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Chimney Query..


robtheplod

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Hi All

 

We have a 12" single skin chimney (to fit 6"). I'm looking at getting a double skin one to stop gunk leaking out and was looking at ones from chandlers. Read lots on this and looks like I can just buy the inner skin but not 100% sure how this fixes - does it just wrap round and push in? Also read i need to ditch the rain hat but not sure if this is true?  any pointers much appreciated!!

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5 minutes ago, robtheplod said:

Hi All

 

We have a 12" single skin chimney (to fit 6"). I'm looking at getting a double skin one to stop gunk leaking out and was looking at ones from chandlers. Read lots on this and looks like I can just buy the inner skin but not 100% sure how this fixes - does it just wrap round and push in? Also read i need to ditch the rain hat but not sure if this is true?  any pointers much appreciated!!

No gunk, double skin with hat.

  • Greenie 1
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Hi, I made a double skin unit up fairly easily, rolled the inner leaf up and fed it into the outer leaf and filled the gap with fibre glass and ran some high temp silicone sealer round top and bottom to secure it. Make sure you leave enough single skin outer to fir over the collar. Works well, no tar drips. Also use a 'hat'.

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The reason to ditch the 'hat' is that tar can condense on the underside of it and drip off outwith the chimney, onto the roof.  I wondered why I was getting tar on the roof after fitting an inner skin to the chimney, then actually saw this happening one cold day.  It depends what fuel you are burning - more likely with wood which I burn.  Try it with the hat on, and if it's OK, then fine.

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4 minutes ago, Mac of Cygnet said:

The reason to ditch the 'hat' is that tar can condense on the underside of it and drip off outwith the chimney, onto the roof.  I wondered why I was getting tar on the roof after fitting an inner skin to the chimney, then actually saw this happening one cold day.  It depends what fuel you are burning - more likely with wood which I burn.  Try it with the hat on, and if it's OK, then fine.

 

Use dry wood, not wet wood ...

 

Under 20% moisture content is the usual starting point, lower is better.

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I also burn smokeless fuel, using a double-skinned chimney, but I do find that a small amount of tar condenses under the hat and then runs onto the roof especially when it's raining. For that reason I don't usually have the hat in place when the fire is burning well; I tend to have a dilemma when it is raining overnight as the fire is set low ie slightly smoky and not hot enough to quickly evaporate any raindrops that enter. I wonder if it makes a difference whether the chimney is vertical or angled - the slight angle may make the condensate all run to the lowest point and thus make a drip?

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57 minutes ago, Alastair said:

If you take the hat off, rain will run down the chimney and into the stove. What bothers you more, some tar stains on your roof, or rusted holes in your stove?

If the stove is lit, rain will evaporate before getting anywhere near the stove, If the stove is not lit, replace chimney with bean can or similar cover.

 

On the original query, Midland certainly used to do a separate inner which was a piece of metal rolled into a funnel shape.  We used one for a while. Easiest method of fitting we found was to put the small end of the inner into the flue, then ft the chimney over the top. Tight seal between iner and flue, and also between inner and chimney, so no need to insulate the gap.

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1 hour ago, Keeping Up said:

I also burn smokeless fuel, using a double-skinned chimney, but I do find that a small amount of tar condenses under the hat and then runs onto the roof especially when it's raining. For that reason I don't usually have the hat in place when the fire is burning well; I tend to have a dilemma when it is raining overnight as the fire is set low ie slightly smoky and not hot enough to quickly evaporate any raindrops that enter. I wonder if it makes a difference whether the chimney is vertical or angled - the slight angle may make the condensate all run to the lowest point and thus make a drip?

It can't be that hard to design a chimney hat with a sort-of stalagtite underneath so the tar is directed back to the flue?

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3 hours ago, LEO said:

Hi, I made a double skin unit up fairly easily, rolled the inner leaf up and fed it into the outer leaf and filled the gap with fibre glass and ran some high temp silicone sealer round top and bottom to secure it. Make sure you leave enough single skin outer to fir over the collar. Works well, no tar drips. Also use a 'hat'.

and enough inner skin to fit inside the top of the flue so condensate is directed back down the flue and not over whatever seals the top of the flue so it pools on the seal and collar.

26 minutes ago, doratheexplorer said:

It can't be that hard to design a chimney hat with a sort-of stalagtite underneath so the tar is directed back to the flue?

another coolie hat inverted and rivited to the underside of the top one would do the job but more difficult to manufacture so would people be prepared to pay if, as it seems here, many do not suffer tar drips. I know I did     even though I only burned well seasoned wood and smokeless fuel.

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1 hour ago, Iain_S said:

On the original query, Midland certainly used to do a separate inner which was a piece of metal rolled into a funnel shape.  We used one for a while. Easiest method of fitting we found was to put the small end of the inner into the flue, then ft the chimney over the top. Tight seal between iner and flue, and also between inner and chimney, so no need to insulate the gap.

 We have a stainless one of those. We had a galvanised steel one which rotted in a year.

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