Fire surround

[SusieC]

Domestic stove installer suggesting Skamolex board direct onto wood, behind the stove in my barge -thoughts onthis? I'm in Ireland so not subject to Bss, and we don't have boat stove installers here. I proposed the 10mm gap and 25mm calcium silicate recommendation from Solfitel, but he felt that was over the top.......

[Tracy D'arth]

I understood that there should always be a gap.

[blackrose]

It depends to some degree on the gap between the stove and the surface behind that's being protected. I have about a 10" gap behind the stove and no gap between the Masterboard and wooden bulkhead. Perhaps the anodised aluminium reflects the heat but the wood behind is accessible through a hole that one of the backboiler pipes goes through and it doesn't get very warm.

 

 

Edited November 28, 2023 by blackrose

[Jen-in-Wellies]

Thermal conductivities:

Skamolex 0.2W/m.K

Air 0.026W/m.K

So for the same thickness, an air gap is nearly ten times better than Skamolex. Lower thermal conductivity is better for preventing heat getting through to the wood. You can't easily stick tiles to air, but it is a very good idea to have an air gap between the temperature resistant stuff you stick them to and wood.

[blackrose]

Lots of people insist on an airgap behind the fireproof board, but how many people bother to line the area behind the flue? I've seen scorching behind and above  unlined flues in boats. I think it's just as important.

 

Also some people create the airgap behind the board using wooden battens which is a complete waste of time.

Edited November 28, 2023 by blackrose

[magnetman]

I would like an air gap. Always nice to have a bit of air around a fire.

 

One of my boats had a sheet of 3mm stainless bolted to the back of the fire slightly larger than it and it was mounted on those long nuts you can get so it was about an inch away from the fire. This was a fire with no boiler on the back, There was also a tiled hearth area. I found this an interesting approach but I don't know how effective it was as I took the fire and hearth out and the fire I have now including the flue is at least 6 inches clear of anything else to the sides and above and sits on a 3 inch thick piece of paving slab.

 

 

This has two advantages for me. One is I can decommision the fire in warmer weather easily and secondly a free standing fire means heat goes out in all directions so it will warm the boat more effectively.

[Jen-in-Wellies]

30 minutes ago, magnetman said:

I would like an air gap. Always nice to have a bit of air around a fire.

 

One of my boats had a sheet of 3mm stainless bolted to the back of the fire slightly larger than it and it was mounted on those long nuts you can get so it was about an inch away from the fire. This was a fire with no boiler on the back, There was also a tiled hearth area. I found this an interesting approach but I don't know how effective it was as I took the fire and hearth out and the fire I have now including the flue is at least 6 inches clear of anything else to the sides and above and sits on a 3 inch thick piece of paving slab.

 

 

This has two advantages for me. One is I can decommision the fire in warmer weather easily and secondly a free standing fire means heat goes out in all directions so it will warm the boat more effectively.

The stainless reflects some of the heat back to the stove. What heat it does absorb is transmitted straight through and radiated to the tiles, so keeping it shiny is important. The stainless sheet does help create a convection chimney between it and the stove, transferring heat from the stove and plate to the air.

[David Mack]

6 hours ago, magnetman said:

One of my boats had a sheet of 3mm stainless bolted to the back of the fire slightly larger than it and it was mounted on those long nuts you can get so it was about an inch away from the fire.

The sheet will block the radiant heat from the stove body from reaching the wall behind. The sheet itself will heat up, but with a large surface area on two sides, that in turn will warm the surrounding air creating more convection which distributes heat around the whole cabin. This loss of heat from the sheet to the surrounding air then keeps the sheet temperature down, meaning it can radiate much less heat to the wall behind. So beneficial from both fire protection and heating effectiveness perspectives.

[IanD]

13 hours ago, David Mack said:

The sheet will block the radiant heat from the stove body from reaching the wall behind. The sheet itself will heat up, but with a large surface area on two sides, that in turn will warm the surrounding air creating more convection which distributes heat around the whole cabin. This loss of heat from the sheet to the surrounding air then keeps the sheet temperature down, meaning it can radiate much less heat to the wall behind. So beneficial from both fire protection and heating effectiveness perspectives.

Once you do this there's no real need for a huge gap between the sheet and the wall, it just needs to be big enough to allow effective convection of air up behind it (like a radiator) so a couple of inches should be fine.

 

Before anyone says "but the wall will then get hotter!", the way that heat radiation works means this isn't true unless the gap is huge, it needs to be more than half the width of the sheet to have any effect.

