Did I goof badly? Metal bracket against exterior sheathing
My typical wall section on part of my house is 5″ of stone, two layers of 2 1/4″ EPS rigid foam, Grace waterproofing, plywood sheathing with 2×4 studs and blown fiberglass between the studs.
At the chimney it’s the same but only one layer of exterior foam faced with 5″ of stone. I needed to mount some heavy steel brackets to the chimney made of 1/4″ plate steel. The contractor was wary of mounting these with lag bolts to the face of the foam and wanted to put the face of the brackets directly against wood to be sure there would be no deflection. (I was arguing that the foam is good for 25 PSI but not prevailing).
I conceded and we mounted 2 brackets measuring about 36″ x 6″ to the wood sheathing. Now I am worried that steel, being an excellent conductor, will bring winter temperatures directly to the wood sheathing and the studs and the dew point there will cause the wood to rot.
Am I over thinking this? I still have the chopped fiberglass between the studs (which is all most houses would have). On the other hand, the flue from the gas fireplace on the other side of the wall will create a strong temperature gradient on the other side of the wall. I have three options:
1) leave well alone
2) take the brackets down, put the foam back and reinstall before the mason gets further up the wall with exterior stone (not easy and would require cutting 2″ out of the brackets and re-fabricating)
3) Add a 4′ x 4′ layer of foam behind the brackets inside the chimney structure (although that will not be continuous and will not address warm air getting behind it.
Any advice appreciated – oh this is in south west CO – alpine desert climate zone 4 with winter night temps often in the minuses. Thanks for any suggestions you can give me……………..Gary
Brown painted box shaped brackets on the wall cut into the foam: