John will be able to give you the professional view of the black art (okay, a science that I only have the basics of) of your acoustics, but...
...one of my most successful rooms for home studio recording was a previous house where a full 2/3 of one wall was a patio door/window. I hung heavy curtains on a rod that protruded five or six inches out from the wall so the total gap back to the windows was almost a foot behind the curtains. When recording, I tended to place people in front of the windows (so the mic(s) faced the curtains, sometimes straight on or slightly angled with more formal acoustic treatment on the opposite walls.
It worked well for me.