[Sea Dog]

13 hours ago, David Mack said:

The sheet will block the radiant heat from the stove body from reaching the wall behind. The sheet itself will heat up, but with a large surface area on two sides, that in turn will warm the surrounding air creating more convection which distributes heat around the whole cabin. This loss of heat from the sheet to the surrounding air then keeps the sheet temperature down, meaning it can radiate much less heat to the wall behind. So beneficial from both fire protection and heating effectiveness perspectives.

My Bubble corner stove also has this, and it certainly makes a difference to the heat reaching the tiled surround. In my recent refurbishment I replaced black ceramic tiles with light coloured porcelain, both of which I think also work well at further reducing the heat making it to the backing.

[IanD]

21 minutes ago, Sea Dog said:

My Bubble corner stove also has this, and it certainly makes a difference to the heat reaching the tiled surround. In my recent refurbishment I replaced black ceramic tiles with light coloured porcelain, both of which I think also work well at further reducing the heat making it to the backing.

Colour has very little effect on heat radiation (infra-red) at the temperatures we're talking about here, the same as for radiators -- and if it doesn't affect the amount of heat radiated from the hot surface (heat shield), physics says it won't make any difference to the amount of heat picked up by the cool surface (wall). It does however make a big difference for solar heating and light reflection, hence all the discussion about roof colours.

 

https://www.bestheating.com/info/does-the-colour-of-your-radiator-affect-its-heat-output/

 

"Strictly speaking in scientific terms, matt black is the very most efficient colour choice. However, the difference in heat output between this style and a white radiator, for instance, would only be around 1%."

[ditchcrawler]

2 minutes ago, IanD said:

Colour has very little effect on heat radiation (infra-red) at the temperatures we're talking about here, the same as for radiators -- and if it doesn't affect the amount of heat radiated from the hot surface (heat shield), physics says it won't make any difference to the amount of heat picked up by the cool surface (wall). It does however make a big difference for solar heating and light reflection, hence all the discussion about roof colours.

 

https://www.bestheating.com/info/does-the-colour-of-your-radiator-affect-its-heat-output/

 

"Strictly speaking in scientific terms, matt black is the very most efficient colour choice. However, the difference in heat output between this style and a white radiator, for instance, would only be around 1%."

Surly with tiles we are talking about reflected heat, the tiles are not a heat source 

[magnetman]

I used to get the 'what colour is most efficient for a radiator' question in physics at school. I always said black but every time it came up the teacher would say I was wrong and that white was more efficient. I still maintained it was black but was marked down. 

 

I think the teacher had white rads in his house. 

 

 

[IanD]

3 minutes ago, ditchcrawler said:

Surly with tiles we are talking about reflected heat, the tiles are not a heat source 

There's no difference between the equations for heat reflection and absorption. If there was, you'd have the makings of a perpetual motion machine... 😉

 

2 minutes ago, magnetman said:

I used to get the 'what colour is most efficient for a radiator' question in physics at school. I always said black but every time it came up the teacher would say I was wrong and that white was more efficient. I still maintained it was black but was marked down. 

 

I think the teacher had white rads in his house. 

 

 

You were theoretically right and he was theoretically wrong -- but as noted above the difference so small (about 1%) that it doesn't matter.

Edited November 29, 2023 by IanD

[magnetman]

It was the theory I was interested in not the central heating. 

[ditchcrawler]

4 minutes ago, IanD said:

There's no difference between the equations for heat reflection and absorption. If there was, you'd have the makings of a perpetual motion machine... 😉

 

You were theoretically right and he was theoretically wrong -- but as noted above the difference so small (about 1%) that it doesn't matter.

Get back in the real world, you know as well as me that a light colour surface doesn't absorb as much radiated heat as a dark one never mind you fancy scientific equations 

[IanD]

24 minutes ago, ditchcrawler said:

Get back in the real world, you know as well as me that a light colour surface doesn't absorb as much radiated heat as a dark one never mind you fancy scientific equations 

In the real world -- according to all the sources who actually understand the subject, not just me -- the colour makes almost no difference *for radiators* (and the tiles behind heat shields), which is exactly what I said.

 

I also said that this didn't apply to solar radiation, so the thread about light roofs being cooler than dark ones in the sun (and white ends of lock beams cooler than the black beams) was correct.

 

If you want to get technical, it's to do with the wavelength/energy of the radiation (temperature of heat source) -- white and black determine how much light and short-wavelength infra-red are reflected/absorbed (from sun at 6000C), but for lower temperatures (like radiators) it makes close to zero difference. If you had a camera that could see deep infra-red then both black and white would look the same colour.

