In reply to Brian.

You called it. For about two months we were burning GREEN PINE because that was all that was available. I knew at the time that we were probably cruising for trouble. But there was no other option. The single walled stove pipe is actually a GOOD thing because we get more of the stove's heat in our space that way. I think that the condensing effect is part of it as well, but a minor contributor. Luckily, we're burning dry hardwoods this month... but we're almost out. Who knows what will be available next month? Dung, perhaps?