How can I seal a double wall stove pipe?
One effective way to prevent smoke escaping through double wall stove pipe seams is to seal these seams. This can prevent smoke that otherwise might leak out through these seams when there is not sufficient heat in the pipe to carry the smoke up and out of the house. Another factor that can create this smoke seepage is a downdraft sometimes created by a high wind.
Sealing Your Stove Pipe
When your stove pipe is cool, use a small trowel to apply furnace cement into the stovepipe seams. Carefully apply the cement to edges of each seam until the cement completely fills all the seams where pipe sections overlap.