I'm in the process of replacing the fireplace in my home. I removed the fireplace today and stepped into the bump-out space for the very first time. As I expected the builder took shortcuts and I have issues in there. I have this one chance and one chance only to make this space as it should be.
The bump-out "room" is two stories high with a built-in "ladder" for climbing the wall. I noticed at the top that the builder punched holes in the wall under the siding, presumably for ventilation. I don't understand why this was done. I thought that this space should be completely enclosed within the building envelope. Would I be doing harm by sealing it?
The builder only insulated half of the exterior wall with fiberglass and he faced the paper face to the outside. I know this isn't right. I'm thinking about removing it completely or turning it around and covering the interior wall with some sort of fire barrier (not sure what yet).
Should I board up those holes, insulate the remaining wall cavities and air-seal the entire space or should I leave it vented?
I appreciate any and all advice.