Chimney Chase

[Barry J]

Chinmey chase
There is a chase built around my chimney in the attic. The chimney goes straight up the middle of my house. Around the chase, it is only sealed half way around the chimney with flashing, on the floor side of the chimney. Hot air is coming up from the cellar and mixing with cold air in the winter, and causing condensation. I can not reach into the chase to install more flashing to seal up, not enough space.. Can install flashing around the top of the chase and seal it?
Thanks Barry

 

[Dana]

Short answer is "yes".

Ideally there would be metal air-barriers at every floor, but if you can seal it at both the top and bottom it'll reduce the stack-effect infiltration drives pretty dramatically. As long as it's blocked from flowing entirely through the moisture transport will be 1-2 orders of magnitude lower than if allowed to leak constantly. If you can seal it up at the attic floor level that's half the battle, but seal it in the basement too if you can.