Closed Mesh.3dm (672.4 KB)
Open to closed (527.6 KB)

try with mesh+

or you can use _FillMeshHole in rhino


Thank you.

The Mesh+ command kind of works, but doesn`t do the job for all open meshes.
I get the error: 1. The object reference was not set to an object instance. (line: 0)

The _fillmeshhole component in rhino doesn`t let me select more than one mesh and I have several thousend.

the problem in the meshes themselves