The duct-work in the basement for my forced air heating system has been modified at various points over its long history and as a result had quite a few leaks when I moved in recently. I used foil tape to fix most of them, but I'm having trouble with the biggest leak:
- The red arrow is the main branch from the furnace, showing the direction of airflow.
- Blue shows the branch leading to the register. This register is the second one on this branch, and the most "direct" (the other leads through a section of smaller duct-work). The register is located directly above the floor joists shown.
- Green shows where the leak is -- the duct (blue) butts against this joist, and where it meets the main branch (red) there is a gap about 1/4" (0.5 cm) wide, for the width of the duct. Between the joist (green) and the main branch (red) there is just enough space to get my fingers. This is the space that needs to be filled or sealed to stop the leak.
Since I have failed to get tape in to seal this joint, how else can I seal it? I'm thinking of getting a piece of foam insulation or perhaps tube wrap to shove in the gap, but would this be wise?
Some additional details:
- Moving the main branch to get better access is probably more trouble than it's worth.
- Location is an unfinished basement.
- The space is already warm enough given the small size and the fact that the furnace and lots of duct work is radiating enough heat to keep it warm.