Chimney Lining & Vermiculite

greyteam1959

I am going to replace my 25 year old multi fuel stove with a new one.
The house is now about 100 years old & I will be lining the chimney with a flexible 904 liner.
I have been told that I should have the chimney 'back filled' with vermiculite after the liner has been fitted. This will stop the new flue moving about when being swept & provide insulation.
20 bags at £20 per bag.........
Is this an expensive add on or a reasonable thing to do ???
Oh & what happens if you need to replace the liner at some stage if the chimney is loose filled with vermiculite ??

[Deleted User]

mervyn11 wrote: »

I am going to replace my 25 year old multi fuel stove with a new one.
The house is now about 100 years old & I will be lining the chimney with a flexible 904 liner.
I have been told that I should have the chimney 'back filled' with vermiculite after the liner has been fitted. This will stop the new flue moving about when being swept & provide insulation.
20 bags at £20 per bag.........
Is this an expensive add on or a reasonable thing to do ???
Oh & what happens if you need to replace the liner at some stage if the chimney is loose filled with vermiculite ??

Sounds like a good plan to me but not sure if expensive.

highrisklowreturn

Have they explained what you will do, or what it will cost, should the liner crack, and the broken bit is inaccesible owing to having back filled it with vermiculite?

muckybutt

Best person to ask would be Hethmar he's a fitter.

A._Badger

The man who installed my stove (HETAs registered, for what that's worth) doesn't recommend it - implying that it's 'a nice earner' for installers but can cause problems with damp. I didn't press him on exactly what these problems were but as he is the main local installer in an area with a lot of stoves. I took his advice.

greyteam1959

I have done some more research on this.
I have a feeling that using vermiculite or any other back fill product may not be such a good idea as it sounds.
If the liner has ever to be replaced 20 bags of sooty vermiculite is going to cause a right mess when it has to be removed !!
Dampness also seems like it might be an issue with the stuff as well.
I was a little suspicious that it sounded like a 'nice little earner' when it was suggested by the place that was selling the new stove.

Williwoodburner

My sweep says insulating a liner is not needed on an internal stack, only if the stack is on an outside wall of the house.
This made sense to me as a stack on an outside wall will be colder than a stack in the middle of the house .

Willie.

hethmar

Sorry, only just seen this. We always recommend using insulation - usually vermiculite if its an average flueway or rock wool wraps in a large flueway. It is also recommended by the manufacturers of the liners and a must do in thatched properties.

It provides insulation and support for the liner. A warm flue is less likely to have any resin problems or transfer heat to resin already in the brickwork. We also put a metre long insert in at the top of the flueway as additional protection for the liner in its most vulnerable place.

Its not a nice little earner actually - its a hard old slog up and down ladders and across roofs carrying the bags of material - hence why many an installer will not recommend or mention it. Much easier to sling down the liner, hang it by a diy pot hanger (without even removing the pot) and be on your way.

But, you pays your money and takes your choice. (20 bags is a huge amount for a standard flueway - if its a large one, then ask for wraps to go round the liner)