Our windows stand about 16 degree off vertical, so they have a slight angle to them. The sun is so low in the sky in the winter time, that is what it worked out to be. We build our roof to over hang the windows of the atrium to help keep the rain and hail off of them. But in the winter, we do have to sweep the snow off of them. Yes, the atrium is the greenhouse in the front of the earthship. When they are done, I anticipate the performance to improve. We have many months of cloud during the late fall and early winter. But the earthship stores so much heat through the summer that we don't start burning wood until most other people have turned on their furnaces for the season. I hope this helps. Thanks for dropping by and participating in the conversation. Peace to you.