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I'm renting a property which has a wood burning stove. Recently I've been investigating ways to make my house warmer (secondary glazing on sash windows etc) and started to wonder how much air could be rushing up what appears to be a relatively open chimney.

My initial thoughts were to make or buy some sort of metal sheet to stick around the pipe which leads up the chimney. Coincidentally I had previously wondered why the fire sometimes didn't draw very well and where the soot came from which occasionally rained down from the chimney. Well now I know the answer; the pipe that comes out of the top of the stove is only about 5ft tall and is just open to the chimney.

I've been googling since I made this discovery and a lot of sites seem to suggest that this is a dangerous thing to have running as it can lead to build ups of soot and tar which are a major cause of chimney fires.

So my questions are:

  1. Is what's already there safe.
  2. Is it possible to add a metal sheet to cap the gap between the pipe and the chimney wall and if so, is it DIY-able or does it have to be bought?
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This setup is downright evil. You have no way of cutting off air and damping a flue fire. Been there, done that, got away with burned holes in the tee shirt. My teenage memory is of handing buckets of earth up the ladder to my dad so he could dump them down the chimney to seal off the warped damper in the fireplace. Not some place you want to be. Thankfully it was a howling burner and not the gas explosion type of vaporized creosote that blows flame out the top and downwards into the living area causing an instant conflagration. –  Fiasco Labs Nov 21 '12 at 6:07

1 Answer 1

up vote 3 down vote accepted

The way fire insert stoves work is relatively simple in conversion.

You cut the damper out of the fireplace, run stainless steel pipe (6" dia.) up the inside of the chimney. The lengths are held together with 3-6 sheetmetal screws so this is an actual inside pipe assembly and it hangs off a sheetmetal cap that covers the top of the chimney and is silicone caulk sealed to the top of the chimney flue tile so it's air tight to prevent exactly the type of heat loss you mention. The pipe that extends above the sheetmetal sealing cap gets a standard stovepipe cap to prevent downdrafts and water intrusion from precipitation.

The bottom gets a piece of flex stainless pipe that joins the chimney stack to the stove.

The advantage of this is you are no longer at the mercy of cracked flue tiles and the fire hazard that represents. The 6 inch pipe runs at a higher temperature and tends to not creosote up. There are standard round chimney brushes for these so the soot that accumulates near the top is easily removable by popping the cap off and running the brush and 3-4 rods down the length of pipe.

Depending on where you live and your county's rules, this conversion may require a permit, but it saves you a lot of lost heat and drastically lowers your liability from flue fires.

The stainless pipe will need inspection periodically for pinholes and monitoring for soot buildup and a good brushdown every so often.

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