Here is a thought of something you could try. Take a glazed piece of poly carbonate (used for greenhouse walls and roofs). Place this against the window. Then you put your plants in the window sill where they already were. And lastly put up some curtains that have a white backside to reflect light back at the plants and make a make shift grow room. You would still get to use the suns free energy. With a little more work you could seal it off decently and then add and inlet and hook up a small exhaust fan with a carbon filter and you wouldnt have to worry about mold from still air or smell if you are worried about the guard catching a wiff of the plants. I'm just offering an opinion.Good luck with the grow