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Insulated flues ?


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I noticed that insulated flues are becoming the recommended standard now by various authorities for narrow boat stove installations, there are gains in safety and emissions using these but they also cut out the flue as a radiator of heat into the cabin, in my opinion that's a lot of heating lost. 

 

My questions are does anyone agree there was a safety issue with non insulated flues in the first place?  ( I don't )

 

Is this over the top BSS for the sake of it  or a good improvement in safety standards? 

 

Have you ever been burned or had a fire from an uninsured flue? ( I haven't )

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5 hours ago, waterworks said:

using these but they also cut out the flue as a radiator of heat into the cabin, in my opinion that's a lot of heating lost. 

 

I worked out on my boat the surface area of the flue was almost the same area as the stove - hence I would lose approximately 50% of the radiated heat.

 

5 hours ago, waterworks said:

My questions are does anyone agree there was a safety issue with non insulated flues in the first place?  ( I don't )

 

There is a potential issue, if you fall against the flue whilst bouncing 'thu the waves' you could put your hand out to stop you falling and burn it. Although, you could fall, bang your head on the stove and burn your face on the stove.

 

5 hours ago, waterworks said:

Is this over the top BSS for the sake of it  or a good improvement in safety standards? 

 

This is not covered in the BSS - that is just scaremongering.

 

5 hours ago, waterworks said:

Have you ever been burned or had a fire from an uninsured flue? ( I haven't )

 

No

 

(I didn't realise you could insure your flue separately !)

 

 

There is no legal requirement to install a stove in any particular method, or using any particular materials, there is a BS Specification for 'domestic' (house) installation and applying as much of it as is practical when installing on a boat is 'best practice'. In the event of a 'problem' your insurers would not look favourably if you had not used 'best practice' and would wriggle out of the claim.

Edited by Alan de Enfield
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I think this is a case of bods from the ISO/BS writing their stuff with insufficient experience in the field.  I am sure an uninsulated flue 20ft tall on the outside of a building will suffer flue gas cooling and thus lack of draw and even the possibility of back flow as the fire dies and CO inside the building so I fully understand the need for insulated flues in this type of case.

 

There has been sufficient years of use safe use of uninsulated flues on inland boats to show an uninsulated flue is not a safety issue but poor maintenance and/or installation is.

 

As I have said before, if I were concerned about people touching a hot flue I would surround the flue with a tube of punched metal as a guard.

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6 hours ago, waterworks said:

I noticed that insulated flues are becoming the recommended standard now by various authorities for narrow boat stove installations, there are gains in safety and emissions using these but they also cut out the flue as a radiator of heat into the cabin, in my opinion that's a lot of heating lost. 

 

My questions are does anyone agree there was a safety issue with non insulated flues in the first place?  ( I don't )

 

Is this over the top BSS for the sake of it  or a good improvement in safety standards? 

 

Have you ever been burned or had a fire from an uninsured flue? ( I haven't )

In short, its all bollox and you are indeed correct. It makes as much sense as the Irish central heating system with all the radiators being lagged so the heat doesnt escape into the room. A nice un PC 1970s joke was that one.

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7 hours ago, waterworks said:

I noticed that insulated flues are becoming the recommended standard now by various authorities for narrow boat stove installations, there are gains in safety and emissions using these but they also cut out the flue as a radiator of heat into the cabin, in my opinion that's a lot of heating lost. 

 

My questions are does anyone agree there was a safety issue with non insulated flues in the first place?  ( I don't )

 

Is this over the top BSS for the sake of it  or a good improvement in safety standards? 

 

Have you ever been burned or had a fire from an uninsured flue? ( I haven't )


You can see from this thread that there are a lot of people who don’t see the point of insulated flues. I suspect that none of these people have had any experience of insulated flues - but that doesn’t stop them having an opinion, of course!

