Hi, Greg.
I have problems with some objects and a transparency shader, generally, though, ray-traced objects tend to work fine for me. Thd built-in sphere renders noisy, black spots when atmosphere passes through it but a RT rock object renders that fine.
In all these GI tests following, the spheres are built-in rock objects and the tabletop they're sitting on is a 6 sided cube object, just like your windows, the transparency shader rendered them all fine.
Volume 1 Colour/Density creates a faked 'milky' effect, colour is self explanatory, density is how 'thick' the 'milkiness' appears. Imagine a muddy puddle, you can see through the water only so far until the mud volume obscures the transparency. However, there's a problem with the 'volumetric' shadowing in the water shader, in that the shadows appear very noisy along the edges, there are no quality settings, that I know of, that can reduce the noise. Raising render detail/ray detail maybe but that can't really be called a 'fix' as even full quality settings does not remove the noise and it's really wasteful of render time to go even higher. The error/effect looks similar to Soft-Shadows lacking samples on regular surfaces, noisy blurring, no smooth falloff. A water volume quality slider would be a handy thing here but I don't know how easy that would be to implement. The Water Shader 'volume' is a fake 2D approximation, not a full 3D volumetric effect.