Drywall is one of the least sustainable finishes available today. It remains a wall so long as you keep it dry, but let it get wet, and it turns into a soggy, mold-and-mildew-slathered mess. This means that it’s a bad idea to leave your windows open because you never know when a summer shower might blow up and your drywall might get wet. And windows forever left closed usually mean the heating and cooling equipment is always on. Here are some alternative wall and ceiling finishes to consider. All except the last two images are either the work of Studio Sky or of Studio Sky partners Eric Moser, Julia Sanford or Steve Mouzon.