Excluding glass in windows from light calc (probably shadow casting) can actually have negative effect. In Corona, unlike other renderers, fakes can actually penalize your rendertime, rather than improve it.
There are two ways to have light shining through the glass correctly.
1, Make special window material, which will be your usual glass, but in refraction settings, set the mode to twosided, and then, make sure your glass in windows is one one sided (one polygon, no thickness) this will give you usual glass reflections, but it will not slow down rendering in any way.
2, In Alpha V5, there will be a hybrid glass mode, which behaves like twosided mode, but renders realistic refraction, so you can apply it onto glass geometry with thickness.
But you should make sure there are no objects with disabled shadows in your scene unless you really need them to be.
;)
