Insulating a Decommissioned Chimney
I have a client project where they have an existing large stone fireplace and chimney …see photos attached…that they no longer want to use. We are in Climate Zone 5 outside of Philadelphia and we are planning to add a 2nd Flr on top of the existing room where the fireplace is located so we are planning on extending the chimney using CMUs and then wiring and stuccoing the entire chimney on the exterior. The interior stone work on the 1st floor will remain exposed and the stone work + CMU that will be visible in the 2nd Flr will be covered with brick veneer. My question is, what is the correct (best?) way to decommission that chimney and are there ways to insulate the new chimney extension that would help mitigate the heat sink of the chimney for the 2nd Flr? Stuff rockwool insulation into the flue down in the 1st Floor fireplace and call it good? We are planning on capping off the new chimney extension with an aluminum cap to keep out water. Should this cap be vented in some way so that condensation that might form inside the chimney can evaporate? Would lining the inside of the CMU chimney with 2″ rigid foam be of some value? Are there specific code requirements? I am find a variety of conflicting info…so I am looking for better clarity here at GBA.
Any guidance here would be much appreciated!
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