 

Whilst I agree that it is counter-intuitive to think that an insulated flues is more efficient, in fact they are and this is born out by my personal experience. The gliding club I am a member of has a rather cold clubhouse room with a high ceiling and bare concrete walls. There is a large wood burner in the corner with a long flue going up to the ceiling. Originally this was non-insulated. The room was always cold and we got through a lot of wood. Eventually one of our members, who was a professional stove installer, could stand it no longer and he fitted a new stove of similar output, but with a double skinned/insulated flue. At the time, people moaned that they would be losing all that lovely heat from the long flue.

 

But they were wrong. The new stove made the room much warmer and we burnt noticeably less wood. The stove combustion chamber remained hot even when the stove was shut down - the stove would stay in better eg when we all decamped to the pub. And of course the draw when lighting was much better.

 

Why? Well I think it is because of the extra draw from keeping the flue gasses hot, means that the stove can be shut down more. The flow of air into the stove and up the chimney is less. If you can reduce the flow of air up the chimney you both reduce the escape of hot gases, and reduce the incoming flow of freezing cold outside air that has to replace it.

 

So IMO whilst there are some minor safety benefits of insulated flues, the main benefit is an improvement in efficiency and the way stove operates, even though that seems counter-intuitive. With short flues on boats, maximising the draw by insulating the flue seems eminently sensible.

 

Our boat does not have an insulated flue, but if we ever get a new stove it will have!

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25 minutes ago, David Mack said:

Interesting. But I wonder if the relative performance of insulated and non-insulated flues is different in the case of your high-ceilinged long-flued club room and the short flues of a narrow boat.

Nicks just haveing a usual long winded rant. We had a squirrel with an insulated flue in our Tea room. It was fine. We have lived aboard several boats for a long time and there is no way stove performance in a boat and a building can be compared. When we need another flue for the boat it will be without doubt a single skin born out of many many winters as full time liveboards experience. 

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45 minutes ago, David Mack said:

Interesting. But I wonder if the relative performance of insulated and non-insulated flues is different in the case of your high-ceilinged long-flued club room and the short flues of a narrow boat.

You would think that would favour the boat version over the tall room version simply because there is a lot more flue in the tall room version to (allegedly) “lose the heat output from”.

17 minutes ago, mrsmelly said:

Nicks just haveing a usual long winded rant. We had a squirrel with an insulated flue in our Tea room. It was fine. We have lived aboard several boats for a long time and there is no way stove performance in a boat and a building can be compared. When we need another flue for the boat it will be without doubt a single skin born out of many many winters as full time liveboards experience. 

Single skin flues are perfectly adequate. Insulated flues are better.

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5 minutes ago, nicknorman said:

You would think that would favour the boat version over the tall room version simply because there is a lot more flue in the tall room version to (allegedly) “lose the heat output from”.

In your club room with the uninsulated flue, the gases would have chilled quickly and most of the flue length would have been cold anyway, so the loss of its heat contribution to the room would have been minimal, whereas the (claimed) efficiency improvement will presumably apply.

The same isn't true in a boat.

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1 hour ago, nicknorman said:


You can see from this thread that there are a lot of people who don’t see the point of insulated flues. I suspect that none of these people have had any experience of insulated flues - but that doesn’t stop them having an opinion, of course!

 

Whilst I agree that it is counter-intuitive to think that an insulated flues is more efficient, in fact they are and this is born out by my personal experience. The gliding club I am a member of has a rather cold clubhouse room with a high ceiling and bare concrete walls. There is a large wood burner in the corner with a long flue going up to the ceiling. Originally this was non-insulated. The room was always cold and we got through a lot of wood. Eventually one of our members, who was a professional stove installer, could stand it no longer and he fitted a new stove of similar output, but with a double skinned/insulated flue. At the time, people moaned that they would be losing all that lovely heat from the long flue.

 

But they were wrong. The new stove made the room much warmer and we burnt noticeably less wood. The stove combustion chamber remained hot even when the stove was shut down - the stove would stay in better eg when we all decamped to the pub. And of course the draw when lighting was much better.

 

Why? Well I think it is because of the extra draw from keeping the flue gasses hot, means that the stove can be shut down more. The flow of air into the stove and up the chimney is less. If you can reduce the flow of air up the chimney you both reduce the escape of hot gases, and reduce the incoming flow of freezing cold outside air that has to replace it.