 

Nothing wrong with scientific equations when correctly applied... 😉

 

https://en.wikipedia.org/wiki/Thermal_radiation

 

"Lighter colors and also whites and metallic substances absorb less of the illuminating light, and as a result heat up less; but otherwise color makes little difference as regards heat transfer between an object at everyday temperatures and its surroundings, since the dominant emitted wavelengths are nowhere near the visible spectrum, but rather in the far infrared. Emissivities at those wavelengths are largely unrelated to visual emissivities (visible colors); in the far infra-red, most objects have high emissivities. Thus, except in sunlight, the color of clothing makes little difference as regards warmth; likewise, paint color of houses makes little difference to warmth except when the painted part is sunlit."

 

"Most household radiators are painted white, which is sensible given that they are not hot enough to radiate any significant amount of heat, and are not designed as thermal radiators at all – instead, they are actually convectors, and painting them matt black would make little difference to their efficacy."

Edited November 29, 2023 by IanD

[TandC]

Try to stick to the original question... they weren't asking about what colour spectrum for radiators.... 

 

Hearth/fireback construction detail was the query:  And to answer that - purely from my experience/view for what that's worth

 

I've had a fireback that was 5mm thick tiles onto 18mm plywood - simple.  The Squirrel stove when installed was about 100mm away.  Never had any problems and when I removed that when we stripped the boat, I made a point of chipping a tile off and from what i could see, there was no burning.  

 

But - I think that there is no definitive standard/guidance if you're building for RCD compliance (someone correct me if there is) - and in the absence of black and white clarity, then this approach as described here is what a lot of people aim to follow: http://www.soliftec.com/boat stoves 1-page.pdf

 

Air gap, calcium silicate, etc - .  It's what i've followed for my new installation because I've tried to do it to whatever standards i can apply.  I've also got a 5mm layer of tile backer board stuff because i wasn't sure how well the CS board would take a tile (not yet got to tiling yet).   The problem is that it makes for a very thick detail, pushing the whole hearth construction further into the room. 

 

 

[magnetman]

It seems that pyrolisis is the problem rather than actual burning, until it is too late. 

 

 

"PYROLYSIS IN A NUTSHELL
Pyrolysis is derived from the Greek words pyro (fire) and lysis (separating). It is a process where the chemical composition in organic material changes when exposed to prolonged heat. When this happens it lowers the flash point required for wood to burn.
Wood stoves located too close to combustible materials can cause a phenomenon called pyrolysis. Over time, the heat from the stove causes a chemical change in the wood, lowering the temperature required to make it burn. For instance, a normal piece of 2"x4" will spontaneous ignite above 660F/350C.
If the wood stove or flue pipe is too close to the wood it will draw the moisture out from the 2"x4". When this happens repeatedly, the piece of wood can spontaneously ignite as low as
390-570F/200-300C. Generally this happens in 3-5 years. The wood stove can be used for years without a problem, then suddenly there is a fire.
NOTE: The process of pyrolysis has been known for centuries and is still used today to produce charcoal."

I've got minimum 8 inches on the flue and the fire itself is about 15 inches from flammable objects. 

 

hopefully that is enough air gap as it is a very hot fire. 

[LadyG]

On 28/11/2023 at 14:23, blackrose said:

Lots of people insist on an airgap behind the fireproof board, but how many people bother to line the area behind the flue? I've seen scorching behind and above  unlined flues in boats. I think it's just as important.

 

Also some people create the airgap behind the board using wooden battens which is a complete waste of time.

I would think a frame of hardwood battens would have the wood a distance from the stove, but  they would be better made of a non flammable material.

I chiselled the fire cement the previous owner used to seal the flue under the roof, the fire was very hot, and the deckhead was ready to ignite, judged by smell of paint burning. There is now an air gap, plus I have the collar inside wrapped with exhaust tape. The deckhead can get warm but not hot 

Edited December 6, 2023 by LadyG

[Jen-in-Wellies]

17 minutes ago, magnetman said:

It seems that pyrolisis is the problem rather than actual burning, until it is too late. 

