You mentioned somewhere you had some windows you drywalled over. I'm in TN so my climate is a little warmer than your's but I think we both qualify for heating and cooling seasons.
I worried abotu how to handle the "plugs". I really dont' need to remove them except for a catastrophy (tree falls through window, etc.). Drywalling over them is the easy button. I have them framed and ready to case out, I was going to just plug the openings with independent (from the rest of the wallboard) "plugs". Maybe seal the first layer with acoustic sealeant, and mud the crack without tap on teh final, visible layer. It will grow a little crack there which in this case is good, so I can see where the plug is should I need to remove it. Walls get fabric so cosmetics aren't an issue.
So, here's the question... how did you handle your windows insulation and vapor barrier-wise? I'm worried about them getting condensate and then mold in that little cavity. I was thinking a faux windows treatment (for benefit of the outisde lookign in view), then insulation, then a vapor barrier, then my drywall.
How are your's performing? Any issues?