99% of our house was very well insulated when we built it in '06. Comfort Foam and blown cellulose have led to reasonable energy bills and no drafts, with one exception. An unrelated repair on a low voltage outlet revealed a previously hidden but MASSIVE air penetration, incredibly cold air entering the space beside some bookcases.

After much investigation including the purchase of a borescope, I've determined that our contractor forgot to insulate the spaces on the sides of our chimney. I posted a sketch in a link at the bottom (excuse my lack of artistic skill) but here's the gist of it:

To the left and right of our fireplace are alcoves about 2 feet deep by 3 feet wide, and 9 feet tall. The back of them is the exterior of the house. Each one had comfort foam and blown cellulose on the rear wall and the non-chimney-facing wall, but the inner wall (against the chimney) was mistakenly skipped (the contractor claims they're not allowed to put comfort foam against the chimney, but acknowledges that there should have been cellulose or something else in the space). They were drywalled, then bookcases and a mantle were installed.

Because of the lack of insulation in the space between the chimney and the drywall, the only thing preventing air from coming in from outside is a line of caulk on the outside of the house between the exterior trim and the chimney. Since that's a sizable gap, and the brick is porous, you can imagine the caulk is not doing much.

So air can enter the space along the full length of that joint, and then circulate between the drywall and chimney, and between the drywall and the bookcase. This is putting stress on the wood of the bookcases, and of course is massively inefficient from an insulating perspective.

The challenge is that the bookcases and mantle were an elaborate install. It would be very tough to try and remove them to properly insulate the space. I'm hoping to fix the problem *through* the bookcase with as little damage to the bookcase as possible. My leading candidate so far involves 20 cans of GreatStuff's maximum expanding foam. I can drill holes through the bookcase and the drywall into the chimney space and just start pumping the stuff in. It will take awhile since I can probably only do 6 or 8 inches of foam before needing to give it 21 hours to cure. The space I'd be filling is about 10 inches wide, 4 inches deep and 9 feet tall, with one firebreak in the middle. So it's a lot of foam.

If I knew this would work, I'd get started, but my concern is that since I won't be able to SEE the result, I may end up leaving a gap here or there and would not be able to fix it. If it's a smallish gap it could continue letting in enough cold air to eventually warp the bookcases, but not enough that I would feel it and know the repair had failed.

So, any better ideas I should consider? I could probably augment this fix by going to the outside of the house, removing the caulk and putting Great Stuff in that gap as well then recaulking, but I probably won't attempt that until warmer drier weather. I don't want to have it rain on me before I get to recaulk the joint.

Thanks for any advice, and sorry it takes so many words to describe the challenge.

Jason

Here is a link that might be useful: {{gwi:1541117}}