 

 

"PYROLYSIS IN A NUTSHELL
Pyrolysis is derived from the Greek words pyro (fire) and lysis (separating). It is a process where the chemical composition in organic material changes when exposed to prolonged heat. When this happens it lowers the flash point required for wood to burn.
Wood stoves located too close to combustible materials can cause a phenomenon called pyrolysis. Over time, the heat from the stove causes a chemical change in the wood, lowering the temperature required to make it burn. For instance, a normal piece of 2"x4" will spontaneous ignite above 660F/350C.
If the wood stove or flue pipe is too close to the wood it will draw the moisture out from the 2"x4". When this happens repeatedly, the piece of wood can spontaneously ignite as low as
390-570F/200-300C. Generally this happens in 3-5 years. The wood stove can be used for years without a problem, then suddenly there is a fire.
NOTE: The process of pyrolysis has been known for centuries and is still used today to produce charcoal."

I've got minimum 8 inches on the flue and the fire itself is about 15 inches from flammable objects. 

 

hopefully that is enough air gap as it is a very hot fire. 

See the Marine Accident Investigation Board report on the Lindy Lou narrowboat fire and deaths for more on pyrolysis from wood near stoves and why you don't want it on your boat.

https://assets.digital.cabinet-office.gov.uk/media/547c703a40f0b6024100008b/LindyLouReport.pdf

 

[David Mack]

41 minutes ago, Jen-in-Wellies said:

See the Marine Accident Investigation Board report on the Lindy Lou narrowboat fire and deaths for more on pyrolysis from wood near stoves and why you don't want it on your boat.

https://assets.digital.cabinet-office.gov.uk/media/547c703a40f0b6024100008b/LindyLouReport.pdf

 

Back in 2009 someone asked on a similar thread "What happens if I get it wrong?" and I posted some pictures from the MAIB Lindy Lou report and added the words "and a dead girlfriend". 

That post got deleted. But sometimes shock tactics are needed!

(The owner of Lindy Lou got out of the boat when he woke in the night to find the boat on fire, his girlfriend did not.)

[magnetman]

Some good pictures in the report. 

 

 

Worth getting the stove installation right I guess. 

[Alan de Enfield]

3 minutes ago, magnetman said:

Worth getting the stove installation right I guess. 

 

A tragedy, and one that may have been avoided had the stove been fitted to the manufacturers instructions.

 

THE STOVE WAS NOT installed in accordance with the manufacturers instructions. It could hav easily been correctky installed but it wasn't.

 

Villager Stoves Owner’s Manual

The Owner’s Manual for the Puffin stove fitted on board Lindy Lou, states that it should be installed in accordance with BS 8303 and BS 6461, and by a competent person, in compliance with all national and local Building Regulations and codes of practice. The manual also highlights the potential fire risks present when fitting a stove to a boat, caravan or other mobile structure, due to the combustible materials used in their construction. The importance of stoves standing on a non-combustible hearth, suitably insulated from any combustible material, with the stove itself suitably insulated from combustible materials, is also stressed.

Specifications for the hearth and stove location, are also provided, largely reflecting the requirements of BS 8303 and BS 6762. Key requirements are:

• The solid, non-combustible hearth should extend 300mm in front of the stove and 150mm on each side and to the rear, although the hearth width can be less, provided it extends to suitable heat resistant or non-combustible walls.

• The clearance around the stove to non-combustible materials should be 75mm either side, 150mm above and 25mm from the rear wall. These are ideal recommended measurements, but if the integrity of the services (i.e. marble, tiles, etc.) is in doubt, heat resistant material should be used to clad the hearth.

• The clearance from the flue to any wooden beam must be at least 3 x the flue diameter, unless the wood is shielded with a non-combustible material

 

 

Had the solid fuel stove on Lindy Lou been installed in the manner recommended by the manufacturers, the risk of a fire starting would have probably been reduced. However the stove and hearth arrangement on Lindy Lou is not dissimilar to many modern canal boats, where the constrained dimensions pose challenges for the provision of stoves with adequate hearth surroundings. Although standards exist for installing solid fuel stoves in buildings, park homes and transportable accommodation units, no such standard currently exists for boats, despite the risk of fire being at least as great.

[Bee]

There are many installations on boats that in my opinion are only just safe.  Part of the danger is that boats do not have the luxury of lots of space - that much is obvious. The stove is usually jammed into a corner or backed up against the side and too close to seats or other stuff. The flue can also get very hot indeed and is sometimes too close to the cladding and where it goes through the roof can be terribly close to wood or other material.  You really cannot be too careful. I used to cut away the cladding near to the back and sides of any stove, right back to the steel and the insulation if it was polystyrene or foam and then cover the horrible hole with fireproof sheet. I would also do the same around the top of the flue. The finished result looked like any other boat but it was nice to know it was probably a bit safer.