When drawing multiple layers of transparency, which is what I think you want to do, you need to think about the drawing order and your depth sorting. You will also perhaps need to think about the alpha blending values you assign to colours and/or textures to get various effects.
If you draw the windows of the building first and then the glass inside if you are using depth masking the internal glass will not be drawn as it is behind the windows of the building and as far as OpenGL is concerned (wrt to depth functions) all polygons are opaque.
This may be of help…
After that you then perhaps need to think about reflections of environments to give the effect of glass and that opens a whole pandoras box of either environment maps and / or shaders for getting reflections and refractions.
I am not sure if you want to go quite that far for this, but let me know if you do and I can post some other links.