Now that you have a fresh air pipe, you can stuff the damper shelf and all around the flue liner with 100% fire proof Roxul insulation to prevent that nice heated warm room air from going up the chimney$$I know this is an old thread with much debate but here's my experience. House was gutted and remodeled out in the country and not much wind break, 60 yrs old on a slab but pretty efficient from the windows to insulation. Unfortunately it's isnt perfect. I have a Winslow pi 40 sat into an old but awesome looking brick fireplace. I was getting the draft and air leaks that people were speaking of so I rented a 2" boring bit and heavy duty hammer drill, bored through 15" of wall and threaded 2" flexo pipe for exhaust work from advance auto which cost $16 and connected to the stove. I siliconed where the pipe and brick are on the outside and siliconed in place a 3" drain cover over the pipe for bugs and mice which I got at lowes for $3. As I type this THERES no draft what so ever as compared to before and the glass is as clean now as this morning when I cleaned it, which it would be greying up a bit by now. It's in the 30's and my stove is on 1 and its 74 in a 1950 sq ft house. I can't say the stove is burning any better but I can say the house is a few degrees warmer from front to back due to no drafts. Total cost including the drill rental was about $70.