 

So IMO whilst there are some minor safety benefits of insulated flues, the main benefit is an improvement in efficiency and the way stove operates, even though that seems counter-intuitive. With short flues on boats, maximising the draw by insulating the flue seems eminently sensible.

 

Our boat does not have an insulated flue, but if we ever get a new stove it will have!

 

The problem with your example is that I bet the combined flue and chimney length in your clubhouse is long enough to make a difference, whereas on a boat it's very unlikely to. 

 

I've never had an insulated flue on my boat but I did try a 1m insulated chimney many years ago and it made no difference at all to the draw or anything else. 

 

I also spoke to a flue supplier who has a lot of experience and his view was that I'd be wasting my money on an insulated flue and chimney for such a short lengths, even though it was in his interest to sell me the stuff.

 

He said the flue gases wouldn't cool down significantly over such a short length

Edited by blackrose
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It is not mandatory, yet, to have insulated flues on boats. It is wholly correct that installing an insulated flue cuts out the radiating effect of the hot flue. But there is case to fit an insulated flue if the stove is near steps. For instance my stove is at the bow and in the corner of the saloon. Next to it are the steps to the cratch. It would be very easy for someone, my grandchildren for instance, to put their hand out and put it on the flue. For that reason only I have insulated my flue.

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25 minutes ago, pete.i said:

It is not mandatory, yet, to have insulated flues on boats. It is wholly correct that installing an insulated flue cuts out the radiating effect of the hot flue. But there is case to fit an insulated flue if the stove is near steps. For instance my stove is at the bow and in the corner of the saloon. Next to it are the steps to the cratch. It would be very easy for someone, my grandchildren for instance, to put their hand out and put it on the flue. For that reason only I have insulated my flue.

 

In that case it sounds like a good idea simply from a safety perspective

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35 minutes ago, pete.i said:

It is not mandatory, yet, to have insulated flues on boats. It is wholly correct that installing an insulated flue cuts out the radiating effect of the hot flue. But there is case to fit an insulated flue if the stove is near steps. For instance my stove is at the bow and in the corner of the saloon. Next to it are the steps to the cratch. It would be very easy for someone, my grandchildren for instance, to put their hand out and put it on the flue. For that reason only I have insulated my flue.

But you don't need a fully insulated flue for that. What you need us a guard, spaced away from the flue pipe and with small enough holes or slots to prevent young (and old) fingers from touching the flue pipe itself.

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30 minutes ago, David Mack said:

But you don't need a fully insulated flue for that. What you need us a guard, spaced away from the flue pipe and with small enough holes or slots to prevent young (and old) fingers from touching the flue pipe itself.

Agreed, as I said in post 4ish

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3 hours ago, David Mack said:

But you don't need a fully insulated flue for that. What you need us a guard, spaced away from the flue pipe and with small enough holes or slots to prevent young (and old) fingers from touching the flue pipe itself.

 

Getting a grid or something similar made up would not only be difficult but expensive and not easy to find. Whereas the materials for an insulated flue are readily available and reasonably cheap. Brackets and fixings for a grid type of protection would all have to be specially fabricated. I'm also not sure whether an uninsulated grid would be cool enough neither are the advocated for that type of thing for that matter. Personally I would rather be safe than sorry and install a ready made and tested insulated flue system rather than some heath robinson affair that might or might not protect little and big fingers. I do concede that an insulated flue does not radiate much if any heat into the boat (mine gets warm to the touch but not hot enough to burn) but in all honesty I do not think it makes much difference. It's a bit like the stove top fan argument. Generally speaking my stove kicks out enough heat without thinking about what I'm losing from the flue.

 

Just for the record before anyone jumps in saying that the stove gets even hotter and that is exposed. Yes it is on other's boats but not on mine. I bought a three section fire guard from Homebase that fits just tidily around the sides and in front of my stove and a cake stand on top works just fine. I think Bizzard made one out of Meccano. Cannot use a "snake oil" fan on ttop of the stove though.

