Wood stove: Insulating above the closure plate, is it common? Good idea?

[carbs for arbs]

Hi all

 

I've got a wood burner installed in a builder's opening. Single wall flue into a flexible chimney liner. The thin steel closure plate is higher than the lintel in front - i.e. you can't see it when stood in front of the stove. I therefore often wonder how much heat gets "trapped" in that pocket of space behind the lintel, and subsequently escapes through the closure plate into the chimney void.

 

So I've been thinking about insulating above the closure plate using mineral wool and wondered what people think to the idea? I've not come across much info of people doing that. Seems sensible to me but perhaps I'm overlooking something.

 

I did mention it to the chimney sweep when he was last here and he was against the idea. Not sure how much I trusted his opinions though (on that and other things!). One of his concerns was the mineral wool combusting. I told him that in my limited knowledge it's not combustible but he wasn't having any of it!

 

Any thoughts?

 

Many thanks

[sime42]

With all due respect to your Sweep; I'm certain that he's wrong! Mineral wool will never burn, if indeed it is mineral wool, as it's essentially just glass fibre.

 

I'm interested in the wider question as I have the same set-up. I've never thought about the issue of heat escaping via the closure plate, but my hunch is that it can't be a lot.

 

 

[Bob The Dog]

I had a wood burning stove installed some years ago, with a flexi stainless steel liner. The fitter backfilled the void with Vermiculite loose fill insulation. He suggested that it would help to prevent condensation and tar / creosote build up. Seemed worth the extra and certainly hasn’t caused any issues in having it done. 

[Stubby]

40 minutes ago, Bob The Dog said:

I had a wood burning stove installed some years ago, with a flexi stainless steel liner. The fitter backfilled the void with Vermiculite loose fill insulation. He suggested that it would help to prevent condensation and tar / creosote build up. Seemed worth the extra and certainly hasn’t caused any issues in having it done. 

As above . Vermiculite beads .

[carbs for arbs]

Many thanks for the replies.  

 

The void wasn't filled with anything. Not sure why. Can't remember if it just wasn't discussed at the time or whether the fitter had reasons not to. I know access to the top of the opening in the loft is restricted, so that might have been a reason. Anyhow, it is what it is I guess, and I've no intention of adding it retrospectively as I'd have to undo much of the fitter's work.

 

Thinking about it though, from what I remember the space around the flexi flue liner is not all that much at all. It's a narrow space. Perhaps that's why vermiculite wasn't used? Not sure...

 

Cheers

[openspaceman]

1 hour ago, carbs for arbs said:

I know access to the top of the opening in the loft is restricted,

please explain? the flue liner is normally continuous from the register plate to the chimney pot

[carbs for arbs]

We don't have a chimney pot.  The chimney was removed years ago, but the chimney breast remains in the loft.  It was capped quite close to the rafters.  I didn't go up and see it when they uncapped it to add the twin wall flue to get through the roof.  Shame, would have been nice to see it.  

 

Cheers

[Mik the Miller]

A stove top fan will move the hot air out into the room ...

[openspaceman]

10 hours ago, carbs for arbs said:

We don't have a chimney pot.  The chimney was removed years ago, but the chimney breast remains in the loft.  It was capped quite close to the rafters.  I didn't go up and see it when they uncapped it to add the twin wall flue to get through the roof.  Shame, would have been nice to see it.  

 

Cheers

I see so the lining extends from the register plate to the top of the reduced chimney breast and then the twinwall carries the flue up through the roof.

 

I wouldn't worry as all the heat lost from the lining just heats the brickwork and gets back into the house.

 

I depend on the flue gas heating my concrete lined chimney for retained heat once the fire goes out.

[devon TWiG]

I have an unlined chimney and the entire chimney breast is effectively a giant heat sink acting a bit like a night storage heater , one good reason not to line a chimney if it is not essential ....