Chimney chase question
I have a 90s era home with a framed chase on an exterior wall along a metal flue pipe. it’s in St. Louis, MO with hot/humid summers and cold winters. The fireplace is freezing in the winter when not in use because only the front (inside) wall of the chase has insulation.
I’m preparing to convert from a wood burning insert to a gas fireplace and have a chance to rectify some of the energy and comfort issues while the front wall of the chase is torn out.
a.) Should I insulate the front wall of the chase or just the 3 exterior facing walls?
b.) I can only insulate up to the drywall top (firestop). How do I insulate the top? Should I sandwich mineral wool between the existing drywall firestop and another layer of drywall, respecting the 1″ clearance around the flue? I’d use high temp caulk to air seal the metal collar that the flue passes through on the original top.
c.) Where should the vapor barrier go? It’s currently behind the drywall on the insulated interior wall.
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