Insulated flue above roof

[Polishicebreaker]

I know it's a controversial topic to go single or double skin flue but I've decided to do double where the flue exits the roof.

Stove fitters guidelines suggest 600mm outside. Does this mean I need to do it in 2 sections with the first finishing just above roof and a removable section on top? Problem is I have 1 section of double wall flue( with the single from the stove of course) that I wanted to use but that would leave me around 300mm above roof. Would that be a sufficient draw for the stove do you reckon?

Thanks

[Dave Payne]

You need to fit a collar on the roof, this then takes the flue from stove to collar, then from collar above roof goes the chimney.

 

I think you are asking about running a fluestraight through a hole with no collar? This is not a good idea.

http://m.ebay.co.uk/itm/321993639034?_mwBanner=1

Edited October 11, 2016 by Dave Payne

[Tony Brooks]

As Dave says you are probably talking about the chimney, although you might be considering a 2 metre plus lash-up as seen on some livaboards around the system. As far as the chimney is concerned they come in single skin and double skin. Either will do the job but a single skin one is likely to cause condensation on the inside face which then runs down all over the roof and paintwork. With a double skin you ensure the inner skin has a slightly smaller diameter than the actual flue and hangs down enough to project slightly into the flue. Now any condensation will fallback into the fire. However gasses can still get between the skins so some fill the void with crumpled kitchen foil while I fill with spray foam capped with kitchen foil. This will not totally eliminate tar on the roof but will go a very long way towards it but that was not your question.

[Dave Payne]

The soliftec link actually shows a straight pipe running from stove to top with a cap, no collar, but I really see this as a bad idea, for me I want to keep everything separate, rust will come and us rather just swap out a chimney than half the flue.

[Sea Dog]

Also, if you fit a collar as advised above you can replace the chimney with a short vented cap when the stove is not in use.

 

My own chimney is as Tony suggests and I get no tar on my roof at all. It helps to have a stove thermometer to ensure you're burning hot enough to avoid creosote too.

[cuthound]

The soliftec link actually shows a straight pipe running from stove to top with a cap, no collar, but I really see this as a bad idea, for me I want to keep everything separate, rust will come and us rather just swap out a chimney than half the flue.

And chimneys are much easier (and cheaper) to replace after an incident with a low bridge!

[Polishicebreaker]

That looks good but I wanted to only have a short piece of single skin from the stove and then switch to 125mm double wall insulated.

Do I still need a collar or would my insulated flue just protrude out above the roof and I'd have a short removable section on top of that of 600mm or so if that makes any sense?

That looks good but I wanted to only have a short piece of single skin from the stove and then switch to 125mm double wall insulated.

Do I still need a collar or would my insulated flue just protrude out above the roof and I'd have a short removable section on top of that of 600mm or so if that makes any sense?

[Tony Brooks]

The collar gives you a method of packing & sealing the joint between flue and collar and sealing between collar and roof so it is all weatherproof. The only other way apart from a bodge is to weld the flue into the roof so yes you do need a collar. However the flues outer case may have to be cut away to allow the inner to fit the collar.

[sooty]

If you look at the marine morso twin wall flue kit (very expensive !) the 'collar' is simply a piece of thin plate (with a hole for the flue in it) which fastens to the roof. You then seal the gap around the flue and plate with a high temperature sealant. The flue protrudes about 150mm above the roof, on top of this is attached a short length of flue with a chimney top.

The outer case of the twin flue at the roof point does not get overly hot but a gap of 60mm is required on the inside of the roof between flue and ceiling of course.

I fitted this to my first boat and was still good after 3 years.

 

On my current boat I simply made a neat hole in the steel roof (doing away with the thin plate, surplus in my opinion) and ran a 1.5mtr flue straight to the fire, The roof hole sealed well with a high temperature quality flexible sealant. It protrudes about 200mm above the roof on top of which I put a 500mm flue piece (and chimney cap) which can be removed.

It has been installed 18 month and never moved/leaked and looks tidy if you get the sealant right (I used masking tape on final application). If you cant cut a neat hole there are flue plates available with a 'nice' hole in them on fleabay.

[WotEver]

If you cant cut a neat hole there are flue plates available with a 'nice' hole in them on fleabay.

Who ever thought there would be a market for selling holes...

[Polishicebreaker]

Sounds like a good plan. I can cut a fairly best hole with the jigsaw so will go for that.

I did see you can get a storm collar so I might put this on as well to get a double seal.

I like the idea of then using a 500mm section on top, sounds like a good height for drawing the stove.

Thanks

 

If you look at the marine morso twin wall flue kit (very expensive !) the 'collar' is simply a piece of thin plate (with a hole for the flue in it) which fastens to the roof. You then seal the gap around the flue and plate with a high temperature sealant. The flue protrudes about 150mm above the roof, on top of this is attached a short length of flue with a chimney top.

The outer case of the twin flue at the roof point does not get overly hot but a gap of 60mm is required on the inside of the roof between flue and ceiling of course.

I fitted this to my first boat and was still good after 3 years.

 

On my current boat I simply made a neat hole in the steel roof (doing away with the thin plate, surplus in my opinion) and ran a 1.5mtr flue straight to the fire, The roof hole sealed well with a high temperature quality flexible sealant. It protrudes about 200mm above the roof on top of which I put a 500mm flue piece (and chimney cap) which can be removed.

It has been installed 18 month and never moved/leaked and looks tidy if you get the sealant right (I used masking tape on final application). If you cant cut a neat hole there are flue plates available with a 'nice' hole in them on fleabay.

'Neat' hole not 'best'

Damn predictive text

[Dave Payne]

I would have to look at all the boats with collars and think maybe, just maybe they use them for a reason?

[sooty]

A collar is absolutely required on single skin flues .

Could you get a conventional collar the correct diameter for twin walled ?? , mine is 7" overall diameter.

Seen lots of variations on roof exit for twin walled, including the 'storm collar' the op mentioned (on a boat next to me) .

The boaty 'morso' kit certainly doesn't come with a 'collar', just a thin bit of plate with the hole in it.