Here's a render I submitted at RDNA that is lit exclusively through a window. It may not be the greatest or most accurate lighting, but my method was to use a single spot light as the sun, directed through the window at an angle such that the shadows looked the way I wanted them. I believe I added an almost imperceptible atmosphere too.

With the multiple reflections, the atmosphere, the light coming through the transparency of the window and then through the transparent parts of the flowers, plus the IDL settings needed to reduce the blotchiness on the walls and window frames, this render took half a day for a mere 1200 x 900 pixel resolution. I had to do two versions which I composited: one without the flowers at a higher IDL settings, and one with the flowers but with blotchy walls (I added a patterned texture to them to reduce the effect). I could have rendered it all in one go, but I think my machine would have needed a couple of days to finish.

Now maybe it's heresy to use a spot light for the sun, but if it looks okay to me, I don't see a problem with it.

**ETA: Those are BB's shaders all over the place. The render wouldn't look anything like that without them.

---

PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.