This summer I tore down the top 14′ of a massive chimney that adorned the cabin I share with my partner. The concrete block exterior of the 6′ x 2′ cross section chimney has been rapidly degrading and it was apparent that it would not stand on its own for many more years.  The chimney itself is a huge heat sink directly connecting an attractive field stone fireplace on the interior. We’re in a cold climate with temperature often well below zero in the heart of the winter.

I’ve left the lower ~ 6′ of chimney intact, filled in the portion that was a barbecue with rubble and block and capped the top with a couple of inches of concrete sloped slightly to the exterior.  My plan is to clad the exterior block work with an inch to an inch and a half of polyisocyanurate. Tapcon furring strips over the insulation and an appropriate interval and apply a board and batten over that to match the cabin. I’ll build a small 4/12 sloped metal roof over the top of the chimney stub and extend it ~ 6″ on the sides and 18″ off the front to protect a pellet stove vent that will rise ~ 3′ from where the vent exits the back of the fireplace firebox.   My thought is that any even an inch of polyisocyanurate  wrapped around the masonry will make it sustantially less of a heat sink.

I didn’t take the chimney all the way down to the ground as it supports ~ 6′ of the roof line and the interior field stone fireplace is an attractive back drop the pellet stove. It’s certainly a possibility to do that down the line but for now getting the unstable, tall,  house eating chimney down was a top priority.

Thoughts regarding cladding polyisocyanurate onto masonry?  Should edges be foil taped to prevent insect entry  into the foam itself?  Will furring on 24″ centers be sufficient?  Any alternative ideas? I believe I’ll have access to recycled foam for the project.

Thanks for your thoughts.