Opacity maps/ how do they work in unity?

Unity Engine
1

Hi I have a problem, getting opacity maps to work
properly.

I have an object with some windows,
when i import the opacity map covering,
the area of the windows.
The entire object becomes translucent.

I have tried different combinations under bumped diffuse.

I dont know if the solution is to make the windows,
as separate objects with the opacity map?

2

If object has completely opaque parts, it’s better to split them off into a separate object. You’ll get much less transparency sorting issues.