This past winter I found I had a cold wall in my home around my chimney. I want to replace the fiberglass insulation in that wall with spray in closed cell foam. I dont want to open up the sheetrock. It would be much easier to pull off the siding and spray it in from the outside. Would this be problematic?
Jimmie
YES... It is MUCH easier to deal with sheetrock repairs on the inside of the wall than it is to cut open a small section of the outside of the wall, removing the siding, then sheeting to access the inside of the wall cavity... Then having to close up the wall, replacing the sheeting then residing all while making sure it is weather tight...
If you are worried about blending in the wall -- strip off the sheetrock on that entire wall surface and insulate the entire wall the same way, rather than one or two stud bays... The sheetrock repairs to the entire wall would be easier as your only transitions would be in the corners and at the edges...
That is exponentially EASIER to deal with than ripping into the wall of the building to insulate it from the outside in...
~~ Evan
use care insulating around chimneys. a camera inspection is a excellent idea.
spray foam is very flammable
It would probably be better to remove drywall and insulate with Rock Wool for the fire protection.
YES, you do not want to do this when the chinmey is in use. Not even a hot water heater. Personally, I'd put fireproof fiberglass by a chimney. Code may not even allow the foam.
A problem is you wont know how much to put in, to little and its not going to fill the cavity, to much and you will Bow the wall. I had a house done, years later Ive opened several walls and non are fill up right. The cold could be just from the cold brick itself transfering in cold, or poor exterior brick to wall air seal.
pros have a minimally expanding foam that wouldnt bow walls.never seen it DIY and around a chimney its likely not a good idea.
how old is the home / chimney.
does the chimney have a working fireplace on it or just a flue?
Fireplace is made for wood burning but has had a gas log in it from day one.
Jimmie
Ive got to pull the siding off anyway for some other repairs, I was hoping I could do the insulation from that side while I was in there.
Jimmie
Not all spray foam is flammable. There are a number of them out there that don't support combustion - you remove the flame and the foam won't burn any more.
To the OP: It is pretty common in these parts to insulate from the outside as you're planning to do. If you can easily pull some of the siding (you didn't say what type of siding), then it's certainly worth looking into. Be aware that code calls out a 2" spacing around the chimney, and that by adding insulation the requirement for that spacing is even more important. You mentioned a gas log in a subsequent post, and that helps matter as the heat produced won't be as great as a roaring wood fire.
The camera inspection is a very good idea. Unless you can verify that the stud bays are completely sealed, and the foam won't expand beyond the stud bays, it's probably a bad idea to spray foam into a wall at a chimney.
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