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7 hours ago, nicknorman said:


You can see from this thread that there are a lot of people who don’t see the point of insulated flues. I suspect that none of these people have had any experience of insulated flues - but that doesn’t stop them having an opinion, of course!

 

Whilst I agree that it is counter-intuitive to think that an insulated flues is more efficient, in fact they are and this is born out by my personal experience. The gliding club I am a member of has a rather cold clubhouse room with a high ceiling and bare concrete walls. There is a large wood burner in the corner with a long flue going up to the ceiling. Originally this was non-insulated. The room was always cold and we got through a lot of wood. Eventually one of our members, who was a professional stove installer, could stand it no longer and he fitted a new stove of similar output, but with a double skinned/insulated flue. At the time, people moaned that they would be losing all that lovely heat from the long flue.

 

But they were wrong. The new stove made the room much warmer and we burnt noticeably less wood. The stove combustion chamber remained hot even when the stove was shut down - the stove would stay in better eg when we all decamped to the pub. And of course the draw when lighting was much better.

 

Why? Well I think it is because of the extra draw from keeping the flue gasses hot, means that the stove can be shut down more. The flow of air into the stove and up the chimney is less. If you can reduce the flow of air up the chimney you both reduce the escape of hot gases, and reduce the incoming flow of freezing cold outside air that has to replace it.

 

So IMO whilst there are some minor safety benefits of insulated flues, the main benefit is an improvement in efficiency and the way stove operates, even though that seems counter-intuitive. With short flues on boats, maximising the draw by insulating the flue seems eminently sensible.

 

Our boat does not have an insulated flue, but if we ever get a new stove it will have!

Surely the draw is the volume of air being sucked into the stove, more draw and you only need a smaller air intake but it's still the same volume of air going in?

 

 

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49 minutes ago, pete.i said:

 

Getting a grid or something similar made up would not only be difficult but expensive and not easy to find. Whereas the materials for an insulated flue are readily available and reasonably cheap. Brackets and fixings for a grid type of protection would all have to be specially fabricated. I'm also not sure whether an uninsulated grid would be cool enough neither are the advocated for that type of thing for that matter. Personally I would rather be safe than sorry and install a ready made and tested insulated flue system rather than some heath robinson affair that might or might not protect little and big fingers. I do concede that an insulated flue does not radiate much if any heat into the boat (mine gets warm to the touch but not hot enough to burn) but in all honesty I do not think it makes much difference. It's a bit like the stove top fan argument. Generally speaking my stove kicks out enough heat without thinking about what I'm losing from the flue.

 

Just for the record before anyone jumps in saying that the stove gets even hotter and that is exposed. Yes it is on other's boats but not on mine. I bought a three section fire guard from Homebase that fits just tidily around the sides and in front of my stove and a cake stand on top works just fine. I think Bizzard made one out of Meccano. Cannot use a "snake oil" fan on ttop of the stove though.

Refleks stoves come with a stainless steel grid to protect the flue, as standard I think. They must be more or less mass produced.

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Another point I disagree with is the often quoted " boats only have short flues so need help in achieving a good draw " .

 

Well my stove is on high legs, the flue is only 1000 mm, if I open the air intake fully it will run out of control like a blast furnace, there is no lack of draw in my installation.

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15 minutes ago, Rebotco said:

Don't see any logic to putting a guard around the flue for safety reasons, when the stove itself is larger and hotter and closer to touch.

 

It's helpful where idiots have the stove installed right next to the door.  That puts the flue exactly where someone sticks out their hand if they stumble on the steps.

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25 minutes ago, Rebotco said:

Don't see any logic to putting a guard around the flue for safety reasons, when the stove itself is larger and hotter and closer to touch.

 

Our flue was a great aid to stabilising ones self as you descended the cabin steps. It was in the front corner. However it only worked well if the stove wasnt on.

 

It was something I only did once when it was.

 

That said there must be loads of boats with the same configuration.

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