Fireplace insert: Insulate the exterior, or not?

[pdqdl]

I remember you saying your house was tight but houses less tight sometimes have a 'house chimney effect', meaning hot air is leaking from the living space into the attic space via air leaks near ceilings.

There won't be any appreciable leakage into the attic. There are no cracks whatsoever in the drywall, about 9 inches of blown cellulose insulation and a tight-fitting attic stairway. The attic fan louver will be leaking a bit of air, but not enough, I think, to cause any significant air movement. I'd speculate that the sewer vent stack is completely uninsulated as it passes into the attic, but I have never found a cold-air dump area on the lower floor. Quite frankly, I don't know where it is located; I think it's hidden inside a wall.

We only spend about $100 per month on natural gas in the winter time, so it is pretty well insulated. I've put in double pane windows everywhere, and insulated the heck out of them with spray foam between the aluminum window frames and the wood framing on the house. This house is a split level, with a double garage on the north half, and the "basement" on the south half is holding the fireplace insert.

 

[pdqdl]

An update: I am still defeated by the flexible pipe attached to the top/rear of the stove. I took my heavy-duty air chisel home from work, and it didn't even wiggle. It hits so hard that the stove coupler pressed into the stove started to come out and the air chisel was happy to blow holes in the heavy duty flex-pipe. I gave up. Tomorrow I'll get in there and chop it off with my battery operated disk grinder. I'll be able to extract the 2" remaining piece out when I can pull the stove out of the hearth.

In my first house(1978 to 1993) I had a 7 inch heavy duty stainless steel liner fabricated(22ft long) and rested this liner on a 1/4" steel plate through which it passed. I then poured vermiculite insulation from the top and fill the space between the liner and the chimney. I used a RiteWay Model 37(which if still own) and it used a 7" chimney. It was way cheaper than 22ft of double wall chimney plus it fit well in the 12 x 12 flue tile. Worked great.

I am very interested in how long that single-wall pipe lasted. I cannot justify $50 to 100+ per foot for the double-walled chimney pipes. I figure if the flexible pipe is good enough to go up past the damper, it is good enough to go all the way to the top. I really like your idea about insulating the whole column with vermiculite, too.

How long did that last? After 22 years, the "stainless" flexible pipe that couples my wood burning insert out past the damper is still quite sturdy, although thoroughly rusted and stiff. I'd happily re-use it, but it looks like I will destroy it getting the stove out of the hearth, first. I figure if a single-wall flexible pipe is good enough for the first 4 feet, it ought to be good enough for the last 20 feet.

Anybody have objections to this plan?

 

[Del_]

An update: I am still defeated by the flexible pipe attached to the top/rear of the stove. I took my heavy-duty air chisel home from work, and it didn't even wiggle. It hits so hard that the stove coupler pressed into the stove started to come out and the air chisel was happy to blow holes in the heavy duty flex-pipe. I gave up. Tomorrow I'll get in there and chop it off with my battery operated disk grinder. I'll be able to extract the 2" remaining piece out when I can pull the stove out of the hearth.



I am very interested in how long that single-wall pipe lasted. I cannot justify $50 to 100+ per foot for the double-walled chimney pipes. I figure if the flexible pipe is good enough to go up past the damper, it is good enough to go all the way to the top. I really like your idea about insulating the whole column with vermiculite, too.

I lived in that house for 14 years moving from there in 1993. No problem at all during that time.

I'm sure it would last a very long time. I believe it was 20 gauge stainless but don't remember for sure. It was custom fabricated by a local heating and air company.

I doubt the owners are heating with wood today but they might be.